Assessment of the impacts of a new artificial lake mouth on the hydrobiology and fisheries of Chilika Lake, India

The degraded state of the fragile ecosystem of Chilika Lake, located on the east coast of India, was undergoing restoration through an effective hydrological intervention during the year 2000. Studies on the lake’s hydrobiology and fisheries for the period of 7 years before and 7 years after the hydrological intervention indicated a rapid recovery of the lake fishery immediately after opening of the new lake mouth, with a sixfold increase in the average annual fish landings. During 2000–2001 to 2006–2007, the average fisheries output (11 051.3 t), catch per unit effort (6.2 kg boat^?1 day^?1), the economic valuation of the average annual catch (637 million rupees) and productivity (11.97 t km^?2) exhibited dramatic increases of 498%, 464%, 1177% and 498.5%, respectively, compared with the 7‐year pre‐intervention data. Multivariate statistical analysis inferred that most of the lake’s environmental variables are strongly associated with salinity factor, which seems to have governed the lake ecology. The salinity dynamics of the lake are governed by both freshwater inflows and seawater ingress through the new artificial lake mouth. Correlation analysis indicated that salinity was positively correlated with prawn catch (R² = 0.542; d.f. = 25; P < 0.01), crab catch (R² = 0.628; d.f. = 25; P < 0.001) and fish catch (R² = 0.476; d.f. = 25, P < 0.05). The average increase in the salinity regime (43.8%) for the lake during the post‐hydrological intervention period, compared with the pre‐hydrological intervention period, appears to have positively impacted the fish, prawn and mud crab catches. A gradual decrease in total fisheries output since 2005–2006, however, was attributed mainly to a continuing increase in destructive fishing practices in the absence of any conservation and regulatory measures for fishing, and large‐scale collection of shrimp juveniles from the outer channel for shrimp aquaculture. Thus, carefully planned conservation and regulation measures must be ensured, with active participation of local communities during this early phase of lake restoration. In the absence of such measures, the present scenario of fisheries enhancement might not be sustained over the long term.     

水体沉积物重金属质量基准研究综述

沉积物作为重金属污染物的源和汇,对水生环境有着至关重要的影响。如何准确有效的建立沉积物的质量基准已成为当前水环境学的紧迫课题。经过近三十年的发展,沉积物质量基准（Sediment Quality Criteria,SQC）的建立方法有了很大的发展。笔者结合各种文献和国内外最新研究介绍了常用的几种SQC的建立方法,并分析了各种方法的优劣性,最后详细介绍了当前最为流行的两种SQC的建立方法：相平衡分配法和生物效应数据库法。通过对各种方法的比较,对如何建立SQC提出了几点建议,以期为建立适合我国的SQC有所启发。     

Trace metal concentration in water and sediments of satellite lakes within Lake Victoria (Kenya) basin

Lakes Kanyaboli, Sare and Namboyo are three important freshwater satellite lakes in the northern region of the Lake Victoria (Kenya) basin. Lake Simbi, a small alkaline -saline crater-lake is located near the southern shoreline of the Nyanza Gulf of Lake Victoria. The three freshwater lakes provide unique aquatic habitats for the important indigenous fish species and other aquatic biodiversity, as well as serving as water resources for the surrounding communities. Surface and sediment samples were collected and examined to characterize these lake systems. Metal partitioning among the various defined geochemical phases also was determined. Based on the measured concentrations, the satellite lake waters are relatively uncontaminated with regard to Al (aluminium), manganese (Mn), zinc (Zn), copper (Cu) and chromium (Cr). Levels of most elements were below detection limits, as well as being well below the desirable drinking water guideline values proposed by the World Health Organization. The exception was the elevated iron (Fe) contents (>300 μg L⁻¹). The sediments exhibited a relatively low level of contamination with regard to heavy metals. The mean values of the measured metals in the sediments were compared to levels in adjacent Lake Victoria. The study results from these poorly-studied, and relatively unperturbed ecosystems, compared to the main body of lake Victoria, highlight their importance as conservation areas, despite the small-scale fishery activity, potential threats from human activities and their sensitivity to fluctuating environmental conditions.     

