Schwermetallbelastung von Dreissena polymorpha in Donau und Drau und ihre Bedeutung als Bioindikator

Goal and Scope

This study was undertaken to investigate the differences in heavy metal burden between the organisms and environmental compartments and to evaluate the role of Dreissena polymorpha as a bioindicator organism.

Methods

The concentrations of zinc, copper, cadmium and lead in whole soft body and selected tissues of D. polymorpha at two river habitats in Austria were examined using atomic absorption spectroscopy (AAS). Concentrations in organisms were compared to those in sediment and water.

Results and Conclusion

Zebra mussels of the river Drau showed generally higher heavy metal concentrations as compared to mussels of the river Danube and contained elevated zinc and cadmium levels as compared to metal concentrations found in soft tissues of zebra mussels from uncontaminated sites in Germany and The Netherlands. The essential metals zinc and copper were mainly accumulated in gills, foot and byssal gland tissue of the mussel, in contrast to the non-essential metals cadmium and lead which were found predominantly in the midgut gland. The heavy metal concentrations in both, sediments and mussel tissue, were higher than in water samples. There was no correlation between the concentrations in water and in the organisms except for zinc. In contrast, correlations were found between concentrations in sediments and mussel soft tissue.

Recommendation and Perspective

Further investigations should include the examination of sediments and consider the mechanism of food uptake to assess the role of D. polymorpha as a bioindicator organism.     

Health risks of heavy metals in the mediterranean mussels as seafood

In recent years, mussels have already become commercially important seafood species worldwide. Mussels accumulate a wide range of metals in their soft tissue. Thus, the determination of accumulated concentrations of heavy metals, such as Pb, Cd, Hg, and As, in mussels is essential because of their usage as seafood and the potential adverse effects of their consumption on human health. In this review, these issues are presented and discussed using the Mediterranean mussel Mytilus galloprovincialis as an example. M. galloprovincialis is very efficient at converting low value victuals into high quality animal protein. The production of M. galloprovincialis in Mediterranean countries has been increasing rapidly, but Spain is still the largest producer of mussels. Only China has a larger production of these mussels than Spain. M. galloprovincialis is a filter feeding animal and accumulates a wide range of metals from their environment. The metal concentrations in the soft tissue of M. galloprovincialis are indicators of marine ecosystems contamination. In the same time, the bioaccumulation of heavy metals remains an issue concerning the consumption of mussels. Thereby, the Cd, Pb, Hg, and As concentration measurement in mussel soft tissue as a seafood have become significant. A review of literature data revealed large variations in the Cd, Pb, Hg, and As concentrations in M. galloprovincialis from their endemic areas, e.g., Mediterranean, Adriatic, and Black Sea, and the concentrations of these toxic metals were generally in the following order: As > Pb > Cd > Hg. The guidelines on heavy metals for seafood safety set by different countries and associations are reviewed. Comparison of the published data with European legislation showed that the levels of the heavy metals generally did not exceed the existing limits in all the mussels analyzed, excluding mussels from hot spots, such as lagoons and harbors, in the Mediterranean, Adriatic, and Black Sea.     

Evaluation of a “mussel watch” project for heavy metals in Scottish coastal waters

Results are presented of an extensive survey of the heavy metal content of intertidal mussels, Mytilus edulis (L.), from around the Scottish coasts. An important first conclusion is that areas can be identified in which mussels acquire relatively elevated concentrations of certain heavy metals. In general, areas of known pollution display elevated concentrations of several metals, but some areas not greatly influenced by man's activities also show elevated concentrations of a single metal. Comparisons are made of the strategies employed in this and other similar surveys and suggestions made for the design of future exercises.     

Use of different soft tissues of Perna viridis a s biomonitors of bioavailability and contamination by heavy metals (Cd,Cu, Fe,Pb, Ni,and Zn) in a semi-enclosed intertidal water,the Johore Straits

Green-lipped mussels, Perna viridis, were collected from the eastern and western parts of the Johore Straits in September 2004 and January 2005. Based on the heavy metal concentrations in the different soft tissues (gonad, foot, mantle, gills, muscle, and remaining soft tissues) of these mussel samples, the eastern part of the Johore Straits (which is divided into two portions by a causeway), recorded higher levels of bioavailability and contamination by Cd, Cu, Fe, Ni, and Zn when compared to the western part, while Kg. Pasir Puteh in the eastern part was found to record the highest bioavailability and contamination by heavy metals. The use of different soft tissues of P. viridis as biomonitors of bioavailability and contamination by Cd, Cu, Fe, Pb, Ni, and Zn in the semi-enclosed Johore Straits is proposed, since erroneous results due to spawning and the problem of defecation before dissection could be overcome. Hence, a more accurate interpretation of the bioavailability and contamination by heavy metals in coastal waters could be obtained. To our knowledge, this is the most detailed study on the bioavailability and contamination of heavy metals in the Johore Straits on the Malaysian side of the waterway carried out by using the different soft tissues and metal distribution based on the Mussel Watch approach.     

