Investigation the heavy metal contents in surface water and sediment collected in thadluang marsh (lao PDR)

VIETNAM NATIONAL UNIVERSITY, HANOIVNU UNIVERSITY OF SCIENCE PHETDALAPHONE BOUTTAVONG INVESTIGATION THE HEAVY METAL CONTENTS IN SURFACE WATER AND SEDIMENT COLLECTED IN THADLUANG MARSH LAO

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

VIETNAM NATIONAL UNIVERSITY, HANOI

VNU UNIVERSITY OF SCIENCE

PHETDALAPHONE BOUTTAVONG

INVESTIGATION THE HEAVY METAL

CONTENTS IN SURFACE WATER AND SEDIMENT

In Vientiane, water and sanitation management in the urban area is experiencingstagnant pollution Unsanitary conditions and threat of seasonal pollution in selectedspots is likely to occur and increase with the growing urban population Thesanitation system entails an on-site disposal of human waste without introduction offull water-borne sewerage with treatment facility and safe disposal arrangement Themajorities of households relies on water flush latrines and are connected to a pit orchamber for containment of excreta However, due to the low permeability of the soiland the high groundwater table around Vientiane, many soak-a-ways fail to operateeffectively resulting in discharge of sewage from tanks into drainage channels or lowlying areas This pollution leads to effluent overflows, environmental degradationand health hazards

For the sake of assessment in what extent is water polluted, an analytical methodwith high sensitivity and the capability and providing a good accuracy and precisionshould be used Atomic absorption spectroscopy (AAS) is a spectroanalyticalprocedure for the qualitative and quantitative determination of chemical elementsemploying the absorption of optical radiation (light) by free atoms in the gaseousstate 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 makesuse 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 inThadLuang Marsh in Vientiane Capital City Providing an overview about alarminglypolluted situation, this research based on determination of Copper, Lead, Cadmiumand Zinc by Flame – Atomic absorption spectroscopy

I would like to thank, DAAD, Deutscher Akademischer Austauschdienst (GermanAcademic Exchange Service) and Technich University Dresden for providing thescholarship of the Master’s program My sincere thanks also due to the Dean offaculty Environmental of sciences in National University of Lao P.D.R for the kindpermission 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 myadvisor Prof Bernd Bilitewski for his excellent guidance, excellent encouragementand valuable suggestions throughout this study Special appreciation is extended toProf Dr Nguyen Thi Diem Trang and Prof Dr Do Quang Trung committeemembers for their valuable recommendation and dedicated the valuable time toevaluate my work and my study during being in Vietnam

During studying in Hanoi University of Science, I felt very lucky, it give me theopportunity to have lots of good friends, good memories, so I would like to saythanks and pleasure to meet all of you Even though we came from differentcountries, we can make friend together I hope and wish that I would work togetherand meet each other again in some conferment

Finally I would like to express deep appreciation to my lovely family and relativesfor their love, kind support, and encouragement for the success of this study Thisthesis is dedicated for you

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

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

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

Figure 3.4: The Map of water quality of Thadluang Marsh

Figure 3.5: The Map of sediment quality of Thadluang Marsh.

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 usingICP- MS techniques

Table 3.1: Investigation of HNO3 and NH4CH3COO effects on analysis of Pb, Cd,

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 (µg/L)

Table 3.10: Heavy metal content (mg/kg) in sediment collected in Thadluang marsh.Table 3.11: Proposed Surface Water Quality standard

The Lao People’s Democratic Republic (Lao PDR) is a small landlocked andsparsely populated country in the South East Asia Laos is characterized by two maingeographical zones: the central plains along the Mekong River and the mountainousregions to the north, east and south Lao PDR has a land area of 236,800 squarekilometers (sq km.) It is long and slender, the length from north to south is nearly1,000 kilometers and the width has only 150 kilometers to 400 kilometers [STEA,2004] The total population is approximately 5,621,982 people, in which womenaccounted for 51%, according to the 2005 population and housing census Thepopulation density of the country is around 24 people per hectare which is the lowestpopulation densities in Asia 39% of Lao population is classified as poor and 36% areunder poverty line [MRC, 2006] Their living condition depends on nature, huntingwildlife, foraging for forest products and practicing slash and burn cultivation fortheir crops with a low profit in order to survive

