Post on 05-Mar-2015
i
ENVIRONMENTAL ASSESSMENT OF
GULDAGER MØLLEDAM & GULDAGER MØLLEBÆK
Masters of Environmental Technology and Management
Presented by: Aghogho Ekpruke
Elinor Slotte
Fabian Sander
Samuel Obiri-Yeboah
Supervisor: Prof. Jens Peter Thomsen
ii
ACKNOWLEDGEMENT
We would like to thank Prof. Jens Peter Thomsen for his guidance during the course of this
project (the ping-pong was fun). We are also grateful to the entire staff of the Chemical and
Biological laboratory of the University of Aalborg, Esbjerg campus for their kind assistance,
advice and support.
iii
DECLARATION
This project was submitted to Aalborg University, Esbjerg as a part of the Masters
programme in Environmental Technology and Management.
We hereby declare that the information in the project is either reference based or based on our
own thoughts and ideas. The references used are stated in the text as well as a list of
references is attached in the end.
With our signature we give the authorization to publish and use this project for scientific
purposes.
7th
of December 2009, Aalborg University, Esbjerg, Denmark
……………………………. ……………………………..
Aghogho Ekpruke Elinor Slotte
……………………………. ………………………………
Fabian Sander Samuel Obiri-yeboah
iv
ABSTRACT
The environmental state of Guldager Mølledam and Guldager Møllebæk has been evaluated
in this project and the results have been compared with its previous environmental state and
current legislation. The study also looks at the lake restoration project carried out in
1998/1999 to see if it has been successful.
The results indicate that Guldager Mølledam is shallow, well mixed (no stratification), has a
high buffering capacity and a high dissolved oxygen content. It functions as a sink and source
of filter for external load of nutrients that flows into it from its catchment. Phosphorus
content in the sediment is low and is mainly bound to iron. The cholorophyll α content in the
lake suggests that the trophic state of Guldager Mølledam is mesotrophic, and the results
from the Secchi depth as well as dissolved phosphorus indicates the same. There is a
relatively high abundance of diatoms and macrophytes. While Guldager Møllebæk showed a
Danish Stream Fauna Index value of 4.
The results show that the restoration project was successful as the lake quality is improved
since and the quality is within the range of current environmental standards
However, these results are only applicable to the condition of the lake as at the time and date
of sampling and analysis.
v
TABLE OF CONTENTS
1 INTRODUCTION ............................................................................................................. 1
2 LAKES ............................................................................................................................... 3
2.1 Classification of Lakes ................................................................................................ 3
2.1.1 Based on origin .................................................................................................... 3
2.1.2 Based on Water source and type of outflow ........................................................ 4
2.1.3 Based on formation process ................................................................................. 4
2.1.4 Based on productivity .......................................................................................... 4
2.2 Lake restoration and factors affecting lake water pollution ........................................ 5
2.2.1 Lake restoration ................................................................................................... 5
2.2.2 Restoration related to problematical algal growth ............................................... 7
2.2.3 Problems related to Macrophyte growth .............................................................. 8
3 Guldager Mølledam and Guldager Møllebæk ................................................................... 9
3.1 Mølledam and Møllebæk before the restauration ....................................................... 9
3.2 Guldager Mølledam and Møllebæk today ................................................................. 12
3.3 Legislation ................................................................................................................. 14
3.3.1 European legislation........................................................................................... 14
3.3.2 Danish legislation............................................................................................... 15
4 FACTORS AFFECTING LAKES AND THEIR INTERACTIONS .............................. 17
4.1 Light, Primary production and Respiration ............................................................... 17
4.2 Dissolved Oxygen (DO) ............................................................................................ 18
4.3 Temperature, density and seasonal changes .............................................................. 19
4.4 Thermal stratification in lakes ................................................................................... 20
4.5 Nutrient loading and primary production .................................................................. 22
4.6 Limiting factor for lakes ............................................................................................ 23
5 PARAMETERS FOR LAKE QUALITY ASSESSMENT ............................................. 24
5.1 Physical properties .................................................................................................... 24
5.1.1 Temperature ....................................................................................................... 24
5.1.2 pH ....................................................................................................................... 25
5.1.3 Turbidity and transparency ................................................................................ 26
5.1.4 Secchi-depth ....................................................................................................... 26
5.1.5 Conductivity ....................................................................................................... 27
5.1.6 Total solids ......................................................................................................... 27
vi
5.1.7 Alkalinity ........................................................................................................... 28
5.2 Chemical properties................................................................................................... 30
5.2.1 Dissolved Oxygen .............................................................................................. 30
5.2.2 Organic matter ................................................................................................... 30
5.2.3 Nutrients ............................................................................................................. 30
5.2.4 Iron ..................................................................................................................... 32
5.2.5 Biochemical Oxygen Demand (BOD5) .............................................................. 33
5.3 Biological properties ................................................................................................. 34
5.3.1 Aquatic macrophytes ......................................................................................... 34
5.3.2 Phytoplankton .................................................................................................... 35
5.3.3 Zooplankton ....................................................................................................... 36
5.3.4 Chlorophyll α ..................................................................................................... 36
5.3.5 Macroinvertebrates ............................................................................................ 37
5.4 Danish Stream Fauna Index (DSFI) .......................................................................... 38
6 SAMPLING AND ANALYSIS OF SAMPLES ............................................................. 39
6.1 In-situ measurements................................................................................................. 39
6.2 Water sample measurements ..................................................................................... 41
6.2.1 Sampling.................................................................................................................... 41
6.2.2 Analysis of water samples ......................................................................................... 42
6.3 Sediment sample measurements................................................................................ 46
6.3.1 Sampling.................................................................................................................... 46
6.3.2 Analysis of sediment samples ................................................................................... 47
6.4 Biological measurements .......................................................................................... 49
7 RESULTS ........................................................................................................................ 53
7.1 Results of In-situ measurements ............................................................................... 53
7.2 Results of water sample measurements ..................................................................... 56
7.3 Results of sediment sample measurements ............................................................... 61
7.4 Results of biological measurements .......................................................................... 63
8 DISCUSSION OF RESULTS ......................................................................................... 68
8.1 In-situ measurements................................................................................................. 68
8.2 Water sample measurements ..................................................................................... 70
8.3 Sediment sample measurements................................................................................ 71
8.4 Biological measurements .......................................................................................... 72
vii
8.5 Comparison with legislation ..................................................................................... 72
8.6 Comparison with previously performed assessments ............................................... 74
9 CONCLUSION ................................................................................................................ 77
REFERENCES ........................................................................................................................ 77
APPENDICES ......................................................................................................................... 85
viii
LIST OF TABLES
Table 1 The morphological and hydrological data for Guldager Mølledam 1987 .................... 9
Table 2 Data from inlet and outlet streams at Guldager Mølledam ......................................... 11
Table 3 Results from water samples taken in Guldager Mølledam ......................................... 11
Table 4 Results from sediment samples, in g/kg dry stuff, taken in Guldager Mølledam ....... 12
Table 5 Concentration of metals analysed in the sediment samples ........................................ 12
Table 6 Classification of lakes and ponds based on alkalinity. ............................................... 29
Table 7 The average results from in-situ measurements ......................................................... 53
Table 8 The flow measurements for the inlet .......................................................................... 54
Table 9 Flow measurements for outlet..................................................................................... 54
Table 10 Results from alkalinity measurements ...................................................................... 56
Table 11 Total Solids results .................................................................................................... 57
Table 12 Total phosphorus in the Inlet, Lake and Outlet ........................................................ 59
Table 13 Ortho-phosphate in the Inlet, Lake and Outlet ......................................................... 60
Table 14 Iron content results .................................................................................................... 60
Table 15 Chlorophyll a results ................................................................................................. 60
Table 16 Sediment analysis results .......................................................................................... 61
Table 17 Macro-invertebrates in Guldager Møllebæk ............................................................. 65
Table 18 Limit values for total phosphorus concentrationin shallow and deep lakes ............. 73
Table 19 Comparison of limit values and our measurements .................................................. 73
Table 20 Comparison of results ............................................................................................... 74
ix
LIST OF FIGURES
Figure 1 Solubility of oxygen in water. ................................................................................... 19
Figure 2 Various strata’s in a stratified lake. ........................................................................... 20
Figure 3 Seasonal temperature cycles in stratified lakes ......................................................... 21
Figure 4 Distribution of temperature and dissolved oxygen during summer thermal
stratification of an eutrophic lake. ........................................................................................... 25
Figure 5 Secchi disk depth measurement................................................................................. 27
Figure 6 Forms of inorganic carbon at different pH levels. ..................................................... 29
Figure 7 Macrophytes in a lake ................................................................................................ 35
Figure 8 Phytoplankton ............................................................................................................ 35
Figure 9 Some species of Zooplankton .................................................................................... 36
Figure 10 Structure of Blue green algae (Left) and Algae bloom (Right) ............................... 37
Figure 11 Field analyzers used for the in-situ measurements: Secchi disk (Left); and pH and
Conductivity meter (Right) ...................................................................................................... 40
Figure 12 Current meter as used in the flow measurement ..................................................... 40
Figure 13 Lake water sampling ................................................................................................ 42
Figure 14 Radiometer Analytical ............................................................................................. 43
Figure 15 Oxitop BOD5 determination flasks. ........................................................................ 43
Figure 16 FIASTAR 5000 ....................................................................................................... 45
Figure 17 Location of sampling points for sediment samples and lake depths ....................... 47
Figure 18 Location of sampling points for sediment samples and lake depths ....................... 48
Figure 19 Atomic Absorption Spectrometer ............................................................................ 48
Figure 20 Net for collecting phytoplankton ............................................................................. 50
Figure 21 Olympus 249113 Microscope used for identification of plankton .......................... 50
Figure 22 Kick sampling and pick sampling ........................................................................... 51
Figure 23 Microscope for Macro-invertebrate analysis ........................................................... 52
Figure 24 BOD5 Results .......................................................................................................... 56
Figure 25 Total Nitrogen (mg/l) results ................................................................................... 58
Figure 26 Nitrogen Oxides (mg/l) results ................................................................................ 59
Figure 27 Organic Matter in Sediment samples ...................................................................... 62
Figure 28 Various species of Phytoplanktons .......................................................................... 65
Figure 29 Macrophytes at Guldager Mølledam ....................................................................... 67
x
Figure 30 Variations in temperature, pH, and DO between inlet, lake, and outlet water .Error!
Bookmark not defined.
1
1 INTRODUCTION
Humans, animals, plants and a huge diversity of aquatic species are completely dependent on
adequate and sustainable fresh water sources. Evaporating water from the surface returns as
precipitation, flows across the land thus replenishing aquifers, lakes, ponds, wetlands, streams
and finally discharges into the sea, bringing nutrients to marine life. All life, and all human
economics and cultures are dependent on this cycle. Most fresh water is still bound in ice.
Out of the liquid portion, 99% is in underground aquifers. The amount in lakes and streams is
small, but renewed rapidly, making them the primary source for fresh water in most regions.
In Denmark, however the primary source of drinking water origins from the groundwater.
Lakes in Denmark are mainly used for recreational purposes as is the lake Guldager
Mølledam. Guldager Mølledam is a small, artificial lake north of Esbjerg, close to the
suburban area of Guldager. The outlet is Guldager Møllebæk which runs out into the sea at
Ho Bay. Until 1987 the cleaned wastewater from Guldager was discharged into the stream
leading to Mølledam. In 1987 the discharge of the waste water was cut off, however the
wastewater had already been polluting the lake significantly with phosphorus and metals.
These pollutants were stored within the sediment. Due to the fear of phosphorus leaking out
into the lake water the decision was made to restore the lake by sediment removal. The
sediment removal was performed in 1998/1999 and increased the lake water quality
significantly as well as in the outlet stream, Guldager Møllebæk (Ribe Amt, 1998).
The European Union established the Water Framework Directive in 2000 (2000/60/EC), the
main purpose of the directive was to ensure good quality in freshwaters. The objective is to
prevent or reduce pollution into freshwater basins and to provide tools for the environmental
management of these freshwater sources. By the end of 2015 all water sources within
Member States shall have a good ecological status. The Annex V in the Directive gives
guidelines on how to assess the quality for these water sources, however each Member State
shall provide the EU with a management programme by the end of 2006 on how they will
perform this evaluation. (Water Framework Directive 2000/60/EC.) To ensure the good
quality of lakes in Denmark there are several laws, which aids in the protection against
pollution of lakes and any surface waters. The Danish environmental Protection Act is the
foundation for environmental protection in Denmark. The main objective within the Act
follows the principle of Polluters Pays and Best Available Technology.
2
The aim of the project is to investigate which factors affect the lake water quality and to
assess the water quality in Guldager Mølledam. By looking into the physical properties, the
chemical properties and the biological properties of the lake we are able to assess the
environmental condition of the lake. This is performed by taking water samples from the inlet
stream, the outlet stream and the lake. Some sediment samples are taken from the lake bottom
in order to evaluate the situation in the sediment today, 11 years after the sediment removal.
The flow is measured at the inlet and outlet stream in order to calculate the retention time for
the lake. The analysis of the samples are performed in the laboratory at Aalborg University,
Esbjerg. The results can be compared with the data before the sediment removal.
The stream Guldager Møllebæk is assessed based on the Danish Stream Fauna Index (DSFI).
The DSFI is a standardized method for biological assessment of running waters in Denmark.
The species of the macroinvertabrates found in the stream are defined and based on them the
ecological quality for the stream can be assessed.
This report gives a short introduction to all parameters, which are to be taken into
consideration when assessing lakes, where after it focuses on the methods used in order to
evaluate the parameters. The final part of the report focuses on assessing the results achieved
and comparing them with the data before the restoration.
3
2 LAKES
Lakes are enclosed bodies of water (usually freshwater) totally surrounded by land and with
no direct access to the sea. They satisfy different human requirement such as drinking or
irrigation, navigation, recreation or fisheries (UNESCO/WHO/UNEP 1996). The main
sources from which lakes receive its water are; flow from streams and rivers, direct
precipitation from rainfall, groundwater, runoff from the watershed, and man made sources
from outside the catchment area. Water leaves lakes through groundwater or surface water
flow, evaporation, extraction by humans. Most lakes have an inlet, a drainage basin
(catchment area) and an outlet. The changes in the level of lakes, is controlled by the
difference between the sources of inflow and outflow, compared with the total volume of the
lake (Byrun, S. Et al 2009).
Lakes make up about 0.008% of the total distribution of water on the earth’s surface. They
are useful as a source of water, habitat for aquatic organisms, recreational activities etc. Most
lakes contain freshwater and are continuously supplied from a stream but if the supply of
freshwater is limited, minerals from the bottom of the lake can concentrate the water making
it salty. The Dead sea is an example of a salt lake (Byrun, S. Et al 2009, Sand-Jensen, K. Et al
2006). Lakes can also help protect water quality. Eroded sediments, debris and other
pollutants washed from watersheds are deposited in lakes by inflowing streams so that
outflowing streams often carry less of these pollutants. (Michaud, J.P. 1991)
2.1 Classification of Lakes
There are various ways by which lakes can be classified. These are; based on origin, based on
formation process, based on water source and type of outflow, and based on productivity.
2.1.1 Based on origin
Lakes can be classified in to two broad categories based on origin. These are natural and
artificial lakes. Although this classification is quite broad, the general idea is that some lakes
have been formed as a result of mans activities like the building of dams while others
(majority) are as a result of natural ongoing processes.
4
2.1.2 Based on Water source and type of outflow
Seepage lakes: these are natural lakes which get their water mainly from precipitation,
groundwater and limited runoff. They do not have stream outlets and lose their water mainly
by evaporation.
Groundwater drainage lakes: natural lakes fed mainly by groundwater, precipitation and
limited runoff. They have stream outlets.
Drainage lakes: lakes fed by streams, groundwater, precipitation and runoff and drained by a
stream.
Impoundment lakes: these are manmade lakes created by the building of damns around a
stream. They are also drained by a stream (WAL 2009)
2.1.3 Based on formation process
This classification includes tectonic lakes (formed as a result of movement of the earths
crust), volcanic lakes (formed as a result of volcanic eruptions), glacial lakes (formed as a
result of melting of glaciers) and artificial lakes (formed as a result of human activities).
(Softpedia 2009)
2.1.4 Based on productivity
Lakes can be classified on the basis of their richness in nutrients. Nutrient availability is
important for the quality of a lake as it can influence the state of productivity. Certain aquatic
organisms can be found in high nutrient lakes while other types can be found in low nutrient
lakes. The main nutrients of concern are phosphorus and nitrogen. Using this classification,
lakes can be categorised into four main groups;
Oligotrophic lakes: These are lakes with low primary productivity and low nutrient
concentrations. They are generally clear and tend to be saturated with oxygen throughout the
water column.
Eutrophic lakes: These are lakes with high concentration of nutrients and are associated with
high biomass production, usually with low transparency. If deep enough to thermally stratify,
the bottom waters are devoid of oxygen.
5
Mesotrophic lakes These are lakes which exhibit characteristics between the oligotrophic
and eutrophic lakes.
Hyper-eutrophic lakes: These are lakes with exceedingly high nutrient concentrations and
associated biomass production. Anoxia or complete loss of oxygen occurs in the hypolimnion
during summer stratification. (JPT 2009)
2.2 Lake restoration and factors affecting lake water pollution
2.2.1 Lake restoration
There are a number of methods employed in the restoration of lakes. These include;
Dredging
In this method the lake sediments are removed and dumped in artificial basins where the
particles are allowed to sink. It is then treated with aluminium sulphate or iron chloride to
reduce the phosphorus concentration. The resulting phosphorus-metal complex precipitates
and is removed by mechanical processes. The water can then be returned to the lake.
Sometimes, however, the water can be returned directly before treatment. This method is
suitable mainly in small shallow lakes and ponds due to economic reasons.
The removal of lake sediment, also called dredging, is an effective, but expensive, lake
management technique. It can result in control of both algae and macrophytes. It is frequently
recommended for deepening shallow lakes for biomass control, eliminating contaminated
layers of toxic substances, and controlling nutrient loading by removal of enriched sediment
layer. It has a significant long-term advantage over nutrient inactivation. The disadvantages
are high costs, requiring of dredging material and disposal sites of the sediment (Cooke et
al.,1993).
The Riplox method
In this method the amount of phosphorus that is released from the sediment into the water is
reduced by oxidising the sediment surface while at the same time causing the phosphate to
precipitate in metal complexes. By pumping calcium nitrate (Ca(NO3)2) and adding iron
chloride (FeCl3) into the sediment, both oxygen and iron concentrations are increased. The
oxygen produced, acts as a lid preventing the release of phosphorus from sediment into the
6
water while iron combines with the phosphorus forming phosphate precipitates. The pH is
stabilised by adding calcium hydroxide and, at suitable pH, denitrifying bacteria will convert
the nitrate in the Ca(NO3)2 into N2 which is released into the atmosphere (Cooke et al.,1993).
Biomanipulation
Biomanipulation is the deliberate alteration of an ecosystem by adding or removing species,
particularly predators. The basic idea of this method is to increase the grazing rate on algae in
eutrophicated lakes, thereby decreasing the likelihood of algae blooms. In order to achieve
this, the predation pressure on large zooplanktons (which feed on algae) is reduced by
removing fishes which prey on them. Apart from the zooplanktons feeding on the algae, the
process also allows for increased biomass of submerged macrophytes in the sediment surface.
The submerged macrophytes absorb large amounts of nutrient from the sediment making it
unavailable for phytoplankton and they oxidise the sediment surface, thereby reducing
sediment loading. The removal of the fish is also helpful as it means reduced excretion of
nutrients in the lake water. It is also a removal of large amounts of phosphorus bound to the
bodies of the fish. All of these processes, which help in the treatment of the eutrophicated
lake, are triggered by the removal of fishes (Cooke et al.,1993).
