Field Methods of Monitoring Aquatic Systems Unit 1 – Water Analysis and Sampling Copyright © 2011...
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Transcript of Field Methods of Monitoring Aquatic Systems Unit 1 – Water Analysis and Sampling Copyright © 2011...
Field Methods of Monitoring Aquatic Systems
Unit 1 – Water Analysis and Sampling
Copyright © 2011 by DBS
Distribution of Earth’s Water
Source: http://ga.water.usgs.gov/edu/waterdistribution.html
Purified via hydrologic cycle
Purified via percolation
Est. adequate water to support 20-40 billion
Still shortages due to spatial availability
Question
Write down some of the constituents found in natural river water
Ions derived from commonly occuring inorganic salts, e.g. Na+, Ca2+, Cl-, SO4
2-
Transition metal ions derived from less commonly occuring salts
Insoluble solid material, either from plants or particles from geological weathering
Soluble or colloidal compounds from decomposition of plants
Dissolved gases
Water Quality Parameters
Water properties and processes
Ions Found in Natural Waters
Conc. Range
(mg L-1)
Cations Anions
0-100 Ca2+, Na+ Cl-, SO42
-, HCO3-
0-25 Mg2+, K+ NO3-
0-1 Fe2+, Mn2+, Zn2+ PO43-
0-0.1 Other metal ions NO2-
Reeve, 2002
Ariola et al, 2004
Rain water
mg L-1
River water
mg L-1
Sea water
g l-1
similar
Ca2+/Cl-
Cl-/SO42-
Gibbs, 1970
Composition of Water is Never Static
• Weathering of rocks• Sedimentation of suspended
material• Effect of aquatic biota• Aeration• Volatilization/evaporation• Additional water volumes
River Example
Question
How would you expect the composition of groundwater to be different from surface water?
Could be more concentrated in salts leached from mineral deposits. Percolation through organic material can lower oxygen content
Primary Water Quality Standards
• EPA sets Maximum Contaminant Levels (MCL)• Primary: health hazards• Secondary: aesthetic qualities• NB: also includes organics
Inorganic Contaminant
MCL)(mg/L)
Sb 0.006
Asbestos 7 MFL
As 0.01
Ba 2
Be 0.004
Cd 0.005
Cr 0.1
Cu 1.3
CN- 0.2
F- 4
Pb 0.015
Hg 0.002
Ni 0.1
NO3- 10
NO2- 1
Se 0.05
Tl 0.002
Source: http://www.epa.gov/safewater/mcl.html
MO Contaminant MCL
Total Coliform 5%
Fecal coliform 0 per 100 mL
Giardia lambia 0 per 100 mL
Viruses 0 per 100 mL
+ organics and radionuclides
Secondary Water Quality Standards
Secondary: aesthetic qualities – taste, corrosion, staining
Source: http://www.epa.gov/safewater/mcl.html
Contaminant MCL
(mg/L)
Al 0.05-0.2
Cl- 250
Cu 1.0
F- 2.0
Na+ 20
Soaps/detergents 0.5
Fe 0.3
Mn 0.05
pH 6.5-8.5
Ag 0.10
SO42- 250
TDS 500
Zn 5
Water Qualityexample records
e.g Moon Twp 2005
Summary of Course
• We will be measuring a variety of parameters, e.g.– TDS– DO– Col. Bacteria– pH and alkalinity– Anions: F-, Cl-, NO3
-, SO42-, PO4
3-
– Cations: Na, Ca, Mg
• Goals– Design a sampling plan– understand the chemical principles used– Critically evaluate and interpret data– Write a report that effectively conveys the data to the outside world
Question
Decode the following lab notebook page
Sampling
Objective:
Collect a portion of material small enough in volume to be transported and large enough for analysis while still accurately representing the material being sampled
Representative Samples
Environment is variable (sampling strategy needs to account for this)
– no two organisms exposed in exactly the same way
– day/night cycling of factories
– hour by hour, day by day, seasonal e.g. NO3
- in river water
Different results would be found a few km downstream due to physical, chemical and biological transformations
Lab or Field Analysis?
What are the relative merits of lab and field analyses?
Lab
Pros: analyses performed under optimum conditions, leading to maximum accuracy, precision will also be maximized
Cons: transport, time delay in getting results, changes to sample during storage, cost to operate lab
Field
Pros: instantaneous results, no errors due to storage, possible to analyze in-situ, possible to use continuous monitoring
Cons: conditions may not be optimum, lower precision and accuracy,
Question
Can you guess which of the following determinations are best made in the lab or in the field?
