Interspecific variation in heavy metal body concentrations in biota of Sunderban mangrove wetland, northeast India

The coastal environment of West Bengal, recognized as the most diversified and productive ecosystem among all the maritime states of India, faces organic pollution from domestic sewage and urban and industrial effluents leading serious impacts on biota. The present paper aims at providing information on concentration level of heavy metals among the tissues of benthic polychaetes, bivalve molluscs and finfishes collected from Sundarban mangrove wetland, northeast coast of India. An overall common trend in bioaccumulation was revealed with the following decreasing order: Zn>Mn>Cu>Cr>Se>Hg with few exceptions. Both species dependent variability and temporal variations were pronounced. A high degree of organ specificity was evident in the bivalves where gill and mantle exhibited higher metal accumulation due to ion exchange property of the mucous layer covering these organs. Variability between closely related species is a reflection of different uptake rates, physiology and impact of environmental factors. The results of this analysis suggest that mollusks can play a significant role in trace metal trophic transfer studies, especially as their representatives are intertidally and subtidally ubiquitous.     

Levels of elements in the surficial estuarine sediments of the Hugli River, northeast India and their environmental implications

The present paper is the first document of a detailed geochemical and mineralogical study of muddy to sandy mud estuarine sediments of the Hugli River collected from five different sites along its course in the coastal areas of West Bengal, northeast India. The present work attempts to establish the status of distribution and environmental implications of 52 elements in the surficial estuarine sediments and their possible sources of derivation. The level of both metallic and non-metallic elements shows a wide range of variation all along the course of the estuary and can be attributed to their differential derivation from the source rocks and differential discharge of untreated effluents originating from industrial, agricultural, aquacultural as well as domestic sewage. The element contents, particularly the heavy metal content in the sediments, are the lowest in the upstream part of the estuary at Diamond Harbor, whereas, these are slightly higher in the intermediate stretch of the estuary at Haldia to highest in the mouth of estuary at Gangasagar. These changes indicate that the metals that are carried from upstream find their ultimate depositional sink at the delta mouth near Gangasagar, where almost all the elements showed elevated values. The majority of the elements have their highest concentrations at Canning, a site within the tidal channel network of the Hugli-Matla drainage basin away from the direct influence of the Hugli River. This site is severely contaminated with huge organic load from domestic sewage, aquaculture, intensive trawling activities and agricultural runoff. Moreover, the site suffers from heavy siltation load causing an almost moribund condition of Matla River at this point. Equi-dimensional quartzo-feldspathic mineral grains are consistent components in the siliciclastic composition of the sediments and their sizes at each station are controlled by respective hydrodynamic conditions. Various flaky minerals (mica, chlorite, hornblende) are also present but show inconsistent patterns of distribution. These flaky minerals remain in suspension for a long time and do not follow the usual law of settling of particles depending on the hydrodynamic regime prevailing in the area. Presented data will serve as a baseline against which future anthropogenic effects may be assessed. A comprehensive account of heavy metal content in sediments from different coastal regions of peninsular India has also been presented for purpose of comparison.     

Accumulation of 99Tc in duckweed Lemna minor L. as a function of growth rate and 99Tc concentration.

This study focuses on the question of whether short-term studies can be used to forecast the accumulation of the long-lived fission product 99Tc in duckweed, Lemna minor L., grown in the field; in other words, are the accumulation parameters independent of changing growth rates typical of natural populations of duckweed. Two processes determine the 99Tc accumulation: (i) uptake and release of 99TcO4-, characterised by a concentration factor, Kd, and (ii) first-order reduction and complexation of TcVII, characterised by kred. At various 99Tc concentrations, the growth, total Tc and TcO4- accumulation were monitored over 10 days; parameters were fitted and compared with earlier results. Both Kd and kred turn out to be independent of time, concentration and growth rate up to a concentration of 10(-6)mol l(-1) 99TcO4-. Concentrations above this level result in toxic effects. The Tc accumulation in field populations of duckweed at Tc concentrations which generally occur in the environment can be forecasted by using the results from short-term experiments.     