Reduction of the algal biomass will prevent algae bloom and allow for light penetration
which is favourable for good lake quality.
Wetlands construction
This method focuses on reducing the amount of nutrients and sediments flowing into the lake
from an inflowing stream or drainage pipes from farmlands. This is achieved by constructing
a wetland in connection to these output sources. By allowing such incoming water to spread
out on a larger area, such as a wetland, the water flow rate decreases giving time for
suspended particles (some of which are nutrient rich) in the stream to sink to the bottom. In
addition, wetlands are shallow and this allows for high growth rate of macrophytes which
incorporate large amount of nutrients in their tissue. Also the vegetation allows for growth of
denitrifying bacteria which transfer nitrogen from water into the atmosphere. Hence wetlands
remove nutrients by sedimentation, denitrification and direct uptake by plants. (Bronmark
and Hansson 2005)
7
2.2.2 Restoration related to problematical algal growth
As a rule, algae are not a health concern, however some “blue-green” algae can produce
endotoxins or exotoxins which can be harmful above certain concentrations. Algae
production occurs rapidly under suitable conditions and can cover streams, lakes and
reservois in large floating blooms. Three species of the blue-green algae, Anabaena flos-
aquae, Microcystis aeruginosa and Aphanizomenon flos-aquae produce exotoxins which have
resulted in illness or death in mammals, birds and fish that have ingested a sufficient dose.
The algal biomass is dependent on the concentration of limiting nutrients in the photic zone.
The primary cause of excess algae is high nutrient concentration from external sources which
should be controlled first. (Measured in cells/ml)
Phosphorous
Internal release of phosphorous may be the most significant source that could delay
improvement of water quality. Sediment phosphorous release can be controlled by the
popular technique of adding aluminum salts to the water column resulting in an aluminium
floc that settles to the sediment surface forming a barrier to further release (Cooke et
al.,1993).
Dilution
The technique of dilution involves the addition of low nutrient water to virtually wash lake
nutrient concentrations out of the lake. While effective, the use of such technique has limited
application due to the availability of large quantities of water with low nutrient level (Cooke
et al.,1993).
Land use modifications
Land-use modifications can be used to control nutrient loss from the watershed from urban
runoff. This method can be used in areas that are already undergoing development. The
hypolimnetic withdrawal of nutrient enriched waters can be achieved through pumping,
siphoning, or selective discharge (through building of dams) instead of low-nutrient surface
waters. This can enhance the phosphorous export, reduce surface phosphorous concentration,
and improve hypolimnetic oxygen content (Cooke et al.,1993).
8
Artificial circulation
Artificial circulation is used to prevent or eliminate thermal stratification through the mixing
column of rising air bubbles. Dissolved oxygen content will increase and reduce iron and
manganese. Furthermore it can cause light to limit algal growth in situations where nutrients
are uncontrollable and can control blue-green algae (Cooke et al.,1993).
Removal of algae
Grazing of algae by large zooplankton can be enhanced by eliminating planktivorous fish
through physical removal. This technique is cheap and effective, but usually for a limited
time (Cooke et al.,1993).
Copper sulphate
Copper sulphate treatment has been commonly used for lakes suffering from algal biomass
and taste and odor problems. The problems of this treatment is the short lasting effect – it can
be considered a detrimental aspect (Cooke et al.,1993).
2.2.3 Problems related to Macrophyte growth
Problems are often associated with eutrophication and increased inputs of sediment. The
reduction of in-lake nutrient concentrations does not affect macrophytes, as their nutrient
demands are largely supplied through root uptake from the sediment. Therefore, more direct
methods are used to deal with excessive biomass.
Macrophyte harvesting
The removal of macrophyte biomass through harvesting is often an effective, sometimes
cosmetic, treatment. Nutrients are physically removed, which in some lakes can be a
significant source of internal loading. It must be ensured though, that the removal of plants
must be performed thoroughly. A quick grow back sometimes results from cutting plant
stems, while grow back can be lowered by cutting the roots. Harvesting can have negative
effects, such as fish removal, sediment phosphorous release and dispersal of plant fragments
to uninfested areas of the lake (Cooke et al.,1993).
9
3 Guldager Mølledam and Guldager Møllebæk
Guldager Mølledam is a small, shallow artificial lake in the community of Esbjerg. The lake
is located around seven kilometres north of Esbjerg, in the close vicinity of the suburban area
Guldager. The inlet source to Guldager Mølledam originates from Guldager. Guldager
Møllebæk is the outlet from the lake and runs out into the North Sea at Ho Bay. Before 1987
the wastewater treatment plant discharged the cleaned wastewater directly into the inlet
channel to Guldager Møledam but in 1987 the discharge was directed to the wastewater
treatment plant Esbjerg Reningsanlæg Vest. Due to this the lake was highly polluted by the
wastewater especially by phosphorus and heavy metals. The phosphorus and heavy metals
settled into the sediment, creating a large storage. The lake was restored in 1998/1999 due to
fear of phosphorus leaking out into the water, thereby polluting the entire lake and Møllebæk.
(Ribe Amt., 1994.)
3.1 Mølledam and Møllebæk before the restauration
There were two inlet flows into Guldager Mølledam, the main inlet source was at the
northeast corner of the lake. The other inlet source was over a larger area and was somewhat
diffuse in the northwest corner of the lake. The wastewater from Guldager was discharged
into the main inlet source until 1987, when it was cut off. The inlet rate has been measured in
1998 to be 10 – 40 l/s at the main inlet source. The outlet source for Guldager Mølledam is
located at the southern end of the lake. The outlet flow measured in 1998 was 20 – 74 l/s.
(Ribe Amt., 1994.) The lakes hydrological and morphological data from 1986 is presented in
Table 1.
Table 1 The morphological and hydrological data for Guldager Mølledam 1987 (Ribe Amt.
1994)
Area (m2) 25,000
Volume (m3) 11,000
Largest depth (m) 0.75
Average depth (m) 0.44
Average inlet flow (l/s) 21.4
Average outlet flow (l/s) 38.6
Average hydrolic retention time (days) 3
10
The average hydrolic retention time was relatively short and therefore the water within the
lake was mixed very well. The water in the lake used to be clear even though the nutrient
load was high. This might be due to short hydrolic retention time since no algae blooming
could occur but also due to the fact that the lake was very shallow. During windy days the
Secchi depth might be reduced since bounded material can be resuspended and thereby
decrease the Secchi depth. (Ribe Amt., 1994)
The area specific runoff from the lake was 5.57 l/s/km2 when the average inlet flow of 21.4
l/s and the catchment area of 3.85 km2 were taken into consideration. The catchment area for
the inlet source to the lake had an area of 3.30 ha and the residual catchment area was 0.55
ha. The annual runoff from the inlet catchment area was 579 million litres, from the residual
catchment area 97 million litres, from groundwater 543 million litres and from the lake 1218
million litres. (Ribe Amt., 1994)
Nutrient and pollution into Guldager Mølledam
Until 1987 the cleaned wastewater from Guldager was directly discharged into the stream
leading to the lake. In 1987 the wastewater was diverted to Esbjerg Rensningsalæg Vest. As a
result of this the water quality in the inlet stream improved significantly, however the
phosphorus and heavy metals that originated from the wastewater was stored in the sediment
of Mølledam. The phosphorus in the sediment was released into the lakewater and thereby
continuously polluted the water quality. Since the wastewater from Guldager was cut off
there aren’t any known pollution sources, however even if the nutrient input from the
surrounding agricultural areas are a reality, they are of no significant importance compared to
the pollution stored in the sediment. (Ribe Amt., 1994)
In the tables below the data from the analysed samples taken in 1987 and 1990 are presented.
The data is average results from water samples taken from the lake, the inlet and the outlet
source. The last table presents the results from sediment samples taken from the lake. (Ribe
Amt., 1994)
11
Table 2 Data from inlet and outlet streams at Guldager Mølledam. (Modified Ribe Amt.,
1994)
Parameters Inlet Stream Outlet Stream
Total N (mg/l) 10.53 5.91
NH4 (mg/l) 0.11 0.24
NO2 + NO3 (mg/l) 8.92 4.87
Total P (mg/l) 0.12 0.25
Ortho P (mg/l) 0.09 0.19
pH 6.28 7.11
Q (l/s) 18.72 38.0
The data was collected during one year, taking samples every month. The results are shown
as averages, however it is significant to remember that many of the parameters are influenced
by temperature and season. The results are from samples taken in 1987. (Ribe Amt., 1994.)
Table 3 Results from water samples taken in Guldager Mølledam (Ribe Amt., 1994)
Parameters Mølledam
Total N (mg/l) 4.95
NH4-N (mg/l) 0.22
NO2 + NO3 (mg/l) 4.06
Total P (mg/l) 0.22
Ortho P (mg/l) 0.19
pH 7.24
Conductivity (mS/m) 29.38
Alkalinity 0.94
Silicates 7.49
Chlorophyll a 2.23
The data was collected during an eight month period, from April to November. The samples
were taken once a month. The results presented are averages based on the single data
acquired. Many of the parameters are influenced by temperature and season, which has to be
taken into consideration when evaluating the results. The samples were taken in 1987. (Ribe
Amt., 1994)
12
Table 4 Results from sediment samples, in g/kg dry stuff, taken in Guldager Mølledam (Ribe
Amt., 1994)
The samples were taken in 1989. The data represents the average between depths ranging
from 0 – 50 cm. The sampling points were all in Mølledam, the inlet represents the sample
taken close to the inlet source and the outlet represents the sample take close to the outlet
source. (Ribe Amt., 1994)
Table 5 Concentration of metals analysed in the sediment samples. (Modified Ribe Amt.,
1994)
The analyses were performed on the sediment samples representing 0 – 30 cm in depth. The
samples were taken in 1989.
3.2 Guldager Mølledam and Møllebæk today
After the restoration of the lake, the water quality of the lake improved significantly. The
depth of the lake increased since almost 22.000 tons of sediment was removed. Today the
surroundings and quality of the lake has changed significantly since the evaluation done in
1994. The catchment area of Guldager Mølledam is 389 ha of which the lake itself covers 2,5
ha. The surrounding area is mainly covered by agriculture and suburban area. There are a few
hectares of forests and lakes. In the close vicinity of the lake there are grasslands to the north
and east of the lake, on the southeast side there is vegetation of alder and some scirpus. On
the west side there are trees growing all the way down to the lake and also some scirpus.
Today the lake is mainly used for recreational purposes. (Ribe Amt., 2002.)
Parameters Inlet Middle Outlet
Easily absorbed P 0.11 0.08 0.01
Iron-P 0.84 2.38 3.74
Ca-P 0.09 0.18 0.33
Residual P 0.94 1.13 1.83
Total P 2.51 2.01 5.58
Total Fe 28.8 26.4 44.0
Parameters Amount
Cadmium (mg/kg dry stuff) 6.9
Mercury (mg/kg dry stuff) 0.227
Lead (mg/kg dry stuff) 60
Nickel (mg/kg dry stuff) 46
Dry stuff (%) 11.4
13
The following figure gives an overview of the lake location, the estimated catchment area due
to slope and road boundaries.
Figure 1 Location of Guldager Mølledam with catchment estimation.
According to the measurements done in 1999 the retention time had increased to 8,5 days.
The deepest point in the lake is 2,75 meters and the average depth is 1,14. The Secchi depth
was measured in February and was 1,93 metres. After the restoration the volume increased
significantly and was, in 1999, 30.000 m3. The amount of total phosphorus input was 0,034
mg/l and 0,074 mg/l for the outlet, and in the lake 0,086 mg/l. The amount of total
phosphorus is still higher in the outlet, which suggests that there is still phosphorus stored in
the sediment. The concentration of total nitrogen was 8,71 mg/l in the inlet and 7,56 mg/l in
the outlet, and in the lake water 7,1 mg/l. The amount of nitrogen in the lake is higher in
comparison with similar lakes in Denmark. The groundwater plays a significant role in the
nutrient input to the lake, and it has been calculated that there is a 5 mg N/l and 0,07 mg P/l
input into the lake from groundwater. The amount of Chlorophyll α was 15 – 150 µg/l
depending on the season. The iron concentration in Guldager Mølledam was 0,4 mg/l. (Ribe
Amt., 2002.)
The amount of total phosphorus in the sediment was measured in 1992 and the phosphorus
content was high, 0,5 – 7,3 g P/kg DS, the iron content was low during that time, only 10 –
60 g/kg DS. A survey of heavy metals in the sediment was done in 2000, which showed that
the cadmium content was still high even after the restoration. (Ribe Amt., 2002.)
14
3.3 Legislation
3.3.1 European legislation
On the 23rd
October in 2000, the European Union established the Water Framework Directive
(WFD) 2000/60/EC formally known as “Directive 2000/60/EC of the European Parliament
and of the Council of 23 October 2000 Establishing a framework for Community action in the
field of water policy”. The Directive entered into force on the 22nd
of December 2000. The
aim of the WFD is to provide Member States with a framework for water protection and
management in order to prevent and reduce pollution of inland surface waters, groundwater,
transitional waters as well as coastal waters. The WFD also gives guidelines to promote
sustainable water use, protect the aquatic environment, to improve the status of aquatic
ecosystems and to lessen the effects from floods and droughts. (Water Framework Directive
Information Center; European Communities, Water Framework Directive.)
All Member States shall have achieved a good status for all surface waters and groundwater
shall have a good status in both quantity and chemical quality within 15 years after the
enforcement of the WFD. The status qualification focuses on the impacts from human
activities where a water body with a good status has few impacts from human activities. All
Member States shall have established an integrated monitoring programme by December
2006. The monitoring programme shall contain physical, chemical and biological data. The
monitoring programme is essential for assessing the status of surface and groundwater
bodies. (Article 8, Water Framework Directive.)
Annex V in the WFD provides guidelines on how to design the programme, what are the
parameters that are to be monitored and how the results are to be presented. For classifying
the ecological status for rivers and lakes several parameters within the biological,
hydromorphological, morphological as well as chemical and physico-chemical elements has
to be evaluated. A complete list of these parameters is presented in Appendix 1 (Annex V,
Water Framework Directive).
The waters are classified based on these parameters as waters with a high, good or moderate
ecological status. Waters that do not meet the requirements for moderate status are classified
as poor or bad.
Until 2015 there are, however, still some other Directives in force regarding water protection.
The Council Directive on the quality of water intended for human consumption (98/83/EC),
15
defines the quality standards for drinking water. In Directive 76/160/EEC, Council Directive
of 8 December 1975 concerning the quality of bathing water, the European Union sets
requirements on the quality of bathing water. The Directive was repealed by Directive
2006/7/EC. The Council Directive 91/27/EEC gives guidelines in reducing water pollution
from urban waste water. The Directive on the quality of fresh waters needing protection or
improvement in order to support fish life (2006/44/EC) is constructed for the protection of
fresh waters where certain fish species lives. Directive 2006/113/EC states the quality
requirements for shellfish waters.
3.3.2 Danish legislation
The Danish Environmental Protection Act, which entered into force in 1974, is the
foundation for environmental protection in Denmark. The Act has been amended several
times during the years. The early focus of the Act was on pollution prevention for
groundwater and surface water. Today the focus is on any pollution activity such as noise, air
pollution, vibrations etc. The main objective when administrating the Act is on the principle
Polluters Pays and Best Available Technology.
The main environmental law regulating the environmental protection is the Protection of
Nature Act. The law was established on January the 3rd
in 1992 and was consolidated in
August the 18th
in 2004. The aim of the Protection of Nature Act is to provide means on how
to conserve resources in nature and its fauna and flora as well as to protect natural and
cultural monuments. The Act is divided into 14 chapters and chapter 2 focuses on the
protection of i.e. lakes and watercourses. §16 set a minimum distance, 150 meters to the
watercourse that shall be left untouched. Within these protection zones no buildings can be
set up nor can the environment be altered. These regulations are, however, only for lakes with
a size over 100 m2.
The Planning Act is of significant importance considering protection of lakes. The protection
of watercourses is to be taken into consideration in the land use plan which each county are
obliged to make. In 1998 the Action Plan for the Aquatic Environment II came into force.
This was a result of the EU Nitrates Directive, and its objective is to reduce discharged of
nitrates into the aquatic environment. The Environmental Objectives Act is the national
implementation of the Water Framework Directive into Danish legislation. The Act came into
force in 2003.
16
Natura 2000 is an European network of protected sites. These sites have the highest value of
natural habitats and species and animals which are rare, endangered or vulnerable. Natura
2000 applies to birds sites, habitat sites and marine environment. Areas within the Natura
2000 network are more stringly protected. In 2006, Denmark had 254 sites of Community
Importance, 113 sites of Special Protection Areas and 27 Ramsar Sites. All of these are
included in the Natura 2000 network. (Miljøministeriet, Danish Natura 2000).
17
4 FACTORS AFFECTING LAKES AND THEIR INTERACTIONS
There are a number of physical, chemical and biological factors which affect lakes and their
entire aquatic ecosystem. These factors and their interactions are referred to as the abiotic and
biotic frame. Variations and temporal fluctuations in this frame within lakes play major role
in determining the variety of habitats and organisms contained in them. Examples of these
factors are sediment conditions, nutrient concentrations, light availability, pH, temperature,
oxygen content, photosynthesis etc. Some of these factors and their interactions are discussed
below.
4.1 Light, Primary production and Respiration
Light is a major factor that influences lake condition. Energy from sunlight provides the
major energy input into lakes. This is transformed into potential energy by biochemical
processes such as photosynthesis and to heat by absorption by particles, dissolved substances
and by water itself. Light intensity at the lake surface varies seasonally with cloud cover and
decreases with depth down the water column. The rate at which light decreases with depth
depends upon the amount of light-absorbing dissolved substances and the amount of
absorption and scattering caused by suspended substances in the water.
Light is necessary for photosynthesis i.e. the process by which green plants convert carbon
dioxide and water into sugar and oxygen. It supplies the energy used by organisms like
algae (phytoplankton), algae attached to surfaces (periphyton), and vascular aquatic plants
(macrophytes) in this conversion process. The more the amount of light the more
photosynthesis can occur and thus the deeper into the water column light can penetrate the
lower the depth at which photosynthesis can occur (Bronmark and Hansson 2006).
6CO2 + 6H2O + Light C6H12O6 + 6O2
Photosynthesis is vital process in lakes as it is a source of dissolved oxygen. Based on this
relationship between light, photosynthesis and respiration, lakes can be divided into three
zones. That portion of the water column supplied with enough light so that photosynthesis
(primary production) exceeds respiration (P > R) is the Photic zone. Solar radiation reaching
this zone is high hence leading to high a rate of photosynthesis in this zone. The underlying
18
water is part of the Aphotic zone which receives very little or no solar radiation and as such
primary production in this zone is less than respiration (P < R). The Compensation zone is
the transition between the Photic and Aphotic zones. This zone marks the Compensation
depth which is the depth at which only 1% of the surface light remains. It is the maximum
depth, where photosynthesis process can occur and thus here primary production equals
respiration (P = R) (Dodds, 2002).
4.2 Dissolved Oxygen (DO)
Dissolved oxygen (DO) is a measure of the amount of gaseous oxygen O2, dissolved in lakes
and ponds at a particular pressure and temperature. It is essential particularly for respiration
of aquatic life and is utilised in other activities such as in the decomposition of organic matter
(Bronmark & Hansson, 2005). Changes in the amount available in the lake could have
significant impact on the behavior and existence of organisms which could lead to death in
extreme deficiency.
