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Transcript of Investigation the heavy metal contents in surface water and sediment collected
Phetdalaphone BOUTTAVONG 2009-2011
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VIETNAM NATIONAL UNIVERSITY, HANOI
VNU UNIVERSITY OF SCIENCE
PHETDALAPHONE BOUTTAVONG
INVESTIGATION THE HEAVY
METAL CONTENTS IN SURFACE WATER AND
SEDIMENT COLLECTED IN THADLUANG
MARSH (LAO PDR)
MASTER THESIS
HANOI, 2011
Phetdalaphone BOUTTAVONG 2009-2011
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VIETNAM NATIONAL UNIVERSITY, HANOI
VNU UNIVERSITY OF SCIENCE
PHETDALAPHONE BOUTTAVONG
INVESTIGATION THE HEAVY METAL
CONTENTS IN SURFACE WATER AND SEDIMENT
COLLECTED IN THADLUANG
MARSH (LAO PDR)
MASTER THESIS
Supervisor: Assoc. Prof. PhD. Ta Thi Thao
HANOI, 2011
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Abstract
In Vientiane, water and sanitation management in the urban area is experiencing
stagnant pollution. Unsanitary conditions and threat of seasonal pollution in selected
spots is likely to occur and increase with the growing urban population. The
sanitation system entails an on-site disposal of human waste without introduction of
full water-borne sewerage with treatment facility and safe disposal arrangement. The
majorities of households relies on water flush latrines and are connected to a pit or
chamber for containment of excreta. However, due to the low permeability of the soil
and the high groundwater table around Vientiane, many soak-a-ways fail to operate
effectively resulting in discharge of sewage from tanks into drainage channels or low
lying areas. This pollution leads to effluent overflows, environmental degradation
and health hazards.
For the sake of assessment in what extent is water polluted, an analytical method
with high sensitivity and the capability and providing a good accuracy and precision
should be used. Atomic absorption spectroscopy (AAS) is a spectroanalytical
procedure for the qualitative and quantitative determination of chemical elements
employing the absorption of optical radiation (light) by free atoms in the gaseous
state. In analytical chemistry the technique is used for determining the concentration
of a particular element (the analyte) in a sample to be analyzed. The technique makes
use of absorption spectrometry to assess the concentration of an analyte in a sample.
My study focuses on heavy metals content in surface water and sediment collected in
ThadLuang Marsh in Vientiane Capital City. Providing an overview about
alarmingly polluted situation, this research based on determination of Copper, Lead,
Cadmium and Zinc by Flame – Atomic absorption spectroscopy.
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Acknowledgements
I would like to thank, DAAD, Deutscher Akademischer Austauschdienst (German
Academic Exchange Service) and Technich University Dresden for providing the
scholarship of the Master’s program. My sincere thanks also due to the Dean of
faculty Environmental of sciences in National University of Lao P.D.R for the kind
permission offered me to study.
Thank Assoc. Prof. Dr. Ta Thi Thao - my supervisors for encouragement,
constructive guidance's
I would like to express the profound gratitude and the great appreciation to my
advisor Prof. Bernd Bilitewski for his excellent guidance, excellent encouragement
and valuable suggestions throughout this study. Special appreciation is extended to
Prof. Dr. Nguyen Thi Diem Trang and Prof. Dr. Do Quang Trung committee
members for their valuable recommendation and dedicated the valuable time to
evaluate my work and my study during being in Vietnam.
During studying in Hanoi University of Science, I felt very lucky, it give me the
opportunity to have lots of good friends, good memories, so I would like to say
thanks and pleasure to meet all of you. Even though we came from different
countries, we can make friend together. I hope and wish that I would work together
and meet each other again in some conferment.
Finally I would like to express deep appreciation to my lovely family and relatives
for their love, kind support, and encouragement for the success of this study. This
thesis is dedicated for you.
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Contents List of Figures .............................................................................................................. 7
List of Tables ................................................................................................................ 8
List of Abbreviations .................................................................................................... 9
INTRODUCTION ...................................................................................................... 10
CHAPTER 1: OVERVIEW OF WATER AND SEDIMENT POLLUTION IN
THADLUANG MARSH............................................................................................10
1.1. Topography of ThadLuang marsh ................................................................... 13
1.2. Present status of water and sediment pollution in ThadLuang marsh ............. 14
1.3. Toxicity of Cadmium Cd, Copper Cu, Lead Pb, Zinc Zn ................................ 16
1.3.1. Cadmium Cd .............................................................................................. 16
1.3.2. Copper Cu .................................................................................................. 17
1.3.3. Lead Pb ...................................................................................................... 18
1.3.4. Zinc Zn ...................................................................................................... 20
1.4. Analytical methods for determination of heavy metals in water and sediment
samples .................................................................................................................... 22
1.4.1. Electrochemical methods ........................................................................... 22
1.4.2. Spectrophotometric methods ..................................................................... 24
CHAPTER 2: EXPERIMENTS ................................................................................. 28
2.1. Research Objects and research contents .......................................................... 28
2.1.1. Research objects ........................................................................................ 28
2.1.2. Research contents ...................................................................................... 28
2.2. Chemicals and Apparatus ................................................................................ 29
2.2.1. Chemicals .................................................................................................. 29
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2.2.2. Apparatus ................................................................................................... 29
2.2.3. Equipments ................................................................................................ 30
2.3 Sampling and Sample Preparation .................................................................... 30
2.3.1. Study Area ................................................................................................. 30
2.3.2. Sampling and sample preparation ............................................................. 35
2.3.3. Sediment samples ...................................................................................... 35
2.4. Analytical methods for determination of Cu, Pb, Cd, Zn ................................ 36
2.4.1. Flame atomic absorption spectroscopy method (F-AAS): determination of
heavy metal content in sediment samples ........................................................... 36
2.4.2. Inductive couple plasma – mass spectrophotometry (ICP-Ms) for the
determination of heavy metal contents in surface water samples ....................... 40
2.4.3. Quality control of analytical methods ....................................................... 43
CHAPTER 3: RESULTS AND DISCUSSION ......................................................... 45
3.1. Optimizations of some chemical factors influencing to absorbance in F- AAS
method ..................................................................................................................... 45
3.1.1. Study the effects of sample matrix and matrix modifier to F-AAS .......... 45
3.1.2. Calibration curves of Pb, Cd, Zn and Cu measurements. .......................... 49
3.1.3. Limit of detection (LOD) and Limit of quantitation (LOQ) ..................... 53
3.1.4. Effect of interferences to the determination of Pb, Cd and Cu, Zn by
FAAS. .................................................................................................................. 54
3.2. Determination of Pb, Cu, Zn, Cd in surface water samples using ICP-MS .... 57
3.2.1. Calibration curves for the determination of Cu, Zn, Pb and Cd in water
samples. ............................................................................................................... 57
3.2.2. Method validation ...................................................................................... 59
3.3. Total concentrations of Cu, Pb, Cd, Zn in surface water and sediment of
ThadLuang marsh ................................................................................................... 60
3.3.1. Water sample: ............................................................................................ 60
3.3.2. Sediment sample ........................................................................................ 60
3.4. Application of GIS to find out spartial distribution of heavy metals .............. 64
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CHAPTER 4: CONCLUSION .............................................................................. ….66
REFERENCE..............................................................................................................65
List of figures
Figure 1.1: Target Villages around ThadLuang Marsh
Figure 2.1: Spectrometer atomic absorption novAA 6800, Shimazhu
Figure 2.2: The map of Thatluang marsh showing water sampling sites.
Figure 2.3: The map of Thadluang marsh showing sediment sampling sites.
Figure 2.4: Operation principle of an atomic absorption spectrometer
Figure 2.5: Block diagram of atomic absorption spectrometer
Figure 2.6: Instrumentation for low-resolution ICP-MS.
Figure 3.1: The investigation of linear ranges for the determination of Pb, Cd, Zn and
Cu using F-AAS
Figure 3.2: The calibration curves for the determinations of Pb, Cd, Zn and Cu in
standard solutions
Figure 3.3: Calibration curves for the determination of Cu, Cd, Pb and Zn using ICP-
MS.
Figure 3.4: The Map of water quality of Thadluang Marsh.
Figure 3.5: The Map of sediment quality of Thadluang Marsh.
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List of tables
Table 1.1: Some data published on pollution in ThadLuang marsh
Table 2.1: Characteristics of the sampling points in Thadluang marsh
Table 2.2: Characteristics of the sediment points in Thadluang marsh
Table 2.3: The optimal conditions of F-AAS for measuring Pb, Cd, Zn, Cu
Table 2.4: The experimental conditions for determination of Cu, Pb, Cd and Zn using
ICP- MS techniques
Table 3.1: Investigation of HNO3 and NH4CH3COO effects on analysis of Pb, Cd, Cu
and Zn
Table 3.2: Two - way ANOVA table for evaluating effects of HNO3 and
NH4CH3COO
Table 3.3: Influence of types of acid media HCl, HNO3 and H2SO4 effects on Cu2+
and Pb2+
analysis
Table 3.4: The absorbance of each metal atom (after subtracting the absorbance of
the blank solution) vs. their concentrations
Table 3.5: The absorbance of each heavy metal standard solutions in the linear range
of concentrations
Table 3.6: LOD and LOQ of the determination of Pb, Cd, Zn and Cu using F-AAS
method
Table 3.7: Result of errors and repeatability of the measurements
Table 3.8: Accuracy and recovery of CRM using FAAS and ICP-MS
Table 3.9: The concentration of Pb, Cd, Zn, Cu in surface water samples of
ThadLuang Marsh (g/L)
Table 3.10: Heavy metal content (mg/kg) in sediment collected in Thadluang marsh.
Table 3.11: Proposed Surface Water Quality standard
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List of abbreviations
Lao PDR The Lao People’s Democratic Republic
EDTA Ethylene-diamine-tetracetic acid
DME Dropping mercury electrode
SMDE Static mercury drop electrode
AES Atomic emission spectroscopy
F-AAS Flame Atomic absorption spectroscopy
ICP-Ms Inductive couple plasma – mass spectrophotometry
ANOVA The analysis of variance
LOL The limit of linearity
LOD Limit of detection
LOQ Limit of quantitation
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INTRODUCTION
The Lao People’s Democratic Republic (Lao PDR) is a small landlocked and
sparsely populated country in the South East Asia. Laos is characterized by two main
geographical zones: the central plains along the Mekong River and the mountainous
regions to the north, east and south. Lao PDR has a land area of 236,800 square
kilometers (sq. km.). It is long and slender, the length from north to south is nearly
1,000 kilometers and the width has only 150 kilometers to 400 kilometers. [STEA,
2004] The total population is approximately 5,621,982 people, in which women
accounted for 51%, according to the 2005 population and housing census. The
population density of the country is around 24 people per hectare which is the lowest
population densities in Asia. 39% of Lao population is classified as poor and 36% are
under poverty line. [MRC, 2006] Their living condition depends on nature, hunting
wildlife, foraging for forest products and practicing slash and burn cultivation for
their crops with a low profit in order to survive.
Lao PDR has rich water resources, mainly good quality fresh water. The amount of
average water flow in the Mekong and its tributaries amount to about 8,500 m3/s.
Currently most of the water occurs in the agricultural sector, for instance, irrigation,
fisheries, plantations and livestock watering. 60 percent of urban population and 51
percent of rural population has access to clean water. [Draft Agreement, March 2009]
The total of annual water flow in Lao PDR is estimated at 270 billion cubic meters,
equivalent to 35% of the average annual flow of the whole Mekong Basin. The
monthly distribution of the flow of the rivers in Lao PDR closely follows the pattern
of rainfall: about 80% during the rainy season (May-October) and 20% in the dry
season, from November to April. For some rivers in the central and southern parts of
the country (particularly Se Bang Fai, Se Bang Hieng and Se Done) the flow in the
dry season is less: around 10 to 15% of the annual flow. [Agricultural Statistics
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[April 2005]. The rivers outside the Mekong Basin flow through Viet Nam into the
South China Sea. These rivers are Nam Ma, Nam Sam, and Nam Neune. The limited
information on these rivers restricts assessment of their potential.