Fractionation studies and bioaccumulation of sediment-bound heavy metals in Kolleru lake by edible fish

Kolleru lake is the largest fresh water lake in the districts of East and West Godavari of Andhra Pradesh, India. Many anthropogenic sources contribute to the heavy metal pollution in the lake and the bioaccumulation of heavy metals in fish helps in assessing the aquatic pollution. Total contents and fractionation of selected heavy metals, viz., Zn, Cu, Cd, Pb, Cr, Ni and Co were measured in sediment sample and three edible fish. The investigation aimed at revealing differences in the accumulation pattern of heavy metals in fish inhabiting sediments characterized by varying metal bioavailability. The metal concentrations were found to be greater than the background concentrations of sediments indicating the anthropogenic origin of metals. Good recovery values were obtained for metal contents in sediments and fish. Large fractions of Zn, Cd and Cu were associated with mobile fraction of sediment and showed greater bioaccumulation in fish whereas Ni and Co were least mobilisable. The results clearly indicate that the fish of Kolleru lake are contaminated with metals and not advisable for human consumption.     

Channel migration zone mapping of the River Ganga in the Diara surrounding region of Eastern India

River channel migration is the universal phenomenon that is common in almost all alluvial rivers. The holy River Ganga, the heartbeat of India, is also not an exception in this case. It has shifted its course from time to time. After crossing the Rajmahal hills that is situated in the north-eastern corner of the Chota Nagpur plateau, this main river of India has started its lower course by flowing over the great low-lying flat plain of Bengal. In this flat plain area, the channel migration is a common phenomenon which is observed in the River Ganga also. The study is done in the segment of the Ganga River which is situated in the Diara surrounding area. Diara is a physical cum administrative region of the Malda district of the state of West Bengal of India which occupies an area of almost 900 km². For the identification of channel migration zone, several methods are used like construction of historical migration zone (HMZ), erosion buffer (EB), avulsion potential zone (APZ), restricted and un-restricted migration area (RMA and UrMA) and retreating migration zone (RMZ). The impact of the channel migration over the villages of the Diara region has also been depicted in this study. Remote Sensing and Geographical Information System (RS–GIS) is used to perform this study by taking the help of historical maps, Survey of India topographical sheets, LANDSAT imageries, etc. The results show that the river has a historical migration zone of 855.55 km² during 1926–2016 period which is near the entire area of the Diara region (i.e. 900 km²). The construction of EB over the Ganga River for the next 100 years shows that more than half of the area of the Diara region will go under the river bed.     

Analysis of soil characteristics of different land uses and metal bioaccumulation in wheat grown around rivers: possible human health risk assessment

The present study was conducted to determine the physico-chemical properties and heavy metal contents in soils under three land uses (agricultural, riverbank and roadside) from areas situated around rivers (Beas and Sutlej) in Punjab, India. Heavy metal contents in wheat samples (grain and fodder) growing in the area were also analyzed in order to find out potential human health risk through wheat consumption. The studied soils under the three land uses were found to be basic in nature with sandy texture, low soil organic matter and other soil nutrients. Comparatively higher amounts of soil nutrients were observed in soils under agricultural land use as compared to riverbank and roadside land uses. The amounts of heavy metals (Cr, Cu, Co and Pb) analyzed in soils were lower than the various national and international maximum permissible limits, but heavy metal contents observed in wheat fodder samples exceeded the maximum permissible limits for fodder. The soil-to-plant metal bioaccumulation factor was found to be highest for Cu (3.812 for soil–wheat grain and 1.874 for soil–wheat fodder), which showed the bioaccumulation of heavy metals from soils to crops, and the wheat straw-to-grain translocation factor was found to be highest for Co (4.375). The hazard index calculated to assess non-carcinogenic health risks was found above 1 for children, meaning that the wheat grains can pose health risks to children.     