When dissolved oxygen is sufficiently present in a water body, organic materials and wastes
are degraded effectively. Under such conditions, nutrients such as, phosphorus is converted to
phosphate (PO4) and nitrogen forms ammonia and nitrates. On the other hand, when the DO
is limited or insufficient to support microbial activity, methane is released from carbon,
odorous amines result from nitrogen and the foul-smelling H2S gas from sulphur.
Oxygen in the aquatic environment mainly comes from the atmosphere by direct diffusion
and photosynthesis by aquatic plant and algae. Oxygen uptake from the atmosphere depends
on factors such as temperature, pressure, salinity and area of exchange surface.
Temperature: Cold water can hold more dissolved oxygen while warm water gets
saturated easily with oxygen. So cool temperature enhances oxygen uptake.
Salinity: This is the amount of salts in the lake. The amount of dissolved oxygen
decreases as salinity increases.
Pressure: The amount of dissolved oxygen increases with increasing water pressure.
Wind: more oxygen dissolves into water when wind stirs the water, as the waves
create more surface area, more diffusion can occur.
19
Figure 2 Solubility of oxygen in water. (JPT, 2009)
The amount of dissolved oxygen in lakes is strongly affected by the rates of photosynthesis
and respiration. Oxygen is produced during photosynthesis and consumed during respiration
and decomposition of dead organic matter. Photosynthesis occurs only in daytime as the
process requires light where as respiration occurs all day. Thus amount of dissolved oxygen
varies at different times of the day. The organic matter content can also affect the level of
dissolved oxygen. Polluted lakes generally have low DO while clean lakes have relatively
high amounts of DO. In essence factors like light (e.g day and night), temperature changes
(seasons, night and day), plant and animal population can lead to significant increase or
reduction depending on the direction of change (Bronmark & Hansson, 2005, JPT 2009).
4.3 Temperature, density and seasonal changes
Processes in lakes are strongly determined by the temperature profile, which in turn depends
on climate (solar radiation), wind, and also on the lake depth. Thus, lakes undergo seasonal
changes with regard to their temperature-density profiles which directly influence various
characteristics of the lake.
The temperature-density relationship for water reflects upon the premise that as water
increases in temperature, it becomes less dense and as its temperature decreases, it becomes
more dense. The exception to this rules however, is that water reaches its maximum density
at approximately 40C. As water cools below 4°C, the number of water molecules joined by
0
2
4
6
8
10
12
14
16
0 5 10 15 20 25 30
Solubility of Oxygen in water
Ox
yg
en(m
g/L
)
Temperature (˚C)
20
hydrogen bonds to form loose clusters, increases. Thus below 40C, water actually becomes
less dense as it cools because of the formation of these structured aggregates.
4.4 Thermal stratification in lakes
Lakes undergo seasonal changes with regard to their temperature-density profiles and these
changes in temperature profile with depth can result in thermal stratification. This is a
phenomenon whereby lakes show a clear physical separation of the water masses of different
densities, usually into three defined strata’s namely: (i) the epilimnion or surface waters of
constant temperature (usually warm mixed throughout by wind and wave circulation, (ii) the
hypolimnion or deeper high density water (this is usually much colder except in tropical
lakes), (iii) a fairly sharp graduation zone between the two which is defined as the
metalimnion.
Figure 3 Various strata’s in a stratified lake (JPT, 2009)
This profile however changes from one season to the next in temperate regions and creates a
cyclic pattern that is repeated from year to year expressing seasonal circulation of water.
With the beginning of spring as shown in figure 3, the ice melts on a lake and the lake water
is generally of the same temperature from the surface to the bottom. Wind allows circulation
and mixing of the lake water and as such surface water can be pushed to the lake bottom and
bottom water can rise to the surface. This is called Spring overturn. This circulation pattern
is very important in that it allows relatively large amounts of oxygen to reach the bottom of
the lake.
21
As spring proceeds into summer, water temperatures will increase with the intensity of solar
radiation. The amount of solar radiation absorbed decreases with depth, thus the lake heats
from the surface down.
Figure 4 Seasonal temperature cycles in stratified lakes (Encyclopaedia Britannica, 1996)
The warm water is less dense than the cold water below resulting in a layer of warm water
that floats over the cold water. Thus Summer stratification occurs with a layer of warm
water at the surface of the lake (epilimnion) and the cold layer (hypolimnion) below the
epilimnion, both separated by a layer of water (metalimnion) which rapidly changes
temperature with depth. During the summer, there is limited supply of oxygen at the lake
bottom (hypolimnium). This is because there is no mixing to provide oxygen and inadequate
light for photosynthesis due to the stratification. The available oxygen is thus depleted during
respiration. Oxygen is further used up by aerobic bacteria for the decomposition of algae
which die during this time. This is known as summer stagnation. Anaerobic bacteria will then
begin to decompose the dead algae which gradually accumulate at the bottom of the lake. The
anaerobic bacteria produce H2S, thereby emitting a “rotten egg” smell. Some of the sulphur in
the H2S may combine with iron to form pyrite (FeS2) known as “fools gold”.
As autumn approaches temperatures decreases and the epilimnion begins to decrease in
depth. Eventually the epilimnion gets so shallow and the lake loses its stratification. Thus as
22
in the spring, the lake water in the autumn has generally uniform temperatures and wind can
once again thoroughly mix the lake water. This is known as the Autumn or Fall overturn.
In addition, surface water, which is in direct contact with the cold air, gets cooled faster than
the water below. This cold, dense water sinks and further helps to mix the lake, and once
more oxygen and nutrients are replenished throughout the lake.
The surface water is eventually cooled below 4° C as winter approaches. At this point, the
water no longer sinks. The water temperature at the surface reaches 0°C and ice begins to
cover the surface of the lake. During the winter, ice cover prevents wind from mixing the
lake water. Thus Winter inverse stratification occurs with a layer of low density water
colder than 40C, but warmer than 0
0C forms just under the ice. Below this water, the
remainder of the lake water is usually near 40C. As spring approaches, the seasonal cycle
begins again (JPT, 2009; GVHU; Encyclopaedia Britannica, 1996).
4.5 Nutrient loading and primary production
Nutrient loading refers to the enrichment of a lake by nutrients (especially nitrogen and
phosphorus compounds, but also other organic matter). This increase in nutrients can occur
under natural or anthropogenic conditions which include nutrient inputs from sewage
discharges, increase usage of nutrient based fertilizers on farm land, changes in land use
causing erosion and weathering.
The increase in the concentration of nutrients in lakes can trigger a chain of events starting
with massive increase in primary producers since they are generally growth-limited by
nutrients especially phosphorus in freshwater ecosystem. Thus there is a planktonic algae
proliferation in the photic (surface layer) zone of lakes which is the productive layer. This
proliferation of algae in the photic zone can prevent the penetration of sunlight into the lake
which can in turn disrupt the production of oxygen. This whole situation leads to an
imbalance in the nutrient and material cycling process in the lake. Consequences derived
from the eutrophication process often affect most of the vital uses of the water. These
consequences in some cases are appearance of abnormal colours, bad smells, depletion in fish
diversity and changes in the composition of the populations of organisms (reduced
biodiversity). Lakes can be classified based on nutrient loading into oligotrophic lakes,
mesotrophic lakes, eutrophic and hyper-eutrophic lakes.
23
4.6 Limiting factor for lakes
These are factors which determine the level of production in water bodies i.e the nutrient
whose absence reduces or stops production. In lakes, the limiting factor is usually phosphorus
while in seas nitrogen becomes the limiting factor. This situation changes when the limiting
factor is in abundant supply e.g if the concentration of phosphorus is very high in lakes,
nitrogen becomes the limiting factor.
In lakes, the rule of thumb for limiting factors is given below;
Rule 1
P is most often limiting when [NTotal] / [PTotal] > 12-15. Here there is abundance of
nitrogen and less phosphorus.
N is most often limiting when [NTotal] / [PTotal] < 9-10. Here the concentration of
phosphorus is not very high.
Rule 2
P is limiting when [PTotal] < 0.05 mg/l
N is limiting when [PTotal] > 0.1 mg/l
“In lakes with P- limitation, ortho-phosphate concentration under production maximum will
be approximately zero”. This is because ortho-phosphate is usually the form that is used for
productions. Therefore, it would be used up at maximum production (Jens Peter 2009).
24
5 PARAMETERS FOR LAKE QUALITY ASSESSMENT
This chapter introduces the parameters which are to be taken into consideration when
assessing lakes. The subchapters will give a short description on what the parameters present
and why they are vital for lake water quality assessments. The first subchapter regards the
physical parameters, the second the chemical parameters and the third presents the biological
parameters.
5.1 Physical properties
5.1.1 Temperature
The temperature of water is considered as one of the main factors for the ecosystem which
can affect behaviour, metabolic rates and distribution patterns of organisms. Seasonal and
vertical changes of water temperature are the main determinant for behaviour of organisms,
as most of them adapt their body temperature to changes in water temperature (Cooke et
al.,1993).The main source of heat for lakes is solar radiation, which results mostly in seasonal
but also daily changes of temperature. The so called thermal stratification of lakes is a result
of solar radiation heating up the upper layer of a lake, whereas the lower layer does not
experience light, due to absorption of most light during the first meters. High density, low
temperature water settles, while water with higher temperature and lower density will remain
on the surface. These two layers occur during summer and winter months. During the autumn
and spring, the water temperature distribution is relatively equal, and the lake can be assumed
to be well mixed if no thermal difference is detected. Temperature should be determined at 1
m intervals with depth, but usually one profile at the deepest point is adequate if the water
body is small (Cooke et al.,1993).
The following graph presents one example of temperature and oxygen changes in a deep lake
(not Mølledam). With increasing water depth, the level of dissolved oxygen gradually
decreases, simultaneously to the temperature (Cooke et al.,1993).
25
Figure 5 Distribution of temperature and dissolved oxygen during summer thermal
stratification of an eutrophic lake (Cooke, et al., 1993).
5.1.2 pH
pH is defined as the negative logarithm of hydrogen ions concentration. It is an indication of
the acidity, alkalinity or neutral state of a substance. The pH scale ranges from 0 to 14.
Acidity decreases from 7 to 0, a neutral substance has a pH of 7 whereas alkalinity increases
from 7 to 14. pH is an important parameter for chemical and biological processes. For
instance pH determines the solubility of heavy metals in lakes and heavy metals can be quite
toxic to aquatic life especially when very soluble in water. Metals tend to be more soluble at
low pH. pH can also affect the form in which phosphorus is most abundant as well as
determine whether aquatic life can use it. It is thus a good indicator of water quality.
The pH values of lakes and ponds show regional differences and this can be due to variables
such as geological structure of catchment area, input of chemical substances from inlet, acid
rain and anthropogenic carbon dioxide. However, most lakes and ponds on earth have a pH
range of 6.0 to 9.0 (Bronmark & Hansson, 2005). This range is favourable for the life of
aquatic organisms and deviation can significantly affect aquatic life and may even lead to
0
5
10
15
20
25
0 5 10 15 20 25 30
Dep
th (
m)
Water temp°(C)
Temperature and Dissolved Oxygen (DO) in
eutrophicated stratified lakes.
DO (mg)
Temp (°C)
26
death. High pH changes in particular areas can be due to the presence of acidic or alkalinic
chemicals etc. (Michaud J 1991, Bronmark & Hansson, 2005).
5.1.3 Turbidity and transparency
The turbidity of lakes and water in general is affected by particles in water. Such water with
high turbidity is cloudy, i.e. has a high concentration of particles shielding the penetration of
light into the water. For lakes, this has a negative effect on plant and fish life, as life is mostly
depending on the availability of light. Water with low turbidity, such as clear mountain lakes,
is considered to be favored by human. Water containing high turbidity, such as the yellow
river in China, has a high density of solid particles. This should not be confused with
pollution, as sand particles, for example, are not pollutants in water. Suspended sediments
often come from sources such as resuspension from the lake bottom, construction sites,
agricultural fields, and urban storm runoff. Turbidity and transparency are indicators of the
impact of human activity on the land surrounding the lake. Transparency can be measured in
the field to indicate the level of biological activity; the estimation of such light penetration is
determined with the secchi disk. (Carlson, Simpson. 1996)
5.1.4 Secchi-depth
The determination of water transparency with a Secchi disk is one of the most reliable,
frequently used and meaningful indicators of lake quality. The Secchi depth is measured
insitu and immediately tells about the quality of the lake water. The depth of transparency is
the path length in Beer´s law equation trough which light is scattered and absorbed as a
function of particle concentration in the water. As the concentration increases, transparency
depth decreases exponentially. In essence, the light entering the water will be either absorbed
or scattered by particles, dissolved colored matter, and the water itself. However,
transparency can be intermitted through particles from algae and other suspended solids. The
higher the visible depth, the better state of lake can usually be expected. The secchi disk is a
white disk with a diameter of about 20 cm, which is lowered into the water of a lake until it
can be no longer seen by the observer. It can be expected, that light can penetrate about 1.7
times the secchi disk depth until it can no longer be seen. (Carlson, Simpson. 1996)
27
.
Figure 6 Secchi disk depth measurement
5.1.5 Conductivity
Conductivity is a measure of the ability of water to conduct an electrical current. The current
is conducted by moving ions which mainly come from dissociation of inorganic compunds.
Therefore conductivity measurements show the concentration of dissolved salts/solids in
water and other ions (Centre for Educational Technology 2004). Other factors that determine
conductivity are temperature, oxidation state and mobility of the ions. Organic compounds
and colloidal silica do not conduct electric current. The unit of conductivity is microsiemens
per centimeter (μS/ cm). Conductivity in fresh water ranges from 10μS/ cm to 1000 μS/ cm,
but may by higher in polluted water bodies, especially those polluted by sewage or fertilizers
(UNESCO/WHO/UNEP 1996).
5.1.6 Total solids
This is the total amount of the dissolved and suspended solids in water. Dissolved solids
include ions like calcium, iron, bicarbonate, phosphorus etc. that are dissolved in the water
and cannot be separated by filtration. Some of these ions are essential for aquatic life as cells
also depend on the density of total solids to determine the amount of water that flows in and
out of the cell. Suspended solids consist of such substances as clay, silt and various particles
which are suspended in the water and not dissolved. Suspended solids can affect the turbidity
and light penetration in a lake and hence affect the rate of photosynthesis. Dissolved solids
are able to pass through filter with 2μm pores while suspended solids cannot.
Total Solids (TS) = Total dissolved solids (TDS) + Total suspended solids (TSS)
28
The level of total solids in a lake can serve as an indication of the state of health of the lake in
that the total solids will support life either positively or negatively depending on its quantity
and quality. In addition, by comparing the total solid values at the inlet and the outlet,
information about the stocking of sediments and particles in the lake can be obtained.
Particles are usually introduced into lakes through the inlet stream and while some of these
solids may flow out at the outlet stream some may remain in the lake and eventually settle at
the bottom. The difference between the total solid at the inlet and the outlet can be used to
estimate how much particles are deposited in the lake. According to (APHA et al 1992) the
Total dissolved solids (TDS) can be calculated theoretically by multiplying the conductivity
of the lake by a factor (ranging between 0.55-0.9, depending on the water body). The total
suspended solids (TSS) can then be derived by subtracting the product from the amount of
total solids in the lake.
The total solid (also referred to as total residue) of a water sample can be determined by
evaporation and drying of that water sample and is measured in mg/L.
5.1.7 Alkalinity
The capacity of water to neutralize acid is known as alkalinity. It is the buffering capacity of
the water body (Bronmark and Hasson 2005). It is the sum of all the bases that can be titrated.
Alkalinity in water is due to the presence of different compounds. In many surface waters,
alkalinity is mainly a function of carbonate (CO3−2
), bicarbonate (HCO3−) and hydroxide
(OH−) content and it gives an indication of the concentration of these components. However,
if borates, silicates, phosphates, or other bases are present, the measured value may include
contributions from them. Forms of inorganic carbon at different pH levels are shown in
Figure 7.
29
Figure 7 Forms of inorganic carbon at different pH levels (COTF).
Another source of alkalinity is chemical composition of the soil. Water bodies are more
alkaline when the surrounding soil contains calcium carbonate (CaCO3, Limestone), while
granite or quartz bedrock leads to lower alkalinity (Addy et al., 2004).
Alkalinity is important in lake water because it protects fish and other aquatic life against
sudden pH changes. Living organisms, especially aquatic organisms function best in a pH
range of 6-9. Water with higher alkalinity is more resistant to pH changes as it has higher
buffering capacity for acid input, (acid rain, acidic wastes). Water with pH lower than 4.6
does not have the ability to neutralize strong acids as they are acidic and do not contain
HCO3− and CO3
−2. In well buffered lakes, daily fluctuations of CO2 concentration cause only
small changes in pH value (Addy et al., 2004). For protection of aquatic life, alkalinity should
not be lower than 20mg/l of CaCO3 (Greenberg et al., 1992).
Table 6 Classification of lakes and ponds based on alkalinity (URI, 2009).
30
5.2 Chemical properties
5.2.1 Dissolved Oxygen
The concentration of dissolved oxygen is a good indicator of the quality of water in the lake
and its ability to support aquatic life. Dissolved oxygen (DO) is a measure of the amount of
gaseous oxygen O2, dissolved in lakes and ponds at a particular pressure and temperature. It is
essential particularly for respiration of aquatic life and is utilised in other activities such as in
the decomposition of organic matter (Bronmark & Hansson, 2005). Changes in the amount
available in the lake could have significant impact on the behaviour and existence of
organisms which could lead to death in extreme deficiency. DO can be measured using a
probe meter or by nitration method in the laboratory. It is measured in mg/L.
5.2.2 Organic matter
Organic matter content in a lake can be used as an indication of the level of pollution in a
lake. High organic content may be an indication of water pollution. The sources of organic
matter in a lake can be natural or anthropogenic. The primary source of organic matter to
lake sediments is the plants in and around the lake (Meyers and Teranes 2002). Natural
substances include: humic acids, proteins, carbohydrates, starch, chlorophyll and other
compounds synthesized by aquatic organisms. Other organic substances may be introduced
into lakes as a result of anthropogenic activities like agriculture, wastewater effluents, acid
rain etc.
Organic matter within sediment samples can be quantified by burning a known amount of the
sediment at 550°C for one hour and then recording the decrease in weight.
5.2.3 Nutrients
The main nutrients of concern in lakes and stream are nitrogen and phosphorus. They are
indicators of water quality as excessive amounts usually result in eutrophication and algae
blooms. The main source of these nutrients for water bodies includes leaching fertilizers,
pesticides, animal manure from agricultural land, untreated waste water from industries,
municipal and sewer.
31
Total phosphorus
Phosphorus is one of the key nutrients required by all organisms for existence. Phosphorus is
essential for all organisms as it is needed for synthesis of enzymes, organic material (DNA,
RNA) and highly energetic molecules of adenosine triophosphate (ATP). Its presence and
that of other elements provide adequate environments for productions in lakes and other
water bodies. It occurs in water bodies both in organic and inorganic forms. The aggregation
of all phosphorus present in water is what is referred to as total phosphorus. It exists in
organic forms as part of the organism and in inorganic form as metaphosphates,
polyphosphates and orthophosphates (PO43-
) which is the form that is essential for organisms
(Bronmark & Hansson, 2005).
Phosphorus compounds enter the surface waters by weathering of rocks, decomposition of
organic matter, run-offs from agriculture, municipal and industrial wastewater. Under aerobic
conditions phosphates form insoluble compounds with iron Fe3+
and aluminium Al3+
ions
under acidic conditions and with calcium Ca2+
ions under alkaline conditions, and
precipitates. It then accumulates at bottom sediments where it is not available for
phytoplankton. However leaching of phosphorus from sediment is possible depending on pH
and dissolved oxygen (Loon and Duffy 2000) (Shaw et al, 2004).