Nitrate, metals, temperature, pH, DO
Field
Temperature
pH
DO
Lab
Metals
Nitrate
Organics
Quality
• How to produce an accurate analysis?– Sampling should produce a representative sample– No contamination or change during storage– No contamination in laboratory or during analysis– Losses on extraction, separation and concentration
minimized– No interferences from other components– Results calculated correctly and archived for future
reference
Types of Sampling
• Judgmental– Not representative– Worst or best case scenario
• Systematic– Division of site into grids
• Random– No pattern or reason
Kegley, 1998
Sampling Devices
Van Dorn Sampler
Grab - bucket, bottle, bag, messenger (Niskin, Kemmerer or Van Dorn type), peristaltic pump Depth Integrating – verical water column
Automated – remove samples at fixed intervals
Container Choice
• Plastic is typically used• Glass – hard glass (Pyrex) recommeded for all
organics• Amber Glass – recommended for light-sensitive
compounds• 1 L sample necessary for most analyses
See p1-33 of Standard Methods Book
1-33
Standard Methods (1998)
Technique
• Fill without pre-rinsing with sample(may bias results)
• To fill or not to fill?– Organics – full– Inorganics and MO – space left for mixing
• Trace levels need special precautions• Metals require total or dissolved fractional sampling, must be
filtered immediately through 0.45 micron filters• Composite samples are not recommended for many analytes
due to instability
Bottle Technique
Source: http://www.epa.gov/volunteer/stream/vms50.html
Leave a space
Replicates
• Contaminated equipment or poor lab technique can give unexpectedly high or low results
• Could be ‘real’ but no way to know• Bottles may break or leak, not
possible to sample again under the same conditions
• May not be critical at all locations, especially inportant at inflows and outflows
• Planning is important!
Blanks
• Ensure samples are representative of the site
– no contamination
– are all pure DI water
Type Contaminant Procedure
Field air exposed to air at site
Trip container taken to site but not opened
Equipment sampling equipment rinsing solution
Background sample
- taken near site
Don’t forget also need reagent blanks during analysis!
Preparation: Acid Washing
• Inspect glassware
• If very dirty – No-chromix (H2SO4 + ammonium persulfate) and rinse
• Soap and water + scrubbing brush
• Rinse all surfaces with 25 mL 8 M HNO3, Rinse all surfaces with 25 mL 1.2 M HCl
• Rinse with DI 3 times
500 mL bottle500 mL filter flask10, 50, 100 mL cylinders100 mL volumetric flask
DO NOT REUSE RINSE WATER
Storage
• Concentration of species to be analyzed should remian unchanged during transportation and storage
• Potential problems– Volatile, degradable or reactive
species– Adsorption onto containers– Leaching from containers
• Storage before filtration should be at 4 °C no more than 2 days
• Storage after filtration should be at 4 °C no more than 30 days
Examples
NO3- - stored at 4 °C to lower MO
degradation
Pesticides - store in dark to avoid decomposition by light
Metals - acidify to prevent adsorption
BOD - no preservation is possible
Example Strategy
• What analyses are required?– Analytical technique affects size, bottle type, storage method– Is sufficient lab time available for analysis? (preservation kept to minimum)
• Decide on a programme– Variation may be periodic– Sources of pollution - site history– Effects of dilution - location of inflows and outflows, natural variations– No. of samples and timing of sampling is affected
• Decide no. of samples (see 1-31)– Each location should be done in duplicate– Take into consideration time required for analyses– Statistical treatment requires sufficient numbers of samples
• Decide location and apparatus– Ease of access, weather may not be perfect– Topography - a map is useful, bathymetrical survey for deep sampling– Composite or individual samples? Surface, sub-surface, integrated?
• Decide sample volume and container type– Volatiles/gases container must be full, others better if container not full – Check for contamination in apparatus
• Decide on storage method
What Analyses are Required?