Studies on heavy metal accumulation in aquatic macrophytes from Sevan (Armenia) and Carambolim (India) lake systems

Aquatic macrophytes are unchangeable biological filters and they carry out purification of the water bodies by accumulating dissolved metals and toxins in their tissue. In view of their potential to entrap several toxic heavy metals, 45 macrophytes belonging to 8 families collected from two different physiographic locations (36 from Sevan Lake, Armenia; 9 from Carambolim Lake, Old Goa, India) were studied for estimation of 14 heavy metals. The study was aimed at understanding the importance of these macrophytes in accumulation of toxic metals and controlling the heavy metal pollution and suggesting the remedial measures, if any, for the preservation and restoration of lake ecosystem. Inductively Coupled Plasma-Atomic Emission Spectrometric (ICP-AES) analyses of these aquatic macrophytes have shown the importance of aquatic macrophytes in accumulation of heavy metals and maintaining the clarity of water bodies beside their role in trophic systems. Accumulation of most of the heavy metals was higher in root system. The representative macrophytes from two different physiographic locations show similar trends and order in accumulating different metals generally. Of the 14 metals investigated, 9 (Ca, Fe, Al, Cr, Cu, Ba, Ti, Co and Pb) showed higher rates of accumulation in the root whereas 3 (Mn, Zn and Mg) showed more accumulation in stem and 1 (Ca) showed higher accumulation in the leaves. In most of the samples Cu was accumulated more in the roots (50+/-47.15 microg/g) and less in flowers (9.52+/-3.97 microg/g). Occurrence of heavy metal was much higher in macrophytes of Sevan Lake than that of the Carambolim Lake. The accumulation of 14 elements was in order of Ca>Mg>Fe>Al>Mn>Ba>Zn>Ti>Cu>Cr>Co>Ni>Pb>Cd. The present study revealed that the aquatic macrophytes play a very significant role in removing the different metals from the ambient environments. They probably play a major role in reducing the effect of high concentration of heavy metals. Therefore, the macrophyte community of the Sevan Lake area needs to be protected and restored on a priority basis. Accumulation of highly toxic metals like--Cr, Cd, Pb and Ni was lower as compared to the essential metals like Ca, Fe and Mn in all the macrophytes from both the lake systems, consequently high metal concentrations observed in both the areas may not directly reflect on the pollution level.     

Managing the village-level open-access water resources in a region facing rapidly declining water availability

Growing population, human settlements, industrialization and intensification in groundwater-based cultivation have resulted in severe onslaught on underground aquifers in West Bengal, an eastern province of India with high population density. The present paper focuses on this water resource management issue. The study shows that traditional, village-level surface water reservoirs which for centuries had supplemented irrigation in addition to providing water for all sorts of domestic needs are now in doldrums. Through statistical analysis, the study shows that for all practical purposes, there is very little effective management of these precious open-access water resources. The situation calls for paradigm shift in policy on water resource management that entails development of community-based management catalyzed by government intervention, external agencies and NGOs under supervision and control of local elected bodies.     

Perceptions and patterns of human–elephant conflict at Barjora block of Bankura district in West Bengal, India: insights for mitigation and management

Human–elephant conflict is an issue of great concern regarding the growing competition between people and wildlife for food and shelter throughout Asia and Africa. The situation the Asian elephant faces is much critical. According to IUCN (Big hopes for endangered Asian Elephants, News Release, Gland, 2006), one of the prime factors to the decline of elephant population in India is the increasing trend in human–elephant conflict. Barjora block of Bankura district in West Bengal is one of the severe conflict prone zones in West Bengal, where elephant raid in every year has now become an inevitable phenomenon. As a result, crop damage, infrastructural damages, disturbances of daily activities, occurrence of human death and injuries have no doubt annihilated and frustrated the social fabric of life. This paper is an empirical attempt to address various consequences of human–elephant encounters which have an adverse impact on social, economic as well as the cultural life of the people. Instead of pursuing some traditional mitigation techniques, we argued much on understanding peoples’ perception to explore some sustainable mitigation measures to ensure the interest of both human and elephant and also to safeguard ecological integrity.     