Growth,mortality and stock status of mullets (Mugilidae) in Chilika Lake,India

The growth, mortality and stock status of grey mullets Chelon parsia (Ham. 1822), Chelon planiceps (Val. 1836) and Mugil cephalus (Linn. 1758) were investigated during December 2010 to November 2011 from Chilika Lake, Asia, largest brackish water lake. The length‐based analysis, using length frequency data collected from fish landing centres, formed the basic study methodology. Growth function and population parameters were studied using FAO ‐ICLARM Stock Assessment Tools‐II (FiSAT ‐II ). The von Bertalanffy growth function (VBGF ) was established as L _t  = 321 mm*(1 ? exp (‐0.98 year^?1 × (t + 0.085 year)) for C. parsia , L _t  = 315 mm × (1 ? exp (?0.80 year^?1 × (t  + 0.105 year)) for C. planiceps and L _t  = 700 mm*(1 ? exp (?0.70 year^?1*(t  + 0.097 year)) for M. cephalus . Lower K and higher L _∞ values for M. cephalus indicated slow growth and high longevity of the species, compared to other grey mullets. Length–weight relationships were derived, indicating isometric growth for grey mullets. Recruitment of mullets was observed throughout the year, with a peak during April–July. About 50% of the mullets were caught by fishing gear before reaching their first year of age. The level of exploitation (E  ≥ 0.60) was more than the optimum level (E  = 0.4 for pelagic stock), indicating overexploitation of grey mullets in Chilika Lake. Moreover, the average annual yields of three mullets were observed to be higher than the estimated maximum sustainable yields (MSY ), also indicating overharvesting of mullets. Thus, the mullets could be considered one of the highly overexploited resources in Chilika Lake. The findings of this study will facilitate the development of appropriate management strategies for the mullet fishery in Chilika Lake.     

River, reservoir and lake sediment contamination by heavy metals downstream from urban areas of Switzerland

This paper quantifies sediment contamination by heavy metals in four reservoirs and one lake located downstream from major urban areas in Switzerland. The waterbodies include the Wettingen Reservoir (located on the Limmat River downstream from Zürich), the Klingnau Reservoir (on the lower Aare River), the Wohlen Reservoir (downstream from Berne), the Verbois Reservoir (downstream from Geneva) and Vidy Bay (Lake Geneva, city of Lausanne). For all sediment cores and contaminants, a trend is observed from high contaminant values in the lower part of the cores, decreasing to lower concentrations in the upper part of the cores. However, for each site and each element, specific features are recognized. Applying the criteria of the Swiss ordinance on soil protection, all sediment cores must be classified as contaminated by one or more contaminants and at variable levels. From these data, it is concluded that: reservoirs and lakes located downstream from major urban centres in Switzerland have accumulated significant volumes of contaminated sediments in the past, representing the largest, but not the most intensely, contaminated sites on a national scale; the main environmental risk is remobilization of the contaminants and their return to the food chain, particularly by infiltration into the groundwater; and although the processes of remobilization are identified, the conditions of occurrence and the amplitude of the processes are still poorly known. Different options of reservoir and lake sediment management also are discussed and further research topics defined.     

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

West 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 freshwater genetic resources. Noting that it has been extensively affected by pollution, the objective of the present study was to examine the extent of heavy metal contamination of the sediments and commercially important biota in the lake. Heavy metal concentrations in the sediment from most of 24 samples in West Lake exceeded the Ontario Ministry of Environment Screening Level for chromium (Cr), copper (Cu), manganese (Mn), lead (Pb) and zinc (Zn) concentrations. Aquatic organisms from the lake also were found to be contaminated by heavy metals. The average Zn concentrations in snails and mussels tissues ranged between 174 and 415 µg g⁻¹, and the Pb concentrations between 3.5 and 5.2 µg g⁻¹. The Cu concentration in shrimp (52 µg g⁻¹) and snail (189 µg g⁻¹), and the Pb concentration in all fish species and shrimp from the lake (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 for the effective management of the food and ecological resources of West Lake are discussed.     

Assessment of heavy metal contamination in coastal lake sediments associated with urbanization: Southern Kerala,India

