Assessment of heavy metals in sediments and aquatic organisms in West Lake (Ho Tay), Hanoi, Vietnam

Lakes & Reservoirs: Research and Management 2007 12: 285–294

© 2007 The AuthorsDoi: 10.1111/j.1440-1770.2007.00343.x Journal compilation © 2007 Blackwell Publishing Asia Pty Ltd

Blackwell Publishing Asia Original ArticlesHeavy metals in West Lake, VietnamAssessment of heavy metals in sediments and aquatic

organisms in West Lake (Ho Tay), Hanoi, VietnamNga Thi Thu Pham, Alexandra Pulkownik and Rodney T. Buckney

Department of Environmental Sciences, Faculty of Science, University of Technology, Sydney (UTS), PO Box 123, Broadway, New South Wales, Australia

AbstractWest Lake (Ho Tay) is the largest freshlake in Hanoi, Vietnam. It has a surface area of ≈ 500 ha and a total volume of>107 m3, and is 1–3.5 m in depth. West Lake has been classified as needing protection because of its valuable freshwatergenetic resources. Noting that it has been extensively affected by pollution, the objective of the present study was toexamine the extent of heavy metal contamination of the sediments and commercially important biota in the lake. Heavymetal concentrations in the sediment from most of 24 samples in West Lake exceeded the Ontario Ministry of EnvironmentScreening Level for chromium (Cr), copper (Cu), manganese (Mn), lead (Pb) and zinc (Zn) concentrations. Aquaticorganisms from the lake also were found to be contaminated by heavy metals. The average Zn concentrations in snails andmussels tissues ranged between 174 and 415 µg g–1, and the Pb concentrations between 3.5 and 5.2 µg g–1. The Cuconcentration in shrimp (52 µg g–1) and snail (189 µg g–1), and the Pb concentration in all fish species and shrimp from thelake (2.0–5.2 µg g–1) exceeded the Food Standard Australia-New Zealand (FSANZ) health standards for human consumption.The Cd concentration in Cyprinus carpio also exceeded the FSANZ standard. The implications of these study findings forthe effective management of the food and ecological resources of West Lake are discussed.

Key wordsaquatic organisms, Hanoi, heavy metals, sediment, West Lake.

INTRODUCTIONHeavy metals in water can originate both from naturalsources and from industrial, agricultural and domesticactivities in the drainage basin of a water system. Theheavy metals of most environmental concern in water arelead (Pb), chromium (Cr), arsenic (As), cadmium (Cd),copper (Cu) and zinc (Zn) (Martin & Coughtrey 1982; Larset al. 1986; Abel 1989). Contamination by these heavymetals can be expressed by their high concentrations inwater, as well as in sediments and aquatic organisms.Contamination of sediments by heavy metals and otherpollutants is considered by many regulatory agencies to beone of the major threats to aquatic ecosystems. Heavymetal contamination of sediments has been reportedfor some Asian countries, with accompanying negativeimpacts on aquatic organisms (reviewed by Karadede &Ünlü 2000; Alam et al. 2001; Marke et al. 2001; Shen et al.

2005). Contamination of water and sediments also canaffect the health of aquatic animals, either directly byuptake by the animals of the materials from water, orindirectly through their diet (Martin & Coughtrey 1982;Lars et al. 1986; Kime et al. 1996). As aquatic organismsare a part of the natural diet of aquatic mammals and ofterrestrial organisms (e.g. birds, humans), their healthalso is of concern when water systems are polluted (Kimeet al. 1996). Benthic organisms can be affected directlyby heavy metal contamination via contaminated sediment.Other studies (Liang et al. 1999; Karadede & Ünlü 2000;Moissenko & Kudryaytsev 2001; Rashed 2001; Alam et al.2002; Wagner & Bomam 2003; Sekhar et al. 2004; Wagner& Bomam 2004; Begum et al. 2005) have reported directlyon heavy metal contamination of fish and mussels.

Heavy metals absorbed by living organisms can bind tocellular components (proteins, nucleic acids, etc.) andinterfere with normal functions of the organisms (Larset al. 1986). The effects of such heavy metal toxicity can bevery serious, leading not only to diseases but also havingpotential genotoxic effects (Martin & Coughtrey 1982).

*Corresponding author.