Lao PDR has rich water resources, mainly good quality fresh water The amount ofaverage 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 51percent 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 Themonthly 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 dryseason, from November to April For some rivers in the central and southern parts ofthe country (particularly Se Bang Fai, Se Bang Hieng and Se Done) the flow in thedry season is less: around 10 to 15% of the annual flow [Agricultural Statistics

[April 2005] The rivers outside the Mekong Basin flow through Viet Nam into theSouth China Sea These rivers are Nam Ma, Nam Sam, and Nam Neune The limitedinformation 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; thecountry has the potential to produce 23,000 megawatts of electricity Currently 5% ofthat capacity has been exploited [Would Back, 2007] The plenteous supply of water

in Lao PDR, especially in the rainy season, provides good condition for watertransport, industrial development and water supply Sixty percent of urban populationand 51 % of rural population has access to clean water

Currently there are some problems related to waste and polluted water in majorurban areas from varied community use (residential density, hotels, hospitals andentertainments centers) In addition there is water pollution from agricultural andindustrial sectors, including mineral exploitation This is not a major problem now,but the problem could escalate The degradation of natural water and watercatchments from sedimentation, land erosion and drying out continues

However, as continued development takes place in all of these areas, increasingscarcity and competition for water can be expected Increasing impacts ofdevelopment on water quality and on human health and the natural environment willalso take place Finally, floods and drought can have serious negative impacts andmay, in fact, increase as climate change takes place

Vientiane Capital is located on an alluvial plain along the left bank of Mekong Rivereast to west The area of Vientiane is about 3,920 km2 and the elevation of theground ranges from 160 m to 170 m above the sea level The city comprises 9districts; Chanthabuly, Hadxayfong, Meungparkngum, Naxaithong Sangthong,Sikhottabong, Sisattanak, Saysettha and Xaythany The population is around 672,912people The area designated for urbanization extends along the left bank of MekongRiver and occupies an area of 210 km2 [JICA, 2009] For Thadluang wetland, itswater 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 andsewage (from the city area) discharged into the marsh

Especially, no sooner do many factories appear and develop increasing fast thanwater 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 inhuman 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 mineralsexploiting area The main reason leading to heavy metals pollution is pouring intowater environment a large amount of industrial and untreated wastewater Pollution

by heavy metals accumulated through foods directly into organism has negativeeffects on life environment In order to reduce consequence of this problem, it isnecessary to cultivate measures of water treatment

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 VientianeMunicipality, located on the eastern edge of the capital city of Lao PDR The marshitself is approximately 20 km2 and is a part of the ThadLuang Basin drained fromVientiane City and surrounding areas A large portion of the wetland has beenconverted to rice cultivation although changes in water regimes have resulted inannual floods and cultivation has been limited to between 700 - 1000 ha(approximately half of the wetland area) in recent years The remaining area iscovered with permanent and seasonal aquaculture ponds, shrub and grassland, andpeat land [NUOL, March, 2002] Water draining into the ThadLuang Marshlandcomes primarily from irrigation canal at the Donnokkoom rice field, Hong Ke andHong Xeng stream, which collects its water from drainage canals running throughoutVientiane Water running out of the marsh follows Houay Mak Hiao River dumpinginto 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 ofhouseholds as relatively better off category Because of the structure of ruralemployment, the livelihoods of households around ThadLuang Marsh are highlydepended upon the ThadLuang marsh, and the water resources availability at themarsh This is because agriculture and sale of agriculture produce are the primaryincome generating activity for over 70 % of households living around the ThadLuangmarsh About 7 percent of the total households there are without a primary form ofincome from agriculture (farming), and it is likely that they rely heavily on collectingfish and aquatic produce from the marsh area [STO, 2009] Therefore, being one ofmain reasons leading to poverty, water and sediment pollution in ThadLuang marshaffect significantly on life of people here