The study of the spatiotemporal variation of heavy metals in lake sediments is of great importance because heavy metals can result in toxic effects on aquatic biota through bioaccumulation. This study was undertaken to evaluate the degree of heavy metal contamination in the lacustrine sediments and the corresponding environmental deterioration in a tropical, urban, coastal lake (Akkulam–Veli), located in Kerala, India. The spatiotemporal variations of the cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), manganese (Mn), nickel (Ni) and zinc (Zn) concentrations in the lake sediments, as well as various indices of anthropogenic contamination, including Contamination Factor (CF), Pollution Load Index and Geoaccumulation Index (Igeo), were used to assess the degree of contamination. This study indicated contamination of the lake sediments with Cu, Pb and Zn. Urban domestic sewage and land run‐off are the major drivers of the heavy metal loads to the lake. During the pre‐monsoon, sediment contamination occurs in the upstream portion of Akkulam Lake because of a high clay content in the sediments. During the monsoon period, Akkulam Lake and the upstream portion of Veli Lake exhibit sediment contamination owing to high silt content. Domestic sewage is the main source of copper and zinc to the lake. Sewage bypass into the drains in the lake basin is largely responsible for the copper and zinc sediment contamination. High traffic levels and wastewater discharges from service stations/workshops are the main cause of the Pb loads entering the lake. Rubber particles of vehicle tires contain zinc and copper pigments that can accumulate on the surface of busy streets, entering the drains during rainfall events. Based on these study results, the accumulation of copper, zinc and lead in lake sediment can be controlled to a great extent by restricting the above‐noted activities. As the sediment content of lead, zinc and copper is confined to the clay fraction during the non‐rainy season and to the silt fraction during other seasons, lake restoration work should largely incorporate treating the clay and silt fractions, respectively, during both the non‐rainy season and rainy season.     

Intervention of Naraj Barrage: Its effects on sediment inflows into Chilika Lake,India

Chilika Lake, Asia's largest brackish water lagoon, is located in the state of Odisha on the east coast of India. It was designated as a Ramsar site in 1981, being the first Indian wetland of international importance under the Ramsar convention. Siltation of the lake is become a major concern, because it is leading to various geomorphic changes that are affecting the shape and size of the lagoon, which receives a major silt load through the Daya and Bhargovi rivers (both being branches of the Mahanadi river) via the Kathajodi and Kuakhai rivers. The Naraj barrage was constructed at the mouth of the Kathajodi river to regulate its inflow, and also its silt load, into the lagoon. Two observatories are established in the Daya and Bhargovi rivers to determine the quantity of silt entering Chilika Lake through the rivers, with the bed load and suspended (total solids) being measured. Various effects of siltation in the lagoon because of the barrage are analysed in this study, to include the pre‐ and postconstruction situation. By considering different flood situations in the Mahanadi river, various alternate strategies for operation of the Naraj barrage were studied, with the goal of minimizing the siltation in Chilika Lake. These alternate operation strategies, and their potential effects on the inflow into the lagoon, are analysed and discussed in this report.     

南四湖表层底泥重金属空间分布及污染程度评价

测试南四湖湖区29个表层底泥中重金属Hg、Cd、Cr、Pb、Ni、Cu、Zn和类金属As的质量比,得到南四湖湖区重金属污染的空间分布特征。结合地质积累指数法和潜在生态风险指数法,对南四湖重金属污染程度进行评价。结果表明,南四湖已受到重金属元素的污染,属于中等程度污染湖泊,其中以As、Hg、Cd、Pb元素污染严重。除了As、Cd元素在下级湖表层底泥中的质量比略高外,其他重金属元素在上级湖的污染程度普遍比在下级湖的高;二级坝以北的昭阳湖湖区潜在生态危害最为严重,其次是南阳湖、微山湖、独山湖和二级坝以南的昭阳湖湖区。     

Use of the fish endoparasite Ligula intestinalis (L., 1758) in an intermediate cyprinid host (Rastreneobola argentea) for biomonitoring heavy metal contamination in Lake Victoria, Kenya

Use of some fish parasites as bioindicators of heavy metal pollution has been demonstrated as a promising approach because of their capacity to bioconcentrate such elements. This study evaluated the effects of a cestode parasite, Ligula intestinalis , on the accumulation of lead (Pb), cadmium (Cd), chromium (Cr) and copper (Cu) in the cyprinid fish, Rastreneobola argentea , in Lake Victoria, Kenya. This L. intestinalis / R. argentea model also was assessed as a bioindicator system for heavy metal contamination in the lake. Samples of 125 fish, 63 parasites, water and sediments were collected at four sites in the Kenya portion of the Lake Victoria basin characterized by variable heavy metal concentrations, for ICP-OES element analysis. The concentration of all four heavy metals in the fish and parasite samples exhibited site-specific variations relative to the metal concentrations in the water. The Pb, Cr and Cd concentrations in the L. intestinalis were higher than in the fish samples by a factor 11, 18 and 14 respectively, whereas the Cu concentration in L. intestinalis was increased by a factor of 2.5, relative to the Cu concentration in fish. The Pb, Cd and Cr concentrations in the parasite body increased, relative to their concentrations in fish samples, suggesting in the bioaccumulation of these metals by the parasite. The Cu concentration in the fish parasite decreased, relative to increased Cu levels in the fish. This finding was interpreted as being a competition for these elements between the parasite and its fish host. Moreover, the increased Cd and Cr levels in the fish were significantly influenced by the increased abundance of the parasites in the abdominal cavity of the fish samples. Based on the results of this study, the L. intestinalis / R. argentea system is proposed as a promising bioindicator model for evaluating environmental Pb, Cd and Cr concentrations where these species occur.     