Email: [email protected]

Accepted for publication 22 July 2007.

286 N. T. T. Pham et al.

© 2007 The AuthorsJournal compilation © 2007 Blackwell Publishing Asia Pty Ltd

West Lake (Ho Tay), located near Hanoi, Vietnam, at21°04′′N, 105°05′′E, was created from a section of the RedRiver ≈1000 years ago, being the largest lake in the delta ofthe Red River. It has a surface area of ≈ 500 ha and atotal water volume of >107 m3. The lake is shallow (depth of1–3.5 m), and has a thick layer of bottom mud (50–80 cm)(Tran 2000). West Lake has been classified as one of500 valuable lakes requiring protection for its valuablefreshwater genetic flora and fauna resources. Threespecies of fish in West Lake are listed as threatened in theVietnamese Red Book, including Megalobrama terminalis,Mylopharyngodon piceus, and Ophiocephalus striatus (Mai2000).

West Lake is currently one of the most attractive naturalbodies in Hanoi. Open spaces are being developed forvarious recreational activities, including fishing, boating,swimming, and sightseeing for locals and tourists. Thelake also is commercially important as a source of seafood,providing fish (400–600 tons year–1), shrimp (50 tons year–1),snail and mussels (200 tons year–1) (Nguyen et al. 1998). Alarge proportion (60%) of the tax revenues in the Tay HoDistrict is derived from services and aquatic products ofWest Lake (Tran 2000). The lake also contributes to the area’secosystem services via flow regulation, mitigation ofwater pollution, and habitat protection for fish and otheraquatic organisms (Nguyen et al. 1998; Mai 2000).

It has been reported that West Lake’s sediments areheavily contaminated by heavy metals and organic chemicals(Nguyen 1997; 2000; Marke et al. 2001). A combineddrainage system exists in Hanoi for domestic, service andindustrial waste water (paper, leather, brewery, wine, beer,etc.) and rain water. The lake receives water from sevenmain drainages, including Truc Bach, Thuy Khue, TrichSai, Truc Bach Paper Company, Thang Loi, Quang Ba, and

Tay Ho Hotel, as well as 15 small drainages in the ThuyKhue area. Trich Sai is the biggest drain, with a diameterof 3.5 m, which delivers ≈2600 m3 waste water per day toWest Lake. The largest wastewater inputs to West Lake arefrom the Truc Bach drainage (≈10 000 m3 day–1), followedby Thuy Khue (3600 m3 day–1). Other drains normallydeliver ≈500 m3 day–1 of waste water to the lake. Only theXuan La drain normally takes water out of West Lake.Between August and October, however, if the water level ofWest Lake is higher than in the surrounding areas, wateractually can flow out of the lake through the Thuy Khueand Trich Sai drains. Waste water draining into the lakecontains a range of water pollutants, including pesticides,fertilizers, organic substances, detergent, faeces andheavy metals (Nguyen 1997, 2000). It is assumed that themost likely sources of heavy metal inputs to the lake areindustrial effluents. The characteristics of waste waterfrom the main drains to the lake are summarized inTable 1. Although some factories (e.g. Truc Bach PaperCompany; Thuy Khue Shoes Company; Hanoi LeatherShoes Company) in the Truc Bach and Thuy Khue areaswere either closed or relocated during the early 1990s(Nippon 1999), other companies (e.g. Thang Long WineCompany; Hanoi Beer Company; Hai Ha Chemical Company;Vietnam Movie Company) are still located around West Lake.

As a result of rapid growth of tourism and residentialdevelopment in recent years, West Lake is at risk ofbecoming seriously polluted from increasing organicpollutant loads. It receives untreated waste water(≈10 000–30 000 m3 day–1) from domestic sources (18 000people), traditional craft villages, hotels, restaurants (95)and tourist cruise boats (15), as well the 51 factories in thearea involved in ink, leather, plastic, paper, pigment, steeland beer production (Nguyen et al. 1998).