Most of the water use occurs in the agricultural sector such as irrigation, fisheries,
plantations and livestock watering. In addition the water is used for hydro-power; the
country has the potential to produce 23,000 megawatts of electricity. Currently 5% of
that capacity has been exploited. [Would Back, 2007] The plenteous supply of water
in Lao PDR, especially in the rainy season, provides good condition for water
transport, industrial development and water supply. Sixty percent of urban
population and 51 % of rural population has access to clean water.
Currently there are some problems related to waste and polluted water in major urban
areas from varied community use (residential density, hotels, hospitals and
entertainments centers). In addition there is water pollution from agricultural and
industrial sectors, including mineral exploitation. This is not a major problem now,
but the problem could escalate. The degradation of natural water and water
catchments from sedimentation, land erosion and drying out continues.
However, as continued development takes place in all of these areas, increasing
scarcity and competition for water can be expected. Increasing impacts of
development on water quality and on human health and the natural environment will
also take place. Finally, floods and drought can have serious negative impacts and
may, in fact, increase as climate change takes place.
Vientiane Capital is located on an alluvial plain along the left bank of Mekong River
east to west. The area of Vientiane is about 3,920 km2 and the elevation of the ground
ranges from 160 m to 170 m above the sea level. The city comprises 9 districts;
Chanthabuly, Hadxayfong, Meungparkngum, Naxaithong Sangthong, Sikhottabong,
Sisattanak, Saysettha and Xaythany. The population is around 672,912 people. The
area designated for urbanization extends along the left bank of Mekong River and
occupies an area of 210 km2. [JICA, 2009] For Thadluang wetland, its water quality
is a part of the water quality-monitoring project of Mekong Secretariat, in the vicinity
of Vientiane Capital City. Main problems found are wastewater and sewage (from
the city area) discharged into the marsh.
Especially, no sooner do many factories appear and develop increasing fast than
water is polluted by heavy metals is over allowable limit. Owing to not taking part in
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biochemical process, heavy metals such as Cd, Pb, Zn, Cu … are accumulated in
human body, which leads to harmfulness for organism. The fact that water is polluted
by heavy metal is often seen in rivers near industrial area, big cities and minerals
exploiting area. The main reason leading to heavy metals pollution is pouring into
water environment a large amount of industrial and untreated wastewater. Pollution
by heavy metals accumulated through foods directly into organism has negative
effects on life environment. In order to reduce consequence of this problem, it is
necessary to cultivate measures of water treatment.
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CHAPTER 1: OVERVIEW OF WATER AND SEDIMENT
POLLUTION IN THADLUANG MARSH
1.1. Topography of Thad Luang marsh
The ThadLuang Marshland is the largest remaining wetland in Vientiane
Municipality, located on the eastern edge of the capital city of Lao PDR. The marsh
itself is approximately 20 km2 and is a part of the ThadLuang Basin drained from
Vientiane City and surrounding areas. A large portion of the wetland has been
converted to rice cultivation although changes in water regimes have resulted in
annual floods and cultivation has been limited to between 700 - 1000 ha
(approximately half of the wetland area) in recent years. The remaining area is
covered with permanent and seasonal aquaculture ponds, shrub and grassland, and
peat land. [NUOL, March, 2002] Water draining into the ThadLuang Marshland
comes primarily from irrigation canal at the Donnokkoom rice field, Hong Ke and
Hong Xeng stream, which collects its water from drainage canals running throughout
Vientiane. Water running out of the marsh follows Houay Mak Hiao River dumping
into the Mekong 64 km south east of Vientiane.
Based on a recent government survey in the That Lung area, about 90 percent
of households around ThadLuang Marsh are classified as poor and only 10 percent of
households as relatively better off category. Because of the structure of rural
employment, the livelihoods of households around ThadLuang Marsh are highly
depended upon the ThadLuang marsh, and the water resources availability at the
marsh. This is because agriculture and sale of agriculture produce are the primary
income generating activity for over 70 % of households living around the ThadLuang
marsh. About 7 percent of the total households there are without a primary form of
income from agriculture (farming), and it is likely that they rely heavily on collecting
fish and aquatic produce from the marsh area. [STO, 2009] Therefore, being one of
main reasons leading to poverty, water and sediment pollution in ThadLuang marsh
affect significantly on life of people here.
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Figure 1.1.Villages around ThadLuang Marsh
1.2. Present status of water and sediment pollution in ThadLuang marsh
ThadLuang Marsh receives domestic sewage discharge from a large
proportion of Vientiane city by way of several canals. While Vientiane has a
sewerage system, there is currently no functioning waste treatment facility near the
urban area. Sewage is either hauled to a waste treatment plant 17 km outside of the
city limits or, more commonly, discharged into natural water bodies, either as raw
wastes or as seepage from septic tanks. Sewerage and sanitation systems rely on the
infiltration of wastewater into the ground. However due to the low soil permeability
and the high groundwater table in Vientiane, many soak ways fail to operate
efficiently meaning that sewage is discharged from tanks and drains directly into
urban wetlands. As a result of considerable quantity of household waste and sewage
is discharged into Nong Chang, and then flows into ThadLuang Marsh before
entering the Mekong. Textile, detergent and paper plants discharge directly into open
drains without any treatment, and contribute wastewaters into ThadLuang Marsh.
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There are two tanneries although the larger of these has sophisticated treatment
facilities, in practice wastes bypass these and are discharged untreated. The brewery
on the southern shore of ThadLuang passes waste through an oxidation pond.
Because of the importance of ThadLuang with issues directly relating to
Vientiane environment, it is irrefutable that researching water pollution in
ThadLuang is necessary and must be done immediately. Some data published on
pollution in ThadLuang marsh is shown in table 1.1.
Table 1.1: Some data published on pollution in ThadLuang marsh.
Parameters Unit 2002 2003 Standard
(STEA, 2000)
pH (mg/l) 7.8 8.8 6 – 9.5
Temperature o
C 28 32.6 *
Electrical Conductivity (EC) (micro/cm) 266 438 *
Dissolve Oxygen (DO) mg/l 2.8 1.1 >2
Biological Oxygen Demand (BOD) mg/l 39 78.3 4
Ammonia nitrogen (NH3-N) mg/l 0.294 0.389 0.2
Nitrate-Nitrogen (NO3-N) mg/l 3.064 3.991 <5.0
PO4-P (mg/l) 5.4 6.45 30
Total-N (mg/l) 5.6 3.19 *
Total-P (mg/l) * 5.951 *
This table only mentions about some norms such as BOD, COD, EC, DO …
Most scientific research has shown that there is no data on heavy metals pollution
until now. This study will provide more information to this missing part. According
to this table, pH, BOD, Ammonia nitrogen (NH3-N) and PO4-P parameters are much
higher than standard while Dissolve Oxygen (DO) and Nitrate-Nitrogen (NO3-N) are
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lower. There is sound that water pollution appears compared to Surface Water
Quality Standard in Lao PDR. Also, by the fact that it exist wastewater and sewage
(from the city area) discharged into the marsh. Especially, no sooner do many
factories appear and develop increasing fast than water is polluted by heavy metals is
over allowable limit.
1.3. Toxicity of Cadmium Cd, Copper Cu, Lead Pb, Zinc Zn
1.3.1. Cadmium Cd
The most dangerous form of occupational exposure to cadmium is inhalation
of fine dust and fumes, or ingestion of highly soluble cadmium compounds.
Inhalation of cadmium-containing fumes can result initially in metal fume fever but
may progress to chemical pneumonitis, pulmonary edema, and death. [Ayres, Robert
U, 2003]
Cadmium is also an environmental hazard. Human exposures to environmental
cadmium are primarily the result of fossil fuel combustion, phosphate fertilizers,
natural sources, iron and steel production, cement production and related activities,
nonferrous metals production, and municipal solid waste incineration. However,
there have been a few instances of general population toxicity as the result of long-
term exposure to cadmium in contaminated food and water. In the decades leading up
to World War II, Japanese mining operations contaminated the Jinzū River with
cadmium and traces of other toxic metals.[National Research Council (U.S.), 1969) ]
As a consequence, cadmium accumulated in the rice crops growing along the
riverbanks downstream of the mines. Some members of the local agricultural
communities consuming the contaminated rice developed itai-itai disease and renal
abnormalities, including proteinuria and glucosuria.
The victims of this poisoning were almost exclusively post-menopausal
women with low iron and other mineral body stores. Similar general population
cadmium exposures in other parts of the world have not resulted in the same health
problems because the populations maintained sufficient iron and other mineral levels.
Thus, while cadmium is a major factor in the itai-itai disease in Japan, most
researchers have concluded that it was one of several factors. Cadmium is one of six
substances banned by the European Union's Restriction on Hazardous Substances
(RoHS) directive, which bans certain hazardous substances in electrical and
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electronic equipment but allows for certain exemptions and exclusions from the
scope of the law.
Although some studies linked exposure to cadmium with lung and prostate
cancer, there is still a substantial controversy about the carcinogenicity of cadmium.
More recent studies suggest that arsenic rather than cadmium may lead to the
increased lung cancer mortality rates. Furthermore, most data regarding the
carcinogenicity of cadmium rely on research confounded by the presence of other
carcinogenic substances.
Tobacco smoking is the most important single source of cadmium exposure in
the general population. It has been estimated that about 10% of the cadmium content
of a cigarette is inhaled through smoking. The absorption of cadmium from the lungs
is much more effective than that from the gut, and as much as 50% of the cadmium
inhaled via cigarette smoke may be absorbed. [Jarup, L. (1998)]
On average, smokers have 4-5 times higher blood cadmium concentrations
and 2 - 3 times higher kidney cadmium concentrations than non - smokers. Despite
the high cadmium content in cigarette smoke, there seems to be little exposure to
cadmium from passive smoking. No significant effect on blood cadmium
concentrations has been detected in children exposed to environmental tobacco
smoke.
Cadmium exposure is a risk factor associated with early atherosclerosis and
hypertension, which can both lead to cardiovascular disease.
1.3.2. Copper Cu
Copper toxicity refers to the consequences of an excess of copper in the body.
Copper toxicity can occur from eating acid food that has been cooked in un-coated
copper cookware, or from exposure to excess copper in drinking water or other
environmental sources.
Copper in the blood exist in two forms: bound to ceruloplasmin (85–95%) and
the rest "free" loosely bound to albumin and small molecules. Free copper causes
toxicity as it generates reactive oxygen species such as superoxide, hydrogen
peroxide, the hydroxyl radical. These damage proteins, lipids and DNA.
[Federal
Register, 1976]
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Acute symptoms of copper poisoning by ingestion include vomiting,
hematemesis (vomiting of blood), hypotension (low blood pressure), melena (black
"tarry" feces), coma, jaundice (yellowish pigmentation of the skin), and
gastrointestinal distress. Individuals with glucose-6-phosphate deficiency may be at
increased risk of hematologic effects of copper. Hemolytic anemia resulting from the
treatment of burns with copper compounds is infrequent.
Chronic (long-term exposure) effects of copper exposure can damage the liver
and kidneys. Mammals have efficient mechanisms to regulate copper stores such that
they are generally protected from excess dietary copper levels.