Overloading of lakes with phosphorus leads to high productivity and this results to high level
of eutrophication. This eutrophication prevents the penetration of sunlight to deeper parts of
the lake resulting in low activity. When the plants die, their decomposition by aerobic
microorganisms leads to a high oxygen demand creating a low concentration of dissolved
oxygen in the bottom region of the lake.
Total phosphorus can thus be used to assess the quality of a lake and this is tied to nutrient
load and production. A high production corresponds to high nutrient load which in turn
relates to a high phosphorus concentration (Shaw et al, 2004).
Total nitrogen
This is the sum of the nitrogen present, in all the forms (organic and inorganic), in the lake or
stream. Naturally, nitrogen finds it way in lakes through precipitation, nitrogen fixation and
from surface and ground water drainage (Bronmark & Hansson, 2005). Anthropogenic
sources are mainly fertilizers from agricultural activities which leach during rainfall and other
32
activities into the lakes (Alma & Etheridge, 1993). It also occurs in organic forms during the
decay of plant and animal proteins from water organisms and waste water.
Like phosphorus, nitrogen is an essential nutrient for the growth and development of aquatic
organisms especially plants (as core element in DNA formation). Thus, high load leads to
high level of production in the lake like algae blooms. It is important to note that the effect of
nitrogen load depends on the concentration of phosphorus (limiting factor) i.e high nitrogen
load might not necessarily lead to eutrophication in the absence of phosphorus (Bronmark &
Hansson, 2005). However, this situation reverses in many polluted lakes where nitrogen
becomes the limiting factor.
Nitrogen content can be measured as total nitrogen or in the various forms in which it exists
in water. These forms are listed below;
Nitrates (NO3-) - This is the dominant form of nitrogen in water at normal concentration of
dissolved oxygen (Environment Canada, 2005) and it is the form of nitrogen that is readily
taken up by plants. Determination of its concentration gives an indication of the nutrient level
in the lake. Typical NO3- values range from between less than 1mg/L for unpollutet waters to
5mg/L for waters influenced by human activities. Natural concentrations of NO3- seldom
exceed 0.1mg/L. Extreme pollutions may lead to levels up to 200mg/L.
(UNESCO/WHO/UNEP 1996).
Nitrites (NO2-) - This the product of a nitrification process which is eventually converted to
nitrates for plant uptake.
Ammonia (NH3) – Ammonia in lakes is a product of the decomposition of organic materials
by heterotrophic bacteria especially in the low oxygen zones. It exists primarily in water as
ammonium ion (NH4+) and also as undissociated ammonium hydroxide (NH4OH) which is
toxic to aquatic life. The concentration of ammonia is an indication of the level of toxicity of
the lake.
5.2.4 Iron
One of the main chemical process affecting the flux of phosphorus at the sediment-water
interface is the complex binding of phosphate with iron in the presence of oxygen and the
released of phosphorus during anoxic conditions. (Bostrom et al. 1982). A chemical process
where electrons are lost is called oxidation and the opposite process where electrons are
33
gained, is called reduction. A reduction is always coupled with an oxidation and are together
called a reduction-oxidation reaction, or a redox reaction. A high redox potential is related to
well oxygenated environments (Bronmark and Hasson 2005).
At low oxygen concentration (low redox potential), iron occurs as Fe2+
which is soluble in
water. If the oxygen concentration increases (the redox potential increases), the chemical
equilibrium of the redox reaction is forced to the right and iron is oxidised to Fe3+
Fe2+
⇌ Fe3+
+ e−
Fe3+
which is not soluble in water but forms complexes with other molecules, precipitates and
sinks to the bottom of the lake. Phosphate, which is the main actor in the eutrophication
process, has a high affinity for forming such precipitates. This makes phosphate less
bioavailable for phytoplankton. However, as the oxygen concentration declines, iron will
transform to its reduced, soluble form (Fe2+
) and release its phosphate, again making it
available for phytoplankton growth in a process called internal loading (Burns and Ross
1971).
5.2.5 Biochemical Oxygen Demand (BOD5)
The BOD5 is one of the most common determinations of water quality in regards of bacterial
activity and organic material available for bacteria digestion. Bacteria consume oxygen
during digestion of the organic material available, which can be measured in respect of their
activity. The BOD5 determines the amount of oxygen consumed by the mater matrix after 5
days at 20°C storage. The higher the value, the more biological available the water sample.
Typical values of BOD are given in mg/L and range between 1mg/L for drinking water, 200-
300mg/L in domestic waste water to several thousand mg/L in pure manure from cattle.
(Bank, 1994)
The value is determined every 24 hours after the test is started and should increase with time.
For example, the BOD of 500mg/L indicates that a sample of one litre water consumed
500mg of pure oxygen within 5 days at 20°C.
34
5.3 Biological properties
5.3.1 Aquatic macrophytes
Aquatic macrophytes are plants, growing in water or in wet areas which are visible to the eye.
Examples are mosses, macroalgae, ferns angiosperms etc. They are of great benefit as they
serve as a source of oxygen and food for the macroinvertebrates (US EPA, 2008a). They
occur in three main different forms:
Emergent Macrophytes (when the plants are rooted in the sediments and protrude up
above the surface of the water),
Submergent Macrophytes (when they grow completely below the surface),
Floating and Free floating Macrophytes (floating when the plants are rooted to the
bottom with leaves floating on the surface of the water or free-floating when they are
not rooted to the bottom but their leaves are still floating on the surface).
Macrophytes are excellent indicators of water quality because of
their noticeable response to toxic chemicals, metals and conditions like nutrient
loading and turbidity
the ease in sampling using aerial photography or transects
Overabundance of macrophytes may interfere with lake processing and recreational activities.
(US Environmental Protection Agency, 2008a; Kesab Website).
35
Figure 8 Macrophytes in a lake
5.3.2 Phytoplankton
Phytoplankton are small microscopic plants which float in the water body. They are the
autotrophic part of plankton and thus are primary producers (photosynthetic) in the aquatic
food chain fixing large amount of carbon and producing oxygen. Phytoplankton are very
small (microscopic) but when appearing in big numbers they can be seen as green coloration
in the water due to the presence of chlorophyl within their cells. The size of phytoplankton is
about 0.002 mm to 1 mm. They include diatoms, dinoflagellates, cyanobacteria and ciliata.
They depend on light since they are photosynthetic and so they have to live in the surface
layer (photic zone) of the water body.
Figure 9 Phytoplankton
The growth or decline in the population of certain species of phytoplankton can be an
indication of water quality as their population can correspond to the enrichment or reduction
of certain minerals like phosphates and nitrates. For example a high population of the
chlamydomonas sp (algae bloom) in a lake or stream is an indication of a eutrophication
36
while a low population may indicate low contamination. Regular monitoring of Diatoms
enforces environmental legislation in some countries of Europe. Diatoms contain silica on
their body and presence of Diatoms relates the Silicate in the lake water. Trophic Diatom
Index for Lakes (TDIL) can be used to assess the ecological lakes (Csilla et al., 2007).
5.3.3 Zooplankton
These are tiny animals classified as flagellates and protozoans which are able to float, drift or
partially swim in water bodies. They are dependent on water current to move any distance.
Most of them are too small to be seen with the naked eyes. There are two kind of
zooplankton: holoplanktonic organisms which spend their complete life cycle as a part of
plankton, and meroplanktonic organisms which spend a larval or reproductive stage in the
plankton. Zooplanktons are mainly heterotrophic, feeding on the phytoplankton population.
They also serve as food for consumers on higher trophic level (Michaud 1991, ETE 2004).
Their increase is an indication of high nutrient activity which could be due to human
activities like agriculture.
Figure 10 Some species of Zooplankton (Wikipedia, 2009)
5.3.4 Chlorophyll α
Chlorophyll a is the green pigment that allows plants to convert sunlight into organic
compounds through the process of photosynthesis. It is the most common of the five
37
photosynthetic pigments present in every plant that performs photosynthesis and is a useful
parameter for determining the biological productivity of a water body. An excessive amount
of chlorophyll a is a sign of excessive nutrient load, which subsequently reduces the amount
of dissolved oxygen. This can eventually result in eutrophication. This unusually high
concentration of chlorophyll a is more often than not attributed to anthropogenic sources.
Chlorophyll is a measure of all green pigments whether they are active (alive) or inactive
(dead) and is a measure of the portion of the pigment that is still active i.e, the portion that
was still actively respiring and photosynthesizing at the time of sampling”. It is measured in
μg/L. The chlorophyll-a concentration is associated with high algae population. Therefore, it
also has influence on dissolved oxygen, nutrients, pH changes in the lake. High algae
concentration may also cause aesthetic problems. The algae of concern in this case are a
group called the “blue-greens” – named after their particular pigment colour.
Figure 11 Structure of Blue green algae (Left) (Michaud 1991) and
Algae bloom (Right) (Nature Report,2008)
5.3.5 Macroinvertebrates
Macro-invertebrates are the animals without backbone (invertebrates) and are visible to the
eyes. These include insects like the stoneflies (plecoptera), mayflies (ephemeroptera),
crustaceans like the crayfish (parastocoidea), molluscs like snails and clamps, worms
(annelids) etc all of which live in a river channel, pond, lake, wetland or ocean. These aquatic
organisms particularly those live in bottom part of the lakes (benthic macroinvertebrates) are
38
usefull as water quality indicators. This is because they are sensitive to pollution, and also
since they have limited mobility they mainly stay in areas that will encourage their survival.
Their presence in waters can thus be an indication of the present state of stream or lake. They
are also easy to collect and identify. The orders Ephemeroptera, Plecoptera, and Trichoptera
are very important and sensitive to pollution and thus they are used as unpolluted water
quality indicators (ETE 2004).
5.4 Danish Stream Fauna Index (DSFI)
The Danish Stream Fauna Index (DSFI) is a standardised method for biological assessment
(biomonitoring) of running waters in Denmark. The DSFI has been developed primarily to
detect the impact of organic pollution using microinvertebrate taxa. It was introduced in
1998 and is currently used yearly at 1051 stations in the National Monitoring Programme for
the Aquatic Environment NOVA. It is also widely used by regional water authorities.
In the DSFI the ecological quality in running waters is described by index values ranging
from 1 to 7, with the highest number representing the best ecological quality. The table
showing the values and taxas of the DSFI can be found in the appendix. (DSFI 2009)
39
6 SAMPLING AND ANALYSIS OF SAMPLES
The samples were taken together with the other MET groups. The workload was shared
between both groups and the aim was to have one group member from each group
performing the different sampling. The samples were not taken according to any standards
nor were the samplers accredited samplers. This has to be taken into consideration when
evaluating the sampling methods used and when evaluating the analysis results.
The macro invertebrate samples were taken on the 7th
October 2009. Water and sediment
samples were taken on the 16th
October. In this chapter the sampling method, the sampling
locations and method of analysis are presented. The parameters that were measured are
reported under the subchapters: in-situ measurements, water sample measurements, sediment
sample measurements and biological measurements.
6.1 In-situ measurements
The parameters that were measured in-situ are; dissolved oxygen, temperature, pH,
conductivity and flow rate.
Dissolved oxygen, Temperature, pH and Conductivity
Dissolved oxygen, temperature, pH and conductivity were measured in-situ using a dissolved
oxygen and temperature meter, pH meter and a digital conductivity meter respectively. Water
samples were collected into water bottles and the parameters were measured by dipping the
above mentioned measuring instruments into the bottles. Their values were recorded.
Measuring these parameters on site will give more reliable results since transportation and
storage time will affect these parameters.
The Secchi-depth was also measured at the lake by using Secchi-disk. The Secchi disk is a
20cm disk, which was lowered into the water of the lake until it was no longer seen.
40
Figure 12 Field analyzers used for the in-situ measurements: Secchi disk (Left); and pH and
Conductivity meter (Right)
Flow rate
In order to determine the input and output of water and nutrients to and from the lake, the
flow of the inlet and the outlet stream are measured. For this measurement, a current meter
equipped with an electric counter, as shown in the figure below, was used.
Figure 13 Current meter as used in the flow measurement
Principle (Flow measurement)
The principle relies on the current of the water which causes a small propeller to rotate. The
rotation is electronically counted for a period of 50 seconds at different positions along the
stream’s transect. Therefore, the profile is divided into different sections and the flow is
measured each at different depths just below the water surface. Based on the rotation
measurements, the flow velocities and the areas of different depths - the volume flows can be
calculated by means of a mathematical algorithm. Subsequently, the retention time of water
in the lake (turnover time) can be determined by dividing the lake’s volume by its output
flow. Moreover, if the volume flow [l/s] and the nutrient concentrations [mg/l] are known, it
41
is possible to determine the annual input and output of nutrients to and from the lake caused
by the runlets.
Inlet
The survey of Guldager Mølledam revealed that there is one inlet at the north shore of the
lake. The Inlet had a shallow, very slow flow and relatively wide profile embedded with a lot
of organic deposits. Two flow measurements were undertaken which is a representative of the
Inlet stream flow. Based on the wide cross-sectional area and the flow velocity, which was
determined by means of a current meter and formula provided by the measurement
equipment, the flow had been determined. For each of the sub-areas the flow velocity was
measured separately and the total inlet flow equal the sum of the partial flows.
Outlet
Guldager Møllebæk is the only outlet of the lake and is much larger than the inlet runlet. As it
flows through a pipe below a bridge providing defined geometric dimensions, the hydraulic
profile can be divided into sub-areas as shown in the diagram. For each of the sub-areas the
flow velocity was measured separately and the total outlet flow equal the sum of the partial
flows.
6.2 Water sample measurements
6.2.1 Sampling
The water samples were taken on the 16th
October. The water sample from the outlet stream
was taken from the other side of the road, close to the road drum. The location is presented in
figure 13. Five litres of water was taken and placed into plastic flasks with a lid. The water
sample from the inlet stream was taken approximately 20 metres upstream from the lake. It
was not possible to take the sample closer to the lake due to dense vegetation. Five litres of
water was taken.
Temperature was measured at several points in the lake as well as depth in order to establish
that the lake water was well mixed. Since the temperature difference between the points were
not significant, the decision was made to take three water samples from one sampling point.
The purpose of taking three samples was to be able to calculate that the samples were
statistically representative for the lake water. The samples were taken in the middle of the
42
lake and will represent the water quality in the entire lake. From the same sampling point the
Secchi-depth, water temperature and water depth was measured. Five litres of water sample
was taken and also one one-litre sample to measure the alkalinity.
Figure 14 Lake water sampling
6.2.2 Analysis of water samples
The parameters that were analysed from the water samples include: alkalinity, BOD5, total
solids, total nitrogen, total phosphorus and orthophosphate, iron, chlorophyll a.
Alkalinity
Alkalinity was determined using Radiometer Analytical. Alkalinity of water was determined
by end point titration with a strong acid solution. Phenolphtalein alkalinity corresponds to
titrable alkalinity at pH 8.3 and total alkalinity corresponds to titratable alkalinity at pH 4.5.
This application note is an application of international standard ISO 9963-1.
We calibrated the electrode with pH 4.005 and pH 10.012 IUPAC Series pH standards and
pipetted 100ml of water into a flask. The electrode was dipped and delivered tipped in the
sample. The method was started by pressing the RUN key on the Radiometer Analytical and
the results were provided.
43
Figure 15 Radiometer Analytical
BOD5
Water samples collected for BOD measurement must not contain any added preservatives and
must be stored in glass bottles. Ideally the sample should be tested immediately since any
form of storage at room temperature can cause changes in the BOD (increase or decrease
depending on the character of the sample) by as much as 40 per cent. Storage should be at 5°
C and only when absolutely necessary. The determination was performed through the
OXITOP measurement.
Figure 16 Oxitop BOD5 determination flasks. (ENVCO)
44
Total solids
Dry and empty beakers were weighed on the electronic weighing balance and their
measurements taken. 50 ml of the water samples (inlet and outlet) were then measured into
the beakers using a pipette after which the beakers were placed on the heater and the samples
evaporated to dryness. The weight of the beakers was then measured on the weighing
balance. The difference in weight of the empty beakers after heating and before heating
represents the total solids.
Calculation : Total solids (mg/L) = mlvolumesample
BA
,
1000)(
Where: A = weight of dried residue + beaker (after evaporating and drying)
B = weight of empty and dry beaker (before evaporating and drying)
Measurements for total solids were not taken at the middle of the lake but it can be expected
that the value for the amount of totals solids at the middle of the lake should be between the
results for the inlet and outlet.
Total Nitrogen
The determination of nitrogen was divided into two parameters, the total nitrogen asessment
and the subconsequent nitrate. The analytics were performed through the FIA STAR 5000, 2
weeks after the water samples were taken. The total amount of nitrogen in the sediment
samples was analysed with FIASTAR 5000.
The total nitrogen assessment and the subsequent nitrate were performed during this project
work. Theoretically, samples taken for the determination of total nitrogen, nitrate and nitrite
should be collected in glass or polyethylene bottles and filtered and analysed immediately.
According to the literature, if this is not possible, 2-4 ml of chloroform per litre can be added
to the sample to retard bacterial decomposition. The sample can then be stored at 3-4° C.
45
Figure 17 FIASTAR 5000
Total Phosphorus and Orthophosphate
Total phosphorus was measured in the water samples using FIASTAR 5000 Analyzer, each
sample was analyzed twice. The concentrations obtained were very low, approximately to
zero. We were then advised by the Laboratory Technician to analyse for orthophosphate in
the water samples at a lower calibration curve which will be approximately the same as the
concentration for total phosphorus. The analysis was carried out two weeks after collection of
the sample. Samples from the lake, inlet and outlet stream were analyzed without the
treatment of autoclave. The samples were filtered through 0.45 m membrane filters for the
analysis.
Iron
Iron in the water samples was measured with Atomic Absorption Spectrometry (AAS). AAS
is used for the determination of trace elements in water samples and in acid digests of
sediment. The water samples were pre-treated by taking 40-ml of sample, adding 10-ml
concentrated nitric acid and put into the autoclave for 30 minutes. Standards were prepared
with the concentrations of; 1 ml/l, 5 ml/l and 10 ml/l. The standards were run through the
AAS in order to obtain a calibration curve, where after the samples were analyzed.
46
Chlorophyll a
The amount of chlorophyll a in the samples was measured following a protocol obtained from
a Danish standard for water and environment (DS2201). The following steps were undertaken
(for every sample in duplicate):
a. 400ml of each sample was filtered through Whatman GF/C filter paper (4.7cm)
making use of a vacuum pump.
b. Each filter paper was transferred to a 10ml centrifuge tubes and stored in the fridge at
–80 C for one day
c. The centrifuge tubes were filled with 96% ethanol, wrapped in aluminium foil and
kept for 20 hours
d. The samples were centrifuged at 10000rpm for 10 minutes
e. The volume of ethanol was filled up to 10ml
f. The samples were analysed with a spectrometer at two different wavelenght namely
665 nm and 750 nm. Plastic cuvettes were used.
The concentration of chlorophyll a in g/L was then calculated based on the results.
6.3 Sediment sample measurements
6.3.1 Sampling
Sediment samples were taken from three sampling points, one in the middle of the lake, one
close to the inlet stream and one close to the outlet stream. The location of the sampling
points for the sediment samples together with the approximate distance from the shore is
presented in figure 18.
47
Figure 18 Location of sampling points for sediment samples and lake depths
The purpose of the locations for the sediment samples was to be able to compare the
distribution of substances in the lake sediment. The sampling points were given a number
where 1 is the middle of the lake, 2 is close to the inlet, and 3 is close to the outlet.
6.3.2 Analysis of sediment samples
The parameters analyzed in the sediment samples are: metals and phosphorus, iron, nitrogen
and organic matter.