Table 1. Characteristics of waste water from seven main drains to West Lake

Parameters Truc Bach Thuy Khue Trich Sai Truc Bach Quang Ba Tay Ho Thang Loi

pH 7.5 7.7 7.2 7.5 7.5 7.6 7.5

DO (mg L−1) 5.0 3.3 3.2 2.5 3.5 3.1 3.4

COD (mg L−1) 120 100 120 175 160 226

BOD5 (mg L−1) 42 70 55 45 85 67 93

CaCO3 (mg L−1) 130 285 240

NH3 (mg L−1) 2.4 2.4 4.0 0.37 0.004 0.007 0.001

Mn (mg L−1) 0.001 0.001 0.001 0.001

Cd (µg L−1) 0.395 0.398 0.229 0.225

Pb (µg L−1) 5.22 2.2 5.21 1.71

Hg (µg L−1) 0.392 0.11 0.387 0.095

BOD, biochemical oxygen demand; CaCO3, calcium carbonate; Cd, cadmium; COD, chemical oxygen demand; DO, dissolved oxygen;

Hg, mercury; Mn, manganese; NH3, ammonium; Pb, lead.

Heavy metals in West Lake, Vietnam 287


The relatively few studies of water quality of West Lakeindicated that the range values of water quality parameters(e.g. pH: 7–9; dissolved oxygen (DO): 2–10 mg L–1;biochemical oxygen demand (BOD): 35–90 mg L–1; BOD5:4–57 mg L–1, chemical oxygen demand (COD): 30–140 mg L–1)are higher than Vietnamese surface water standards, andthat the lake is in a eutrophic condition (Nguyen 1997,2000; Nguyen et al. 1998; Ho 1999). Preliminary researchby Marke et al. (2001) suggests that heavy metalcontamination of lake sediments and biota (snails,mussels, carp, etc.) represents a potentially serious healthhazard to the consumers of aquatic food products takenfrom the Lake.

Studies of tropical lake sediments and their associatedecological risks are relatively uncommon. Although anumber of studies have been conducted on metals intemperate lakes and their sediments, the associatedenvironmental risks have rarely been the main focus. Arecent example is the report of Jones et al. (1999), whileYaru and Buckney (2000) principally studied the risksassociated with sediment-borne copper in some lakes inPapua New Guinea.

Compared to temperate lakes, tropical lakes such asWest Lake have special management requirements(Brenner 1994). High water temperatures (22–30°C) intropical lakes generally translate into rapid biologicalproduction at all levels of the food chain. Moreover, thehigh water temperatures can be expected to makesediment-bound metals more easily available by diffusionin tropical lakes, than observed for temperate lakes(Brenner 1994). Coupled with the shallowness of WestLake, and the subsequent short diffusion and food chainpathways for metals, these factors suggest that the metal-contaminated sediments in West Lake could be moreeasily accessible to the food chain, thereby posing aspecial risk to users of food products from the lake.

The purpose of this study was to investigate heavy metalcontamination in sediments and aquatic organisms of WestLake, in order to acquire and analyse the scientificinformation and data needed for the development of asound lake management strategy.

MATERIALS AND METHODS

Sampling of sedimentsWest Lake was sampled in November 2004 (dry season) toassess the degree of metal contamination in the lake andits biota. Samples were collected at 24 sites (Fig. 1)grouped into six areas, including Lac Long Quan (sites 1,2, 5, 8), Quang Ba (3, 6, 9, 11), Trich Sai (4, 7, 10, 15), YenPhu (12, 13, 14, 17), Thuy Khue (16, 19, 20, 23), and Truc

Bach (18, 21, 22, 24). This grouping of sites was based onthe location of the influent drains to the lake, and its flowpatterns (Fig. 1). The water temperature (20 cm under thewater surface) and depth were measured at each site, andthe sediments were sampled with a sediment grab,following the procedure outlined by Crepin and Johnson(1993). The sediment from three grabs (1.5–2 kg per site)was pooled, homogenized and sealed immediately inpolyethylene bags and stored on ice. The pH of thesediment samples was determined immediately afterhomogenizing them in each polyethylene bag, and beforetheir storage on ice.

Sediment analysesThe sediments were transported to the laboratory anddried for 3 days at 60°C. They were then ground with amortar and pestle, and sieved through a 2-mm meshstainless steel sieve. The sieved material was used foranalysis of sediment particle size and content of heavymetals. The sediment particle size analysis was estimatedon the basis of the method of Sammis (1996), which yieldsthe percentage particle size distribution by volume.