The U.S. Environmental Protection Agency's Maximum Contaminate Level (MCL)
in drinking water is 1.3 milligrams per Liter. The MCL for copper is based on the
expectation that a lifetime of consuming copper in water at this level is without
adverse effect (gastrointestinal effect). The U.S EPA lists evidence that copper
causes testicular cancer as "most adequate" according to the latest research at
Sanford-Burnham Medical Research Institute. The Occupational Safety and Health
Administration (OSHA) has set a limit of 0.1 mg/m3 for copper fumes (vapor
generated from heating copper) and 1 mg/m3 for copper dusts (fine metallic copper
particles) and mists (aerosol of soluble copper) in workroom air during an 8-hour
work shift, 40-hour workweek. [Curtis D. Klassen, Ph.D., McGraw-Hill]
1.3.3. Lead Pb
Lead is a poisonous metal that can damage nervous connections (especially in
young children) and cause blood and brain disorders. Lead poisoning typically
results from ingestion of food or water contaminated with lead; but may also occur
after accidental ingestion of contaminated soil, dust, or lead based paint. Long-term
exposure to lead or its salts (especially soluble salts or the strong oxidant PbO2) can
cause nephropathy, and colic-like abdominal pains. The effects of lead are the same
whether it enters the body through breathing or swallowing. Lead can affect almost
every organ and system in the body. The main target for lead toxicity is the nervous
system, both in adults and children. Long-term exposure of adults can result in
decreased performance in some tests that measure functions of the nervous system. It
may also cause weakness in fingers, wrists, or ankles. Lead exposure also causes
small increases in blood pressure, particularly in middle-aged and older people and
can cause anemia. Exposure to high lead levels can severely damage the brain and
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kidneys in adults or children and ultimately cause death. In pregnant women, high
levels of exposure to lead may cause miscarriage. Chronic, high-level exposure has
shown to reduce fertility in males. The antidote/treatment for lead poisoning consists
of dimercaprol and succimer.
The concern about lead's role in cognitive deficits in children has brought
about widespread reduction in its use (lead exposure has been linked to learning
disabilities). Most cases of adult elevated blood lead levels are workplace-
related. High blood levels are associated with delayed puberty in girls. Lead has been
shown many times to permanently reduce the cognitive capacity of children at
extremely low levels of exposure.
During the 20th century, the use of lead in paint pigments was sharply reduced
because of the danger of lead poisoning, especially to children. By the mid-1980s, a
significant shift in lead end-use patterns had taken place. Much of this shift was a
result of the U.S. lead consumers' compliance with environmental regulations that
significantly reduced or eliminated the use of lead in non-battery products,
including gasoline, paints, solders, and water systems. Lead use is being further
curtailed by the European Union's RoHS directive. Lead may still be found in
harmful quantities in stoneware, vinyl (such as that used for tubing and the insulation
of electrical cords), and brass manufactured in China. Between 2006 and 2007 many
children's toys made in China were recalled, primarily due to lead in paint used to
color the product. [Stellman, Jeanne Mager (1998).]
Older houses may still contain substantial amounts of lead paint. White lead
paint has been withdrawn from sale in industrialized countries, but the yellow lead
chromate is still in use; for example, Holland Colours Holcolan Yellow. Old paint
should not be stripped by sanding, as this produces inhalable dust.
Lead salts used in pottery glazes have on occasion caused poisoning, when
acidic drinks, such as fruit juices, have leached lead ions out of the glaze. It has been
suggested that what was known as "Devon colic" arose from the use of lead-lined
presses to extract apple juice in the manufacture of cider. Lead is considered to be
particularly harmful for women's ability to reproduce. Lead (II) acetate (also known
as sugar of lead) was used by the Roman Empire as a sweetener for wine, and some
consider this to be the cause of the dementia that affected many of the Roman
Emperors.
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Lead as a soil contaminant is a widespread issue, since lead is present in
natural deposits and may also enter soil through (leaded) gasoline leaks from
underground storage tanks or through a waste stream of lead paint or lead grindings
from certain industrial operations.
Lead can also be found listed as a criteria pollutant in the United States Clean
Air Act section 108. Lead that is emitted into the atmosphere can be inhaled, or it can
be ingested after it settles out of the air. It is rapidly absorbed into the bloodstream
and is believed to have adverse effects on the central nervous system, the
cardiovascular system, kidneys, and the immune system. [Hong, Youlian and
Bartlett, Roger, ed (2008)].
In the human body, lead inhibits porphobilinogen synthase and ferrochelatase,
preventing both porphobilinogen formation and the incorporation of iron into
protoporphyrin IX, the final step in hemi synthesis. This causes ineffective hemi
synthesis and subsequent microcytic anemia. At lower levels, it acts as a calcium
analog, interfering with ion channels during nerve conduction. This is one of the
mechanisms by which it interferes with cognition. Acute lead poisoning is treated
using disodium calcium edentate: the calcium chelae of the disodium salt of
ethylene-diamine-tetracetic acid (EDTA). This chelating agent has a greater affinity
for lead than for calcium and so the lead chelae is formed by exchange. This is then
excreted in the urine leaving behind harmless calcium.
1.3.4. Zinc Zn
Although zinc is an essential requirement for good health, excess zinc can be
harmful. Excessive absorption of zinc suppresses copper and iron absorption. The
free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate
fish. The Free Ion Activity Model is well-established in the literature, and shows that
just micro molar amounts of the free ion kills some organisms. A recent example
showed 6 micro molar killing 93% of all Daphnia in water. [Barceloux, Donald G.;
(1999)].
The free zinc ion is a powerful Lewis acid up to the point of being corrosive.
Stomach acid contains hydrochloric acid, in which metallic zinc dissolves readily to
give corrosive zinc chloride. Swallowing a post-1982 American one cent piece
(97.5% of zinc) can cause damage to the stomach lining due to the high solubility of
the zinc ion in the acidic stomach.
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There is evidence of induced copper deficiency at low intakes of 100–300 mg
Zn/day; a recent trial had higher hospitalizations for urinary complications compared
to placebo among elderly men taking 80 mg/day [Fosmire GJ (1990)]. The USDA
RDA is 11 and 8 mg Zn/day for men and women, respectively. Even lower levels,
closer to the RDA, may interfere with the utilization of copper and iron or adversely
affect cholesterol. Levels of zinc in excess of 500 ppm in soil interfere with the
ability of plants to absorb other essential metals, such as iron and manganese. There
is also a condition called the zinc shakes or "zinc chills" that can be induced by the
inhalation of freshly formed zinc oxide formed during the welding of galvanized
materials.
The U.S. Food and Drug Administration (FDA) has stated that zinc damages
nerve receptors in the nose, which can cause anomies. Reports of anomies were also
observed in the 1930s when zinc preparations were used in a failed attempt to
prevent polio infections. On June 16, 2009, the FDA said that consumers should stop
using zinc-based intranasal cold products and ordered their removal from store
shelves. The FDA said the loss of smell can be life-threatening because people with
impaired smell cannot detect leaking gas or smoke and cannot tell if food has spoiled
before they eat it. Recent research suggests that the topical antimicrobial zinc
pyrithione is a potent heat shock response inducer that may impair genomic integrity
with induction of PARP-dependent energy crisis in cultured human keratinocytes
and melanocytes.
In 1982, the United States Mint began minting pennies coated in copper but
made primarily of zinc. With the new zinc pennies, there is the potential for zinc
toxic sis, which can be fatal. One reported case of chronic ingestion of 425 pennies
(over 1 kg of zinc) resulted in death due to gastrointestinal bacterial and fungal
sepsis, while another patient, who ingested 12 grams of zinc, only showed lethargy
and ataxia (gross lack of coordination of muscle movements). Several other cases
have been reported of humans suffering zinc intoxication by the ingestion of zinc
coins.
Pennies and other small coins are sometimes ingested by dogs, resulting in the
need for medical treatment to remove the foreign body. The zinc content of some
coins can cause zinc toxicity, which is commonly fatal in dogs, where it causes a
severe hemolytic anemia, and also liver or kidney damage; vomiting and diarrhea are
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possible symptoms. Zinc is highly toxic in parrots and poisoning can often be fatal.
The consumption of fruit juices stored in galvanized cans has resulted in mass parrot
poisonings with zinc.
1.4. Analytical methods for determination of heavy metals in water and
sediment samples
1.4.1. Electrochemical methods
1.4.1.1. Polarography
Polarography is a subclass of voltammetry where the working electrode is
a dropping mercury electrode (DME) or a static mercury drop electrode (SMDE)
useful for its wide cathodic range and renewable surface. It was invented by Jaroslav
Heyrovský, who was for this invention awarded by Nobel’s prize in 1959.
Polarography is an voltammetric measurement whose response is determined
by combined diffusion/convection mass transport. Polarography is a specific type of
measurement that falls into the general category of linear-sweep voltammetry where
the electrode potential is altered in a linear fashion from the initial potential to the
final potential. As a linear sweep method controlled by convection/diffusion mass
transport, the current vs. potential response of a polarographic experiment has the
typical sigmoidal shape. What makes polarography different from other linear sweep
voltammetry measurements is that polarography makes use of the dropping mercury
electrode (DME) or the static mercury dropping electrode.
A plot of the current vs. potential in a polarography experiment shows the
current oscillations corresponding to the drops of Hg falling from the capillary. If one
connected the maximum current of each drop, a sigmoidal shape would result. The
limiting current (the plateau on the sigmoid), called the diffusion current because
diffusion is the principal contribution to the flux of electro active material at this
point of the Hg drop life.
The method has been used for the determination of heavy metals. In Vietnam,
Tu Van Mac and Tran Thi Sau has studied about determination of copper, lead and
cadmium in beer in Hanoi by alternating current differential pulse polarography with
sensitivity accounting for 1ppb. [Tu Van Mac, Tran Thi Sau]
Thanh Thuc Trinh, Nguyen Xuan Lang and their colleagues has applied
polarimetry on determination of Zinc, Cadmium, Lead and Copper in some kinds of
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food and agricultural soil. It is experimented in environment of acetate buffer with
system of 3 polars: hanging mercury drop electrode, reference electrode Ag/AgCl,
auxiliary electrode Pt and electrodeionization potential accounting for -1.05V in 60
seconds [Thanh Thuc trinh, Nguyen Xuan Lang].
1.4.1.2. Voltammetry
Voltammetry is a category of electroanalytical methods used in analytical
chemistry and various industrial processes. In voltammetry, information about
an analyte is obtained by measuring the current as the potential is varied.
Voltammetry experiments investigate the half cell reactivity of ananalyte.
Voltammetry is the study of current as a function of applied potential. These curves I
= f(E) are called voltammograms. The potential is varied arbitrarily either step by
step or continuously and the actual current value is measured as the dependent
variable. The opposite, i.e., amperometry, is also possible but not common. The
shape of the curves depends on the speed of potential variation (nature of driving
force) and on whether the solution is stirred or quiescent (mass transfer). Most
experiments control the potential (volts) of an electrode in contact with the analyte
while measuring the resulting current (amperes). [Zoski, Cynthia G. (2007-02-07)].
Professor Petrovic and his colleagues used Differential pulse stripping
voltametry to determine Cd and Pb in water after separating them from humic acid
by thin layer chromatographic method. [Petrovic and Dewal, 1998]
Selehattin Yilmaz, Sultan Yagmur, Gulsen Saglikoglu, Murat Sadikoglu
studied about direct determination of zinc heavy metal in the tap water carried out by
differential pulse anodic stripping voltammetry technique at the glassy carbon
electrode (GCE). The zinc ions were deposited by reduction at -1.5 V on a bare
glassy carbon surface. Then, the deposited metal was oxidized by scanning the
potential of the electrode surface from -1.5 to -0.8 volt using a differential puls mode.