Fishers’ local knowledge on impact of climate change and anthropogenic interferences on Hilsa fishery in South Asia: evidence from Bangladesh

The anadromous fish species Hilsa (Tenualosa ilisha) constitutes the largest single fishery in Bangladesh and West Bengal, India. River Meghna is the important habitat for Hilsa as the major breeding and nursing grounds are situated along this portion of the river. In this paper, we investigate fishers’ perceptions on effect of climate change and anthropogenic impact on Hilsa fishery at lower Meghna. Fishers’ ecological knowledge indicates that the stock of Hilsa is declining due to several adverse climatic conditions such as increased water temperature, salinity intrusion and low freshwater discharge from upstream. Fishers believe that dams and polders have immense effect on river sedimentation which already blockade several upward migratory route of Hilsa. Fishers’ experience shows that intensity of coastal cyclone is gradually increasing, which causes severe physical and economical damage. The study also indicates that the major constraints to adopt with the change situation are low level of human capital and restricted access to the formal credit system. Therefore, incorporation of local knowledge in governmental policy formulation and public support to improve human skill are essential for the adaptive management.     

Pollution profile of damodar river sediment in Raniganj-Durgapur industrial belt,West Bengal,India

This paper reports on the pollution profile of Damodar river sediment as obtained from analysis of the river sediment at suitable selected sites in the Raniganj-Durgapur industrial belt, West Bengal, India. The parameters measured include (a) silica, mixed oxide, calcium, magnesium, total water-soluble exchangeable cation and anion, chemical oxygen demand, and (b) some toxic and other elements, such as sodium, potassium, arsenic, cadmium, chromium, mercury, manganese, lead, zinc, cobalt, copper, iron nickel, phosphorus, sulphur, and vanadium. The parameters listed under (a) led to the characterization of the sediment, and those under (b) gave an index of metal pollution of the sediment. The elements were estimated by inductively coupled plasma emission spectrometry.     

Threatened access, risk of eviction and forest degradation: case study of sustainability problem in a remote rural region in India

Degradation of common pool resource (CPR) in developing countries has often been traced to high rate attached by poor people in discounting future flow of benefits, market failure, pressure on carrying capacity or sometimes property right failure. However, the concept of poorly enforced property right and particularly risk of eviction as a measure of insecurity of land tenure has not been adequately examined in the context of degradation of CPR. A game theoretic framework is developed where degradation of forest grazing land is explained in terms of changes in perceived risk of eviction from the encroached land. Logit regression is applied to empirically analyse the impact of perceived fear of reduced access and other variables on the state of degradation. For this purpose, a sample of seven villages is considered in tribal dominated region in West Bengal, India. It is observed that apart from a number of socio-economic variables like poverty, mutual trust and other incomes, perceived fear of eviction (represented as a dummy variable) arising from insecurity of forest land tenure, has a significant impact on forest degradation status in the study region.     

Assessment of alpha activity of building materials commonly used in West Bengal, India

This paper, reports for the first time, an extensive study of alpha activity of all widely used building materials (plaster of Paris, stone chips, marble, white cement, mosaic stone, limestone, sand, granite, cement brick, asbestos, red brick, cement tile, ceramic tile and ceramics) in West Bengal, India. The alpha activities have been measured using Solid State Nuclear Track Detector (SSNTD), a very sensitive detector for alpha particles. The samples were collected from local markets of Kolkata. The measured average alpha activities ranged from 22.7+/-2.5 to 590.6+/-16.8Bqkg(-1). The alpha activity of ceramic tiles was highest and provides additional data to estimate the effect of environmental radiation exposure on human health.     