Metals and Phosphorus
The amount of metals and phosphorus in the sediment samples were measured with Perkin
Elmer Optima 3000DV. Inductively coupled plasma atomic emission spectrometry (ICP
AES) is used for qualitative and quantitative measurements of elemental composition in
samples. The samples, for the metal analysis, were pretreated and diluted to 50-ml. Standards
were prepared with the concentration, 1 ml/l, 2 ml/l and 10 ml/l. A calibration curve was
made and the samples were analyzed.
The samples for phosphorus analysis needed different standards than for the metals. The
standards had concentrations of 1 m/l, 5 ml/l, 10 ml/l and 20 ml/l. When measuring
phosphorus with ICP AES, a higher pearch has to be used since the measurements are
performed in low range. This is done by inserting N2-gas that eliminates any air in the
samples.
48
Figure 19 Location of sampling points for sediment samples and lake depths
Iron
The amount of iron in the sediment was measured using Atomic absorption
spectrophotometry (AAS). The same samples were used as for the ICP analyses, however
they had to be diluted one more time by taking 1-ml of sample and diluting it up to 100-ml.
Standards with concentrations of 1 ml/l, 5 ml/l and 10 ml/l were made. The standards were
run through the AAS apparatus, where after the samples were analysed.
Figure 20 Atomic Absorption Spectrometer
49
Nitrogen
The total amount of nitrogen in the sediment samples was analysed with FIASTAR 5000.
The samples were pre-treated and then analysed at the same time the as the water samples.
The sediment samples were treated in the same manner as the water samples.
Organic matter
The furnace was turned on and set to 500°C and allowed to heat up for about an hour.
Defined amounts of each sample, was then transferred into dry and empty crucibles. The
weights of the sample and crucibles were measured on the weighing balance after which they
were transferred into the furnace. The samples were left to heat in the furnace for three hours
after which the furnace was turned off. The samples were then left in the furnace overnight.
The next day the crucibles were removed from the furnace and their weights were
determined. Organic matter content was determined as the loss in weight.
6.4 Biological measurements
The following biological parameters were analysed in this study: phytoplankton and
macro-invertebrates.
Phytoplankton
Sampling
Plankton was sampled in duplicate very close to the outlet of the lake. A cone-shaped sieve
was moved along the surface of the lake and filled with water. The ventil was closed, and the
water was allowed to filter out of the sides, to obtain a concentration of the plankton
concentrated in the small plastic funnel. Then the ventil was opened, and the sample poured
into a bottle. This process was repeated until the bottle was full. Figure 21 shows the plankton
net used for collecting plankton from the lake.
50
Figure 21 Net for collecting phytoplankton
Analysis of phytoplankton
In the laboratory, 3 drops of the sample collected were mounted on a microscope slide and
covered with a cover slip. The specimen was examined under an Olympus 249113
microscope and different magnifications (10x – 40x) and light intensities were used. Pictures
of these micro-organisms were taken and compared to a reference key (Tavlerne Fra Dansk
Planteplankton by Gunnar Nygaard) which were then identified accordingly.
This set up is shown below:
Figure 22 Olympus 249113 Microscope used for identification of plankton
Macro-invertebrates (DSFI Methodology)
The macro-invertebrates were collected and analysed based on the method in the Danish
Stream Fauna Index (DSFI). The biological organisms were collected at the outlet stream,
51
around 50 metres downstream from the lake. The biological samples were obtained by
applying the kick-sampling method and pick sampling. The samples are taken to the
laboratory where the organisms are killed by adding ethanol. When the organisms are dead
they can easily be selected out from the unnecessary debris and placed into the refrigerator
until they are to be evaluated.
Kick sampling
Three transect points approximately 10 metres apart were marked along the stream, and from
each of these transect points, four kick samples were collected. The sampling was done from
downstream to upstream to prevent disturbance of sediment due to water flow. Samples were
then collected by putting the hand net on the stream bed, placing the foot in front and then
moving the foot backward against the current. By this movement animals and sediment are
collected into the net. The animals were then selected from the sediment and put in trays.
Figure 23 Kick sampling
52
Pick sampling
Stones were collected from an undisturbed part of the stream, and from these stones animals
were picked into a dish within 5 minutes. These samples are later on pooled together to get a
composite (a more representative) sample which is then used for analysis.
Laboratory analysis
In the laboratory, the animals were properly selected from the sediments and placed in
ethanol in order to kill and preserve them. They were then stored in the refridgerator
overnight.
Figure 24 Microscope for Macro-invertebrate analysis
Following this, the animals were visually observed using a microscope and identified by their
individual taxa according to literature (Macan, and Quigley). After which, the samples were
then sorted according to their indicator group (IG) and diversity groups as described in the
DSFI methodology and the calculation of the DSFI index value was done. Those with no
classification were disregarded.
53
7 RESULTS
In this chapter the results from the analysis are presented and the reliability of the results is
discussed. The results of the parameters measured are presented under the sub-chapters:
results of in-situ measurements, results of water sample measurements, results of sediment
sample measurements and results of biological measurements.
7.1 Results of In-situ measurements
The average depth measured of the lake was 1,47 m and the highest depth was 1,78 m. The
results of Secchi-depth for the three measured points are 1.5 m, 1.60 m and 1.78 m. The
results of the remaining in-situ measurements are presented in table 7.
Table 7 The average results from in-situ measurements
Sampling
Points
Temperature
(°C) pH
Conductivity
(μS/m)
Dissolved Oxygen
(mg/l)
Inlet 7.0 6.92 402.0 8.65
Middle 7.2 6.85 400.0 10.97
Outlet 7.7 6.91 393.0 11.00
Flow rate
The detailed calculations of the flow including all formulae are presented in the appendix of
the project.
n- Revolution per second
For: 0.52 s−1
≤ n ≤ 1.26 s−1
v = 0.2303.n + 0.040
For: n ≥ 1.26 s−1
v = 0.2485.n + 0.017
Flow: Q = v*A
54
Inlet
Table 8 The flow measurements for the inlet
Sampling Points Point A Point B
Profile (m2) 0.062 0.124
Velocity (rps) 0.440 0.580
Velocity (m/s) 0.141 0.174
Flow (l/s) 8.74 21.56
The calculations for the flow measurements are presented below.
Total Inlet
Flow: Q inlet, total = QA + QB
= 30.3 m3/s
Q inlet, total = 0.0303 m3/s = 30.3 l/s
NO3/NO2: mInput, NO3/NO2 = Q inlet, total × c NO3/NO2
= 30.3 l/s × 8.136 mg/l = 247mg/s
Outlet
Table 9 Flow measurements for outlet
Sampling Points Outlet A Outlet B Outlet C Outlet D Outlet E
Profile (m2) 0.0294 0.036 0.036 0.0262 0.0294
Velocity (rps) 0.98 0.94 0.78 0.76 0.72
Velocity (m/s) 0.266 0.256 0.224 0.215 0.206
Flow (l/s) 7.8 9.22 8.1 5.6 6.1
55
Total Outlet
Flow: Q outlet, total = QA + QB+ QC+ QD+ QE
= 0.0078 m3/s + 0.00922 m
3/s + 0.0081 m
3/s+ 0.0056 m
3/s + 0.0061 m
3/s
Q outlet, total = 0.03682 m3/s = 36.82 l/s
NO3/NO2: mOutput, NO3/NO2 = Q outlet, total × c NO3/NO2
= 36.82 l/s × 5.68 mg/l = 209 mg/s
Turnover time
After calculating the flow, we were able to count the hydraulic turnover time in Guldager
Mølledam in which the entire water masses are exchanged once. The way of calculating and
the results are presented in the following.
Approximate length of lake: 207 m
Approximate width of lake: 80 m
Average lake depth: 1.3 m
Average volume of Guldager Mølledam:
V = length × width × depth
= 207m × 80m × 1.3m = 21,528 m3
Hydraulic turnover time(τ) = V
Q outlet, total
= 21,528 m3
1,161,155 m3/a
= 0.01854016a
Therefore the turnover time of Guldager Mølledam is approximately 6.7 days.
56
7.2 Results of water sample measurements
Alkalinity
The results for the alkalinity measurements are presented in the table below.
Table 10 Results from alkalinity measurements
Number of Sample Alkalinity
(mg CaCO3/l)
1 50.10
2 63.36
3 51.88
4 49.68
5 54.39
Average 53.88
Alkalinity was measured in five water samples. The alkalinity of a water body indicates its
capacity to neutralize acids, which protects and buffers against rapid changes of pH.
BOD5
The BOD5 determination was started one day after the sample was taken from the lake. The
method of measurement was done with OXITOP bottles. The figure below presents the
results of the BOD5 measurement; all values are given in mg/L O2.
Figure 25 BOD5 Results
2 2 2
1 1
0
1
2
3
4
5
mg/l
O2
BOD5 (mg/l)
Inlet1 Inlet2 Middle1 Middle2 Outlet1 Outlet2
After 24
hours48 hours 3 days
4 days 5 days
57
The overall results indicated a very low consumption of oxygen. This suggests low amount of
biodegradable organic matter and thus more available oxygen. This is reflected in the high
amount of dissolved oxygen in the lake. The highest value of 5mg/l can still be considered
with high water quality. The values were close to the detection limit and can therefore show
variations in BOD levels which are virtually impossible to obtain; e.g. the value of inlet 1.
Total Solids
Table 11 Total Solids results
Sample
Wt. of Beaker
and sample
(g)
Wt. of Beaker
(g)
Wt. Of
residue (g)
Total
Solids
(mg/l)
Average
Outlet 1 46.6878 46.6981 0.01030 206 209
Outlet 2 50.6209 50.6315 0.01060 212
Inlet 1 47.9775 47.9915 0.01400 280 293
Inlet 2 43.1152 43.1305 0.01530 306
The difference in the total solids at the inlet and outlet as seen in table 11 is an indication that
particles are being deposited or utilised in the lake. This suggests that the lake acts as a sink
which collects particles from the inflowing stream thereby improving the water quality. The
amount of solids deposited in the lake is calculated by multiplying the total solids at inlet and
outlet with their respective flow rate values and then finding the difference. The results are
given below.
𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑖𝑑𝑠 𝑔𝑜𝑖𝑛𝑔 𝑖𝑛 𝑙𝑎𝑘𝑒 = 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 𝑎𝑡 𝑖𝑛𝑙𝑒𝑡 × 𝑇𝑜𝑡𝑎𝑙 𝑠𝑜𝑙𝑖𝑑𝑠 𝑎𝑡 𝑖𝑛𝑙𝑒𝑡
30.3 𝐿/𝑠 × 293 𝑚𝑔/𝐿 = 8877.9 𝑚𝑔/𝑠
𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑖𝑑𝑠 𝑔𝑜𝑖𝑛𝑔 𝑜𝑢𝑡 = 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 𝑎𝑡 𝑜𝑢𝑡𝑙𝑒𝑡 × 𝑇𝑜𝑡𝑎𝑙 𝑠𝑜𝑙𝑖𝑑𝑠 𝑎𝑡 𝑜𝑢𝑡𝑙𝑒𝑡
36.82 𝐿/𝑠 × 209 mg/L = 7695.38 𝑚𝑔/𝑠
𝐷𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑖𝑛 𝑡𝑒 𝑡𝑤𝑜 𝑣𝑎𝑙𝑢𝑒𝑠 𝑖𝑠 8877.9 𝑚𝑔/𝑠 − 7695 𝑚𝑔/𝑠 = 1182.52 𝑚𝑔/𝑠
Therefore the amount deposited in the lake per second is 1182.52 mg/s
58
Total Nitrogen and Nitrogen Oxides
The storage time for our samples was consequently not suitable for any reliable result. The
following graphs present total nitrogen (TN) and nitrate (NO) concentrations from inlet,
outlet and lake middle sampling.
Figure 26 Total Nitrogen (mg/l) results
The results indicate a higher load of nutrients from the inlet of the lake. The nitrogen
compounds decrease during the retention time inside the lake and eventually leave the outlet
with reduced concentration. This indicates a nutrient fixation of nitrogen inside the lake.
Typical nitrogen concentrations vary from a few micrograms per litre in some lakes to more
than 20 mg/l in raw sewage.
8,1361
6,1436 5,8687
0
1
2
3
4
5
6
7
8
9
Inlet Middle Outlet
Total Nitrogen (mg/l)
59
Figure 27 Nitrogen Oxides (mg/l) results
The determination of nitrate should indicate lower concentrations than the total nitrogen, due
to the fact that nitrate is one of the compounds evaluated with TN. As can be seen from the
graph, this is the case, but most of the TN found in the lake is available in the form of nitrate.
Total Phosphorus and Ortho-Phosphate
In the tables below the measured concentrations of total phosphorus and ortho-phosphate are
presented. The measurements for total phosphorus were below the calibration curve,
however, the advice was given that the concentration of ortho-phosphate will be almost the
same as for total phosphorus.
Table 12 Total phosphorus in the Inlet, Lake and Outlet
INLET MIDDLE OUTLET
Total osphorus
PO4-P
(mg/l)
0.941 0.061 -0.100
0.939 0.088 -0.103
-0.107 0.065 -0.098
-0.108 0.061 -0.094
-0.090 0.060 -0.110
-0.093 0.058 -0.112
Average (mg/l) 0.247 0.036 -0.103
Dilution Factor (0.8) 0.8 0.8 0.8
Total Phosphorus
PO4-P
(mg/l)
0.1976 0.0288 -0.0822
7,9085
4,9895 5,0195
0
1
2
3
4
5
6
7
8
9
Inlet Middle Outlet
NO3- (Nitrate, mg/l)
60
Table 13 Ortho-phosphate in the Inlet, Lake and Outlet
Trial INLET MIDDLE OUTLET
Total Phosphate
PO4-P
(μg/l)
1 10.490 12.539 12.873
2 10.179 11.831 12.704
3 8.878 11.642 12.597
Average (μg/l) 9.849 12.004 12.725
Standard Deviation 0.855 0.473 0.139
Iron
The results from the iron analysis in the water samples are presented in table below.
Table 14 Iron content results
Sample
Point Fe (mg/) measured Fe (mg/l) final
Lake (1) 0.39 0.48
Lake (2) 0.37 0.46
Lake (3) 0.33 0.42
Inlet 0.29 0.37
Outlet 0.34 0.42
The average amount of iron in the lake is 0.45 mg/l. The content of iron is based on
calculations from the measured amount times the dilution factor.
Chlorophyll a
The chlorophyll a concentration in the water samples are presented in Table 15.
Table 15 Chlorophyll a results
Sample
Point Abs 665 Abs 750 A665-A750
Chlorophyll
Concentration
(μg/l)
Average
(μg/l)
Middle (1) 0.0744 0.0253 0.0491 14.49 15.36
Middle (2) 0.0531 0.0002 0.0529 15.93
Middle (3) 0.0910 0.0880 0.0030 0.900 6.79
Middle (4) 0.0603 0.0182 0.0421 12.68
Average 11.08
61
Chlorophyll a is a measure of all green pigments whether they are active (alive) or inactive
(dead). Chlorophyll a is a measure of the portion of the pigment that is still active; that is, the
portion that was still actively respiring and photosynthesizing at the time of sampling.
CALCULATION:
For Sample 1.1: 104 . e. A(665K)
83. v. l
C = 104 . 10ml. 0.0491
83 1 . 4l. 1cm
g.cm
C = 14.79 g/L
Where:
C = concentration of chlorophyll in g/L
e = volume of ethanol in which the sample was diluted (10 ml)
83 = absorption coefficient of 96% ethanol in 1*g−1
*cm−1
I = volume of sample that was filtered (400ml)
V = lenght of the cuvette (10mm)
A(665K) = A(665) – A(750)
7.3 Results of sediment sample measurements
Heavy metals, iron and phosphorus
The results from the sediment analysis are presented in table 16.
Table 16 Sediment analysis results
Sample
Point
Ni
(mg/kg DS)
Pb
(mg/kg DS)
Cd
(mg/kg DS)
Fe
(mg/kg DS)
P
(mg/kg DS)
N
(mg/kg DS)
Middle 29.41 59.14 -1.70 24.69 1.72 0.40
6.55 47.73 -4.30 45.69 0.34 0.34
Inlet 26.26 26.35 -3.25 15.28 0.31 0.43
0.60 10.47 -3.99 0.94 -0.03 0.16
Outlet 28.39 32.44 -2.60 17.56 1.23 0.48
62
25.51 58.13 -3.10 34.65 2.53 0.37
Average 19.45 37.38 -3.16 23.13 1.02 0.36
The results for cadmium were all under the detection limit and therefore negative results are
shown. The cadmium results are not to be considered since they do not represent the actual
situation. The results for the samples from the inlet are not representative since they differ
significantly from other results. The reason for the difference might be due to errors
occurring when pre-treating the sample or dilution of the sample. Even in the reference
sample which was made the same pattern could be followed. The sediment in the bottom
layer at inlet was sandy and smelled of sulphur. This might be the reason to poor results, the
method used is more suitable for soil types with a smaller grain size.
Organic matter
The results for the organic matter analysis are given in the table below.
Figure 28 Organic Matter in Sediment samples
The results show that organic matter is highest at the middle of the lake. The values for both
the upper and lower layer samples at that point are higher than the values from the inlet and
outlet. This suggests that organic matter is being deposited at the bottom point of the middle
of the lake.
0.11
0.1580.137
0.035
0.404
0.14
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
INLET MIDDLE OUTLET
TOP
BOTTOM
63
7.4 Results of biological measurements
Phytoplankton
The microscopic examination indicates the presence of both phytoplankton and zooplankton.
The phytoplankton species belong to the groups of greenalgae, diatoms, euglenoids, and blue-
green algae.
S1.Phacus sueicicus Llemmerman S2.Synedra acus Kützing
Hyalotheca mucosa Ehrenberg
S3.Fragilaria capunica Desmazieres S4.Synedra ulna Ehrenberg
S5. Chlamydocapsa planctonica Fott S6.Tetraedron limneticum Borge
64
S7. Peridinum aciculiferum Lemmerman S8. Diatoma Elongata Agardh
S9. Mallomonas Caudata Iwanoff S10. Mallomonas Teilingii Conrad
S11. Asterionella formosa Hassall S12.Pleurotaenium trabecula Ehrenberg
65
S13. Perinidium palatinum Lauterborn S14. Chlamydocapsa planctonica Fott
Westella botryoides Wildermann
Figure 29 Various species of Phytoplanktons
The processes of photosynthesis and respiration caused by algae ehance changes in lake pH,
and the presence of algae in the water column is the main factor affecting Secchi disk
readings. Algae cause aesthic problems in a lake; a green `Scum,` swimmers itch, and rotting
scent are common problems associated with high algae concentrations.
Macro- invertabrates
The individual macro-invertebrates collected during the sampling, their taxonomy, number,
pictures and diversity groupings are given in the table below.
Table 17 Macro-invertebrates in Guldager Møllebæk
Organism Kick
sample
Pick
sample Image
Diversity
Groups
Common name: Gammarus
pulex
Class: Crustacea
Order: Amphipoda
Family: Gammarus
> 10
4
Positive
(Gammarus)
66
Common name: Hydropsyche
sp.
Class: insectae-larvae
Order: Trichoptera
Family: Hydropsychidae
> 6
> 10
Nil
(non-case
bearing
member of
Trichoptera)
Common name: Dicranota sp.