The stripping current arising from the oxidation of metal was connected with the
concentration the metal in the sample. The concentration of zinc heavy metal found
in tap water sample was determined to be 180 mg L-1
using 0.2 mol L-1
acetate buffer
(pH: 3.50) [Selehattin Yilmaz, 2009].
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1.4.2. Spectrophotometric methods
1.4.2.1. Ultraviolet-visible spectrophotometer
Ultraviolet-visible spectroscopy or ultraviolet-visible spectrophotometer (UV-
Vis or UV/Vis) refers to absorption spectroscopy or reflectance spectroscopy in
the ultraviolet-visible spectral region. This means it uses light in the visible and
adjacent (near-UV and near-infrared (NIR)) ranges. The absorption or reflectance in
the visible range directly affects the perceived color of the chemicals involved. In
this region of the electromagnetic spectrum, molecules undergo electronic
transitions. [ Prabhakar, Dubinskii, Editors and Dekker (2002)]. This technique is
complementary to fluorescence spectroscopy, in that fluorescence deals with
transitions from the excited state to the ground state, while absorption measures
transitions from the ground state to the excited state. UV/Vis spectroscopy is
routinely used in analytical chemistry for the quantitative determination of different
analytes, such as transition metal ions, highly conjugated organic compounds, and
biological macromolecules. Determination is usually carried out in solutions.
Gao Hong – Wen (China) used dithizone combining with Cd separation cells
filter to determination of Cd (II) in sea water by UV/Vis spectroscopy with LOD is
0.006 ppm. [Gao Hong – Wen (1995),]
A.M Garcia Rodriguez, A Garcia de Torres and J.M Cano Pavon studied
about simultaneous determination of iron, cobalt, nickel and copper by UV-visible
spectrophotometry with multivariate calibration. Linear determination ranges of Co,
Ni, Fe and Cu are 0.2–1.3 mg/ml, 0.1–1.2 mg/ml, 0.1–1.1 mg/ml and 0.2–1.2 mg/ml
respectively.A method for the simultaneous spectrophotometric determination of the
divalent ions of iron, cobalt, nickel and copper based on the formation of their
complexes with 1,5-bis(di-2-pyridylmethylene) thiocarbonohydrazide (DPTH) is
proposed.[A.M Garcia, A Garcia and J.M Cano (1998)]
1.4.2.2. Atomic emission spectroscopy (AES)
Atomic emission spectroscopy (AES) is a method of chemical analysis that
uses the intensity of light emitted from a flame, plasma, arc, or spark at a particular
wavelength to determine the quantity of an element in a sample. The wavelength of
the atomic spectral line gives the identity of the element while the intensity of the
emitted light is proportional to the number of atoms of the element. A sample of a
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material (analyte) is brought into the flame as a gas or sprayed solution. [Stefánsson
A, Gunnarsson I, Giroud N (2007)]. The heat from the flame evaporates the solvent
and breaks chemical bonds to create free atoms. The thermal energy also excites the
atoms into excited electronic states that subsequently emit light when they return to
the ground electronic state. Each element emits light at a characteristic wavelength,
which is dispersed by a grating or prism and detected in the spectrometer. A frequent
application of the emission measurement with the flame is the regulation of alkali
metals for pharmaceutical analytics
Krzysztof Jankowski , Jun Yao, Krzysztof Kasiura, Adrianna Jackowska,
Anna Sieradzka studied about multielement determination of heavy metals in
water samples by continuous powder introduction microwave-induced plasma atomic
mission spectrometry after preconcentration on activated carbon. The experimental
setup consisted of integrated rectangular cavity TE and vertically positioned plasma
torch. The satisfactory signal stability required for sequential analysis was attained
owing to the vertical plasma configuration, as well as the plasma gas flow rate
compatibility with sample introduction flow rate. The elements of interest (Cd, Cu,
Cr, Fe, Mn, Pb, Zn) were preconcentrated in a batch procedure at pH 8–8.5 after
addition of activated carbon and then, after filtering and drying of the activated
carbon suspension, introduced to the MIP by the CPI system. [Krzysztof Jankowski ,
Jun Yao, Krzysztof Kasiura, Adrianna Jackowska, Anna Sieradzka (2004)].
1.4.2.3. Atomic absorption spectroscopy (AAS)
Atomic absorption spectroscopy (AAS) is a spectroanalytical procedure for
the qualitative and quantitative determination of chemical elements employing the
absorption of optical radiation (light) by free atoms in the gaseous state. In analytical
chemistry the technique is used for determining the concentration of a particular
element (the analyte) in a sample to be analyzed. AAS can be used to determine over
70 different elements in solution or directly in solid samples. The technique makes
use of absorption spectrometry to assess the concentration of an analyte in a sample.
It requires standards with known analyte content to establish the relation between the
measured absorbance and the analyte concentration and relies therefore on Beer-
Lambert Law. In short, the electrons of the atoms in the atomizer can be promoted to
higher orbitals (excited state) for a short period of time (nanoseconds) by absorbing a
defined quantity of energy (radiation of a given wavelength). [B.V L’vov (2005)]
This amount of energy, i.e., wavelength, is specific to a particular electron transition
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in a particular element. In general, each wavelength corresponds to only one element,
and the width of an absorption line is only of the order of a few picometers (pm),
which gives the technique its elemental selectivity. The radiation flux without a
sample and with a sample in the atomizer is measured using a detector, and the ratio
between the two values (the absorbance) is converted to analyte concentration or
mass using Beer-Lambert Law.
Hüseyin Bağ, A.Rehber Türker , Ramazan Coşkun, Mehmet Saçak, Mustafa
Yiğitoğlu studied about determination of zinc, cadmium, cobalt and nikel by flame
atomic absorption spectrometry after preconcentration by poly(ethylene
terephthalate) fibers grafted with methacrylic acid. The batch adsorption method was
used for the preconcentration studies. Effect of pH, amount of adsorbent,
concentration and volume of elution solution, shaking time and interfering ions on
the recovery of the analytes have been investigated. Recoveries of Zn, Cd, Co and Ni
were 97.3±0.4%, 98.3±0.2%, 94.1±0.3% and 96.5±0.6% at 95% confidence level,
respectively, at optimum conditions. Langmuir adsorption isotherm curves were also
studied for the analytes. The adsorption capacity of the adsorbent was found as 298,
412, 325 and 456 mg/g for Zn, Cd, Co and Ni, respectively. [Hüseyin Bağ, 2000].
Nakashima and his colleagues in Okayama University (Japan) studied about
determination of Cadmium in water by using AAS after separating Cd out of samples
by zirconi oxide. [M.C. Yebra , N. Carro, A. Moreno-Cid (2002)].
In addition, M.C. Yebra , N. Carro, A. Moreno-Cid studied about
determination of copper in sea water by flow-injection- atomic absorption
spectrometry. By using the optimized flow systems, seawater samples were collected
and pre-concentrated in situ by passing them with a peristaltic pump through a mini-
column packed with Amberlite XAD-4 impregnated with the complexing agent 4-(2-
pyridylazo) resorcinol. Thus, copper is pre-concentrated without the interference of
the saline matrix. Once in the laboratory, the mini-columns loaded with copper are
incorporated into a flow injection system and eluted with a small volume of a 40%
(v/v) ethanolic solution of 3 mol l−1
hydrochloric acid into the nebulizer-burner
system of a flame atomic absorption spectrometer. Analysis of certified reference
materials (SLEW-3 and NASS-5) showed good agreement with the certified value.
[Susumu, Masakazu (1983)].
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Conclusion: Because the objects of our research are surface water and sediment
samples containing heavy metals as Cd, Cu, Pb, Zn… the amount of heavy metals
must be determined exactly in order to evaluate the quality of water. Modern
analytical methods such as GF-AAS, ICP-MS… require expensive equipments and
costly fees. In this case, using F-AAS is a reasonable choice with high sensitivity and
the capability to analyze many elements in complex matrices, providing a good
accuracy and precision result, short time for analyzing and cheap price. The
referenced results obtained by ICP-MS will be also included to recognize the ultra
trace of heavy metal contents in some environmental samples.
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CHAPTER 2: EXPERIMENTS
2.1. Research Objects and research contents
2.1.1. Research objects
At present, the environmental impact is still poorly understood in Lao PDR. It is lack
of information for herbicide and pesticide management. The may be some problems
have occurred as:
- People are unaware of dangers of heavy metals content in water and sediment.
- High residue levels in water and sediment.
- Threat to farmers’ health and aquatic ecosystems due to misuse and
misunderstand.
- Using polluted surface water for agricultural purpose leads to accumulate
heavy metals.
This research aims to get quantitative determination of four main heavy metals (such
as Pb, Cd, Zn, Cu) in water and sediment samples in the ThadLuang Marsh and
assessments the distribution these heavy metals contents in environmental samples of
studied mash. No sooner do many factories appear and develop increasing fast than
water is polluted by heavy metals is over allowable limit. Owing to not taking part in
biochemical process, heavy metals such as Cd, Pb, Zn, Cu… are accumulated in
human body, which leads to harmfulness for organism. The fact that water is polluted
by heavy metal is often seen in rivers near industrial area, big cities and minerals
exploiting area. The main reason leading to heavy metals pollution is pouring into
water environment a large amount of industrial and untreated wastewater. Pollution
by heavy metals accumulated through foods directly into organism has negative
effects on life environment. In order to reduce consequence of this problem, it is
necessary to cultivate measures of water treatment.
2.1.2. Research contents
In order to gain a completely process, it is necessary to study systematically the
following issues:
- Investigation of optimal conditions for determination of Pb, Cd, Zn, and Cu
in water and sediment using F-AAS.
- Investigation of sample matrix’s effects.
- Investigation of other interferences to analytical results.
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- Determination of Cd, Cu, Pb, Zn content in water and sediment samples
collected in ThadLuang marsh in May, 2011.
2.2. Chemicals and Apparatus
2.2.1. Chemicals
All reagents were of Merck analytical grade or ultra-pure grade for ICP-MS
measurement. Working solutions of analysed ions were prepared by dilution of
standard solutions of 1000 ppm standard solutions of Zn 2+
, Cu2 +
, Pb+2
, Cd2 +
.
- 2% solutions of HNO3, HCl, CH3COONH4 were prepared from 65% solution
of HNO3 , 36% solution of HCl and 99% solution of CH3COONH4,
respectively.
- 10% solution of HCl, HNO3 was prepared from con.HNO3 68%.
- Super pure water (Resistance >=18.2 MΩ ) and Argon, super pure grade
(>=99.999) for ICP-MS measurement.
All standard reagent solutions were stored in low density polyethylene bottles.
2.2.2. Apparatus
- Beaker 25, 50, 100ml capacity
- Pipettes 1, 2, 5, 10, 25 ml... capicity
- Pipetteman 20, 100, 200, 1000, 5000 μl capicity
- Hopper glass, filter paper, pH indicator...
- Elementary flasks 50, 100, 250 ml... capacity
- Glass volumetric flasks: 25, 50, 100 and 25 ml capacity.
All laboratory glassware and plastic ware, polyethylene sample and reagent bottles
were cleaned by soaking in a detergent solution, rinsed with ultra pure water from a
Millipore Q50
system and soaking in a HNO3 ( 2%), v/v) bath overnight. This was
followed by thorough rinsing with pure and dried before use.
- Calculations: MINITB release 14 for window.
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2.2.3. Equipments
- AAS- novAA spectrometer with pneumatic nebulisation and mono- element
lamps with hollow cathode made by Analytikjena (Fig. 3)
Figure 2.1: Spectrometer atomic absorption novAA 6800, Shimazhu
2.3 Sampling and Sample Preparation
2.3.1. Study Area
2.3.1.1. Water samples
Eight sampling points were located within marsh were shown in Figure 2.2. The
description of the characteristics of water sampling points is given in table 2.1.