Study on the behavior of the heavy metals Cu, Cr, Ni, Zn, Fe, Mn and 137Cs in an estuarine ecosystem using Mytilus galloprovincialis as a bioindicator species: the case of Thermaikos gulf, Greece

Mussels are worldwide recognized as pollution bioindicators and used in Mussel Watch programs, because they accumulate pollutants in their tissues at elevated levels in relation to pollutant biological availability in the marine environment. The present study deals with the use of Mytilus galloprovincialis as a local bioindicator of heavy metal and (137)Cs contamination in an estuarine ecosystem (Thermaikos gulf, Greece in Eastern Mediterranean). M. galloprovincialis samples were collected monthly from two aquaculture farms during the period April to October 2000. Analyses for the heavy metals Cu, Cr, Ni, Zn, Fe, Mn and (137)Cs showed that the concentrations measured were low and similar to those from other non-polluted Mediterranean areas. In terms of the two sampling stations, there were no statistically significant differences between them. On the contrary, the seasonal evolution of either heavy metals or (137)Cs levels presented high variation. The levels were found to increase during the cold period of the year, especially for Cu, Zn, Mn and Cr which are essential for life. Stable metals were positively inter-related and moreover, metals more involved in biochemical activities seem to present more correlations than others with less significant role in the metabolism of the organisms.     

A critical review of the bioavailability and impacts of heavy metals in municipal solid waste composts compared to sewage sludge

The content, behaviour and significance of heavy metals in composted waste materials is important from two potentially conflicting aspects of environmental legislation in terms of: (a) defining end-of-waste criteria and increasing recycling of composted residuals on land and (b) protecting soil quality by preventing contamination. This review examines the effects of heavy metals in compost and amended soil as a basis for achieving a practical and sustainable balance between these different policy objectives, with particular emphasis on agricultural application. All types of municipal solid waste (MSW) compost contain more heavy metals than the background concentrations present in soil and will increase their contents in amended soil. Total concentrations of heavy metals in source-segregated and greenwaste compost are typically below UK PAS100 limits and mechanical segregated material can also comply with the metal limits in UK PAS100, although this is likely to be more challenging. Zinc and Pb are numerically the elements present in the largest amounts in MSW-compost. Lead is the most limiting element to use of mechanically-segregated compost in domestic gardens, but concentrations are typically below risk-based thresholds that protect human health. Composted residuals derived from MSW and greenwaste have a high affinity for binding heavy metals. There is general consensus in the scientific literature that aerobic composting processes increase the complexation of heavy metals in organic waste residuals, and that metals are strongly bound to the compost matrix and organic matter, limiting their solubility and potential bioavailability in soil. Lead is the most strongly bound element and Ni the weakest, with Zn, Cu and Cd showing intermediate sorption characteristics. The strong metal sorption properties of compost produced from MSW or sewage sludge have important benefits for the remediation of metal contaminated industrial and urban soils. Compost and sewage sludge additions to agricultural and other soils, with background concentrations of heavy metals, raise the soil content and the availability of heavy metals for transfer into crop plants. The availability in soil depends on the nature of the chemical association between a metal with the organic residual and soil matrix, the pH value of the soil, the concentration of the element in the compost and the soil, and the ability of the plant to regulate the uptake of a particular element. There is no evidence of increased metal release into available forms as organic matter degrades in soil once compost applications have ceased. However, there is good experimental evidence demonstrating the reduced bioavailability and crop uptake of metals from composted biosolids compared to other types of sewage sludge. It may therefore be inferred that composting processes overall are likely to contribute to lowering the availability of metals in amended soil compared to other waste biostabilisation techniques. The total metal concentration in compost is important in controlling crop uptake of labile elements, like Zn and Cu, which increases with increasing total content of these elements in compost. Therefore, low metal materials, which include source-segregated and greenwaste composts, are likely to have inherently lower metal availabilities overall, at equivalent metal loading rates to soil, compared to composted residuals with larger metal contents. This is explained because the compost matrix modulates metal availability and materials low in metals have stronger sorption capacity compared to high metal composts. Zinc is the element in sewage sludge-treated agricultural soil identified as the main concern in relation to potential impacts on soil microbial activity and is also the most significant metal in compost with regard to soil fertility and microbial processes. However, with the exception of one study, there is no other tangible evidence demonstrating negative impacts of heavy metals applied to soil in compost on soil microbial processes and only positive effects of compost application on the microbial status and fertility of soil are reported. The negative impacts on soil microorganisms apparent in one long-term field experiment could be explained by the exceptionally high concentrations of Cd and other elements in the applied compost, and of Cd in the compost-amended soil, which are unrepresentative of current practice and compost quality. The metal contents of source-segregated MSW or greenwaste compost are smaller compared to mechanically-sorted MSW-compost and sewage sludge, and low metal materials also have the smallest potential metal availabilities. Composting processes also inherently reduce metal availability compared to other organic waste stabilisation methods. Therefore, risks to the environment, human health, crop quality and yield, and soil fertility, from heavy metals in source-segregated MSW or greenwaste-compost are minimal. Furthermore, composts produced from mechanically-segregated MSW generally contain fewer metals than sewage sludge used as an agricultural soil improver under controlled conditions. Consequently, the metal content of mechanically-segregated MSW-compost does not represent a barrier to end-use of the product. The application of appropriate preprocessing and refinement technologies is recommended to minimise the contamination of mechanically-segregated MSW-compost as far as practicable. In conclusion, the scientific evidence indicates that conservative, but pragmatic limits on heavy metals in compost may be set to encourage recycling of composted residuals and contaminant reduction measures, which at the same time, also protect the soil and environment from potentially negative impacts caused by long-term accumulation of heavy metals in soil.     