Biomonitoring of heavy metal (Cd,Cu, Pb,and Zn) concentrations in the west intertidal area of Peninsular Malaysia by using Nerita lineata

Snails, Nerita lineata, were collected from 15 sites along the west intertidal area of Peninsular Malaysia from December 2005 until April 2006. The concentrations of heavy metals (Cd, Cu, Pb, and Zn) were determined in the total soft tissues, operculums, and shells of the snails. Different patterns of heavy metal distributions were found in the different tissues (shell, operculums, and soft tissues) as well as spatial variations of heavy metal concentrations in the snails. This shows that the distribution of metals in the shells and the total soft tissues of N. lineata were not similar which could be due to different rates of metal accumulation, excretion, and sequestration. Since N. lineata is abundant on the rocky shores, below jetties and mangrove trees along the west intertidal area of Peninsular Malaysia and accumulate heavy metals, the snails are therefore potential biomonitors of heavy metal contamination for the west intertidal area of Peninsular Malaysia.     

Source and Effect of Heavy Metal Pollution in the Coastal Taiwan Sediments

Coastal sediments and oyster farming is severely affected by the industrial effluents in the coastal region near LuGong, Taiwan. Surficial sediments and oyster samples were collected from a coastal area near a major electro-plating industry. Spatial variation in heavy metal contents in sediments was studied in relationship to the main pathway of contamination and geochemical association with natural constituents of the sediments.

Spatial trends of heavy metals in the sediment reflected inputs of pollutants from the poorly-treated electro-plating effluents in the surrounding county and transported downstream by the Yang-tse-tru River. Effluent related heavy metal (Zn, Cu, Cd) is extremely high in the study region sediments. the highest concentrations were observed near shore, especially upstream in the Yang-tse-tru River sediments. Heavy metal concentrations decreased rapidly in a seaward direction. Heavy metal concentrations in near shore sediments were as high as some highly industrialized harbour sediments in the USA (e.g. Boston and San Diego).

Significant differences and high concentrations of heavy metals were also observed in oysters from the study region. Heavy metals from the study region were two to five times higher than in oysters from other pristine areas in Taiwan.     

Monitoring of heavy metals and butyltin compounds in coastal waters of Ligurian Sea: Results of a mussel watch project

From December 1994 up to October 1995 a “Mussel Watch Project”; was carried out to assess the quality of water of the Ligurian Sea and to identify the possible sources of heavy metal pollution. Several metals and organotin compounds were measured in mussels (Mytilus galloprovincialis, Lam) transplanted in different months from a marine farm to eight sites of the Ligurian coast.

Spatial differences and temporal trends in tissue concentrations of Zn, Cu, Ni, Cr, Fe, Al, V, Cd and Mn were evaluated. Concentrations resulted in the same range as those obtained in a previous Mussel Watch Project carried out in the same area. In general, areas of known pollution display high concentrations of these metals, but also some areas not greatly influenced by human activities showed high concentrations of some metals.

Data from this study show little evidence of any overall seasonal pattern except for Cu, Zn and V, concentrations of which were a function not only of sampling site, but also of reproductive cycle.

Organotin compounds show differences in terms of both concentration and speciation between the investigated sites.     

Spatial distribution and controlling factors of heavy metals contents in paddy soil and crop grains of rice–wheat cropping system along highway in East China

There is consensus concerning the heavy metal pollution from traffic emission on roadside agricultural land. However, few efforts have been paid on examining the contamination characteristics of heavy metals in roadside paddy-upland rotation field, and especially in combination with detailed quantitative analysis. In this study, we investigated the concentrations of heavy metals (Pb, Cd, Cr and Zn) in soil and crop grains of the rice-wheat cropping system along a major highway in East China in 2008 and analyzed the spatial distribution characteristics of heavy metals and their influencing factors with GIS and Classification and Regression Trees (CART). Significantly elevated levels of heavy metals in soil, rice and wheat grains indicated the heavy metals contamination of traffic emission in roadside rice-wheat rotation field. The contamination levels of Cd, Cr and Zn in wheat grain were higher than rice grain, while that of Pb showed an opposite trend. Obvious dissimilarities in the spatial distributions of heavy metals contents were found between in the soil, rice and wheat grains, indicating that the heavy metals contents in the roadside crop grains were not only determined by the concentrations of heavy metals in the paddy soil. Results of CART analysis showed that the spatial variation of the heavy metals contents in crop grains was mainly affected by the soil organic matter or soil pH, followed by the distance from highway and wind direction. Our findings have important implications for the environmental assessment and crop planning for food security along the highway.     