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 largeproportion of Vientiane city by way of several canals While Vientiane has asewerage system, there is currently no functioning waste treatment facility near theurban area Sewage is either hauled to a waste treatment plant 17 km outside of thecity limits or, more commonly, discharged into natural water bodies, either as rawwastes or as seepage from septic tanks Sewerage and sanitation systems rely on theinfiltration of wastewater into the ground However due to the low soil permeabilityand the high groundwater table in Vientiane, many soak ways fail to operateefficiently meaning that sewage is discharged from tanks and drains directly intourban wetlands As a result of considerable quantity of household waste and sewage

is discharged into Nong Chang, and then flows into ThadLuang Marsh beforeentering the Mekong Textile, detergent and paper plants discharge directly into opendrains without any treatment, and contribute wastewaters into ThadLuang Marsh

There are two tanneries although the larger of these has sophisticated treatmentfacilities, 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 toVientiane environment, it is irrefutable that researching water pollution inThadLuang is necessary and must be done immediately Some data published onpollution in ThadLuang marsh is shown in table 1.1

Table 1.1: Some data published on pollution in ThadLuang marsh

Parameters

(STEA, 2000)

pH

Temperature

Electrical Conductivity (EC)

Dissolve Oxygen (DO)

Biological Oxygen Demand (BOD)

lower There is sound that water pollution appears compared to Surface WaterQuality 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 manyfactories appear and develop increasing fast than water is polluted by heavy metals isover 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 butmay progress to chemical pneumonitis, pulmonary edema, and death [Ayres, Robert

U, 2003]

Cadmium is also an environmental hazard Human exposures to environmentalcadmium 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 withcadmium and traces of other toxic metals.[National Research Council (U.S.), 1969) ]

As a consequence, cadmium accumulated in the rice crops growing along theriverbanks downstream of the mines Some members of the local agriculturalcommunities consuming the contaminated rice developed itai-itai disease and renalabnormalities, including proteinuria and glucosuria

The victims of this poisoning were almost exclusively post-menopausal womenwith low iron and other mineral body stores Similar general population cadmiumexposures in other parts of the world have not resulted in the same health problemsbecause the populations maintained sufficient iron and other mineral levels

Thus, while cadmium is a major factor in the itai-itai disease in Japan, mostresearchers have concluded that it was one of several factors Cadmium is one of sixsubstances banned by the European Union's Restriction on Hazardous Substances(RoHS) directive, which bans certain hazardous substances in electrical and

electronic equipment but allows for certain exemptions and exclusions from thescope of the law.

Although some studies linked exposure to cadmium with lung and prostatecancer, there is still a substantial controversy about the carcinogenicity of cadmium.More recent studies suggest that arsenic rather than cadmium may lead to theincreased lung cancer mortality rates Furthermore, most data regarding thecarcinogenicity of cadmium rely on research confounded by the presence of othercarcinogenic substances

Tobacco smoking is the most important single source of cadmium exposure inthe 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 cadmiuminhaled via cigarette smoke may be absorbed [Jarup, L (1998)]

On average, smokers have 4-5 times higher blood cadmium concentrationsand 2 - 3 times higher kidney cadmium concentrations than non - smokers Despitethe high cadmium content in cigarette smoke, there seems to be little exposure tocadmium from passive smoking No significant effect on blood cadmiumconcentrations has been detected in children exposed to environmental tobaccosmoke

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-coatedcopper cookware, or from exposure to excess copper in drinking water or otherenvironmental sources

Copper in the blood exist in two forms: bound to ceruloplasmin (85–95%) andthe rest "free" loosely bound to albumin and small molecules Free copper causestoxicity as it generates reactive oxygen species such as superoxide, hydrogenperoxide , the hydroxyl radical These damage proteins, lipids and DNA [FederalRegister, 1976]