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Table 2.1: Characteristics of the water sampling points in Thadluang marsh
Sampling point Position Time Potential source of
metal pollution
1. 17°58'34.73"N
102°38'54.35"E
9:56:29AM
28th
May 2011
Market’s waste
2. 17°58'4.86"N
102°38'30.79"E
10:36:37AM
28th
May 2011
Trade waste
3. 17°57'54.09"N
102°39'11.83"E
5:36:23PM
28th
May 2011
Agricultural waste
4. 17°57'8.36"N
102°39'35.47"E
5:04:21PM
28th
May 2011
Agricultural waste
5. 17°56'20.76"N
102°39'33.45"E
4:20:31PM
28th
May 2011
Agricultural waste
6. 17°55'21.34"N
102°39'31.56"E
3:32:22PM
28th
May 2011
Agricultural waste
7. 17°54'30.79"N
102°39'29.47"E
12:27:47PM
28th
May 2011
Agricultural waste
8. 17°52'56.15"N
102°39'27.91"E
2:41:02PM
28th
May 2011
Laos Beer Factory
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Figure 2.2: The map of Thadluang marsh showing water sampling sites.
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2.3.1.2. Sediment samples
Five sampling points were located within marsh were shown in Figure 2.3. The
description of the characteristics of sampling points are given in table 2.2
Table 2.2: Characteristics of the sediment sampling points in Thadluang marsh
Sampling
point
Position Time Potential source of metal
pollution
1 17°58'34.73"N
102°38'54.35"E
9:56:29AM
28th
May 2011
Market’s waste
2 17°57'8.36"N
102°39'35.47"E
5:04:21PM
28th
May 2011
Agricultural waste
3 17°55'21.34"N
102°39'31.56"E
3:32:22PM
28th
May 2011
Agricultural waste
4 17°54'30.79"N
102°39'29.47"E
12:27:47PM
28th
May 2011
Agricultural waste
5 17°52'56.15"N
102°39'27.91"E
2:41:02PM
28th
May 2011
Laos Beer Factory
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Figure 2.3: The map of Thadluang marsh showing sediment sampling sites.
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2.3.2. Sampling and sample preparation
Surface water and sediment samples were collected from various places in
Thadluang marsh. Sample were collected and prepared for experiments in a standard
ways described in the literatures for these kinds of materials.
All laboratory glassware and plastic ware, polyethylene sample and reagent
bottles were cleaned by soaking in a detergent solution, rinsed with ultra pure water
from a Millipore Q50
system and soaking in a HNO3 ( 2%), v/v) bath overnight. This
was followed by thorough rinsing with pure and dried before use.
2.3.2. 1. Water samples
Surface water of ThadLuang marsh were collected and kept in 100 mL LDPE
bottles and transferred to laboratory in HUS to analyze.
At laboratory, transfer a 100-mL aliquot of well-mixed sample to a beaker.
For metals that are to be analyzed, add 2 mL of concentrated HNO3 and 5 mL of
concentrated HCl. The sample beaker is covered with a ribbed watch glass or other
suitable covers and heated on a steam bath, hot plate or other heating source at 90 to
95oC until the volume has been reduced to 15-20 mL.
After heating, the volume of sample was reduced around 15 mL and samples
were transferd to 25 mL volumetric flasks, well mixed with 5 mL CH3COONH4 10%
and distilled water were added to the mark and shacked well before analyzing.
2.3.2.2. Sediment samples
In order to investigating the pollution of four heavy metals in sediment, 100g
of sediment was taken at 5 different positions in ThadLuang marsh and transferred to
Vietnamese laboratory to analyze.
At laboratory, the amount of 0.05 g of each sample was weighted separately
then 2 ml of 63% solution of HNO3 acid, 5 ml of 32% solution of HCl acid were
added. These samples were brought to the pot boiling on the sand about 2 hours.
After being cooled and adding 2 drops of H2O2 ; 2 mL of H2F2, it is boiled until
appearance of white ash.
The residue was filtered through Whatman paper to 50 mL volumetric flasks and 1%
HNO3 was used to make the volume to 50.00 mL.
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2.4. Analytical methods for determination of Cu, Pb, Cd, Zn
2.4.1. Flame atomic absorption spectroscopy method (F-AAS):
determination of heavy metal content in sediment samples
2.4.1.1. Principles
The technique of flame atomic absorption spectroscopy (FAAS) requires a
liquid sample to be aspirated, aerosolized, and mixed with combustible gases, such as
acetylene and air or acetylene and nitrous oxide. The mixture is ignited in a flame
whose temperature ranges from 2100 to 2800 oC. During combustion, atoms of the
element of interest in the sample are reduced to free, unexcited ground state atoms,
which absorb light at characteristic wavelengths, as shown in figure 2.4.
Figure 2.4: Operation principle of an atomic absorption spectrometer.
The characteristic wavelengths are element specific and accurate to 0.01-
0.1nm. To provide element specific wavelengths, a light beam from a lamp whose
cathode is made of the element being determined is passed through the flame. A
device such as photomultiplier can detect the amount of reduction of the light
intensity due to absorption by the analyte, and this can be directly related to the
amount of the element in the sample. [Haswell, S.J., 1991].
Different flames can be achieved using different mixtures of gases, depending
on the desired temperature and burning velocity. Some elements can only be
converted to atoms at high temperatures. Even at high temperatures, if excess oxygen
is present, some metals form oxides that do not redissociate into atoms. To inhibit
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their formation, conditions of the flame may be modified to achieve a reducing, no
oxidizing flame.
Proper nebulization is required to break up an aqueous sample into a fine mist
of uniform droplet size that can be readily burned in the flame. Most instruments
utilize the direct aspiration. During aspiration, the gas flow breaks down the liquid
sample into droplets, and the nebulization performance depends on the physical
characteristics of the liquid. Only about 10% of the sample gets into the flame.
Another option for nebulization is the use of an ultrasonic wave beam, which
generates high frequency waves in the liquid sample. This causes very small liquid
particles to be ejected into a gas current forming a dense fog. [Reynolds, R.J. et al.,
1970].
In a certain limit of concentration, the intensity value depending linearly on
the concentration of the element to be analyzed according to the equation:
Aλ = k.Cb
Where: A λ: absorption intensity spectral lines.
k: constant experimentation.
b: length of absorbing environment. (0<b≤ 1)
C: concentrations of elements necessary to determine the sample
The block diagram of atomic absorption spectrometer with 5 main parts is
depicted in figure 2.5.
Figure 2.5: Block diagram of atomic absorption spectrometer
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Part 1: Power-ray emission of the resonant element analysis (emission
spectral lines characteristic of the element to be analyzed), to compare the
absorption containing atoms of elements freely. It is the hollow cathode
lamp (HCL), the discharge lamps without electrodes (EDL), or continuous
emission sources were be modulated.
Part 2: The atomic system of samples for analysis. In nuclear engineering
chemical flame, this system includes:
+ Division lead aerosol form into the chamber and make the process
of aerosol chemical form (can create aerosols).
+ Light to atoms of the sample (burner head) to ignite the gas mixture
can form in suspensions containing aerosols.
Part 3: The absorption spectroscopy, it is a monochrome, is responsible
for collection, segregation and choose light (spectral lines) to measure the
optical power to focus on detected by AAS signal absorption spectral lines.
Part 4: System indicator signal absorption of spectral lines (i.e. intensity
spectral lines of absorption or concentration of elements to be analyzed).
This system can are equipped with:
+ The simplest design is a power only energy absorption (E) of spectral
lines,
+ A self-recording machine pic of spectral lines,
+ Or is the number digital
+ Or the computer and printer (printer), or analyzer (Integrator).
Part 5: With the AAS spectrometer also has a modern microcomputers or
microprocessor and software systems. Equipped with this type is
responsible for measurement process control and process measurements,
graphing, calculation of sample concentration analysis, etc...
- Inductively couple plasma – mass spectrometer (ICP-MS) Elan 9000,
Perkin – Elmer, USA.
- Auto sample AS-93plus. Tray as-90/as90b.try
Collect and record the results of measuring the intensity of spectral lines
absorbed.
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2.4.1.2. The fixed optimal conditions of instrument F- AAS for the
determination of Pb, Cd, Zn, and Cu
Experiments were carried out to find out the optimal conditions of F-AAS for
measuring each element. Wavelength, slit width, current of HCL, burner height and
fuel gas were investigated and followed by catolog of producers. The optimal
conditions were shown in table 2.3. All experiments in this research were conducted
in these conditions.
Table 2.3: The optimal conditions of F-AAS for measuring Pb, Cd, Zn, Cu
Element
Factors
Pb
Cd Zn
Cu
Instrument
parameters
Wavelength (nm) 217.0 228.8 213.9 324.8
Slit width (nm) 0.5 0.5 0.5 0.5
Current of HCL (mA) 8 6 6 12
Burner height (mm) 8 6 6 8
Fuel gas (mL/min) 60 50 50 45
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2.4.2. Inductive couple plasma - mass spectrophotometry (ICP - Ms) for
the determination of heavy metal contents in surface water samples.
2.4.2.1. Principles:
The plasma sources developed for atomic emission spectrometry have
also been shown to be very suitable ion sources for mass spectrometry. This
is particularly true for electrical discharges at pressures in the 1±5 mbar range
and sources at atmospheric pressure since the powerful vacuum systems became
available, with which the pressure difference between the mass spectrometer (of the
order of 10-5 mbar) and the source can be bridged.
Elemental mass spectrometry, however, goes back to the use of high-
vacuum arcs and sparks, with which ultratrace and survey analyses of metal samples
could be performed. Spark source mass spectrography with high resolution sector
field mass spectrometers, is still very useful for a survey characterization of
electrically-conducting solids down to the ng/g level. The spectra can be recorded
on photographic plates, which are a permanent document and at least enable semi-
quantitative analyses to be made. At the ng/g level this approach is suitable for the
quality control of materials required in micro- electronics. The technique has
become very useful since computer-controlled densitometers have been available,
which automatically record the blackenings of the elemental lines on the photoplates
and convert them into logarithmic intensities, these being proportional to the
logarithmic concentrations.
Spark source mass spectrometry requires expensive sector-field mass
spectrometers and despite the possibility of automated read-out of the spectra,
highly skilled laboratory personnel for data evaluation are also required. This
situation arises from the fact that high-vacuum sparks are very powerful sources
producing vast amounts of multiply charged ions making the spectra line rich. The
analytical precision achievable in spark mass spectrometry is low, however,
special precautions such as the use of rotating electrodes have been found to be
helpful. Spark source mass spectrometry has been used for the analysis of compact
metals, from which electrodes could be made by turning-of or by fixing
drillings in electrode holders. In the case of metals of low melting point, such as
gallium, liquid nitrogen cooled electrodes of the gallium were used. For electrically
conducting as well as non-conducting powders electrodes were pressed from
mixtures with gold powder, which is ductile and leads to electrodes that are
Phetdalaphone BOUTTAVONG 2009-2011
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electrically and heat conductive. The method is very powerful for dry solution
residues as a result of its sensitivity and has been used for impurity detection in
liquid aliquots obtained from trace ± matrix separations in the analysis of high-purity
materials.
In ICP-MS (Fig. 6 ) the ions formed in the ICP are extracted with the
aid of a conical water-cooled sampler into the first vacuum stage where a pressure
of a few mbar is maintained. A supersonic beam is formed and a number of collision
processes take place as well as an adiabatic expansion. A fraction is sampled from
this beam through the conical skimmer placed a few cm away from the
sampler. Behind the skimmer, ion lenses focus the ion beam now entering a vacuum
of 10-5
. This was originally done with the aid of oil diffusion pumps or cryopumps,
respectively, but very quickly all manufacturers switched to turbo molecular pumps
backed by roughing pumps.