Metal analysesThe concentrations of metals in the sediment andbiological samples (0.5 g dry sieved sediment or drytissue) were determined after digestion with concentratednitric acid (HNO3) at 80–100°C and 30% hydrogen peroxide(Krishnamurty et al. 1976). Analysis for heavy metals wasperformed via atomic absorption spectrophotometry(AAS) using a Varian SpectrAA–20 spectrophotometer(Varian Australia Pty Ltd, Victoria, Australia).

Aquatic organismsAquatic biotas were collected to provide metal accumulationdata, in order to assess the potential for human healthrisks. Freshwater snails (Sinotaia aeruginosa, Sinotaiaquadrata histrica) and freshwater mussels (Cristariaplicata, Sinonovacula constricta) were collected fromfishermen around the lake. Nine species of fish (bigheadcarp Aristichthys nobilis; mud carp Cirrhina molitorella; Gray’sgrenadier anchovy Colia grayii; common carp Cyprinuscarpio; goby Eleotris balia; silver carp Hypophtalmichthysmolitrix; black carp Mylopharyngodon piceus; tilapiaOreochromis mossambicus; and golomanka Toxabramisswinhonis) and shrimp (Macrobrachium nipponensis) werepurchased from the West Lake Fishing Enterprise as thefreshly caught material was unloaded from the boats.Different sizes of each species of fish were selected.Samples were placed in clean plastic bags, kept on ice, andtransported to the laboratory. After removal of the shells



(snails and mussels) and excising muscle tissues (fish),the samples were dried at 60°C for 3 days and finelyground. Samples (0.5 g) were then acid-digested andanalysed for heavy metals by the previously noted AASmethodology.

Quality assurance protocolsAll reagents used in these analyses were analyticalgrade. Working standards for AAS were prepared from1000 mg L–1 stock solutions of metal nitrate and sulphatereagents (AR grade, BDH – Merck, Victoria, Australia).Sample blanks (two per 30) were included in the analyses,following the recommendations of Clesceri et al. (1989).Standard reference materials (SRMs) of various certifiedSRMs (oyster, fish liver, and sediment purchased fromGranham B. Jackson Pty Ltd, Dandenong, Victoria, Australia)also were included in the analyses to establish that the

analytical methods were reliable. The average recoveryrates of the metals, in relation to the standardized materials,were 93% ± 12 for Cd; 108% ± 6 for Cr; 92% ± 4 for Cu;94% ± 4 for Mn; 66% ± 7 for Pb; and 96% ± 6 for Zn.

Statistical analysesStatistical analyses was performed, using the Minitabprotocol (Rossman & Chance 1998) One-way analysisof variance (ANOVA) was used to test for significantdifferences between the mean concentrations of metals insediment, animals, and plants.

RESULTS AND DISCUSSION

Water and sediment characteristicsThe characteristics of sediment from dif ferentparts of West Lake are presented in Table 2. The water

Fig. 1. Location of West Lake and

its sampling sites, Hanoi, Vietnam.



temperature was in the range of 22–23°C. The content ofsilt and clay in the sediments was relatively low, being6–15 and 10–19%, respectively. The low proportions of siltand clay in the sediments limit the quantity of sedimentable to be resuspended back into the water column viawave action. This factor, combined with the low dissolvedsolids content of the water, accounts for the low turbidityobserved in West Lake (Ho 1999; Nguyen 2000).

SedimentThe mean concentrations of heavy metals in sedimentstaken from West Lake are summarized in Table 3. The Mnconcentration was high, compared to a 2001 study of WestLake and to other lake systems (Table 4). There was nosignificant difference in the Mn concentrations amongdifferent parts of West Lake (Table 3), based on ANOVA

and Tukey’s pairwise comparisons (P > 0.05). Other thanfor Cr, however, the highest concentrations of the othermetals in the sediments were observed in the Truc Bacharea (P < 0.05), followed by Thuy Khue (P < 0.05). The Crconcentration in the sediments from different areas in thelake decreased in this order: Thuy Khue, Truc Bach, TrichSai, Yen Phu, Lac Long Quan and Quang Ba (P < 0.05).