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), andgastrointestinal distress Individuals with glucose-6-phosphate deficiency may be atincreased risk of hematologic effects of copper Hemolytic anemia resulting from thetreatment of burns with copper compounds is infrequent

Chronic (long-term exposure) effects of copper exposure can damage the liverand kidneys Mammals have efficient mechanisms to regulate copper stores such thatthey 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 theexpectation that a lifetime of consuming copper in water at this level is withoutadverse effect (gastrointestinal effect) The U.S EPA lists evidence that copper causestesticular cancer as "most adequate" according to the latest research at Sanford-Burnham Medical Research Institute The Occupational Safety and HealthAdministration (OSHA) has set a limit of 0.1 mg/m3 for copper fumes (vaporgenerated from heating copper) and 1 mg/m3 for copper dusts (fine metallic copperparticles) and mists (aerosol of soluble copper) in workroom air during an 8-hourwork 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 inyoung children) and cause blood and brain disorders Lead poisoning typicallyresults from ingestion of food or water contaminated with lead; but may also occurafter accidental ingestion of contaminated soil, dust, or lead based paint Long-termexposure to lead or its salts (especially soluble salts or the strong oxidant PbO2) cancause nephropathy, and colic-like abdominal pains The effects of lead are the samewhether it enters the body through breathing or swallowing Lead can affect almostevery organ and system in the body The main target for lead toxicity is the nervoussystem, both in adults and children Long-term exposure of adults can result indecreased performance in some tests that measure functions of the nervous system Itmay also cause weakness in fingers, wrists, or ankles Lead exposure also causessmall increases in blood pressure, particularly in middle-aged and older people andcan cause anemia Exposure to high lead levels can severely damage the brain and

kidneys in adults or children and ultimately cause death In pregnant women, highlevels of exposure to lead may cause miscarriage Chronic, high-level exposure hasshown 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 broughtabout widespread reduction in its use (lead exposure has been linked to learningdisabilities) Most cases of adult elevated blood lead levels are workplace-related.High blood levels are associated with delayed puberty in girls Lead has been shownmany times to permanently reduce the cognitive capacity of children at extremelylow levels of exposure

During the 20th century, the use of lead in paint pigments was sharply reducedbecause of the danger of lead poisoning, especially to children By the mid-1980s, asignificant shift in lead end-use patterns had taken place Much of this shift was aresult of the U.S lead consumers' compliance with environmental regulations thatsignificantly reduced or eliminated the use of lead in non-battery products, includinggasoline, paints, solders, and water systems Lead use is being further curtailed bythe 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 electricalcords), and brass manufactured in China Between 2006 and 2007 many children'stoys made in China were recalled, primarily due to lead in paint used to color theproduct [Stellman, Jeanne Mager (1998).]

Older houses may still contain substantial amounts of lead paint White leadpaint has been withdrawn from sale in industrialized countries, but the yellow leadchromate is still in use; for example, Holland Colours Holcolan Yellow Old paintshould not be stripped by sanding, as this produces inhalable dust

Lead salts used in pottery glazes have on occasion caused poisoning, whenacidic drinks, such as fruit juices, have leached lead ions out of the glaze It has beensuggested that what was known as "Devon colic" arose from the use of lead-linedpresses to extract apple juice in the manufacture of cider Lead is considered to beparticularly 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 RomanEmperors

Lead as a soil contaminant is a widespread issue, since lead is present innatural deposits and may also enter soil through (leaded) gasoline leaks fromunderground storage tanks or through a waste stream of lead paint or lead grindingsfrom certain industrial operations.