A study on the accumulation of nine heavy metals in some important fish species from a natural reservoir in Riyadh,Saudi Arabia

Concentrations of nine heavy metals (Cr, Cd, Pb, Ni, Cu, Zn, Mn, As, and Fe) in the muscles of four fish species (O. niloticus, C. gariepinus, P. latipinna, and A. d. dispar) collected from the Riyadh River were detected using atomic absorption spectrophotometry in two different seasons in 2012. The concentrations of the studied heavy metals except Cd, Pb, Ni, and Cu in Aphanius d. dispar and Poecilia latipinna were found to be below the safe limits suggested by various authorities. This study also showed that Zn was predominant, while Cr was least accumulated metal in the studied fish muscles. Data demonstrated that there was a significant variation in the heavy-metal concentrations in different fish species in the Riyadh River. Significant positive correlations between heavy-metal concentrations in fish muscles were also found both in pre- and post-monsoon seasons. Metal pollution index was calculated to distinguish polluted from unpolluted ecosystems based upon current knowledge of metal bioavailability, bioconcentration, and bioaccumulation patterns. From the human health point of view, this study showed that there was a possible health risk to consumers due to the intake of Aphanius d. dispar and Poecilia latipinna under the current consumption rate in the country.     

重金属积累对土壤酶活性的影响

研究了华北平原某铅冶炼厂附近农田33个土壤样品中重金属积累对土壤酶活性的影响。结果表明,样品中Pb和Cd全量的平均值分别为144和5.59mg·kg-1,DTPA态Pb和Cd含量平均值分别为54.1和0.964mg·kg-1,均超过了未污染农田潮土的正常范围,而Cu、Ni和Zn的有效性和全量与未污染土壤接近;土壤过氧化氢酶活性与DTPA态Pb和Cd含量、全Pb含量均呈显著的负线性关系(P<0.01);与磷酸酶和脲酶相比,土壤脱氢酶活性更易受到土壤中Pb和Cd积累的影响;随DTPA-Ni含量增加,土壤蛋白酶和碱性磷酸酶活性增加(P<0.1);土壤脲酶活性与重金属全量或有效态重金属含量无显著相关性(P>0.1)。以上结果说明,利用土壤过氧化氢酶和脱氢酶活性能够表征基本性质较为一致的土壤中重金属污染程度;与重金属全量相比,有效态重金属对土壤酶活性影响更大。     

Total and bioavailable metals in two contrasting mining regions (Sudbury in Canada and Lubumbashi in DR-Congo): relation to genetic variation in plant populations

Knowledge of total and bioavailable metal contents in soil is important for regional risk assessment and management. The main objective of the present study was to analyse the concentrations of metals in soils in two contrasting mining regions (Sudbury in Canada and Lubumbashi in DR-Congo). Genetic variation of plant populations was investigated to assess the potential impact of metal contamination on forest sustainability. The levels of copper, cobalt, zinc, arsenic, and lead were significantly higher (up to 200-fold) in mining sites in the Lubumbashi compared to the most highly contaminated Sudbury sites. The nickel content in soil samples from Lubumbashi was much lower compared to Sudbury region samples. Only 3.5% and 4 % of total copper and nickel, respectively, were phytoavailable, with values of 6%, 5.7%, 3.6%, and 5.4% for cobalt, magnesium, manganese, and zinc, respectively. There were significant positive correlations between total metal and phytoavailable metal concentrations for copper (r=0.99), nickel (r=0.86), cobalt (r=0.72), strontium (r=0.71), and zinc (r=0.66). Although genetic variation was high in Picea glauca populations from the Sudbury region, no association was found between metal contamination levels and genetic variation within and among the P. glauca populations.     