The results demonstrate that the sediments in WestLake are heavily polluted by a number of heavy metals.The mean concentration of Cr, Cu, Pb and Zn for 24 samplesites (Table 3) greatly exceeds the correspondingstandards of the Ontario Ministry of EnvironmentScreening Level (OMESL). The mean concentration of Crin the Thue Khue area was up to four times higher than theOMESL value, while that for Cu in Truc Bach area was upto five times higher, and the Zn and Pb values for the Truc

Table 2. Water and sediment characteristics of West Lake (mean values ± standard deviation for water pH, depth of water overlying

sediment, and sediment texture for each sampling site; each in-lake area (see Fig. 1) sampled at four sites)

Area in lake

No. of sites

sampled per area

pH of

water

Depth of water

above sediment (m)

Sediment texture (%)

Sand (>63 µm) Silt (2–63 µm) Clay (<2 µm)

Lac Long Quan 4 7.1 ± 0.1 1.8 ± 0.2 74 ± 2 7 ± 2 19 ± 1

Quang Ba 4 7.1 ± 0.1 1.3 ± 0.3 83 ± 3 6 ± 2 11 ± 3

Thue Khue 4 7.3 ± 0.1 1.3 ± 0.3 80 ± 3 8 ± 2 11 ± 1

Trich Sai 4 7.3 ± 0.1 1.4 ± 0.2 81 ± 4 7 ± 2 12 ± 5

Truc Bach 4 7.3 ± 0.1 1.1 ± 0.2 79 ± 2 8 ± 1 13 ± 1

Yen Phu 4 7.4 ± 0.1 1.7 ± 0.3 75 ± 1 15 ± 3 10 ± 4

Table 3. Mean metal concentrations in West Lake sediments (mean values ± standard deviation (in parentheses) for each area sampled, as

indicated in Table 2; a mean lake screening level from Ontario Ministry of Environment (OMESL 1994) and National Oceanographic and

Atmospheric Administration (NOAA; Long & Morgan 1990) are included for comparison)

Area in lake

No. of sites

sampled per area

Metal concentration in sediment (µg g–1)

Cd Cr Cu Mn Pb Zn

Lac Long Quan 4 <0.05 42a (3) 59a (13) 474a (46) 44a (1) 148a (9)

Quang Ba 4 <0.05 33a (5) 44a (13) 444a (59) 40a (11) 133a (30)

Truc Bach 4 0.742b (0.358) 70ab (16) 90b (20) 588a (213) 124b (51) 470b (161)

Thue Khue 4 0.533c (0.123) 105b (66) 56a (22) 454a (23) 68a (17) 254a (42)

Trich Sai 4 0.075a (0.026) 58ab (13) 50a (11) 424a (64) 34a (3) 145a (32)

Yen Phu 4 0.153a (0.107) 43a (5) 44a (16) 447a (65) 53a (14) 181a (75)

Mean 24 0.488 (0.314) 58 (35) 57 (22) 441 (104) 61 (37) 221 (138)

NOAA 1.2–9.6 81–370 34–270 1100 46.7–218 150–410

OMESL 0.6–10 26–110 16–110 – 31–250 120–820

Values indicated by differences superscripts are significantly different (P < 0.05) for each metal.

Cd, cadmium; Cr, chromium; Cu, copper; Mn, manganese; Pb, lead; Zn, zinc.



Bach area were up to four times higher than the OMESLvalues.

The south sample area in the lake (Truc Bach) was themost heavily polluted by heavy metals, while the northarea (Quang Ba) exhibited the lowest metal pollution in itssediments. Truc Bach exhibited the highest concentrationsof the four metals commonly associated with urbanpollution; namely, Cd, Cu, Pb and Zn. Although this latterpollution likely arose from the surrounding industries(paper, milk, leather, brewing), it also could have arisenfrom such services as boats and restaurants, as well as thehigher traffic density on nearby roads for this area,compared to the other areas. The high concentration ofPb, in particular, might reflect the increased use of petrol-fuelled vehicles in recent years (Nguyen et al. 1998). TheThuy Khue area of West Lake has the second highestconcentration of most metals, as well as the highestconcentration of Cr. It is noted that this area is subjected toeffluents from nearby leather, ink and chemical factories,and hospitals. There also appears to have been some north-ward spread of these contaminants, as indicated bythe fact that the Cr concentration at sites in the Trich Saiarea, north of Thuy Khue, is higher than that of the othermetals. The Lac Long Quan area has more Pb and Cupollution than for other metals, likely because it is affectedby vehicles utilizing Lac Long Quan road. Although sedi-ment from the Yen Phu area contains very little Cd, itdoes exhibit Zn, Pb, Cu and Cr concentrations above theOMESL values. The Quang Ba area receives only hoteland domestic waste water, thereby exhibiting the lowestlevels of metal contamination.