Class: Insecta-larvae
Order: Diptera
Family: Tipulidae
> 10
-
Nil
Common name: Baetis rhodani
Class: Insecta-Nymphs
Order: Ephemeroptera
Family: Baetidae
3
-
Positive
(Every family
of
Ephemeropte
ra)
Common name:
Class:
Order: Oligochaeta
Family: Tubificidae
< 100
8
Nil
(Negative
only if ≥100)
Common name:
Class: Insecta
Order: Coleoptera
Family: Helodidae
3
-
Nil
Specie: Erpobdella octoculata
Class: Hirudinea
Family: Erpobdellidae
2
-
Negative
(Erpobdella)
Specie: Lymanae auricolata
Class: Gastropoda
Order: Pulmonata
Family: Planorbiidae
5
1
Negative
(Lymnae)
Specie:
Class: Insecta-Nymphs
Order: Ephemeroptera
Family: Ephermerellidae
13
-
Positive
(Every family
of the
Ephemeropte
ra)
67
Number of Diversity groups (Total positive – Total negative): 3 – 2 = 1
Analyses of the indicator taxa of the animals show they belong to Indicator Group 2 (IG 2)
due to the taxon (Ephemerellidae).
The index value (fauna class) is the value on the DSFI-table where the diversity group and
indicator group intersect. In this case the Index value is 4.
With an index value of 4 can be said to have a good environmental state as at time of
sampling.
Macrophytes
The analysis for macrophytes was done by visual observation. The results showed the
presence of emergent, floating and submerged macrophytes which is indicative of reasonable
sunlight penetration. It also suggests the presence of oxygen and production at that depth in
the lake.
Figure 30 Macrophytes at Guldager Mølledam
68
8 DISCUSSION OF RESULTS
8.1 In-situ measurements
Temperature, pH, Conductivity and dissolved oxygen
All the in situ measurements were taken at different points at the surface, below the surface
and close to the bottom of the lake determine an average value.
Temperature measurements at different points were relatively close in value indicating that
the lake was well mixed and there was no stratification. The average temperature of the lake
was 7.2°C. This value is below the maximum temperature given in the EU Council Directive
2006/44/EC for Salmonoid and Cyprinid waters.
The pH value for Guldager Mølledam was 6,85. This value is close to neutral pH. According
to Bronmark and Hanson (1996) the pH that is conducive for aquatic life in normal natural
waters ranges from 6 to 8. This indicates that the lake has a good and normal pH level.
The average Conductivity of the Lake Guldager Mølledam was 400 µS/cm. According to
UNESCO/WHO/UNEP (1996) Conductivities of most fresh waters range from 10-1,000
µS/cm while that of polluted waters or waters receiving large quantities of land run-off may
have conductivities in excess of 1,000 µS/cm. Thus the conductivity of Guldager Mølledam
falls within the range of most fresh water according to these range values.
The results for dissolved oxygen measurements show that the lake has a value of 10.97 mg/L.
According to UNESCO/WHO/UNEP (1996), dissolved oxygen values in unpolluted waters
are usually close to 10 mg/L. This results therefore indicates an unpolluted state of the lake.
Secchi depth
The secchi depth measurement showed a value of 1.78 m (it was visible all the way down the
bottom). This result is indicative of the presence of few algae and suspended particles. The
trophic state index (TSI) for a lake can be calculated based on the measured Secchi depth
(Michaud 1991) using the formular;
TSI = 60-14.41 (ln SD), where (In SD) stands for the natural log of the secchi depth.
69
natural log of 1.78 = 0.5766
therefore TSI = 60 – 14.41 (0.5766) = 51.69
The results showed that the trophic state for Guldager Mølledam is mesotrophic.
According to Michaud (1991), the transparency of the lake can be calculated by multiplying
the secchi depth by a factor of 1.7. In this case the transparency results in 3.026 meters for the
penetration of sunlight. This implies that light will penetrate up to the bottom of the lake.
Flow and turnover time of lake
Input and Output of Water
The flow measurement in the inlet and outlet stream revealed that about 955,000 thousand m³
of water are entering Guldager Mølledam each year and approximately 1.2 million m³ are
leaving the lake. The data given, based on the flow measurements indicate that the water
level should be decreasing, which in contrast is not the same. The flow measurement provides
just a rough estimation of the real situation and there are various factors which should be
taken into account.
The flow measurement was taken on one day and then was projected to the annual in- and
output of water. Moreover, the inlet and outlet stream are not the only factors responsible for
the input and output of water to and from lake. If there is heavy precipitation there might be
additional temporary inlets supplying water to the lake which were not visible at the date of
examination and thus, precipitation and evaporation also should be taken into consideration.
In addition, there is no information available concerning the hydrogeological situation around
Guldager Mølledam. Hence, it is also possible that the lake might be receiving groundwater
from a closed by ground aquifer.
Furthermore, the flow measurement of the outlet, Guldager Møllebæk, seems to be precise
because it was carried out directly in the concrete tube or pipe at the outlet below a bridge
providing ideal geometric shapes in which the flow was measured in five sub-areas.
Turnover Time
The turnover time was attained by dividing the volume of Guldager Mølledam by the output
flow, a turnover time of 6.7 days has been determined. The turnover time might not be
70
precise because since some factors might contribute in the supplying of water to the lake and
it might be slightly different because of these contributing factors, it can be definitely stated
that the complete exchange of the lake water is very short. This shows that a possible
pollution in the inlet will not affect Guldager Mølledam for long term because the complete
exchange of the lake water is within a few days.
8.2 Water sample measurements
Alkalinity
The alkalinity of Lake Guldager Mølledam is 53.88 mgCaCO3/L. According to (Bronmark
and Hanson 2005) lakes with alkalinity above 25 mgCaCO3/L can be said to have good
buffering capacity and thereby have a low risk of acidification. Since the alkalinity of the
Lake Guldager Mølledam is much higher than this limit, the aquatic organisms are less
affected by pH fluxes. Organisms vulnerable to fluxes in pH have good conditions to live in
this lake based on its alkalinity.
Total Nitrogen and Nitrogen Oxides
The results of nitrogen measurements show nitrate (NO3-) concentrations in lake mølledam of
around 5 mg/L. According to UNESCO/WHO/UNEP (1996), this might be an indication of
human influences on the lake. The catchment includes some areas for agriculture, which are
likely expected to be a reason for this rather high load of nitrogen in the inlet, but also in the
lake itself.
Total Phosphorus and Orthophosphorus
Results obtained from the lower calibration curve using FIAstar 5000 confirmed the
concentration of Orthophosphate in the lake Guldager Mølledam was 12.004µg P- PO4/l.
Moreover, comparing with the inlet stream water which is 9.849µgP- PO4/l and that of outlet
stream water which is 12.725µg P- PO4/l, a significant difference could be observed in the
concentrations of Orthophosphate. This indicates that less amount of Orthophosphates is
coming in from the inlet stream high amount of orthophosphorus is released from the lake
into the outlet stream. Relatively, some of the orthophosphate is released from the sediments
of the lake. This situation could indicate that phosphorus is deposited in the sediments of
71
Lake Guldager Mølledam and this phosphorus released into the outlet stream can be
attributed to internal loading of phosphorus in the sediments. This can also explain the high
concentration of phytoplankton and reeds around the lake.
Based on the concentration of the dissolved phosphorus and according to the division of
trophic levels reflecting the degree of eutrophication Lake Guldager Mølledam should be
classified as Mesotrophic (refer to literature).
Iron content
The amount of iron in lake water influences the freedom of phosphorus. When the oxygen
level is sufficient the phosphorus wil stay chemically bound to iron compounds. The average
amount of iron in the inlet was 0,37 mg/l and in the lake 0,45 mg/l. Since the amount of iron
measured in the outlet was 0,42 mg/l, it can be evaluated that some of the iron in the outlet
samples originate from the sediment. A reduction of iron content in the lake should be seen
over a longer time period.
Chlorophyll a
Chloropyll a concentration in lake water was 11.08g/L. Chlorophyll a concentration gives
an indication of the algal biomass in the lake water, and thus the degree of eutrophication.
Decompostion of algae also causes the release of nutrients to the lake, which may allow algae
to grow. Their processes of photosynthesis and respiration cause changes in lake pH, and the
presence of algae in the water column is the main factor affecting Secchi disk readings. When
decomposition processes predominate, dissolved oxygen levels are considerably reduced in
stratified lakes.
Chlorophyll a concentrations can be used to determine a lake’s trophic status in relation to
lake’s productivity state. According to this, and the result obtained, it can be inferred that
Lake Guldager Mølledam is mesotrophic.
8.3 Sediment sample measurements
Phosphorus
72
Sediment in shallow lakes play a significant role in the overall nutrient dynamic. Phosphorus
in the sediment is chemically bound to iron compounds or fixed in organic forms. If the
oxygen level close to the sediment surface is very low or close to zero, the bound phosphorus
can be released into the water, thereby decreasing the water quality. The amount of
phosphorus bound into the sediment is also dependent on the pH. If pH is below 8, the
phosphate binding to metals is strong. In Guldager Mølledam the pH was 6,85 and the
oxygen content was close to 11 mg/l, this indicates that there will not be a significant release
of phosphorus into the lake water. The relation between iron and phosphorus content is high
(23:1) which supports the statement that phosphorus will be bound to the sediment (Ribe
Amt. 1998).
8.4 Biological measurements
Phytoplankton
The processes of photosynthesis and respiration caused by algae ehance changes in lake pH,
and the presence of algae in the water column is the main factor affecting Secchi disk
readings. Algae cause aesthic problems in a lake; a green `Scum,` swimmers itch, and rotting
scent are common problems associated with high algae concentrations.
8.5 Comparison with legislation
The lake has been classified as B “Naturligt og alsidigt plante- og dyreliv” by Ribe Amt in
2000. The translation of the classification would be “Natural and versatile plant and animal
occurrence”. The classification is mainly based on types of plants and animals living in the
lake. One of the parameters which affect this classification is also Secchi depth. The Secchi
depth for a B classified lake shall be 1 – 3 meters, which our results confirm. Our assessment
did not include investigations on plant- and animal life in the lake and therefore nothing can
be determined in regards to them.
According to the Water Framework Directive (2000/60/EC) all lakes in Member States shall
have a “good ecological status” by the end of 2015. Investigations in Denmark has shown
that the total phosphorus concentration regulates the ecological state in lakes. It has therefore
been suggested that the concentration of total phosphorus shall be used when assessing
ecological quality for lakes. There are different limit values for shallow lakes (< 3 m) and
deep lakes (> 3 m). (Nielsen et al. 2005)
73
Table 18 shows the limit values of total phosphorus content (µg P/l) for shallow and deep
lakes are presented. Based on these values an ecological status can be given for the lake.
Table 18 Limit values for total phosphorus concentration (µg P/l) in shallow and deep lakes.
(Modified from Nielsen et. al, 2005)
High Good Moderate Fair Poor
Shallow < 25 < 50 < 100 < 200 > 200
Deep < 12.5 < 25 < 50 < 100 > 100
Our measurements for total phosphorus were below the detection limit, however the amount
of ortho-phosphate was measured. The concentration of ortho-phosphate should be in the
same range as total phosphorus. The concentration of ortho-phosphate in Guldager Mølledam
was 12,004 µg P-PO4/l. One could suspect that the concentration of total phosphorus would
be below the limit value for high ecological status in shallow lakes. The measured
concentration for total phosphorus in 1999 was 0,086 mg/l and according to the requirements
for this classification system the lake should be classified as moderate.
The European Directive (2006/44/EC) gives classification parameters for supporting fish life
in lakes. The parameters vary for salmonoid and cyprinid waters. In table 19 a comparison
between the limit values and our values are presented.
Table 19 Comparison of limit values and our measurements. (2006/44/EC, Annex 1)
Properties Salmonid Water
Cyprinid
Water Inlet Lake Outlet
G I G I
Temperature (°C) --- 21.5 (10) --- 28
(10) 7 7.2 7.7
Dissolved O2 (mg/l) 50% ≥ 9 50% ≥ 9 50% ≥ 8 50% ≥
7 8.65 10.97 11
100% ≥7 100% ≥5
pH --- 6 – 9 --- 6 - 9 6.92 6.85 6.91
BOD5 (mg/l O2) ≤ 3 --- --- ≤ 6 2 4.5 3
The letter G stands for guideline value and I for mandatory value. The temperature in
parenthesis are the limit value for breeding season for these fish species. Based on these
compared parameters the inlet stream, Guldager Mølledam, and Guldager Møllebæk have
74
sufficient water quality for supporting Cyprinidae. Only the inlet stream fulfils the
requirements for Salmonid waters. The list in Annex 1 (2006/44/EC) contains several more
parameters, however these were not analysed in our project. The result might vary if all of
those parameters are taken into consideration.
8.6 Comparison with previously performed assessments
After the restoration of the lake in 1998/1999, Ribe Amt performed an assessment of the
environmental state of the lake. In the table below the results from the assessment performed
in 1987, 1999/2000 and 2009 (performed by our group) are presented. A sediment
investigation was performed by Ribe Amt in 1990.
Table 20 Comparison of results
Sample Point Parameter 1987 1999/2000 2009
INLET Total Phosphorus (mg/l) 0.12 --- 0.20
Nitrogen (mg/l) 10.53 --- 6.75
LAKE
Depth (m) 0.44 1.14 1.47
Secchi depth (m) 0.4 – 0.7 1.93 1.5 – 1.7
Total Phosphorus (mg/l) 0.22 0.086 0.03
Total Nitrogen (mg/l) 4.95 7.1 5.23
Chlorophyll a (µg/l) 2.23 15 – 150 11.08
Iron (mg/l) --- 0.4 0.45
OUTLET Total Phosphorus (mg/l) 0.25 --- -0.03
Nitrogen (mg/l) 5.91 --- 4.87
Sample Point Parameter 1990 1999/2000 2009
SEDIMENT
Iron (mg/l) 26.4 --- 23.13
Phosphorus (mg/l) 0.5 – 7.3 1.8 1.02
Lead (mg/kg DS) 60 --- 37.38
Nickel (mg/kg DS) 46 --- 19.45
Cadmium (mg/kg DS) 6.9 1.5 -3.16
After the sediment removal the depth of the lake increased significantly. The variation in the
results from 1999/2000 and our measurements in 2009 is likely a result from difference in
measurement locations. This also explains the variations in Secchi depth.
The amount of total phosphorus in the lake between 1987 and 1999/2000 was expected since
the sediment was removed and the phosphor input from the sediment was thereby removed.
The measurements for total phosphorus in 2009 were all under the detection limit and cannot
75
be compared with previous results. The amount of ortho-phosphate was measured and the
results indicate low content of ortho-posphate.
A decrease in total nitrogen content during autumn and winter is normal and this explains the
variations between the results from 1999/2000 and 2009. The amount of nitrogen input
increases during spring/summer since agriculture is the main contributor. The measurements
from 2009 only represent only the situation in October while the other results are expressed
in annual averages. The content of total nitrogen can vary depending on rainfall and
groundwater input. If the amount of rainfall has been high, the runoff from the catchment
area will contain high amounts of nitrogen compounds.
An increase in the amount of chlorophyll α can be seen from 1987 to 1999/2000. This is due
to improved lake water quality after the restoration. The low concentration in 2009 is due to
seasonal variation. During autumn the content of chlorophyll α will normally be lower than
during late summer.
The iron content in the lake water was not measured in 1987. The results from 1999/2000 and
2009 show that the iron content has not changed significantly during the years.
The sediment investigation before the restoration was done in 1990. The iron content as
measured to be low (0,5 – 7,3 g P/kg DS) but the phosphorus content was high. The relation
between iron and phosphorus was low, indicating that there is a possibility of phosphorus
exchange from the sediment into the lake water. In 1999/2000 the results from measurements
during the summer indicate that the same feature can possibly occur, however only in some
parts of the lake. Our measurements from 2009 indicate that the iron and phosphorus relation
is around 23:1, which indicate good binding of phosphorus to the sediment.
The amount of lead and nickel has decreased significantly since 1990 to around half of the
amount. Since our measurements of cadmium content are unreliable, a comparison with
earlier measurements cannot be done. A reduction in cadmium content can be seen from 1990
to 1999/2000, however the cadmium content was still high in 1999/2000 in comparison to the
limit value of 0,8 mg/kg DS.
The comparison of our results with previous analyses shall not be taken too seriously. There
are many factors that affect the results; sampling procedure, samplers and laboratory analysis
are only a few. When Ribe Amt performs assessments for lakes there are experienced
samplers performing the sampling and the analysis are performed by accredited laboratories.
76
The storage time for our samples was too long and this might also influence the accuracy of
the results.
77
9 CONCLUSION
The purpose of our project was to investigate the environmental state for the water quality in
Guldager Mølledam and Guldager Møllebæk. The parameters measured in assessing the
environmental state has been shortly described as well as their influence on the water quality.
The methods used to assess the lake and the stream has been discussed.
Guldager Mølledam used to be polluted with wastewater coming from the suburban area
Guldager. In 1987 the wastewater input was cut off and an environmental assessment of the
lake was performed. The results showed that the lake contained high amount of phosphorus
and heavy metals in the sediment, which resulted in the decision to restore the lake by
sediment removal. This restoration was performed in 1998/1999 and a new assessment was
done in 1999/2000. The results showed an improvement in the environmental state.
Based on the results achieved from our investigations, we have drawn the conclusion that the
environmental state of Guldager Mølledam has improved significantly. The amount of
phosphorus in the sediment is low and is mainly bound to iron. The cholorophyll α content in
the lake suggests that the trophic state of Guldager Mølledam is mesotrophic, and the results
from the Secchi depth as well as dissolved phosphorus indicates the same.
The environmental state of Guldager Mølledam has improved since 1999/2000. In 1999 the
amount of phosphorus in the sediment was still high in relation to the iron content, therefore
there was still a possibility of phosphorus leakage into the lake water. Our research showed
that the relationship between iron and phosphorus has improved significantly and if there are
no fluctuations in pH and oxygen content near the sediment surface, the phosphorus will stay
bound to the sediment.
The amount of total phosphorus can be used to assess the quality of the lake in accordance to
the Water Framework Directive. Our results for total phosphorus are not reliable, but if the
amount of ortho-phosphate is used, the ecological state of the lake can be considered as high.
The aim within the Water Framework Directive is that all lakes within Member States should
have a good ecological state before 2015.
The environmental state of Guldager Møllebæk was based on the Danish Stream Fauna
Index. The environmental state for the stream was assessed as good based on that the stream
had an index value of 4.
78
The results from our study only represents the time when it was performed, October 2009. In
order to make a more describing assessment of the environmental state for Guldager
Mølledam and Møllebæk, investigations should be made that covers the annual fluctuations.
This requires sampling throughout the year. The reliability of the results can be improved by
using standardized sampling methods, samplers as well as laboratory analysis.
79
REFERENCES
Addy Kelly, Green Linda and Hebron Elizabeth (2004). pH and Alkalinity, University
of Rhode Island, URL Watershed Watch, Kingston. Available at:
http://www.uri.edu/ce/wq/ww/Publications/pH&alkalinity.pdf [accessed 18/11/ 2009].
American Public Health Association (APHA), American Water Works Association
(AWWA), Water Environment Federation (WEF) (1992), Standard Methods for the
Examination of Water and Waste water, 18th
Edition. Edited by Greenberg, A, Clesceri,
S& Eaton, A.
ALMA, P. and ETHERIDGE, C. (1993) Environmental Concerns. Cambridge, UK:
University Press.
BIOLOGY ONLINE (2007) Macrophytes [WWW] Biology Online. Available at:
http://www.biology-online.org/user_files/Image/Biodiversity/macrophytes.JPG
[accessed 27/09/2009].
BRONMARK, C. and HANSSON, L. (2005) The Biology of Lakes and Ponds, 2nd
Edition. New York: Oxford Univeristy Press.
Boström, B., Jansson M. & Forsberg, C. 1982. Phosphorus release from lake sediments
Arch. Hydrobiol. Beih. Ergebn. Limnol. 18: 5–59.
Burns, N and Ross, C. Water quality Assessments. London. E & FN SPON. 1971
Byrun, S. Christine, M. Lowell, K. (2009) Understanding Lake Data. Wisconsin
Department of Natural Resources. RP-09-96-3M-275.