Source Common Pollutants
Cropland Turbidity, phosphorus, nitrates, temparature, total solids
Forestry harvest Turbidity, temperature, total solids
Grazing land Fecal bacteria, turbidity, phosphorus, nitrates, temperature
Industrial discharge Temperature, conductivity, total solids, toxics, pH
Mining pH, alkalinity, total dissolved solids
Septic systems Fecal bacteria (i.e., Escherichia coli, enterococcis), nitrates, phosphorus, dissolved oxygen/biochemical oxygen demand, conductivity, temperature
Sewage treatment Dissolved oxygen and biochemical oxygen demand, turbidity, conductivity, phosphorus, nitrates, fecal bacteria, temperature, total solids, pH
Construction Turbidity, temperature, dissolved oxygen and biochemical oxygen demand, total solids, and toxics
Urban runoff Turbidity, phosphorus, nitrates, temperature, conductivity, dissolved oxygen and biochemical oxygen demand
Monitoring Discharges to Rivers
Samples should be taken downstream for the discharge to be completely mixed
Source: Reeve, 2002
Question
What variation would you expect in concentrations of DO and NO3
-?
O2 produced by photosynthesis in daytime, continuously consumed by oxidation of organics. Continuous input from atmosphere. Drop at night is expected
NO3- more complicated. If no inputs it would decrease in
spring and increase in winter. May be increased by fertilizer inputs
Text Books
• Artiola, J.F., Pepper, I.L., and Brusseau, M. (2004) Environmental Monitoring and Characterization. Elsevier, Amsterdam.
• Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., eds. (1998) Standard Methods for the Examination of Water and Wastewater, 20th Edition. Published by American Public Health Association, American Water Works Association and Water Environment Federation.
• Kegley, S.E. and Andrews, J. (1998) The Chemistry of Water. University Science Books.
• Narayanan, P. (2003) Analysis of Environmental Pollutants : Principles and Quantitative Methods. Taylor & Francis.
• Keith, L.H. and Keith, K.H. (1996) Compilation of EPA's Sampling and Analysis Methods. CRC Press.
• Nollet, L.M. and Nollet, M.L. (2000) Handbook of Water Analysis. Marcel Dekker.
• Reeve, R.N. (2002) Introduction to Environmental Analysis. Wiley.
• Rump, H.H. (2000) Laboratory Manual for the Examination of Water, Waste Water and Soil. Wiley-VCH.
• Van der Leeden, F., Troise, F.L., and Todd, D.K. (1991) The Water Encyclopedia. Lewis Publishers.
Natural Constituentstypical analysis
Constituent Major Sources Conc. (mg/L) Issues
CO32- Limestone, dolomite SW: 0
GW: <10
CaCO3 scale retards heat and liquid flow in pipes
HCO3- < 500
> 1000 with excess CO2
SO42- Oxidation of sulfide ores,
gypsum, industrial wastes< 1000
~ 200,000 in brines
CaSO4 similar to above
> 500 bitter taste
> 1000 cathartic
Cl- Weathering of edimentary and igneous rocks
< 10 in humid regions
200,000 in brines
> 100 salty taste
> Physiological damage
F- Amphiboles, apatite, fluorite, mica
GW: < 10
SW: < 1.0
Up to 1600 in brines
0.6 – 1.7 beneficial
> 1.5 ‘mottled enamel’
> 6 disfiguration
NO3- Atmosphere, legumes, plant
debris, animal waste, fertilizersSW: 1.0 - 5.0
GW: up to 1000
> 100 bitter taste
> 45 methemoglobinemia
Kegley, 1998 Appendix A
Natural Constituentstypical analysis
Constituent Major Sources Conc. (mg/L) Issues
Dissolved solids Minerals SW: < 3000
GW: < 5000
> 500 undesirable for drinking
< 300 manufacturing
Silica (SiO2) Feldspars, ferromagnesium and clay minerals, amorphous silica, chert, opal
1.0 - 30 (sometimes 100) With Ca and Mg scale retards heat and liquid flow
Fe Igneous rocks, sandstone rocks
Objects made from cast iron or stell
< 0.50
pH < 8 ~ 10
> 0.1 ppts with air contact Stains, bad taste, discolors
Mn Soils and sediments, metamorphic and sedimentary rocks
< 0.20
GW: 10
> 0.2 ppts with air contact
Stains, bad taste, builds up in pipes
Natural Constituentstypical analysis
Constituent Major Sources Conc. (mg/L) Issues
Ca Amphiboles, feldspars, gypsum, clay minerals etc.
As much as 600 in W streams
Scale retards heat, combine with fatty acid ions to form suds
Mg has a laxative effectMg Amphiboles, olivine, pyroxenes, dolomite, magnesite, clay minerals
Several hundred in W streams
Na Feldspars, clay minerals, evaporites
Up to 1000 in W streams > 50 with suspended solids causes foaming accl. Scale formation
> 65 Na causes problems with ice manufactureK Feldspars, feldpathoids,
clay minerals< 10