Compared to three other lakes located in tropical areas,the concentration of metals in the sediments of West Lakeis high (Table 4). Despite the fact that many of thepollution sources to West Lake were removed in the early1990s (Nippon 1999), these study results also indicate thatthe heavy metal concentrations in the lake sedimentsremain high. The current concentration could be evenhigher than those measured in a previous study (Markeet al. 2001), although the spatial variability in the concentr-ations might explain the dif ferences in this case.Thus, the contamination by heavy metals persists, even aseutrophication processes increase because of residentialdevelopments being developed around the lake (Ho 1999;Nguyen 2000), which is certain to increase the organiccontent and the incidence of anoxia in the lake sediments.

The high level of metal concentrations in the southportion of West Lake can be explained by the sources ofpollution being Truc Bach Lake, and drainage of wastewater from the To Lich River. The activities of touristservices (restaurants and boats) might be another cause ofthis pollution.

Metals in aquatic animalsThe concentrations of selected heavy metals in the tissuesof fish, snails, mussels and shrimp are summarized inTable 5. The results indicate that the concentrationsexceeded the health standards of the Food StandardAustralia-New Zealand (FSANZ) for human consumptionin some species. The concentration of Pb in all aquaticorganisms investigated exceeded the safe standard by fourto 10 times. The Zn concentrations in freshwater musselsand snails tissue also were higher (up to nearly threetimes) than the FSANZ standard. The mean Cuconcentrations in shrimp and snails exceeded the FSANZstandard by a factor of approximately five to 18 times.The Cd concentrations were found to be below 0.33 µg g–1,whereas the Cr concentrations, depending on species,were from 1.5 to 17.6 µg g–1, depending on the species. Incontrast, only the Cr concentration in goby exceeded theUS Food and Drug Administration standard. Althoughsome species of fish and shrimp only contained a smallquantity of Mn (below 18 µg g–1), much higher concentr-ations were found in snails (103–105 µg g–1) and mussel(up to 6736 µg g–1), compared to Pletholophus swinhoeiin Duy Minh, Vietnam (280–840 µg g–1).

The concentrations of heavy metals in freshwater fishmuscle tissues in West Lake are compared with thoseobtained from other comparable lakes in Table 6. Theconcentrations of Zn, Mn, Pb and Cu in the freshwater fishin West Lake were much higher than those for othersimilar lakes.

Table 4. Comparison of heavy metal concentrations (µg g–1) in

sediments of West Lake and other comparable lake systems

(concentrations given as ranges of values)

Metal

West Lake (Vietnam) Lake

Kasumigara

(Japan)‡

Atatürk

Dam

(Turkey)§

Lake

Taihu

(China)¶This study 2001†

Cd 0.05–1.233 0.2–1 <0.04 <0.03 0.1–0.3

Cr 26–163 42–98 10–26 nd 54–67

Cu 24–118 2–27 9–51 14–22 19–26

Mn 329–897 370–630 nd 73–514 nd

Pb 30–200 4–85 10–31 nd 17–23

Zn 101–697 7–83 39–184 59–61 57–119

Data sources: †Marke et al. (2001); ‡Alam et al. (2001);§Karadede and Erhan (2000); ¶Shen et al. (2005).

Cd, cadmium; Cr, chromium; Cu, copper; Mn, manganese; Pb,

lead; Zn, zinc; nd, not determined.



MANAGEMENT AND OTHER ISSUESThe Truc Bach area receives the largest pollutant load inthe West Lake, mainly comprising industrial wastewater

effluents in drains to the Lake. The level of contaminationappears to be moving from the Truc Bach area to the ThuyKhue area, and to other parts of the West Lake to someextent, because mostly of the wind and wave action patternin this shallow lake. These study results indicated thatsediment in the northern parts of West Lake contained lowconcentrations of heavy metals.