The uptake and translocation of selected elements by cole (Brassica) grown using oasis soils in pot experiments

Pot experiments were conducted on cole (Brassica) grown in soils jointly treated with traces of two heavy metals cadmium (Cd) and zinc (Zn). As the concentration of heavy metals in the soil increased, the uptake of these metals by the plants rose. However, the ratio of heavy metal concentration in soil to uptake by plants increased at a slower rate. Bioavailability of heavy metals considered between the roots and soil using non-linear regressions was shown to be statistically significant. Similarly, the bioavailability of these two heavy metals between leaves and roots using a linear regression was also statistically significant. The bioconcentration factors (BCFs) for Cd and Zn were 0.282 and 4.289, respectively. Significant variation of BCF with the heavy metal bioavailability in soil was noted from non-linear models. The transfer factors (TFs) were 4.49 for Cd and 1.39 for Zn. The Zn concentration in leaves under all treatments did not exceed threshold set standards, but Cd levels exceeded these standards when the concentration of Cd in the soil was more than 1.92 mg kg^?1 dry weight (dw). Data indicate that cole (Brassica) is not a suitable crop for oasis soils because of plant contamination with heavy metals, especially Cd.     

Assessment of nutrients and heavy metals enrichment in surface sediments from Taihu Lake,a eutrophic shallow lake in China

Concentrations of the nutrients (TN and TP), phosphorus fractions and heavy metals (Co, Cr, Cu, Mn, Ni, Pb, Sr, Ti, V, Zn and Hg) in 40 surface sediment samples collected from Taihu Lake, a eutrophic shallow lake in China, were determined. The results showed that the northwest region of the lake possessed higher concentrations of TN and TP, as well as the similar spatial distribution trend in the water column. This should be related to excessive anthropogenic input from industrial effluents and domestic sewage in surrounding areas. Similarly, the concentrations of P fractions exhibited significant regularity. In addition, except for Sr showing low concentration, the rest of the heavy metals in the surface sediments had two- to four-folds of magnitude of the concentrations compared with the reference values in earth's crust. In the past decade, concentrations of heavy metals had undergone different levels of variations. Principal component analysis (PCA) and enrichment factors (EFs) of the compositional data aiming at heavy metals showed that Taihu Lake was slightly exposing to heavy metal contamination except Sr. High concentrations of heavy metals were ascribed to the discharge of untreated and partially treated industrial waste water via rivers. Co, Cr, Cu, Mn, Ni, Pb, V and Zn positively correlated with each other (R = 0.78–0.92), that indicated they had analogous sources and/or kindred geochemistry characteristics. Differing from nutrients, randomness in the space indicated that heavy metals had a complex distribution.     

Use of the digestive gland of the oyster Crassostrea rhizophorae (Guilding, 1828) as a bioindicator of Zn,Cd and Cu contamination in estuarine sediments (south-east Brazil)

This study demonstrates the accumulation of Zn, Cd and Cu in the digestive gland of the oyster Crassostrea rhizophorae in response to the contamination of sediments and discusses the potential use of this specific organ in monitoring metal contamination in tropical areas. Sediment and oyster samples were collected from coastal Rio de Janeiro sites with different levels of human impact: Sepetiba Bay, Guanabara Bay and the Paraty coast. Metal concentrations were measured using inductively coupled plasma optical emission spectrometry (ICP OES). Significant statistical differences (p<0.001; p<0.05) were observed for Zn and Cd concentrations in the digestive gland; the highest Zn concentrations were found at Sepetiba, followed by Guanabara and Paraty. The highest digestive gland Cd concentrations were found at Paraty, followed by Sepetiba and Guanabara. These concentrations were proportional to those found in the sediments. There was no significant difference (p>0.05) in Cu among the sampling sites. The highest digestive-gland Cu concentration was also found at Sepetiba, followed by Guanabara. The biosediment accumulation factor indicated a gradient of sediment contamination for Zn and Cd. The digestive gland of C. rhizophorae can be a potential indicator of trace metal contamination in sediments from tropical estuarine environments.     

Geographical and seasonal variation of trace metal bioavailabilities in the Gulf of Gdansk,Baltic Sea using mussels (<Emphasis Type="Italic">Mytilus trossulus</Emphasis>) and barnacles (<Emphasis Type="Italic">Balanus improvisus</Emphasis>) as biomonitors