Lead can also be found listed as a criteria pollutant in the United States CleanAir 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 bloodstreamand is believed to have adverse effects on the central nervous system, thecardiovascular system, kidneys, and the immune system [Hong, Youlian andBartlett, Roger, ed (2008)]

In the human body, lead inhibits porphobilinogen synthase and ferrochelatase,preventing both porphobilinogen formation and the incorporation of iron intoprotoporphyrin IX , the final step in hemi synthesis This causes ineffective hemisynthesis and subsequent microcytic anemia At lower levels, it acts as a calciumanalog, interfering with ion channels during nerve conduction This is one of themechanisms by which it interferes with cognition Acute lead poisoning is treatedusing disodium calcium edentate: the calcium chelae of the disodium salt ofethylene-diamine-tetracetic acid (EDTA) This chelating agent has a greater affinityfor lead than for calcium and so the lead chelae is formed by exchange This is thenexcreted in the urine leaving behind harmless calcium

1.3.4 Zinc Zn

Although zinc is an essential requirement for good health, excess zinc can beharmful Excessive absorption of zinc suppresses copper and iron absorption Thefree zinc ion in solution is highly toxic to plants, invertebrates, and even vertebratefish The Free Ion Activity Model is well-established in the literature, and shows thatjust 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 togive 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 ofthe zinc ion in the acidic stomach

There is evidence of induced copper deficiency at low intakes of 100–300 mgZn/day; a recent trial had higher hospitalizations for urinary complications compared

to placebo among elderly men taking 80 mg/day [Fosmire GJ (1990)] The USDARDA 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 adverselyaffect cholesterol Levels of zinc in excess of 500 ppm in soil interfere with theability 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 theinhalation of freshly formed zinc oxide formed during the welding of galvanizedmaterials

The U.S Food and Drug Administration (FDA) has stated that zinc damagesnerve receptors in the nose, which can cause anomies Reports of anomies were alsoobserved in the 1930s when zinc preparations were used in a failed attempt toprevent polio infections On June 16, 2009, the FDA said that consumers should stopusing zinc-based intranasal cold products and ordered their removal from storeshelves The FDA said the loss of smell can be life-threatening because people withimpaired smell cannot detect leaking gas or smoke and cannot tell if food has spoiledbefore they eat it Recent research suggests that the topical antimicrobial zincpyrithione is a potent heat shock response inducer that may impair genomic integritywith induction of PARP-dependent energy crisis in cultured human keratinocytes andmelanocytes

In 1982, the United States Mint began minting pennies coated in copper butmade primarily of zinc With the new zinc pennies, there is the potential for zinctoxic 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 fungalsepsis , while another patient, who ingested 12 grams of zinc, only showed lethargyand ataxia (gross lack of coordination of muscle movements) Several other caseshave been reported of humans suffering zinc intoxication by the ingestion of zinccoins

Pennies and other small coins are sometimes ingested by dogs, resulting in theneed for medical treatment to remove the foreign body The zinc content of somecoins can cause zinc toxicity, which is commonly fatal in dogs, where it causes asevere hemolytic anemia, and also liver or kidney damage; vomiting and diarrhea are

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 parrotpoisonings 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 adropping mercury electrode (DME) or a static mercury drop electrode (SMDE)useful for its wide cathodic range and renewable surface It was invented by JaroslavHeyrovský , 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 ofmeasurement that falls into the general category of linear-sweep voltammetry wherethe electrode potential is altered in a linear fashion from the initial potential to thefinal potential As a linear sweep method controlled by convection/diffusion masstransport, the current vs potential response of a polarographic experiment has thetypical sigmoidal shape What makes polarography different from other linear sweepvoltammetry measurements is that polarography makes use of the dropping mercuryelectrode (DME) or the static mercury dropping electrode

A plot of the current vs potential in a polarography experiment shows thecurrent oscillations corresponding to the drops of Hg falling from the capillary If oneconnected the maximum current of each drop, a sigmoidal shape would result Thelimiting current (the plateau on the sigmoid), called the diffusion current becausediffusion is the principal contribution to the flux of electro active material at thispoint 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 andcadmium in beer in Hanoi by alternating current differential pulse polarography withsensitivity accounting for 1ppb [Tu Van Mac, Tran Thi Sau]

Thanh Thuc Trinh, Nguyen Xuan Lang and their colleagues has appliedpolarimetry on determination of Zinc, Cadmium, Lead and Copper in some kinds of

food and agricultural soil It is experimented in environment of acetate buffer withsystem of 3 polars: hanging mercury drop electrode, reference electrode Ag/AgCl,auxiliary electrode Pt and electrodeionization potential accounting for -1.05V in 60seconds [Thanh Thuc trinh, Nguyen Xuan Lang].