Nutrient and heavy metal storage and mobility within sediments in Kouris Reservoir,Cyprus

The objective of this study was to evaluate the risks associated with nutrient and heavy metal pollution in the water and sediments of Kouris Reservoir in Cyprus, and to recommend applicable measures to alleviate them. The reservoir drainage area contains various historic abandoned copper mines existing in an ophiolite geological substrate. Kouris Reservoir water is classified as oligotrophic to mesotrophic, with phosphorus being the limiting factor for algae growth. The thermal stratification of the reservoir enhances anoxic conditions in the reservoir hypolimnion, initiating phosphorus release back into the water column from the lake bottom sediments. The increased phosphorus release, in combination with increased water temperatures during the summer months (i.e. reaching 27 °C in August), may be the key factors enhancing the growth of microbial communities and cyanobacteria blooms. The sediment of Kouris Reservoir is classified as ‘low risk’ on the basis of the Ecological Risk Index scheme, in contrast to the Geoaccumulation Index, which indicates a moderate degree of contamination for chromium (Cr), nickel (Ni) and copper (Cu), and a high degree for lead (Pb). Heavy metals are strongly bound to the sediment matrix at pH values between 7 and 9, but can be released back into the water column at potential acid pH values. In addition, the sediments exhibit a high copper and chromium absorption affinity under current water quality conditions in the reservoir, as shown by batch absorption experiments. The experimental results suggest dredging of the reservoir sediment, and its subsequent dumping of the sediments near influent streams, would have adverse effects on the environment in the event of acid rain or other environmental changes that might acidify the sediment.     

Effects of heavy metal contamination from anthropogenic sources on Dasarahalli tank, India

This study examines the concentrations of various heavy metals, and their distribution in a hyper‐eutrophic urban Dasarahalli tank system, which is being polluted from industrial, domestic and sewage effluents. The concentration of iron (Fe), zinc (Zn), copper (Cu), nickel (Ni), chromium (Cr), lead (Pb) and cadmium (Cd) in water, plant (Alternanthera philoxeroides) and sediment samples was determined. The water‐soluble (bioavailable) fractions of heavy metals correlated positively with their total concentration, exhibiting the following sequence of bioavailability: Zn > Cd > Ni > Fe > Cu > Pb > Cr. A. philoxeroides exhibited a maximum bioaccumulation factor for cadmium (3913). The mean values of all types of collected samples were correlated with the corresponding mean values in a control tank (Vasanthapura tank). The sequence of the order of the concentrations of the metals in water, plant and sediment samples exhibiting higher values than those observed in the control tank was as follows: Cr > Ni > Pb > Cu > Fe > Zn, Cd > Cr > Fe ≈ Zn ≈ Cu ≈ Pb and Pb > Cu ≈ Cr > Zn ≈ Ni > Fe, respectively. The geoaccumulation indices of the heavy metals revealed that the tank is moderately contaminated. As A. philoxeroides is extensively used for human consumption and also as cattle fodder, there is a growing health risk that these metals could find their way into the human food chain.     

Heavy metal concentrations in fish of Lake Balaton

The concentration of heavy metals (cadmium, copper, lead, mercury and zinc) found in muscle, gills and liver of eel, bream and pike‐perch living in Lake Balaton (Hungary) varied significantly between fish species and organs. The toxic metals in the muscle of fish, except for cadmium in bream, were below the maximum permissible level for human consumption. Cadmium concentrations above the maximum permissible level occurred in autumn in a few small individuals of bream, which, because they have poor culinary value and are seldom consumed, does not represent a risk for humans. Cadmium, copper, lead and zinc levels proved to be higher in eel and bream compared to pike‐perch, while high mercury concentrations were found in the predator fish, pike‐perch. Mercury accumulated most in the muscle in each species, while other metals were found in higher levels in the gills and liver. Seasonal differences were found for cadmium in each species and for lead in eel; the concentrations being elevated in autumn compared to spring. The fish species studied as bio‐monitors demonstrated that the overall heavy metal pollution of Lake Balaton is not significant, although, during summer an increase of cadmium and lead loading could occur at the catchment area and in the lake. Studies on the size (age) dependency of heavy metal concentrations showed that, in most cases, none or a negative relationship exists for each organ and metal in all species studied, and a positive regression coefficient was characteristic only on some occasions for mercury, cadmium and lead.     