The barnacle Balanus improvisus and the mussel Mytilus trossulus have been used as biomonitors of the trace metals Cu, Zn, Cd, Fe, Pb, Mn and Ni at five sublittoral sites in the Gulf of Gdansk (Baltic Sea) between February 2000 and September 2001. The study has established a benchmark against which future biomonitoring programmes will be able to establish changes in local metal pollution, particularly if metal loadings in the river Vistula (draining into the Gulf) alter in the future. The study highlighted differences in trace metal bioavailabilities to both barnacles and mussels, geographically and over time. Accumulated metal concentrations of Cu, Zn, Fe, Pb and Ni, but not Cd or Mn, were correlated in the barnacles and mussels, suggesting that the bioavailabilities of the former metals to the two biomonitors were similar. The barnacles showed greater discriminatory power than the mussels as trace metal biomonitors. Concentrations of trace metals in surficial sediments (<63 m) did not correlate significantly with accumulated metal concentrations in either barnacles or mussels, indicating that sediment metal concentrations are not necessarily good proxy measures of ambient trace metal bioavailabilities to the local coastal filter feeders.Communicated by J.P. Thorpe, Port Erin     

Concentrations of Heavy Metals in Muscle with Relation to the Growth of Two Marine Fish Species

Heavy metal concentrations in muscle and their relation to thegrowth of two marine fish species,including tonguefish( Cynoglossus arel) and mullet( Mugil cephalus),were studied. The samples were collected in Bach Dang estuary andconcentrations of heavy metals( As,Cd,Co,Mn,Cu,Zn,Pb,and V) in muscle of the fisheswere determined. The result showed that the accumulated trend of heavy metal is different between fish species. The concentration of As,Zn,Mn,V,Cu,Pb,Co and Cd in tonguefish were 73. 7 ± 30. 6,22. 82 ± 4.87,3. 44 ± 2. 13,1. 61 ± 0. 15,0. 71 ± 0. 13,0. 45 ± 0. 24,0. 03 ± 0. 02 and 0. 02 ± 0. 02 mg·g-1,respectively. Meanwhile the concentration of Zn,As,V,Mn,Cu,Pb,Co and Cd in mullet were 83. 41 ±19. 68,9. 78 ± 1. 92,1. 36 ± 0. 54,1. 29 ± 0. 51,0. 65 ± 0. 12,0. 42 ± 0. 20,0. 06 ± 0. 03 and0. 03 ± 0. 01mg·g-1,respectively. Comparison of metal levels among thesespecies indicated that the concentrations of As and Mn in tonguefish were significantly higher than those in mullet,whereas Zn levels in mullet were found to be higher than that in tonguefish. There is no significant differences of Cd,Co,Cu,Pb and V levels in muscle between two species. Significant inversed relationshipsbetween concentration levels of metals and lengths of tonguefish were found for Mn,Cu and Zn,butnot for As,Cd,Pb,and V. There were no significant relationships between the heavy metal concentrations and the length of mullet. In general,decreasesof the heavy metal concentrations corresponded to the increases of fish body lengths,particularly for As,Co,Cu,Mn and V and the exception for Cd. Terefore reduced risks were associated with consuming biggermullet fish,and increased risks of As and Cd were associated with consuming bigger tonguefish in Bach Dang river mouth.     

城市地表颗粒物重金属分布特征及其影响因素分析

城市地表颗粒物作为重金属的重要载体,严重危害城市人群和水体,已成为城市环境的重要研究对象。阐述了对地表颗粒物重金属的空间、粒径、赋存形态等分布特征及其影响因素进行系统分析的意义。通过对国内不同城市不同功能区的重金属（主要为：Zn、Cu、Cd、Pb）数据进行对比分析,各功能区重金属污染情况为：Cu、Pb：工业区〉商业区〉交通区〉居民区〉休闲区;Zn：工业区〉交通区〉商业区〉居民区〉休闲区;Cd：交通区〉工业区〉商业区〉居民区〉休闲区,同时各功能区中Zn、Pb含量波动性较大。整体上国内工业区、交通区和商业区地表颗粒物重金属污染严重。与我国的土壤重金属背景值相比,4种金属中Cd污染程度最为严重。探讨了与国外部分城市地表颗粒重金属污染特征之间的差异,指出国内城市重金属含量均值整体上低于欧美发达城市,而国内一线城市重金属含量明显偏高。系统分析了颗粒物重金属的粒级效应,赋存形态以及生物有效性。综述了城市交通活动（主要为交通流量、车辆行驶速度、变速频率、车辆类型、道路特征等）、降雨冲刷事件、雨前干燥期、大气风力作用、和其他因素对地表颗粒物重金属分布特征的影响。某种程度上,道路车辆的行驶速度和变速对颗粒物重金属累积的影响作用大于交通流量。不同降雨事件和雨前干燥期对重金属分布特征影响的研究结论不一,但地表颗粒对大气PM2.5重金属贡献较大。今后应在以下方面进一步加强对城市地表颗粒物重金属的研究：建立颗粒物粒径划分标准;加强重金属在降雨冲刷过程变化规律的分析;探讨地表颗粒物与大气颗粒物重金属转换关系;还应开展中小型城市,城乡结合部（城中村）地表颗粒物重金属污染特性研究。     