It is clear from this study that the level of heavy metalcontamination in some of West Lake’s commerciallyimportant food species is a matter of concern. This isparticularly the case when one considers human consump-tion of snails, mussels and shrimp. In regard to the firsttwo products, two issues merit mention:

1. The level of metal contamination is sufficiently highfor buyers to consider not consuming them, or for theGovernment to ban their sale. This action would have avery serious impact on the economic livelihoods of someof the poorest users of the lake. The social implicationsof such an action also would be serious.

2. It is common in Hanoi for consumers to place theseorganisms in clean water for up to 2 days before cookingthem. It could be that the metals are eliminated during this2-day cleansing period to the extent that the product meetsappropriate food quality standards. This possibility hasnot been investigated, however, to the present time.

Table 5. Tissue concentration of heavy metals in aquatic organisms in West Lake (mean values ± standard deviation (in parentheses);

n = 3; values higher than FSANZ and USFDA standard indicated in bold)

Species Common name

Metals (µg g–1 dry wt)

Cd Cr Cu Mn Pb Zn

Sinotaia aeruginosa Snails 0.102 (0.05) 9.8 (0.9) 189 (12) 103 (5) 3.5 (1.2) 415 (25)

Sinotaia quadrata histrica 0.155 (0.03) 9.6 (0.6) 186 (14) 105 (7) 4.2 (1.3) 391 (19)

Cristaria plicata Mussels 0.17 (0.12) 9.6 (2.2) 5.1 (1.3) 4308 (752) 3.7 (1.0) 174 (16)

Sinonovacula constricta 0.18 (0.16) 8.6 (1.6) 5.1 (1.7) 6736 (2270) 5.2 (5.2) 234 (100)

Macrobrachium nipponensis Shrimp 0.16 (0.11) 3.1 (1.2) 52 (29) 14 (4.7) 2.4 (0.9) 121 (36)

Eleotris balia Goby 0.03 (0.02) 17.6 (2.0) 2.3 (0.4) 18 (0.1) 3.5 (1.1) 102 (1)

Cyprinus carpio Common carp 0.33 (0.02) 3.1 (3.9) 1.5 (0.2) 1.5 (0.2) 3.1 (1.2) 45 (4)

Toxabramis swinhonis Golomanka 0.06 (0.08) 2.6 (0.3) 2.5 (0.3) 9.2 (1.9) 3.2 (0.7) 155 (6)

Colia grayii Gray’s grenadier anchovy 0.15 (0.03) 2.1 (1.4) 9.2 (8.4) 7.0 (2.0) 2.1 (1.2) 70 (13)

Aristichthys nobilis Blackhead carp 0.15 (0.03) 4.4 (2.7) 1.4 (0.2) 2.7 (0.4) 2.3 (0.9) 26 (6)

Hypophtalmichthys molitrix Silver carp 0.19 (0.12) 3.4 (2.0) 1.6 (0.6) 1.3 (0.2) 2.0 (0.8) 22 (1)

Oreochromis mossambicus Tilapia 0.08 (0.14) 4.4 (2.7 ) 1.1 (0.5) 1.2 (0.5) 3.1 (1.0) 24 (1)

Mylopharyngodon piceus Black carp 0.03 (0.03) 2.6 (0.9) 1.2 (0.4) 0.4 (0.1) 4.1 (1.5) 20 (1)

Cirrhina molitorella Mud carp 0.11 (0.20) 1.5 (0.4) 1.3 (0.6) 0.1 (0.1) 2.8 (1.5) 27 (2)

FSANZ standard 0.2 10 0.5 150

USFDA standard 13

Cd, cadmium; Cr, chromium; Cu, copper; Mn, manganese; Pb, lead; Zn, zinc; FSANZ, Food Standard Australia–New Zealand (FSANZ

2005); USFDA, US Food and Drug Administration (USFDA) (UFDA-CFSAN 2001).