Comparative spatial metal concentrations and partitioning in bottom sediments of two tropical freshwater lake basins,Kenya

Metal concentrations in the water, sediments and biota in alkaline, near neutral water tropical freshwater lake basins were determined and a comparative analysis made on the spatial and accumulated trace metal concentrations, and geochemical partitioning of iron (Fe), manganese (Mn), copper (Cu), chromium (Cr), zinc (Zn), nickel (Ni), cadmium (Cd) and lead (Pb) in bottom lake sediments. Variable accumulated levels were found in the analysed sediments and aquatic biological tissues. Metal partitioning data in the present study from the two areas exhibits similar trends in magnitude. The residual fractions retained relatively higher amounts of metals. Relatively higher contents of Pb, Cr and Cu were found in Lake Victoria sediments. Cd, Ni, Mn and Pb are of concern because a higher percentage of these metals were retained in the more bioavailable fractions in Lake Naivasha. Total levels of sediment mercury were comparable for the two lake basins. Metals were found in significant levels in the tissues of aquatic organisms, highlighting the potential risks to other levels within the aquatic food chain. Although the exposure risk was not evaluated, it is important to continue monitoring these elements in fish, as sediments were found to contain considerable quantities of the metals. Numerous sediment extraction techniques data applied for evaluating metal partitioning in sediments cannot be compared because of the use of different methods. Nevertheless, the information is still useful in differentiating and understanding pollution loads from natural versus anthropogenic sources and their associated risks.     

The seasonal and spatial variations of labile copper, iron, manganese, lead and zinc sediment fractions in Lake Naivasha, Kenya

Lake Naivasha is a freshwater lake with no surface outlet, lying within a closed basin of the Kenyan Rift Valley. It is perceived to be a lake undergoing anthropogenic stresses. This study is intended to determine the speciation of some selected heavy metals in the sediments of Lake Naivasha, as an indicator of potential pollution of the lake. Sediment and water sampling of the lake was conducted in March and May 2003, during the dry and wet seasons, respectively. Analyses of the speciation of heavy metals in sediment samples (<63 µm faction) were performed on sediment samples collected from five sites within the lake. The study results obtained indicated that influent Malewa River was not a source of labile copper (Cu), lead (Pb) or zinc, despite the river having the highest percentage clay content during the wet season (86%). Copper was highly distributed in the residual sediment fraction (average of 90%). Among the labile sediment factions, the highest quantity of Cu was in the oxidizable phase (3.58 and 2.30 µg g⁻¹ during the dry and wet season, respectively). Carbonate‐bound Cu was sparingly distributed during both the dry and the wet seasons, ranging between 0.74 and 1.81 µg g⁻¹. Iron was highly distributed in the oxidizable sediment phase, exhibiting concentrations ranging between 2.0 and 6.0 (×10³) µg g⁻¹. Relative to the other heavy metals, manganese was distributed in lower proportions in the residual sediment fraction. High concentrations of Pb were observed in the oxidizable phase from most of the sampling sites along the lake shore. Zinc was distributed largely in the oxidizable phase, being highest at sampling site SS, which was located near a municipal sewage input to the lake. The sediments collected at the sampling sites located in the deep portion of the lake exhibited the highest concentrations of labile heavy metals.     

太湖底泥氮污染分布规律及生态风险

对太湖污染情况进行了调查研究,全面分析了其底泥的氮污染规律。结果表明,底泥表层受人类活动影响较大,总氮含量总体超标;其第2、3、4、5层,总氮污染程度已大为降低。得出了不同保证率条件下太湖底泥总氮浓度垂向变化规律,并据此确定太湖底泥生态清淤的深度为上层40～50cm。对太湖底泥各层次总氮浓度概率分布的计算发现,它基本符合随机对数正态分布规律。提出了太湖底泥氮污染生态风险分析方法,定义了度量生态风险的指标,并计算了生态风险值,计算结果表明,太湖底泥氮污染生态风险程度较高的区域依次是五里湖、东太湖、梅梁湖南区等,此为生态清淤重点区域。     