The sampler and the skimmer are usually made of stainless steel and are both
conically shaped with different cone angles. The sampler can also be made of copper,
which has a better heat conductivity. In the case of HF containing solutions, platinum
samplers can also be used. This is particularly worthwhile for the analysis of
geological samples subsequent to wet chemical dissolution and removal of the
silicates. The distance between the sampler and skimmer is critical with respect to the
maximum power of detection and minimal ionization interferences. This also applies
to the power transmission to the Rf coil, where considerable differences were
found for coils powered centrally and coils powered at one of the ends. The
processes in the intermediate stage together with their influence on the ion
trajectories in the interface and also behind the second aperture (skimmer) are very
important for the transmission of ions and for related matrix interferences, this
being the topic of fundamental diagnostic studies.
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Figure 2.6: Instrumentation for low-resolution ICP-MS.
(a): nebulizer; (b): sampler; (c): ion optics; (d): quadrupole;
(e): electronics; (f ): detector; (g): RF-generator; (h): roughing pump;
(i): turbo molecular pump: ( j): quadrupole RF generator.
2.4.2.2. Experimental conditions for determination of Cu, Pb, Cd and Zn
in surface water samples
The experimental conditions for determination of Cu, Pb, Cd and Zn using
ICP- MS techniques were fixed as in table 2.4.
Table 2.4: The experimental conditions for determination of Cu, Pb, Cd and Zn
using ICP- MS techniques
Gas flow rate Nebulizer 0.90 L/min
Makeup gas flow rate 2.0 L/min
Plasma gas flow rate 15.0 L/min
Pressure vacuum pump (Quantitative ) 1.2 – 1.3. 10-5
Torr
Pressure vacuum pump ( Standby) 2.0 – 3.0. 10-6
Torr
Sample flush 40s
Sample flush speed -48 +/- rpm
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Read delay 15s
Delay and analysis speed -26 +/- rpm
Wash 60s
Wash speed -48 +/- rpm
Cooling water power 1750W
ICP RF power 1000W
Lens voltage 5,75V
Analog stage voltage -1850V
Pulse stage voltage 1000V
Sweeps/reading 10
Readings/replicate 1
Replicates 3
Detector mode Dual
Other parameters Automatic
2.4.3. Quality control of analytical methods
- Blank samples: - Reagents’ blank were carries out through the entire sample
preparation procedure.
- Method blanks: method blanks reflect laboratory contamination from both the
determinative and preparatory method. Field blanks (e.g., trip blanks and
equipment or rinsate blanks) account for accumulative field and laboratory
activities were used to parellaly analyses.
Blank determinations for total a metal were carried out in the same manner as the
samples using the same acid concentrations.
- Spiked samples: A surface water or sediment sample to which known
concentrations of specific analytes have been added in such a manner as to
minimize the change in the matrix of the original sample. Every spiked
Phetdalaphone BOUTTAVONG 2009-2011
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sample analyzed should have an associated reference to the spike solution
and the volume added.
- Certified reference material (CRM): For calibration and validation of
analytical procedures (FAAS and ICP-MS), CRM- MESS3- sediment was
applied.
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CHAPTER 3: RESULTS AND DISCUSSION
3.1. Optimizations of some chemical factors influencing to absorbance in
F- AAS method
3.1.1. Study the effects of sample matrix and matrix modifier to F-AAS
In F-AAS measurement, type of acid that is used to acidify water samples to
prevent the formation of hydroxo complex, or hydrolysis…and acid concentration
can also reduce or increase the spectrum absorbance in F-AAS. On the other hand,
matrix modifiers (compounds added to the sample before injection or injected to the
atomizer together with the sample) will affect the thermal processes taking place in
the atomizer to minimize losses of analyte during pyrolysis and to enable more
effective matrix components removal. Some modifiers can change the sample matrix
to evaporate the matrix components at lower temperature; other type of modifiers
work as an analyte stabilizer. Therefore, the effect of concentrations of nitric acid
and ammonium acetate were investigated. First, a specific concentration of HNO3
was fixed and the concentrations of NH4CH3COO were gradually varied from 0%-
2%. The investigates were carried out with each solution containing : 3.0 ppm Pb2 +
solution, 0.5 ppm Cd2+
solution, 1.0 ppm Zn2+
solution, and 2.0 ppm Cu2+
solution,
separately. The results (including abs and RSD to check the working stability of
apparatus) were shown in table 3.1.
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Table 3.1: Investigation of HNO3 and NH4CH3COO effects on analysis of Pb,
Cd, Cu and Zn
NH4CH3COO
/ HNO3
0.5% 1.0% 1.5% 2.0%
A RSD(%) A RSD(%) A
RSD(%) A RSD(%)
Pb
0 0.03594 1.19 0.02980 1.07 0.03215 2.02 0.03253 0.80
0.5% 0.02977 1.57 0.02432 0.92 0.02556 0.97 0.02257 2.44
1.0% 0.02698 1.03 0.02723 1.92 0.02645 1.40 0.02739 0.84
2.0% 0.02942 0.89 0.02772 1.78 0.02856 0,73 0.02843 1.45
Cd
0 0.02401 2.45 0.09536 1.33 0.1830 1.09 0.1814 0.88
0.5% 0.02005 1.57 0.07944 2.26 0.1872 1.46 0.1658 0.89
1.0% 0.01565 1.03 0.08564 1.61 0.1902 0.83 0.1521 0.73
2.0% 0.01314 0.89 0.09634 0.47 0.1870 0.64 0.08140 4.04
Zn
0 0.08007 0.08 0.04197 0.87 0.03626 1.58 0.04403 0.64
0.5% 0.06398 0.06 0.03485 0.95 0.03250 1.29 0.04025 1.02
1.0% 0.05265 0.05 0.03292 0.40 0.03366 0.90 0.04356 0.56
2.0% 0.04638 0.05 0.03310 1.76 0.03633 0.77 0.04637 1.31
Cu
0 0.03651 1.59 0.03032 1.91 0.02508 2.03 0.02904 1.73
0.5% 0.03242 1.29 0.02565 1.89 0.02264 1.71 0.01994 2.36
1.0% 0.03345 0.40 0.02822 0.88 0.02550 1.57 0.02321 1.44
2.0% 0.03407 3.16 0.02945 3.57 0.02650 2.18 0.02509 1.82
Based on above results, the first conclusion will be extracted that there may
not be great interferences of HNO3 and NH4 CH3COO concentration to the signal of
absorbance. In order to evaluate the exact effect of HNO3 and CH3COOONH4 to the
absorbance of Pb, Zn, Cd and Cu measurements, the analysis of variance (ANOVA)
with two ways was used. The ANOVA table is expressed in table 3.2.
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Table 3.2: Two- way ANOVA table for evaluating effects of HNO3 and
NH4CH3COO
Pb Source DF SS MS F P
HNO3 3 0.0000252 0.0000084 3.13 0.080
NH4CH3COO 3 0.0001109 0.0000370 13.77 0.001
Error 9 0.0000242 0.0000027
Total 15 0.0001602
S = 0.001638 R-Sq = 84.92% R-Sq(adj) = 74.87%
Cd Source DF SS MS F P
HNO3 3 0.0640037 0.0213346 41.21 0.000
NH4CH3COO 3 0.0014856 0.0004952 0.96 0.454
Error 9 0.0046596 0.0005177
Total 15 0.0701488
S = 0.02275 R-Sq = 93.36% R-Sq(adj) = 88.93%
Cu Source DF SS MS F P
HNO3 3 0.0000252 0.0000084 3.13 0.080
NH4CH3COO 3 0.0001109 0.0000370 13.77 0.001
Error 9 0.0000242 0.0000027
Total 15 0.0001602
S = 0.001638 R-Sq = 82.91% R-Sq(adj) = 76.85%
Zn Source DF SS MS F P
HNO3 3 0.0002419 0.0000806 41.41 0.000
NH4CH3COO 3 0.0000553 0.0000184 9.46 0.004
Error 9 0.0000175 0.0000019
Total 15 0.0003147
S = 0.001396 R-Sq = 94.43% R-Sq(adj) = 90.72%
The results revealed that HNO3 concentrations could significantly affect to
absorbances of Cd and Zn while concentration of NH4CH3COO caused statisticaly
Phetdalaphone BOUTTAVONG 2009-2011
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significant infuence to Pb, Cu and Zn measurements (Pvalue < 0.05). Therefore matrix
of samples should be kept at 2% HNO3 and 1% NH4CH3OO because of having
maximum absorption and lower relative standard deviation.
Beside the effects of HNO3 as an acidic medium, the others of acidic media
affecting on adsorption line intensity of Cu and Pb such as HCl and H2SO4 acid were
investigated through the mesurements of Cu and Pb in seperated solutions of 2.0
ppm. The results are presented in Table 3.3:
Table 3.3: Influence of types of acid media HCl, HNO3 and H2SO4 effects on Cu2+
and Pb2+
analysis
Concentration of
acid (%)
Absorption of Cu (Abs)
HCl HNO3 H2SO4
Cu2+
0 0.1550 0.1550 0.1550
1 0.1543 0.1525 0.1500
2 0.1530 0.1510 0.1480
3 0.1515 0.1490 0.1450
4 0.1502 0.1470 0.1430
5 0.1488 0.1455 0.1402
Concentration of
acid (%)
Absorption of Pb (Abs)
HCl HNO3 H2SO4
Pb2+
0 0.0645 0.0645 0.0645
1 0.0635 0.0600 0.0569
2 0.0628 0.0578 0.0535
3 0.0610 0.0561 0.0510
4 0.0590 0.0549 0.0468
5 0.0578 0.0536 0.0425
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These results show that HCl and HNO3 acids had a smallest effect to the
absorbances. The faster concentrations of acid increased, the more quickly intensity
of adsorption line decreases. However, if the concentration of each acid is too small,
hydrolytic process will happen, relating to the obstacle of atomization. Therefore, 1%
concentration of acids is the reasonable ones. Also, HCl acid represents good
stability and dissolubility. So, 1% solution of HCl acid was accepted.
3.1.2. Calibration curves of Pb, Cd, Zn and Cu measurements.
3.1.2.1. The limit of linearity of Pb, Cd, Zn and Cu measurements
In order to investigate the linear ranges of the determination of Pb2+
,Cd2+
,
Zn2+
, and Cu2+
concentrations, series of their standard solutions with the
concentrations fluctuating from 0.2 to 3.5ppm in the case of Pb2+
, from 0.05 to
1.25ppm with Cd2+
and Zn2+
, from 0.1 to 1.75ppm with Cu2+
were prepared. The
absorbance of each metal atom was measured in the experimental conditions
determined above. The results obtained were depicted in table 3.4.