Table 6. Comparison of metal concentrations in freshwater fish

muscle in West Lake and other comparable lakes

Lake

Metal concentration (µg g–1 dry wt)

Cu Mn Pb Zn

West Lake (this study) 1.1–9.2 0.1–18 2–4.1 20–155

Dhanmondi Lake

(Bangladesh)†

5 18 2 60

Kola Region (Russia)‡ 1.6–2.4 0.8–2.8 nd 20–34

Duy Minh (Vietnam)§ 1.8 2.6 0.3 29

Ataturk Dam Lake (Turkey)¶ 0.05–4.3 0.1–16 <1.67 2–28

Nasser Lake (Egypt)†† 0.3 0.03 nd 0.6

Malibu Lagoon (USA)‡‡ 1.7–6.0 2–22 0.3–4 3–66

Lake Kasumigaura (Japan)§§ 0.3 0.2 0.03 5

Data sources: †Begum et al. (2005); ‡Moissenko and Kudryaytsev

(2001); §Wagner and Bomam (2003); ¶Karadede and Ünlü (2000);††Rashed (2001); ‡‡Moeller et al. 2003; §§Alam et al. (2002).

Cu, copper; Mn, manganese; Pb, lead; Zn, zinc; nd, not

determined.



In contrast to snails and mussels, fresh shrimp are deadwhen purchased. Thus, the possibility of metal eliminationfrom these organisms is very low unless done immediatelyafter harvest. Although such an action would have to beundertaken by the fishing community, the infrastructurefor such an action is presently virtually nonexistent.Moreover, it is not yet clear that metal elimination could beachieved within an appropriate (short) period.

Although there is no standard or guideline for metalcontamination of sediments in Vietnam, establishment ofsuch a standard/guideline is necessary. Guidelines fromother countries, such as Canada or Australia, could beadopted and used in managing contamination of lakes suchas West Lake.

The continuing discharge of sewage to West Lake,which will likely increase as tourism and residentialfacilities are developed around the lake, raises a new issue.Eutrophication will inevitably increase the quantity oforganic matter in the lake sediments (Nguyen et al. 1998;Nguyen 2000; Tran 2000), which will, in turn, increase theintensity and frequency of anoxia in the sediments. Suchdevelopments can lead to a change in the distribution ofmetals between the various sediment components (seeTessier et al. 1979), subsequently making the metals morebiologically available in the future. No evidence ofsediment anoxia, however, has been reported to thepresent time (Nguyen 1997, 2000; Nguyen et al. 1998; Tran2000; Marke et al. 2001). Furthermore, no evidence ofserious anoxia (particularly the characteristic smell ofhydrogen sulphide) was detected during this study.Nevertheless, because the probability of anoxia becomingmore frequent in the future is real, it would be prudent toexamine the speciation and biological availability of heavymetals in the sediments of West Lake under oxygen-depleted conditions.

The evidence that the source of metal contamination ofthe biota in West Lake is from its sediments is currentlycircumstantial. Substantial proof of this possibility willrequire further experimental investigations that mightinclude micro- or mesocosm experiments involvingorganisms being exposed in water to sediments fromvarious parts of the lake. Such issues will be the subject offuture studies of this important lake.

CONCLUSIONSWest Lake is an ecologically and economically valuablelake in many respects. However, the lake has beensubjected not only to heavy metal pollution (Pb, Cu, Cr, Zn,Cd, Mn), but also to eutrophication and, likely, tocontamination with organic chemicals. Although the mainsources of heavy metal inputs to the lake have now been

eliminated, the residual metal pollution (mainly in the lakesediments) is still a matter of concern, particularly in viewof the increasing eutrophication of the lake. As a potentialcause of anoxic conditions in the lake, continuingeutrophication also will increase the possibility ofincreasing the remobilization and biological availability ofmetals from the lake sediments. The highest level of metalcontamination was identified near the southern shore ofthe lake, which still has tourist activities. This study alsoindicated that aquatic organisms in West Lake also wereaffected by heavy metals, with the highest concentrationsbeing found in snail, mussel and shrimp. These factors,coupled with the shallowness of West Lake, and thesubsequent short diffusion pathways and food chainroutes for metals, suggest that the heavy metals in thecontaminated sediments of West Lake are highly availableto the in-lake food chains, thereby also posing a substantialrisk to human users of food products from the lake.

ACKNOWLEDGEMENTSThis study was supported by a grant from the Faculty ofScience, University of Technology, Sydney (UTS), and theVietnamese Ministry of Education and Training. The helpof laboratory staff of the Department of EnvironmentalSciences, UTS, also is gratefully acknowledged. Theauthors also thank officials of the West Lake Investmentand Exploitation Company for their help in the collectionof samples.

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Assessment of heavy metals in sediments and aquatic organisms in West Lake (Ho Tay), Hanoi, Vietnam