Carlson, R.E. and J. Simpson. 1996. A Coordinator’s Guide to Volunteer Lake
Monitoring Methods. North American Lake Management Society. 96 pp
Centre for Educational Technology 2004, Acid Mine Drainage: Conductivity. Available
at: http://www.cotf.edu/ete/modules/waterq3/WQassess3h.html [accessed 18/11/ 2009].
Cooke, G.G., Welch, E.B. 1993. Restoration and management of lakes and reservoirs, 2
nd edition, Lewis Publishers, Boca Raton, FL, USA
Csilla, S. Krisztina, B. Éva H.l and Padisák J Epiphytic, littoral diatoms as bioindicators
of shallow lake trophic status: Trophic Diatom Index for Lakes (TDIL) developed in
Hungary, Hydrobiologia, Springer Netherlands;
80
Available at: http://www.springerlink.com/content/mp300522v5816k71/
[assessed on 17/11/2007]
Danish Ministry of the Environment, 2007. Odense Pilot River Basin. Pilot project for
river basin management planning. Water Framework Directive Article 13. Layman’s
report. Available at: www.OdensePRB.ode.mim.dk. Accessed 6 November 2009.
DODDS, W. K. (2002) Freshwater Ecology: Concepts and Environmental
Applications. Academic Press.
DSFI (2009) Danish Stream Fauna Index Methodology. Available at http://www.eu-
star.at/pdf/DSFI_Methodology.pdf. [accessed on 16/11/2009]
ENVIRONMENT CANADA. (2005) Nitrate.[WWW] Environment Canada. Available
at: http://www.ec.gc.ca/ceqg-rcqe/English/Html/GAAG_Nitrate_WQG.cfm [accessed
01/10/2009]
Environmental Chemistry "by G. W. Van Loon and S. J. Duffy (2000) (Oxford Univ.
Press).
ETE (2004) Exploring the Environment, Water Quality Assessment: Chemical: Macro-
invertebrates; Available at: http://www.cotf.edu/ete/modules/waterq3/WQassess2a.html
[accessed on 07/11/2009]
European Communities. Water Framework Directive. Summaries of EU legislation,
1995 – 2009. Available at:
http://europa.eu/legislation_summaries/agriculture/environment/l28002b_en.htm.
Accessed 20 October 2009.
European Communities. Quality of Drinking water. Summaries of EU legislation, 1995
– 2009. Available at:
http://europa.eu/legislation_summaries/environment/water_protection_management/l28
079_en.htm. Accessed 20 October 2009.
European Communities. Bathing water. Summaries of EU legislation, 1995 – 2009.
Available at:
http://europa.eu/legislation_summaries/environment/water_protection_management/l28
007_en.htm. Accessed 20 October 2009.
European Communities. Urban waste water treatment. Summaries of EU legislation,
1995 – 2009. Available at:
81
http://europa.eu/legislation_summaries/environment/water_protection_management/l28
008_en.htm. Accessed 20 October 2009.
European Communities. Water suitable for fish-breeding. Summaries of EU legislation,
1995 – 2009. Available at:
http://europa.eu/legislation_summaries/environment/water_protection_management/l28
010_en.htm. Accessed 20 October 2009.
European Communities. Quality of shellfish waters. Summaries of EU legislation, 1995
– 2009. Available at:
http://europa.eu/legislation_summaries/environment/water_protection_management/l28
177_en.htm. Accessed 20 October 2009.
GVSU Grand Valley State University website. available at:
http://faculty.gvsu.edu/videticp/stratification.htm. [accessed 07/11/2009].
Jepsen & Pedersen, 2002. Søerne i Ribe Amt 1978 – 2000, Overvågning, tillstand og
udvikling. Teknisk rapport. Ribe Amt.
Kesab Water Care website, Macrophytes, Available at:
http://www.cwmb.sa.gov.au/kwc/programs/why_wetlands/5.html. [accessed on
09/11/2009]
LBK. 2004 Protection of Nature Act. Available at: http://faolex.fao.org/cgi-
bin/faolex.exe?rec_id=015538&database=FAOLEX&search_type=link&table=result&
lang=eng&format_name=@ERALL. Accessed 2 November 2009.
Lett Law Firm. 4.1. The Danish Planning Act. Available at:
http://www.lett.dk/doing_business_in_denmark/environmental_law/4.1_the_danish_pla
nning_act.aspx. Accessed 2 November 2009.
Lett Law Firm. 2.1. Environmental Protection. Available at:
http://www.lett.dk/doing_business_in_denmark/environmental_law/2.1_environmental_
protection.aspx. Accessed 26 October 2009.
Miljøministeriet. Danish Natura 2000 in figures. Updated 02.07.2007. Available at:
http://www.blst.dk/Natura2000plan/English/DK_Natura_2000_facts/. Accessed 1
November 2009.
Miljøsministeriet, 2000. The aquatic environment in Denmark 1996 – 1997.
Miljøstyrelsen, Environmental Investigations No. 4. Available at:
82
http://www2.mst.dk/common/Udgivramme/Frame.asp?http://www2.mst.dk/udgiv/public
ations/2000/87-7944-233-1/html/kap05_eng.htm. Accessed 26 October 2009.
MICHAUD, J. (1991) A Citizen's Guide to Understanding and Monitoring Lakes and
Streams. Washington: Envirovision. Available at: www.ecy.wa.gov/biblio/94149.htm.
[accessed on 29/09/2009]
NAPIER UNIVERISTY (2003) Eutrophication in: Aquatic Ecosystem Management.
[WWW] Napier Univeristy.Available at:
http://www.lifesciences.napier.ac.uk/teaching/EU/FWeu.html [accessed 27/09/2009].
NATURE REPORT (2008) Climate Change [WWW] Nature Report. Available at:
http://blogs.nature.com/climatefeedback/461pxPhytoplankton_SoAtlantic_20060215.jpg
[accessed 27/09/2009]
REYNOLDS, C. (2006) Ecology of Phytoplankton. Cambridge: Cambridge University
Press.
Ribe Amt. 1994. Guldager Mølledam – en tilstandsbeskrivelse. Esbjerg Kommune.
Ribe Amt. 1998. Restaurering af Guldager Mølledam, Projektbeskrivelse, Forslag.
Esbjerg Kommune.
SCHEFFER, M. (1997) The Ecology of Shallow Lakes. Dordrecht, The Netherlands:
Springer.
SCHMIDT-NIELSEN, K. (1997) Animal Physiology: Adaptation and Environment, 5th
Edition. Cambridge: Cambridge University Press.
SHAW, B. et al (2004) Understanding Lake Data. Wisconsin, USA: Cooperative
Extension Publishing.
SKRIVER, J., FRIBERG, N. and KIRKEGARD, J. (2001) Biological assessment of
running waters in Denmark: Introduction to the Danish Stream Fauna Index (DSFI).
Verhandlungen der Internationale Vereinigung für Theoretische und Angewandte
Limnologie, 27(4) , 1822-1830.
SOFTPEDIA (2009). Available at: http://news.softpedia.com/news/How-Many-Types-
of-Lakes-Do-You-Know-76308.shtml. [accessed 15/11/2009]
83
SOLER, A., et al. (1991) Changes in physico-chemical parameters and photosynthetic
microorganisms in a deep wastewater self-depuration lagoon. Water Research Journal
vol. 25 (pt.6) , 689 - 695.
SOMMER, U. (1989) Plankton Ecology: Succession in Plankton Communities. Verlag,
Berlin: Springer.
TAIT, R. V. and DIPPER, F. (1988) Elements of Marine Ecology: An Introductory
Course. Oxford: Butterworth-Heinemann.
UK ENVIRONMENT AGENCY (2009) Eutrophication in lakes in the North West
UK Environment Agency. Available at:
http://www.environmentagency.gov.uk/regions/northwest/346910/347005/1110630/111
0686/1116353/?lang=e [accessed 01/10/2009].
UNESCO/WHO/UNEP (1996) Water Quality Assessments: A guide to the use of Biota,
Sediments and Water in Environmental Monitoring. 2nd
Edition. E & FN Spon, London
US ENVIRONMENTAL PROTECTION AGENCY (2008a) Biological Indicators of
Watershed Health [WWW] United State Environmental Protection Agency. Available
at: http://www.epa.gov/bioiweb1/index.html [accessed 25/09/2009]
US ENVIRONMENTAL PROTECTION AGENCY (2008b) Great Lakes [WWW] US
Environmental Protection Agency. Available at: http://www.epa.gov/glnpo/atlas/glat-
ch4.html [accessed 29/09/2009].
US ENVIRONMENTAL PROTECTION AGENCY (2008c) Natural Process In the
Great Lakes [WWW] US Environmental Protection Agency. Available at: :
http://www.epa.gov/glnpo/atlas/glat-ch2.html [accessed 29/09/2009].
US ENVIRONMENTAL PROTECTION AGENCY (1997) Volunteer Stream
Monitoring: A Methods Manual. Pennsylvania: Diane Publishing.
US FOREST SERVICE (n.d.) Glossary [WWW] US Forest Service. Available at:
http://www.fs.fed.us/r9/chippewa/plan/revision/draft/deis/html/glossary.html [accessed
on 29/09/2009].
WAL (2009) Wisconson Association of Lakes. Available at:
http://www.wisconsinlakes.org/lake_types.htm [accessed 15/11/2009].
84
Water Framework Directive Information Centre. Monitoring requirements. Available at:
http://www.euwfd.com/html/monitoring_requirements.html. Accessed 20 October 2009
WELCH, E. B. and LINDELL, T. (1992) Ecological Effects of Wastewater: Applied
Limnology and Pollutant Effects. London: Taylor & Francis.
WETZEL, R. (2001) Limnology: Lakes and River Ecosystem, 3rd Edition. San Deigo,
California: Elsevier.
WILKES UNIVERSITY (n.d.) Total Phosphorus and Phosphate Impact on Surface
Waters [WWW] Center for Environmental Quality, Environmental Engineering and
Earth Sciences. Available at: http://www.water-research.net/phosphate.htm [accessed
29/09/2009].
Wikipedia,Invertebrates,Available from: http://en.wikipedia.org/wiki/Invertebrate
Source: http://www.uri.edu/ce/wq/ww/Publications/pH&alkalinity.pdf (November 18,
2009)
85
APPENDIX 1 1/2
Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000
Establishing a framework for Community action in the field of water policy, Annex V p. 42 –
43
86
APPENDIX 1 2/2
87
APPENDIX 2 1/3
MEASURING METAL AND PHOSPHOR CONCENTRATIONS IN SEDIMENT
USING ICP
Inductively coupled plasma atomic emission spectrometry (ICP AES) is used for qualitative
and quantitative measurements of elemental composition in samples. A plasma source is used
to excite atoms or ions in the sample to a higher energy level. When the atoms or ions return
back to their ground state they emit photons at a certain wavelength dependent on the
element. The light is recorded and based on that the content of the element in the sample is
calculated. The elements measured with the ICP AES in the sediment samples were: nickel,
cadmium, lead and phosphorus. The wavelengths used for Ni, Cd and Pb elements were:
231,604 nm, 228,802 nm and 283,306 nm respectively.
Pretreatment of samples
The samples were pretreated by taking approximately 1 gram of dry, grinded sample and
added into a 100 mL autoclave flask. There were altogether 12 samples. 20 mL of 7 M Nitric
acid was added. A blank sample was made that contained only 20 mL of 7 M Nitric acid. The
pre-treated samples together with the blank were put into the autoclave for 30 minutes at 200
kPa (120°C).
Preparation and analysis of samples and standards
The samples were then filtrated and diluted up to 50 mL. Standards for measuring the metals
were made by adding a stock solution, Multi-Element Standard. The concentration of the
standards were 1 ml/L, 2 mL/L and 10 mL/L. The blank contained 1% HNO3.The standards
were run through the ICP in order to make a calibration curve. When the calibration curve
was made, the samples were run through the ICP.
For measuring the amount of total phosphorus with the ICP, different standards has to be
made. The concentration for the standards were; 1 mg/L, 5 mg/L, 10 mg/L and 20 mg/L. The
standards were made with a stock solution containing 100 mg/L phosphors. Measuring
phosphorus with ICP requires a higher a high pearch. High pearch essentially means that
gaseous nitrogen is inserted to remove air that is contaminating measurements in low range.
The standards were first run through the ICP in order to make a calibration curve, afterwards
the samples were run through the ICP.
88
APPENDIX 2 2/3
Samples 1 A, 1 AA, 3 A, 3 AA, 3B and 3BB needed to be diluted since the measured results
were above the calibration curve. The samples were diluted by taking 1 mL of sample and
adding 5 mL of water.
Results
The results are presented in the table 1. Samples marked with a star (*) have been diluted an
additional time.
Table 1. Measurement results
Weight of P (mg/L) Amount of P
Sample ID sample (g) measured in g/kg dry stuff
Blank - 0,000 -
Std. 1 (1mg/L) - 1,000 -
Std. 2 (5mg/L) - 5,000 -
Std. 3 (10 mg/L) - 10,000 -
Std. 4 (20mg/L) - 20,000 -
Blank sample 0 -0,142 -
1A 1,0011 29,830 1,490
1AA 1,0019 27,990 1,397
*1A 1,0011 6,080 1,822
*1AA 1,0019 5,402 1,618
1B 0,9999 6,900 0,345
1BB 1,0009 6,903 0,345
2A 1,0035 6,266 0,312
2AA 1,0092 6,244 0,309
2B 1,0023 -1,832 -0,091
2BB 1,0024 0,490 0,024
3A 1,0005 20,580 1,028
3AA 1,0004 20,910 1,045
*3A 1,0005 4,029 1,208
*3AA 1,0004 4,159 1,247
3B 1,0006 43,990 2,198
3BB 1,0009 42,860 2,141
*3B 1,0006 8,577 2,572
*3BB 1,0009 8,294 2,486
89
APPENDIX 2 3/3
The letter A stands for the upper layer of the sediment and B for the bottom layer, AA and BB
are reference samples. The number 1 are samples taken from the middle of the lake, number 2
close to the inlet, and number 3 close to the outlet.
Discussion and Conclusion
The results obtained were fairly accurate and the procedure was easy to perform. The results
might be affected by the fact that the samples had been stored in an exicator with an open lid.
The reason why the lid had to be open was because the samples were hot when they were put
into the exicator. If the lid was not open it would have been impossible to take the samples
out without breaking the exicator. Due to this the samples might have been contaminated with
humidity in the air. The result from sample 2BB is not reliable since in every analyses that we
did there was something wrong with 2BB. 2BB is a reference sample of the bottom layer and
since the results are more reliable of 2B, the results from that shall be used.
90
APPENDIX 3 1/3
MEASURING METAL AND IRON CONCENTRATIONS IN SEDIMENT AND
WATER SAMPLES USING AAS
Atomic absorption spectrophotometry (AAS) is used for the determination of trace elements
in water samples and in acid digests of sediment. AAS determines mainly the presence of
metals in liquid samples such as iron, copper, aluminium, lead etc. In their elemental state,
metals will absorb ultraviolet light at a certain wavelength dependent on the metal. The
sample is aspirated into a flame and lightbeam with a certain wavelength goes through the
flame. The light passes the flame and goes into a monochrometer whereafter it goes onto a
detector. The detector measures the amount of light and based on that calculates the amount
absorbed by the sample. The content of iron was measured in the sediment and water samples.
The specific wavelength for iron was 248,3 nm.
Pretreatment of samples
Sediment samples
The samples were pretreated by taking approximately 1 gram of dry, grinded sample and
added into a 100 mL autoclave flask. There were altogether 12 samples. 20 mL of 7 M Nitric
acid was added. A blank sample was made that contained only 20 mL of 7 M Nitric acid. The
pre-treated samples together with the blank were put into the autoclave for 30 minutes at 200
kPa (120°C).
Water samples
The water samples from the lake, inlet and outlet stream were pretreated by taking 40-ml of
sample and inserting them into 100-ml autoclave bottles. 10-ml of concentrated Nitric acid
was added. The bottles were put into the autoclave for 30 minutes at 200 kPa in 120°C.
Preparation and analysis of samples and standards
Sediment samples
The same samples that were used for measuring with ICP were used, the ones that were
filtered and diluted up to 50 mL. Standards were made, having the concentrations 1mg/L, 5
mg/L and 10 mg/L. The stock solution for the standards was a standard iron solution
containing 1000 mg iron/L. The standards were run through the AAS in order to achieve a
91
APPENDIX 3 2/3
calibration curve. One sample was measured and the result was not within the calibration
curve, therefore was all samples diluted by taking 1 mL of sample and dilutes it up to 100 mL.
Water samples
The pretreated samples were directly analysed. Before analyzing the samples standards were
made having the concentrations of 1 mg/l, 5 mg/l and 10 mg/l. The standards were run
through the AAS and a calibration curve was obtained. The samples were then analysed by
the AAS.
Results
The results are presented in the table 1. The letter A stands for the upper layer in the sediment
and B for the bottom layer. The double letter combination represents the reference sample.
The sample ID number describes from where the sediment samples were taken, where 1 is at
the middle of the lake, 2 is close to the inlet, and 3 is close to the outlet.
Table 1. Measurement results for sediment samples
Table 2. Measurement results for water samples
Sample Weight of Fe (mg/l) Fe
ID sample (g) measured (g/kg DS)
1A 1,0011 5,22 26,06
1AA 1,0019 4,67 23,32
1B 0,9999 9,09 45,46
1BB 1,0009 9,19 45,92
2A 1,0035 3,02 15,06
2AA 1,0092 3,13 15,49
2B 1,0023 0,03 0,16
2BB 1,0024 0,34 1,72
3A 1,0005 4,74 23,67
3AA 1,0004 2,29 11,46
3B 1,0006 5,61 28,02
3BB 1,0009 8,26 41,27
92
APPENDIX 3 3/3
The values for the actual amount of iron was obtained by multiplying the measured value with
the dilution factor 1,25.
Discussion and Conclusion
The results obtained from the analysis seem to be rather accurate and the procedure for
analyzing the water samples was much easier than for the sediment samples. The sediment
samples needed to be diluted further whereas the water samples could be directly analyzed.
The sediment sample 2 shows deviating results compared to the rest of the samples, however
this was found in other analyses performed on the sediment samples. Sediment sample 2 had
very sandy soil and smelled of sulphur. The reason for deviating results might be due to the
grain size of the sample, perhaps the method used require finer grain size.
Sample Fe (mg/l) Fe
ID measured mg/l
Blank sample 0,22 0,28
Lake 1 0,39 0,48
Lake 2 0,37 0,46
Lake 3 0,33 0,42
Inlet 0,29 0,37
Outlet 0,34 0,42
93
APPENDIX 4 1/5
DIRECTIVE 2006/44/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL
of 6 September 2006 on the quality of fresh waters needing protection or improvement in
order to support fish life
94
APPENDIX 4 2/5
95
APPENDIX 4 3/5
96
APPENDIX 4 4/5
97
APPENDIX 4 5/5
98
APPENDIX 5 1/4
Acute toxicity test with marine Acartia Tonsa
Introduction
The experiment was performed on Acartia Tonsa which represents marine zooplankton. The
organism is well represented in Danish coastal waters and feeds on algal plankton. The
organisms are born and grown in the laboratory. Organisms older than ten days are applicable
for toxicity testing. The organisms are placed in seawater with different concentrations of
cupper. The lethal concentration (LC50) is evaluated by counting the amount of alive
organisms after 24 and 48 hours. The LC50 is then calculated based on this data.
Methodology
Preliminary testing
Preliminary testing is important in order to find the concentration range which is to be used in
the definitive test.