Table 3.4: The absorbance of each metal atom (after subtracting the
absorbance of the blank solution) vs. their concentrations
No Pb2+
Cd2+
Zn2+
Cu2+
C(ppm) Abs C(ppm) Abs C(ppm) Abs C(ppm) Abs
1 0.2 0.0034 0.05 0.017 0.05 0.0078 0.1 0.00531
2 0.5 0.0094 0.125 0.0332 0.125 0.0177 0.25 0.01267
3 1.0 0.0189 0.25 0.0732 0.25 0.039 0.5 0.02363
4 2.0 0.0387 0.50 0.1421 0.5 0.0761 1.0 0.04512
5 2.5 0.0471 0.75 0.2143 0.75 0.1143 1.25 0.05503
6 3 0.049 1.00 0.2365 1.00 0.1244 1.5 0.05641
7 3.5 0.0504 1.25 0.2456 1.25 0.1271 1.75 0.05709
Using Origin 6.0 software, the scater plots expressing the ralationship between
absorbances of Pb, Cd, Zn and Cu and concentrations were described in figure
Phetdalaphone BOUTTAVONG 2009-2011
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3.53.02.52.01.51.00.50.0
0.05
0.04
0.03
0.02
0.01
0.00
C-Pb, ppm
Ab
s- P
b
1.41.21.00.80.60.40.20.0
0.25
0.20
0.15
0.10
0.05
0.00
C- Cd, ppm
Ab
s- C
d
1.41.21.00.80.60.40.20.0
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
C- Zn, ppm
Ab
s- Z
n
1.81.61.41.21.00.80.60.40.20.0
0.06
0.05
0.04
0.03
0.02
0.01
0.00
C- Cu, ppm
Ab
s- C
u
Figure 3.1: The investigation of linear ranges for the determination of Pb, Cd, Zn and
Cu using F-AAS
The experimental results provided that the limit of linearity (LOL) of four
heavy metal concentrations is up to 2.5 ppm with Pb; 0.75 ppm with Cd and Zn; 1.25
ppm with Cu measurements.
Phetdalaphone BOUTTAVONG 2009-2011
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3.1.2.2. Calibration curves for the determination of Pb, Cd, Zn and Cu in
solutions
The calibration curves of Pb, Cd, Zn and Cu were determined by measuring 5
standard solutions of separate analyte. The sequences were as follows: method blank
was first and then analysed standard solutions with concentrations varied from 0 ppm
to 2.5 ppm for Pb2+
, 0.0ppm to 1.25ppm for Cu2+,
0.0ppm to 0.75ppm for Cd2+
and
Zn2+
. The results were shown in table 3.5.
Table 3.5: The absorbance of each heavy metal standard solutions in the
linear range of concentrations
No Pb2+
Cd2+
Zn2+
Cu2+
C(ppm) Abs C(ppm) Abs C(ppm) Abs C(ppm) Abs
1 0.2 0.0034 0.05 0.017 0.05 0.0078 0.1 0.00531
2 0.5 0.0094 0.125 0.0332 0.125 0.0177 0.25 0.01267
3 1.0 0.0189 0.25 0.0732 0.25 0.039 0.5 0.0236
4 2.0 0.0387 0.5 0.1421 0.5 0.0761 1.0 0.04512
5 2.5 0.0471 0.75 0.2143 0.75 0.1143 1.25 0.05503
By using Origin 6.0 software, the calibration curves (included the parameters for
the linear regressions) measurement of Pb, Cd, Zn and Cu concentration obtained
in figure 3.2.
0.0 0.5 1.0 1.5 2.0 2.5
0.00
0.01
0.02
0.03
0.04
0.05
Parameter Value Error
------------------------------------------------------------
A -2.34476E-4 3.83332E-4
B 0.01914 2.52323E-4
------------------------------------------------------------
R SD N P
------------------------------------------------------------
0.99974 4.95223E-4 5 <0.0001
-------------------------------------------------------
Ab
so
rba
nce
Concentration of Pb (ppm)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0.00
0.05
0.10
0.15
0.20
0.25
Parameter Value Error
------------------------------------------------------------
A 7.65512E-4 0.00171
B 0.28416 0.00405
------------------------------------------------------------
R SD N P
------------------------------------------------------------
0.9997 0.00233 5 <0.0001
------------------------------------------------------------
Ab
so
rba
nce
Concentration of Cd (ppm)
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0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0.00
0.02
0.04
0.06
0.08
0.10
0.12
Parameter Value Error
------------------------------------------------------------
A -2.14458E-4 6.81429E-4
B 0.15282 0.00161
------------------------------------------------------------
R SD N P
------------------------------------------------------------
0.99983 9.29006E-4 5 <0.0001
------------------------------------------------------
Ab
so
rba
nce
Concentration of Zn (ppm)
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
0.00
0.01
0.02
0.03
0.04
0.05
0.06
Parameter Value Error
------------------------------------------------------------
A 0.00161 4.51406E-4
B 0.04313 5.94264E-4
------------------------------------------------------------
R SD N P
------------------------------------------------------------
0.99972 5.83167E-4 5 <0.0001
---------------------------------------------------
Ab
so
rba
nce
Concentrationof Cu (ppm)
Figure 3.2: The calibration curves for the determinations of Pb, Cd, Zn and Cu in
standard solutions
In order to determine the linear regressions, the following parameters should be
calculated:
- Degree of freedom f= n-2 = 5-2= 3 for each case.
- The table value for t at confidence level of 95% and 3 degree of freedom
t(0.95;3) = 3.112
- The confidence interval for a and b calculated by error (SA and SB) from the
Origin 6.0 software results are as follows:
ΔA = t (0.95; 3). SA and ΔB = t (0.95; 3). SB
So that the complete regressions describing the linear relationships between
absorbance and concentrations of analytes have the following forms:
Abs= (a±a) + (b± b)xC
Where: Absi is the absorbance when spectrum of heavy metal measured(Abs)
C is the concentration of analytes including Pb, Cd, Zn and Cu (ppm)
By replacing the values included in the figure 8 to the general equation, the linear
regressions of heave metal Pb, Cd, Zn and Cu with good correlation coefficients
were obtained as follows
Abs Pb = -(0.0002 ± 0.0012) + (0.0191± 0.0008). CPb
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AbsCd = (0.0007 ± 0.0053) + (0.2841 ± 0.0126). CCd
AbsZn = -(0.0002 ± 0.0021) + (0.1528 ± 0.0050). CZn
AbsCu = (0.0016 ± 0.0014) + (0.04313± 0.0019). CCu
3.1.3. Limit of detection (LOD) and Limit of quantitation (LOQ)
Limit of detection and limit of determination are often used as quality criteria
for analytical methods.
- Limit of detection (LOD): is the lowest quantity of a analyst that can be
distinguished from the absence of that substance (a blank value) within a
stated confidence limit.
- Limit of quantitation (LOQ): is the lowest concentration of analyst in a
sample that can be determined with suitable precision and accuracy under the
stated experimental conditions.
The values LOD and LOQ are often calculated from S/N-ratios or calibration
functions and are not obtained in real samples. Therefore they are not useful as
criteria in routine analysis. Calculations from standard addition can be a helpful tool.
Using the statistics, limit of detection can be computed by the formula:
LOD = 3x Sy / b
Where:
Sy: the standard deviation of the calibration curve
b: the slope of the calibration curve Limit of quantitation of F-AAS method
from the calibration curve:
LOQ = 10 x Sy / b
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From the formulas of calibration curves of Pb, Cd, Cu, Zn, the LOD and LOQ
values could be calculated as depicted in table 3.6.
Table 3.6: LOD and LOQ of the determination of Pb, Cd, Zn and Cu using F-
AAS method
Analyte
No.
Pb Cd Zn Cu
Sy 2.652E-4 0.00233 9.290E-4 5.832E-4
B 0.01942 0.28416 0.15282 0.04313
LOD (ppm) 0.04 0.02 0.02 0.04
LOQ (ppm) 0.14 0.08 0.06 0.14
For the determination of trace elements in river sediments, the above value of
LOD and LOQ can be suitable for using this analytical method. But for the very low
concentration of Pb, Cd in surface water of river, the more sensitivity such as ICP-
MS should be applied.
3.1.4. Effect of interferences to the determination of Pb, Cd and Cu, Zn by
FAAS.
In environmental samples, Pb, Cu, Cd, Zn usually coexist with the same level
of content. These elements can be affected to the absorbance when analyze each one.
Therefore, the effect of other analysts has to be investigated before analyzing by
FAAS. The error of interferences is calculated by the following formula:
%𝑋 = 𝐴𝑡 − 𝐴𝑖
𝐴𝑡× 100%
Where:
+ % X: error.
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+ Ai: The value of the measured intensity of absorption when on interference
present (Abs)
+ At: Absorption intensity value found when the other analytes being exist
(Abs)
The precision of measurements was determined by the quantity of S2
and
value of RSD (%) and were calculated as follows:
𝑆2 = (𝐴𝑡−𝐴𝑖)
2
𝑛−1 𝑆 = 𝑆2 %𝑅𝑆𝐷 =
𝑆
𝐴𝑡𝑏. 100
Where:
+ Atb: The average absorbance.
+ n: number of measurements.
+ S or SD: standard deviation.
+ %RSD : relative standard deviation.
The experimental results is illustrated in table 3.7
Table 3.7: Result of errors and repeatability of the measurements
Pb (2ppm)
Element
(1ppm)
Abs % X
RSD %
Ai = Pb 0.02786
3.07 At = Pb + Cd 0.02895 3.9
At = Pb + Zn 0.02819 1.2
At = Pb + Cu 0.02984 3.9
Cd (2ppm)
Other element (1ppm)
Abs % X
RSD %
Ai = Cd 0.3681
6.13
At = Cd + Pb 0.3988 8.3
At = Cd + Zn 0.4164 13.1
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At = Cd+ Cu 0.4232 14.9
Zn (2ppm)
Other
element (1ppm)
Abs % X
RSD %
Ai Zn 0.09381 0.92
At = Zn + Pb 0.09548 1.8
At = Zn + Cd 0.09500 1.2
At = Zn + Cu 0.0958 2.1
Cu (2ppm)
Other element
(1ppm)
Abs %X
RSD %
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The obtained results showed that the relative error followed the Gaussian distribution
law. The beginning and the end of the linear error of greater suffering in the
concentration between the baseline errors is minimal. But all these errors are less
than the allowable limit of the analysis of ultra-traces is 15%.
In addition, many other cations do not have any affects on the absorbance of
Cu, Pb, Zn and Cd. The fact shows that the samples contain these cations’
concentration much smaller than the concentration of the 4 elements investigated. In
a word, there is no other cation in the samples effects directly on the analytic results.
3.2. Determination of Pb, Cu, Zn, Cd in surface water samples using ICP-
MS
In river water samples, the concentrations of four heavy metals (Pb, Cu, Zn,
Cd) are usually lower than the limit of detection of F-AAS method. Therefore, ICP-
MS techniques with very low limit of detection, and high selective and simultaneous
determination need to be applied to analyze. All the experimental conditions of ICP-
MS method were followed by instructors and manufacturer and were applicable as
the previous studies at Chemical Faculty, HUS.
3.2.1. Calibration curves for the determination of Cu, Zn, Pb and Cd in
water samples.
Four standard solutions of each analyte including Cu, Zn, Pd and Cd in 1%
HNO3 media were prepared and the analytical signal (cps) were obtained at
experimental conditions (part 2.4.2.2). Because of the large dynamic range with the
range of concentration changing from ppt to ppm, it is not necessary to investigate.
Based on the experimental results, the calibration curves of four metals were
investigated and illustrated in figure 3.3.
Ai = Cu 0.02143
4.69 At = Cu + Pb 0.02214 3.3
At = Cu + Cd 0.02391 11.6
At = Cu + Zn 0.02226 3.8
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0 50 100 150 200
0
20000
40000
60000
80000
100000
120000
140000
160000
180000
Parameter Value Error
------------------------------------------------------------
B 843.71621 7.29638
------------------------------------------------------------
R SD N P
------------------------------------------------------------
0.99979 1647.21236 4 <0.0001
------------------------------------------------------
Inte
nsity(c
ps)
Concentration of Cu (ppb)
0 50 100 150 200
0
10000
20000
30000
40000
50000
60000
Parameter Value Error
------------------------------------------------------------
B 264.20003 2.92194
------------------------------------------------------------
R SD N P
------------------------------------------------------------
0.99968 662.57934 4 <0.0001
-------------------------------------------------------
Inte
nsity
(cp
s)
Concentration of Cd (ppb)
0 50 100 150 200
0
50000
100000
150000
200000
250000
300000
350000
Parameter Value Error
------------------------------------------------------------
B 1627.84069 18.16054
------------------------------------------------------------
R SD N P
------------------------------------------------------------
0.99964 4113.33566 4 <0.0001
---------------------------------------------------------
Inte
nsity
(cp
s)
Concentration of Pb (ppb)
0 50 100 150 200
0
10000
20000
30000
40000
Parameter Value Error
------------------------------------------------------------
B 200.02019 2.70788
------------------------------------------------------------
R SD N P
------------------------------------------------------------
0.99992 607.20934 4 <0.0001
-----------------------------------------------------
Inte
nsity(c
ps)
Concentration of Zn (ppb)
Figure3.3: Calibration curves for the determination of Cu, Cd, Pb and Zn using ICP-MS
The concentrations of Cu, Cd, Pb and Zn in real samples were exploited by standard
method.