1.4.1.2 Voltammetry

Voltammetry is a category of electroanalytical methods used in analyticalchemistry and various industrial processes In voltammetry, information about ananalyte is obtained by measuring the current as the potential is varied Voltammetryexperiments 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 bystep or continuously and the actual current value is measured as the dependentvariable The opposite, i.e., amperometry, is also possible but not common Theshape of the curves depends on the speed of potential variation (nature of drivingforce) and on whether the solution is stirred or quiescent (mass transfer) Mostexperiments control the potential (volts) of an electrode in contact with the analytewhile measuring the resulting current (amperes) [Zoski, Cynthia G (2007-02-07)].Professor Petrovic and his colleagues used Differential pulse strippingvoltametry 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 Sadikoglustudied about direct determination of zinc heavy metal in the tap water carried out bydifferential pulse anodic stripping voltammetry technique at the glassy carbonelectrode (GCE) The zinc ions were deposited by reduction at -1.5 V on a bareglassy carbon surface Then, the deposited metal was oxidized by scanning thepotential 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 theconcentration 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 acetatebuffer (pH: 3.50) [Selehattin Yilmaz, 2009]

1.4.2 Spectrophotometric methods

1.4.2.1 Ultraviolet-visible spectrophotometer

Ultraviolet-visible spectroscopy or ultraviolet-visible spectrophotometer Vis or UV/Vis) refers to absorption spectroscopy or reflectance spectroscopy in theultraviolet-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 thevisible range directly affects the perceived color of the chemicals involved In thisregion of the electromagnetic spectrum, molecules undergo electronic transitions [Prabhakar, Dubinskii, Editors and Dekker (2002)] This technique is complementary

(UV-to fluorescence spectroscopy, in that fluorescence deals with transitions from theexcited state to the ground state, while absorption measures transitions from theground state to the excited state UV/Vis spectroscopy is routinely used in analyticalchemistry for the quantitative determination of different analytes, such as transitionmetal 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 cellsfilter to determination of Cd (II) in sea water by UV/Vis spectroscopy with LOD is0.006 ppm [Gao Hong – Wen (1995),]

A.M Garcia Rodriguez, A Garcia de Torres and J.M Cano Pavon studied aboutsimultaneous determination of iron, cobalt, nickel and copper by UV-visiblespectrophotometry 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/mlrespectively.A method for the simultaneous spectrophotometric determination of thedivalent ions of iron, cobalt, nickel and copper based on the formation of theircomplexes with 1,5-bis(di-2-pyridylmethylene) thiocarbonohydrazide (DPTH) isproposed.[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 thatuses the intensity of light emitted from a flame, plasma, arc, or spark at a particularwavelength to determine the quantity of an element in a sample The wavelength ofthe atomic spectral line gives the identity of the element while the intensity of theemitted light is proportional to the number of atoms of the element A sample of a

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 solventand breaks chemical bonds to create free atoms The thermal energy also excites theatoms into excited electronic states that subsequently emit light when they return tothe 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 frequentapplication of the emission measurement with the flame is the regulation of alkalimetals 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 forthe qualitative and quantitative determination of chemical elements employing theabsorption of optical radiation (light) by free atoms in the gaseous state In analyticalchemistry the technique is used for determining the concentration of a particularelement (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 makesuse 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 themeasured 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 tohigher orbitals (excited state) for a short period of time (nanoseconds) by absorbing adefined 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

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 asample and with a sample in the atomizer is measured using a detector, and the ratiobetween the two values (the absorbance) is converted to analyte concentration ormass using Beer-Lambert Law.