Four control samples was made that contained only 25 mL of seawater. Into each control
sample 5 organisms was added, making a total of 20 organisms in the control samples.
The concentration of cupper containing samples were; 0,3 mg/L, 0,6 mg/L, 0,9 mg/L and 1,2
mg/L. Two samples of each concentration were made. The concentration of the standard
solution used was 100 mg/L. The toxicant containing water was diluted to 50 mL for each
concentration. The concentration of the solution was achieved by performing the following;
0,3 mg/L: 0,3 mL of Cupper solution added into volumetric flask and diluted to 50
mL with seawater.
0,6 mg/L: 0,6 mL of Cupper solution added into volumetric flask and diluted to 50
mL with seawater.
0,9 mg/L: 0,9 mL of Cupper solution added into volumetric flask and diluted to 50
mL with seawater.
1,2 mg/L: 1,2 mL of Cupper solution added into volumetric flask and diluted to 50
mL with seawater.
25 mL of solution was added into plastic cups and the cups were marked according to
concentration. The pH and Oxygen content was measured in the lowest and highest
99
APPENDIX 5 2/4
concentrations. In order to continue with the test the pH had to be 7,8 ± 0,2 and the Oxygen
content had to be ≥ 7 mg/L. The values for pH and Oxygen in the lowest and highest
concentrations were 7,91 and 8,4 mg/L, 7,90 and 8,4 mg/L respectively.
Into each sample five organisms were added by using a small net in order to catch them, care
had to be taken since the animals are very fragile and if a body part breaks they might die.
There were altogether ten animals representing each concentration. The samples were placed
in a well ventilated cabin at 20°C. The organisms were counted after 24 and 48 hours.
Table 1. Results from the preliminary test.
The total amount of dead organisms in the control samples could not be above 2, therefore
were the results from the preliminary test not good. The reason for the dead animals in the
control samples might be due to careless handling of the animals. However based on these
results the concentration range for the definitive test was selected.
Definitive test
The concentration range for the definitive test was selected to be 0,1 mg/L, 0,2 mg/L, 0,3
mg/L and 0,5 mg/L. The samples were prepared in the same manner as for the preliminary
test, however in the definitive test four samples representing each concentration was made.
Concentration of Cu 24 h 48 h
Control A 4 3
Control B 4 3
Control C 4 4
Control D 4 4
0,3 A 1 0
0,3 B 2 0
0,6 A 0 0
0,6 B 0 0
0,9 A 0 0
0,9 B 0 0
1,2 A 0 0
1,2 B 0 0
Amount of alive
100
APPENDIX 5 3/4
Also four control samples were made containing only 25 mL of sea water. The concentrations
were prepared in the following manner;
0,1 mg/L: 0,1 mL of 100 mg/L Cu-standard diluted to 100 mL
0,2 mg/L: 0,2 mL of 100 mg/L Cu-standard diluted to 100 mL
0,3 mg/L: 0,3 mL of 100 mg/L Cu-standard diluted to 100 mL, and
0,5 mg/L: 0,5 mL of 100 mg/L Cu-standard diluted to 100 mL
25 mL of each concentration were added into plastic cups, the pH and oxygen was measured
in the lowest and highest concentrations. The pH value for the lowest concentration was 8,06
and oxygen content 8,3 mg/L. In the highest concentration the pH was 8,08 and the oxygen
content 8,3 mg/L. Five organisms of Acartia Tonsa was added into each sample, where 20
animals represented one concentration, five organisms were added into each control sample.
Results
The amount of survived animals was counted after 24 and 48 hours. The amount of alive
animals is shown in Table 2.
Table 2. Results after 24 and 48 hours.
The logarithmic curve drawn based on these results can be seen below. Based on the curve the
LC50 was calculated. The concentration for LC50 after 24 hours could be found at the
Time Concentration T P
h mg/L 1 2 3 4 %
24 0 5 5 5 5 20 0
0,1 4 5 5 5 19 5
0,2 4 1 2 3 10 50
0,3 3 2 2 2 9 55
0,5 1 1 2 1 5 75
48 0 4 4 5 5 18 10
0,1 3 5 3 5 16 20
0,2 2 1 0 1 4 80
0,3 1 1 2 2 6 70
0,5 0 0 0 0 0 100
Number of suvivors
101
APPENDIX 5 4/4
concentration 0,25 mg/L. The concentrations for LC50 after 48 hours was approximately 0,15
mg/L.
Figure 1. Curve drawn based on the results.
Discussion and Conclusions
The test results are not reliable since definitive test was based on the preliminary test. The
preliminary test was not reliable since more than 10 % of the organisms died after 48 hours,
however the concentrations that caused 100 % of the organisms to die could be seen from the
preliminary test. The explanation for the death of the organisms in the control samples could
be careless handling of the organisms when transporting them to the sample cups.
The definitive test showed more reliable results since the control samples were valid. The
reason why after 48 hours there was a decrease in the percentage of dead organisms between
concentrations 0,2 mg/L and 0,3 mg/L is a mystery. It might be explained by human error.
The test organisms are very small and not easy to distinguish in the sample cups therefore
there might have been a counting error. Since more than 50 % of the organisms had already
died the counting error does not effect the results for LC50.
102
Appendix 6 1/4
Calculations on Flow Measurements
Inlet
Assumed Profile of Guldager Møllebæk (cm)
Area A
Profile A: triangular (a=0.40m, h=0.31m)
= 0.40m. 0.31m = 0.062 m2 2 Velocity A: 22 revolutions per 50s. nA = 22 = 0.44 s−1
50 VA = 0.2303. nA + 0.040 = 0.141 m/s
Flow: QA = VA . AA = 0.141 m/s . 0.062 m2 = 0.0087 m
3/s ↔ 8.74 l/s
Area B
Profile B: triangular (a=0.80m, h=0.31m)
= 0.80m. 0.31m = 0.124 m2 2 Velocity B: 29 revolutions per 50s. nB = 29 = 0.58 s−1
50 VB = 0.2303. nB + 0.040 = 0.174 m/s
Flow: QB = VB . AB = 0.174 m/s . 0.124 m2 = 0.02156 m
3/s ↔ 21.56 l/s
103
Appendix 6 2/4
Outlet
Defined profile of Guldager Møllebæk (cm)
Area Calculation:
Aflow, total:
AFLOW: = 𝑎𝑟𝑐𝑐𝑜𝑠 1 −
𝑟 . 𝑟2 − . 2𝑟 − . 𝑟 −
AFLOW:= 𝑎𝑟𝑐𝑐𝑜𝑠 1 −0.28𝑚
0.40𝑚 . 0.40𝑚2 − 0.28𝑚. 2 . 0.40𝑚 − 0.28𝑚 . 0.40𝑚− 0.28𝑚
AFLOW: = 0.1568𝑚2
A2=A3:
A2=A3= a.b= 0.36𝑚 .0.10𝑚 = 0.036𝑚2
A4 = 𝑎𝑟𝑐𝑐𝑜𝑠 1 −
𝑟 . 𝑟2 − . 2𝑟 − . 𝑟 −
A4 = 𝑎𝑟𝑐𝑐𝑜𝑠 1 −0.08𝑚
0.40𝑚 . 0.40𝑚2 − 0.08𝑚 . 2 .0.40𝑚 − 0.08𝑚 . 0.40𝑚 − 0.08𝑚
A4 = 0.0262𝑚2
104
Appendix 6 3/4
A1 = A5 = 𝐴𝑓𝑙𝑜𝑤 ,𝑡𝑜𝑡𝑎𝑙 –𝐴2− 𝐴3−𝐴4
2 =
0.1568 –0.036− 0.036−0,0262
2 = 0.0294𝑚2
Flow:
Velocity 1: 49 revolutions per 50 seconds. → 𝑛1 = 49
50𝑠= 0.98𝑠−1
𝑣1 = 0.2303 .𝑛1 + 0.040
𝑣1 = 0.2303 . 0.98 + 0.040 = 0.266 𝑚/𝑠
Flow 1: 𝑄1 = 𝑣1 .𝐴1 = 0.266𝑚
𝑠. 0.0294𝑚2 = 0.0078
𝑚3
𝑠= 7.8 𝑙/𝑠
Velocity 2: 47 revolutions per 50 seconds. → 𝑛2 = 47
50𝑠= 0.94𝑠−1
𝑣2 = 0.2303 .𝑛2 + 0.040
𝑣2 = 0.2303 . 0.94 + 0.040 = 0.256 𝑚/𝑠
Flow 2: 𝑄2 = 𝑣2 .𝐴2 = 0.256𝑚
𝑠. 0.036𝑚2 = 0.009216
𝑚3
𝑠= 9.22 𝑙/𝑠
Velocity 3: 39 revolutions per 50 seconds. → 𝑛3 = 39
50𝑠= 0.78𝑠−1
𝑣3 = 0.2303 .𝑛3 + 0.040
𝑣3 = 0.2303 . 0.78 + 0.040 = 0.224 𝑚/𝑠
Flow 3: 𝑄3 = 𝑣3 .𝐴3 = 0.244𝑚
𝑠. 0.036 𝑚2 = 0.0081
𝑚3
𝑠= 𝑙/𝑠
105
Appendix 6 4/4
Velocity 4: 38 revolutions per 50 seconds. → 𝑛4 = 39
50𝑠= 0.76𝑠−1
𝑣4 = 0.2303 . 0.76 + 0.040
𝑣4 = 0.2303 . 0.76 + 0.040 = 0.215 𝑚/𝑠
Flow 4: 𝑄4 = 𝑣4 .𝐴4 = 0.215𝑚
𝑠. 0.0262𝑚2 = 0.056
𝑚3
𝑠= 5.6 𝑙/𝑠
Velocity 5: 36 revolutions per 50 seconds. → 𝑛5 = 36
50𝑠= 0.72𝑠−1
𝑣5 = 0.2303 .𝑛5 + 0.040
𝑣5 = 0.2303 . 0.72 + 0.040 = 0.206 𝑚/𝑠
Flow 5: 𝑄5 = 𝑣5 .𝐴5 = 0.206𝑚
𝑠. 0.0294𝑚2 = 0.0061
𝑚3
𝑠= 6.1 𝑙/𝑠
106
Appendix 7 1/4
DETERMINATION OF TOTAL PHOSPHOSPHORUS AND ORTHO-PHOSPHATE
IN WATER BY FIASTAR 5000
This application note describes a method for determination of total Phosphorus and
orthophosphate in various types of water in the following ranges:
0.01-1 mg/l PO4-P (400 l loop), linear calibration
0.5-5 mg/l PO4-P (40 l loop), linear calibration
The Orthophosphate present in the digested sample reacts with Ammonium Molybdate to
form heteropoly Molybdophosphoric acid which is reduced in a second step to
Phosphomolybdenum blue by Stannous Chloride in a Sulphuric acid medium. The heteropoly
compound formed has anintensive blue colour which is measured at 720 nm
Reagents
. Potassium Dihydrogen Phosphate, KH2PO4
. Sulphuric acid, conc. (H2SO4), =1.84 g/ml
. Ammonium Molybdate, (NH4)6Mo7O24 x 4 H2O
. Hydrazinium Sulphate, N2H6SO4 or
. DEHA (N,N-diethylhydroxylamine), C4H11NO, 97%
.Stannous Chloride, SnCl2 x 2 H2O
. Potassium persulphate, K2S2O8
. Sodium hydroxide, NaOH
. Disodium ethylene diamine tetra-acetic acid, Na2-EDTA, C10H12O8N2Na2
107
Appendix 7 2/4
other reagents prepared include
. Carrier solution 0.09 M Sulphuric acid
. Ammonium Molybdate reagent
. Stannous Chloride reagent
Digestion solution
. Sulphuric acid, 4M
. Stock standard solution, 100 mg/l PO4-P (stock A)
. Interim stock standard solution, 1 mg/l PO4-P (stock B)
. Calibrating solutions
The calibrating solutions were prepared for each working range, by diluting stock A and B as
shown in Table 1 and 2 respectively.
Table 1- Calibration Standard for working range 0.01-1 mg/l PO4-P
PO4-P concentration
(mg/l)
Volume interim
standard (Stock B)
(ml)
Volume stock
standard (Stock A)
(ml)
Final
Volume
(ml)
0 0 - 100
10 1 - 100
50 5 - 100
100 10 - 100
500 - 0.5 100
1000 - 1 100
108
Appendix 7 3/4
Table 2- Calibration Standard for working range 0.5-5 mg/l
PO4-P concentration
(mg/l)
Volume stock standard (Stock A)
(ml)
Final volume (ml)
0 0 100
0.5 0.5 100
1 1 100
2 2 100
3 3 100
5 5 100
The volume defined above were measured by pipette 100ml volumetric flasks and diluted to
volume with distilled water. The calibrating solutions were prepared fresh. All standards were
digested according to the digestion procedure.
Solution
65 g of sodium hydroxide, NaOH, and 6 g of Na2-EDTA C10H12O8N2Na4, were dissolved in
1000ml of water.
Apparatus
. Usual laboratory apparatus and
. FIAstar 5000 Analyzer unit
. Method cassette P with interference filters 720 nm and 1000 nm.
. Pipettes of nominal capacity 0.5-10 ml
. Autoclave
. Teflon digestion tubes, 50 ml
109
Appendix 7 4/4
Procedure
Sampling and sample preparation
The analysis was carried out a week after collection of sample. Phosphate is readily adsorbed
onto plastic surface. For this reason good quality borosilicate glass were used. All glassware
were cleaned and allowed to stand overnight with sulphuric acid, the rinsed with distilled
water and stored filled with distilled water.
Usually a distinction is made between total phosphorus and dissolved phosphorus, by using a
filtration step with a 0.45 m membrane filter.
The analysis was carried out two weeks after collection of the sample. Samples from the lake,
inlet and outlet stream were analyzed without the treatment of autoclave.The samples were
filtered through 0.45 m membrane filters for the analysis.
Digestion procedure
Using a pipette 15.0 ml sample or standard was measured into a digestion tube. 3 ml digestion
solution and 0.15 ml 4 M sulphuric acid were added. The solution was heated for 30 minutes
in an autoclave or boiled under pressure at 150-200 kPa, after which it was allowed to cool
and analyzed in the FIAstar analyzer unit. A blank solution (15ml of distilled water) was also
digested.
110
APPENDIX 8 1/1
Table 1: Water sampling from the boat. Lake middle and lake inlet sampling results.
Sample No Temp (°C) pH Conductivity (µS) Dissolved oxygen (mg/l)
Middle Mix 1 7.0 6.85 400 11
Middle Mix 2 7.5 6.9 401 10.9
Middle Mix 3 7.0 6.8 400 11
Lake inlet 1 6.9 6.92 400 8.4
Lake inlet 2 7.1 6.93 404 8.9
111
APPENDIX 9 1/3
DETERMINATION OF TOTAL NITROGEN AND NITRATE IN WATER BY
FIASTAR 5000
This application note describes the method for determination of total nitrogen and nitrate in
various types of water in the following ranges:
Range of calibration:
Total nitrogen: 0.1-5 mg/l N. (40 l loop), linear calibration.
Nitrate: 0.1-5 mg/l NO3-N (40 µl loop), linear calibration.
Method for total nitrogen determination:
The digested sample was mixed with a buffer solution. Nitrate was reduced to Nitrite in a
cadmium reductor. On the addition of an acidic Sulphanilamide solution, Nitrite formed from
reduction of Nitrate forms a diazo compound. This compound is coupled with N-(1-naphtyl)-
Ethylene Diamine Dihydrochloride (NED) to form a purple azo dye. This azo dye was
measured at 540 nm.
Method for nitrate determination:
The sample containing Nitrite/Nitrate was mixed with a buffer solution. Nitrate in the sample
was reduced to Nitrite in a cadmium reductor. On the addition of an acidic Sulphanilamide
solution, Nitrite initially present and Nitrite formed from reduction of Nitrate formed a diazo
compound. This compound is coupled with N-(1-naphtyl)-Ethylene Diamine Dihydrochloride
(NED) to form a purple azo dye. This azo dye was measured at 540 nm.
Reagents for nitrate:
Only reagents of recognized analytical grade and water according to grade 1 of ISO 3696
were used.
Sulphanilamide (4-aminobenzenesulfonamide), C6H8N2O2S
N-(1-naphtyl)-Ethylene Diamine Dihydrochloride , C12H14N2 x 2 HCl
Hydrochloric acid; HCl, 37%
112
APPENDIX 9 2/3
Sodium Nitrite, NaNO2, dried to constant mass at 150 °C
Sodium Nitrate, NaNO3, dried to constant mass at 105 °C
Ammonium Chloride, NH4Cl, dried to constant mass at 105 °C
Ammonia, NH4OH
Reagents for total nitrogen:
Only reagents of recognized analytical grade and water according to grade 1 of ISO 3696
were used.
Sulphanilamide (4-aminobenzenesulfonamide), C6H8N2O2S
N-(1-naphtyl)-Ethylene Diamine Dihydrochloride , C12H14N2 x 2 HCl
Hydrochloric acid; HCl , 37%
Sodium Nitrite, NaNO2, dried to constant mass at 150 °C
Sodium Nitrate, NaNO3, dried to constant mass at 105 °C
Ammonium Chloride, NH4Cl, dried to constant mass at 105 °C
Ammonia, NH4OH
Sulphuric acid, H2SO4
Sodium Hydroxide, NaOH
Potassium peroxodisulphate, K2S2O8, Analytical reagent grade. Containing not more
than 0.001% (m/m) nitrogen as impurity.
Boric acid, H3BO3
Glycine, H2NCH2COOH
Calibrating solutions for nitrate and total nitrogen
Table 1: Working range 0.1-5 mg/l NO3-N
NO3-N concentration (mg/l) Volume interim standard (ml) Final volume (ml)
0 - 100
0.1 0.5 100
0.5 2.5 100
1 5 100
2 10 100
5 25 100
113
APPENDIX 9 3/3
The calibrating solutions were prepared fresh:
Glycine solution, 200 mg/l expressed as N.
1.072 g of glycine (H2NCH2COOH), were dissolved in 800 ml distilled water in a
calibrated flask. This mixture was diluted to one litre with distilled water.
Glycine solution, 2 mg/l expressed as N.
We transferred 10 ml of glycine solution and diluted to 1000 ml. This reagent was
prepared fresh.
Apparatus for both, total nitrogen and nitrate determination.
FIAstar 5000 Analyzer unit.
Method cassette NO2/NO3 +interference filters M=540 nm and R=720 nm.
Prepacked reduction columns, part no. 5000 3139
Volumetric flasks, of nominal capacity 100 ml, 500 ml and 1000 ml.
Pipettes of nominal capacity 0.5-25 ml
pH electrode
Procedure
Sample aliquots used for analysis should be free from turbidity; consequently, we had
to filter it through a 0.45 m membrane filter.
Acidification of the samples with hydrochloric acid to approximately pH 2. Storage at
2-5 C for not more than 24 hours.
Starting of FIA 5000, PC and Software.
Verification that correct method cassettes and corresponding detector filters were
installed.
Start of pump/s and pumping of distilled water through each unit and check the flow.
Start of pumping the reagents. The method selector was in the NO2 position for both
measurements.
When the system was filled with liquid, we turned the method selector to NO2+NO3.
Pumped until all the air in the by-pass tube was gone, stopped the pumps and removed
the by-pass tube.
Installation of the Cadmium reductor and starting of the pumps.
Loading of the method in the software; verification that the correct sample loop was
installed.
Loading the Sampler with the samples and drawing Sample List in the Software.
We loaded the calibration standard/s on the Sampler and made a few Test Injections of
one of the standards to verify that the system was equilibrated. Furthermore, we
checked the efficiency of the cadmium redactor.
Finally, the calibration was checked and the sample list started.