Contribution to the ecotoxicological study of cadmium,lead, copper and zinc in the mussel Mytilus edulis

The understanding of natural fluctuations of metal concentrations in mussels used as bio-indicators is indispensable for a good assessment of the disturbances due to pollution. We have studied thoroughly the factors which condition bioaccumulation by using controlled populations of mussels, Mytilus edulis L., sampled monthly over more than two years (March 1982–May 1984) in the Bay of Bourgneuf, France. Seasonal changes in metal levels have been recognized, maximum values being observed in winter and early spring and minimum in later spring and summer. Depending on metal and size group, the ratios between these maximum and minimum values varied between 1.56 and 3.43. The fluctuations in soft-tissue weight appear to be the main explanatory factor of seasonal variations in metal concentrations in mussels. Fluctuations in metal levels related to size of mussels were observed. Except for cadmium in mussels with a mean dry weight of soft tissues >0.2 g, a slight decrease in metal concentrations was observed for growing individuals: the regression coefficient b was -0.10, -0.11, -0.13 and -0.27 for Cd, Cu, Zn and Pb, respectively. The metals examined were rather uniformly distributed among the different groups of organs (visceral mass, gills and palps, remainder) and, consequently, several analyses of metals in different organs do not provide much more information than one analysis on the whole soft tissues. It is concluded that fluctuations related to size or season are reflected by only moderate differences in the maximum and minimum concentrations of metals in the mussels, but that they are nevertheless sufficient to conceal low chronic or short-term pollution, except at those sites where the normal environmental conditions are well-documented.     

城市湖泊表层沉积物中的重金属污染现状及其风险评价——以武汉墨水湖为例

水体沉积物中的重金属会对生态系统构成直接和间接的威胁.为了研究工业化、城市化过程中城市湖泊沉积物重金属污染现状及其暴露风险，以武汉市墨水湖为研究对象，测定了5种重金属Zn、Cu、Ni、Pb及Cr在表层沉积物中的含量，分析了其污染程度、分布特征，并对其稳定度进行了分析.结果表明，墨水湖表层沉积物重金属污染程度较重，在所有采样点5种重金属含量均高于最低效应阈值（LEL），多数采样点甚至超过了严重效应阈值（SEL）.该湖泊沉积物中重金属分布具有比较明显的空间差异性：排污口区>湖中心水域>城区岸边带>林田岸边带；其稳定程度依次为：Zn < Cu < Ni < Pb < Cr，其中Zn交换态及碳酸盐结合态比例超过50%，稳定程度极低.而Pb、Cr稳定程度较高，其交换态及碳酸盐结合态比例小于10%.像墨水湖这样受纳高污染负荷市政污水、暴雨径流的城市湖泊，其潜在的重金属生物活性，必须引起足够的重视.     

Distribution of Pb,Cr, Cu and Zn in the marine-coastal region of Zanzibar (Tanzanian archipelago,East Africa)

In Tanzania, a large amount of domestic and industrial wastes are daily released to the aquatic environment without prior treatment. The present paper establishes the status of distribution and environmental implications of heavy metals in water, sediment, suspended particulate matter and biota (Anadara antiquata) from two marine coasts in Zanzibar, Tanzania. These metals are derived from the industrial areas through rivers and storm water outflows. Heavy metal concentrations in the collected samples were determined using atomic absorption spectrophotometry. Concentrations were significantly higher in the Malindi compared to the Fumba coast (ANOVA, p?=?.001). Calculation of metal partition coefficients shows that the relative importance of the particulate and the water phases varies in response to water parameters and suspended solid content, but that most elements achieve a conditional equilibrium in these coasts. Higher metal concentrations found in Malindi suggest a pollution effect related to anthropogenic activities. Mean metal burdens in the tissues of A. antiquata from both Malindi and Fumba coasts were significantly higher than in other compartments analysed (ANOVA, p?<.05). Maximum values of contamination factor and contamination degree for metals were noticed for sediments from both Malindi and Fumba coasts. It is imperative to understand that metal concentrations of coastal environments depend not only on industrial and household waste inputs but also on the geochemical composition of the area.