Hüseyin Bağ, A.Rehber Türker , Ramazan Coşkun, Mehmet Saçak, MustafaYiğitoğlu studied about determination of zinc, cadmium, cobalt and nikel by flameatomic 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 onthe recovery of the analytes have been investigated Recoveries of Zn, Cd, Co and Niwere 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 alsostudied 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 aboutdetermination 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 aboutdetermination of copper in sea water by flow-injection- atomic absorptionspectrometry By using the optimized flow systems, seawater samples were collectedand 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 ofthe saline matrix Once in the laboratory, the mini-columns loaded with copper areincorporated 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-burnersystem of a flame atomic absorption spectrometer Analysis of certified referencematerials (SLEW-3 and NASS-5) showed good agreement with the certified value.[Susumu, Masakazu (1983)]

Conclusion: Because the objects of our research are surface water and sedimentsamples containing heavy metals as Cd, Cu, Pb, Zn… the amount of heavy metalsmust be determined exactly in order to evaluate the quality of water Modernanalytical methods such as GF-AAS, ICP-MS… require expensive equipments andcostly fees In this case, using F-AAS is a reasonable choice with high sensitivity andthe capability to analyze many elements in complex matrices, providing a goodaccuracy and precision result, short time for analyzing and cheap price Thereferenced results obtained by ICP-MS will be also included to recognize the ultratrace of heavy metal contents in some environmental samples.

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 andassessments the distribution these heavy metals contents in environmental samples ofstudied mash No sooner do many factories appear and develop increasing fast thanwater is polluted by heavy metals is over allowable limit Owing to not taking part inbiochemical process, heavy metals such as Cd, Pb, Zn, Cu… are accumulated inhuman 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 mineralsexploiting area The main reason leading to heavy metals pollution is pouring intowater environment a large amount of industrial and untreated wastewater Pollution

by heavy metals accumulated through foods directly into organism has negativeeffects on life environment In order to reduce consequence of this problem, it isnecessary 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

- 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-MSmeasurement Working solutions of analysed ions were prepared by dilution ofstandard 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, HNO3was prepared from con.HNO368%

- Super pure water (Resistance >=18.2MΩ) 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

2.2.3 Equipments

- AAS- novAA spectrometer with pneumatic nebulisation and mono- elementlamps 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

Table 2.1: Characteristics of the water sampling points in Thadluang marsh

Figure 2.2: The map of Thadluang marsh showing water sampling sites.

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

Figure 2.3: The map of Thadluang marsh showing sediment sampling sites.

2.3.2 Sampling and sample preparation

Surface water and sediment samples were collected from various places inThadluang marsh Sample were collected and prepared for experiments in a standardways described in the literatures for these kinds of materials

All laboratory glassware and plastic ware, polyethylene sample and reagentbottles were cleaned by soaking in a detergent solution, rinsed with ultra pure waterfrom a Millipore Q50 system and soaking in a HNO3 ( 2%), v/v) bath overnight Thiswas followed by thorough rinsing with pure and dried before use

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 toVietnamese laboratory to analyze

At laboratory, the amount of 0.05 g of each sample was weighted separatelythen 2 ml of 63% solution of HNO3 acid, 5 ml of 32% solution of HCl acid wereadded 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 untilappearance 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

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

Figure 2.4: Operation principle of an atomic absorption spectrometer.

The characteristic wavelengths are element specific and accurate to 0.1nm To provide element specific wavelengths, a light beam from a lamp whosecathode is made of the element being determined is passed through the flame Adevice such as photomultiplier can detect the amount of reduction of the lightintensity due to absorption by the analyte, and this can be directly related to theamount of the element in the sample [Haswell, S.J., 1991]

0.01-Different flames can be achieved using different mixtures of gases, depending

on the desired temperature and burning velocity Some elements can only beconverted 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

their formation, conditions of the flame may be modified to achieve a reducing, nooxidizing 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 instrumentsutilize the direct aspiration During aspiration, the gas flow breaks down the liquidsample into droplets, and the nebulization performance depends on the physicalcharacteristics 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, whichgenerates 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

 Part 1: Power-ray emission of the resonant element analysis (emission

spectral lines characteristic of the element to be analyzed), to compare theabsorption 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 opticalpower 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