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3.2.2. Method validation
Accuracy and repeatability of the analytical process for total metals were
checked using estuarine sediment certified reference material (CM-MESS 3) from
National Institute of Standard and Technology (NIST), during which satisfactory
accuracy and repeatability were realized, with recovery between 85% and 113% as
shown on table 3.8.
Table 3.8: Accuracy and recovery of CRM using FAAS and ICP-MS
Metal
LOD (ppm)
Value
(±SD)
(mg/kg)
Recovery
(±SD)
(mg/kg)
RSD (%)
FAAS
Cu 0.14 33.9 ± 1.6 97 1.3
Pb 0.14 21.1 ± 0.7 113 7.8
Cd 0.08 0.24 ± 0.01 87 9.1
Zn 0.06 159 ± 8 91 2.7
ICP-MS
Cu 0.015x10-3
33.9 ± 1.6 101 4.4
Pb 0.042x10-3
21.1 ± 0.7 110 3.1
Cd 0.012x10-3
0.24 ± 0.01 85 2.0
Zn 0.011x10-3
159 ± 8 92 10.3
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3.3. Total concentrations of Cu, Pb, Cd, Zn in surface water and sediment
of ThadLuang marsh
3.3.1. Water sample:
The absorbance of each sample for each metal was measured by using ICP-MS. The
obtained results were showed in table 3.9.
Table 3.9: The concentration of Pb, Cd, Zn, Cu in surface water samples of
ThadLuang marsh (g/L)
Sample Pb Cd Zn Cu
W1 37.0±0.4 71.7±0.8 25.1±0.3 159±1
W2 29.1±0.3 55.9±0.6 82.5±1.1 34.5±0.3
W3 10.1±0.1 45.6±0.5 86.9±1.1 45.9±0.4
W4 28.2±0.3 66.0±0.7 60.1±0.8 42.3±0.4
W5 17.1±0.2 43.6±0.5 96.3±1.3 44.3±0.4
W6 31.7±0.4 65.2±0.7 106±1 65.7±0.6
W7 56.6±0.6 32.9±0.4 155±2 40.3±0.3
W8 15.1±0.2 76.7±0.8 85.2±1.1 82.2±0.7
3.3.2. Sediment sample
Using the F-AAS, the contents of four elements in the sediment samples were
calculated from the absorbance and the amount of sample (0.05 gram of each
sediment) taken and the following equation:
m (µg) = (Cx. Vo.) 1
0.05
Where: Cx (ppm) concentrations of metals in 25 mL volumetric
Phetdalaphone BOUTTAVONG 2009-2011
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flask.
V0 is the initial sample volume= 25 mL.
Table 3.10 shows the results of contents of four heavy metals analyted.
Table 3.10: Heavy metal content (mg/kg) in sediment collected in Thadluang
marsh.
Sample Element (mg/kg)
Pb Cd Zn Cu
S1 421.1±74.1 123.4±78.0 287.8±61.0 157.6±79.8
S2 417.2±74.1 134.6±77.7 60.45±60.1 95.3±82.6
S3 423.6±74.0 14.68±85.8 121.0±57.6 65.7±84.3
S4 450.6±73.8 163.9±77.2 313.5±62.8 232.6±77.5
S5 446.0±73.8 170.8±77.2 146.2±57.1 176.2±79.1
3.4. Surface Water Quality Standard
The proposed Surface Water Quality Standard is shown in the following table. Since
such standard has not been stipulated so far in Lao PDR, it is newly provided.
Table 3.11: Proposed Surface Water Quality standard
No. Substances Symbol Unit Standard
Value
Method of
Measurement
1. Color, Odor and Test - N -
2. Temperature ◦C N’ Thermometer
3. pH - 5-9 Electronic pH Meter
4. Dissolved Oxygen DO mg/l 6 Azide Modification
5. COD COD ml/l 5 Potassium permanganate
6. BOD5 BOD5 mg/l 1.5 Azide Modification at
20 degree C, 5 days
7. Total Coliform Bacteria Coliform
Bacteria
MPN/100 ml 5,000
Multiple Tube
Fermentation 8. Faecal Coliform Bacteria Faecal
Coliform
MPN/ 100 ml 1,000
9. Nitrate-Nitrogen NO3-N mg/l <5.0 Cadmium Reduction
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No. Substances Symbol Unit Standard
Value
Method of
Measurement
10. Ammonia-Nitrogen NH3-N mg/l 0.2 Distillation
Nesslerization
11. Phenols C6H5-OH mg/l 0.005 Distillation, 4-Amin
anti-Pyrenees
12. Copper Cu mg/l 0.1
Atomic Absorption
Direct Aspiration
13. Nickel Ni mg/l 0.1
14. Manganese Mn mg/l 1.0
15. Zinc Zn mg/l 1.0
16. Cadmium Cd mg/l 0.005
17. Chromium, Hexavalent Cr+6
mg/l 0.05
18. Lead Pb mg/l 0.05
19. Mercury Hg mg/l 0.002 Atomic Absorption Cold
Vapour
20. Arsenic As mg/l 0.01 Atomic Absorption
Direct Aspiration
21. Cyanide CN- mg/l 0.005 Pyridine-Barbituric
22. Alpha ¬ Radioactivity- α Becquerel l/l 0.1
Gas Chromatography
23. Beta ¬ Radioactivity- β Becquerel l/l 1.0
24. Total Organ chlorine mg/l 0.05
25. DDT C14H9Cl5 mg/l 1.0
26. Alpha -BHC α BHC mg/l 0.02
27. Dieldrine C12H8Cl6O mg/l 0.1
28. Aldrin mg/l 0.1
30. Endrin mg/l None
Source: The Draft Agreement of National Standard of Environment in Laos, March 2009
Following the results, heavy metals distributed along the That Luang Marshland
were shown in the Table 3.9. The concentration of Pb, Cd, Zn, Cu in surface water
samples of That Luang marsh (g/L) in this study collected on May, 2011 represent
for rainy season.
The heavy metal concentrations higher than the standard value were witnessed in
Pb2+
accounting for 56.6±0.6 (g/L) of the water samples point 7, 37.0±0.4 (g/L)
of the water samples point 1, 31.7±0.4 4 of the water samples point 6. Concentration
for the Cd2+
accounting for 76.7±0.8 (g/L) of the water sample point 8, 71.7±0.8
(g/L) of the water sample point 1, 66.0±0.7 (g/L) of the water sample point 4,
65.2±0.7 (g/L) of the water sample point 6. Concentration for the Zn2+
accounting
for 155±2 (g/L) of the water sample point 7, 106±1 (g/L) of the water sample
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point 6, 96.3±1.3 (g/L) of the water sample point 5. Concentration of Cu2+
accounting for 159±1 (g/L) ) of the water sample point 1, 82.2±0.7 (g/L) of the
water sample point 8, 65.7±0.6 (g/L) of the water sample point 6.
The heavy metal concentration higher than the standard value were seen in the
concentration of Pb2+
with 450.6±73.8 (mg/kg) of the sediment samples point 4,
446.0±73.8 (mg/kg) of the sediment samples point 5. Concentration of Cd2+
with
163.9±77.2 (mg/kg) of the sediment sample point 4, 170.8±77.2 (mg/kg) of the
sediment sample point 5. Concentration of Zn2+
with 146.2±57.1 (mg/kg) of the
sediment sample point 5, 287.8±61.0 (mg/kg)) of the sediment sample point 1,
313.5±62.8 (mg/kg) of the sediment sample point 4. Concentration of Cu2+
with
157.6±79.8 (mg/kg) of the sediment sample point 1, 232.6±77.5 (mg/kg) of the
sediment sample point 4, 176.2±79.1 (mg/kg) of the water sample point 5.
Water and sediment samples were determined by Inductively coupled plasma mass
spectrometry (ICP-MS) and Flame- Atomic absorption spectroscopy (F-AAS) shown
the result that in water samples were detected concentration of in any point which
mean that its concentration of Pb2+
, Cd2+
, Zn2+
and Cu2+
less than the concentration
of surface water of standard parameter, but for sediment samples were found out
higher accumulation of Pb2+
from 450.6±73.8 (mg/kg) and Cd2+
from 170.8±77.2
(mg/kg) residue in the both point S5, Zn2+
from 313.5±62.8 (mg/kg) and Cu2+
232.6±77.5 (mg/kg) residue in the both point 4 than other point, but we don't have
sediment of standard parameter for compare, due to the location of this area near the
agriculture area and Beer Lao factory .
Heavy metal contents accumulate in the surface water and sediment compartment in
other point, even though the location of this area is very near from ThadLuang
marshland, this point has many canals from the village run to this area. The villagers
mostly worked in paddy field around the canal. This can anticipate that heavy metal
contents contaminated this area come from paddy field, market, factory and other
farm activity.
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3.4. Application of GIS to find out spatial distribution of heavy metals
Figure 3.4 : The Map of water quality of Thadluang Marsh.
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65
Figure 3.5: The Map of sediment quality of Thadluang Marsh.
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CHAPTER 4: CONCLUSION
Water quality for drainage canals and marshes have been getting worse and water
have been increasing due to increasing discharge of domestic wastewater from urban
areas, resulting from improved living standards, rapid economic and population
growth. Urban areas are facing higher population growth rates than the national
average, representing rural urban migration. Present development trends have
stimulated the urbanization process due to increased growth in the industry and
tourism sectors of the city, combined with rural to urban migration that lead to an
increase in environmental problems, degradation of wetland areas and wastewater
management problems.
In this thesis, I studied and received some significant results
- Application of Inductively coupled plasma mass spectrometry (ICP-MS) and
Flame- Atomic absorption spectroscopy (AAS) to analyze
- Investigation of optimal conditions of some chemical factors influencing to
absorbance in F- AAS method
+ Studying the effects of sample matrix and matrix modifier to F-AAS:
matrix of samples should be kept at 2% HNO3 and 1% NH4CH3OO
+ The limit of linearity of Pb, Cd, Zn and Cu measurements: the limit of
linearity (LOL) of four heavy metal concentrations is up to 2.5 ppm with Pb; 0.75
ppm with Cd and Zn; 1.25 ppm with Cu measurements.
- By F-AAS method, the amount of Pb2+
, Cd2+
, Zn2+
and Cu2+
in 5 sediment
samples taken in ThadLuang marsh was determined. Moreover, the
determination of the amount of these 4 elements in 8 water samples was taken
place by ICP Ms, so the extent of pollution is also estimated. The amount of the
heavy metal in water fluctuates from 10 to 159µg/L while the changing is seen
in sediment from 14.68 to 450.6mg/kg. They are in the range of standard values.
From this analysis it can find the way or support the project to establish the factory
or the system for waste water treatment for Vientiane’s city. It can use these data’s to
make or produce the artificial lake for treat the wastewater by using the necessary
plants or bio-treatment in another places.
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