Metals in the sediments of the Huron-Erie Corridor in North America: Factors regulating metal distribution and mobilization

Sediment samples from the Huron‐Erie Corridor (Great Lakes, North America) were collected to quantify the relative importance of natural and anthropogenic sources of contamination, and to study the spatial metal distribution patterns of metals as a function of the characteristics of the Corridor sediments. A stratified random sampling design was used to measure the spatial patterns of metal inputs, settling and sorting along the length of the Corridor. Factors regulating metal mobilization were assessed by determining metal affinities with the total organic fraction (TOM), the mineral fraction (represented as Al), and the granulometric characteristic (represented as <0.063 mm fraction). The study revealed that anthropogenic factors primarily regulated metal distributions and mobilization throughout the Huron‐Erie Corridor. In the St. Clair and Detroit Rivers, the spatial pattern of metal distributions strongly reflected local industrial sources. In the Walpole Delta and Lake St. Clair, however, inorganic (clays) and organic (TOM) particles dominated the contaminant distribution. Sediment contamination issues throughout the Huron‐Erie Corridor were dominated by mercury, released from sources along the St. Clair and Detroit Rivers. The mean enrichment factor EF_Al for mercury in these sediments has reached 68.3. Other metal pollutants were confined to the sediments in the lower depositional reach of the Corridor.     

玄武湖沉积物磷形态的垂向变化和生物有效性

采用不同的化学提取法,分析玄武湖西北湖区沉积物中各形态磷、生物可利用磷(BAP)的垂向变化,探讨了各层沉积物中磷的生物有效性。结果表明,沉积物中总磷以无机磷为主,BAP占总磷的20%~52.6%,玄武湖底泥的磷有较好的生物可利用性。不同地点沉积物各磷形态和BAP的垂向变化有较大的差异。1号采样点的总磷、无机磷、铁磷和BAP质量比在沉积0~20 cm处较高,20~40 cm逐渐减小,说明0~20 cm内释磷潜力较大;2号采样点的总磷和无机磷质量比先减小,20~40 cm逐渐增加,而BAP和铁磷质量比随深度增加呈上升趋势,说明2点深层具有较大的释磷潜力。铁磷与BAP相关性较好,这部分磷具有较大的潜在释放风险。     

阳宗海表层沉积物中的重金属生态风险评估

对从阳宗海湖底表层采集的25组沉积物样品中的10种重金属质量比进行分析,结果表明,Ti、Mn、Zn、V、Cr、Cu、Ni、Co、Pb和As的质量比平均值均超过了当地土壤背景值。而重金属系统聚类分析表明,Zn、Cr、Pb、As高度相关,其污染主要由于人类活动造成;Ti、Mn、V、Cu、Ni、Co的分布特征相似,其污染原因以岩石风化等自然因素为主。单因子富集系数评价表明,阳宗海10种重金属均达到了中度富集程度,其中As、Cu、Cr富集程度较为突出。用Hakanson潜在生态风险指数法评价阳宗海表层沉积物中重金属的生态风险,结果表明,阳宗海表层沉积物中重金属的生态风险总体属轻微程度,阳宗海南岸局部区域达到中等生态风险程度。几种重金属对阳宗海生态风险的贡献由大到小依次为As、Cu、Co、Ni、Pb、Cr、V、Zn、Mn、Ti,其中,As是阳宗海最突出的生态风险因子。     

Modeling of sediment and heavy metal transport in Taihu Lake, China

With the current rapid economic growth, heavy metal pollution has become one of the key issues in the Taihu Lake. Although heavy metal pollution levels and distributions of the Taihu Lake have previously been described, an effective model to describe the transport process of heavy metals between the water column and sediment bed for this lake is not available. It is known that heavy metals in the water column can be related to the resuspension of sediment in the lake bed. In this study, we set up a coupled model of relating hydrodynamics, sediment and heavy metals based on Environmental Fluid Dynamics Code (EFDC), and applied it to Taihu Lake, China. For calibration and validation of the model, we employed two series of field sampling data taken all over Taihu Lake during April and July of 2009. The results show that the hydrodynamics simulations of the coupled model agree with the observations reasonably well and the sediment and heavy metal model shows similar variation trends during the simulation. Our results indicate that the model can be used for simulating the sediment and heavy metal transport process in the Taihu Lake and here we provide an effective tool for water quality management at small time scales.