Municipal solid waste management, source-separated waste and stakeholder’s attitude: a Contingent Valuation Study

Recognition of the social costs associated with traditional practices of urban waste management in India led to the formulation of Municipal Waste Management and Handling rules (2000). However, compliance with the proposed collection and disposal involves higher commitment in terms of both time and money on the part of the residents, local bodies as well as the state and central government. In this context, information about the value of the environmental improvements conferred upon the city dwellers would be important from the planner’s perspective. Given the non-market characteristic of waste disposal services, we infer about beneficiaries’ perceived demand for the proposed service by means of Double-Bounded Dichotomous Choice Contingent Valuation Survey conducted in the Bally Municipality in the district of Howrah, West Bengal. We estimate the average WTP by controlling for anchoring bias and use the annualized value of cost to examine the feasibility of the proposed system.     

The effects of FeCl3 on the distribution of the heavy metals Cd, Cu, Cr, and Zn in a simulated multimetal incineration system

Recognizing that waste-derived chlorine can enhance heavy metal emissions by forming volatile metallic chlorides during municipal solid waste (MSW) combustion, and that in Taiwan, FeCl3-containing sewage sludge may either be landfilled or coincinerated with other MSW, this study thus investigated the effects of FeCl3 on the speciation and partitioning of heavy metals in a multimetal incineration system by using a tubular furnace and FeCl3-spiked simulated wastes. The molar ratio of chlorine content to heavy metal content (referred to as the Cl/ M ratio), ranging from 3 to 200, was used as a parameter to evaluate the effects of chlorine on the movement of heavy metals between the incinerator discharges. Results indicate that speciation and partitioning were related to the affinity between the chlorine and the heavy metals and between chlorine and hydrogen in the combustion system. The effectiveness of increasing the Cl/M ratio to the formation potential of metallic chlorides and on the shift of heavy metals from the bottom ash to the fly ash and/or the flue gases was found to have in increasing order as follows: Zn>Cu>Cr, a phenomenon basically reflecting the volatility of the heavy metals and their chlorides formed during combustion.     

鄱阳湖夏候鸟小白鹭对环境样品中重金属的富集研究

通过采集鄱阳湖区北、中、南段小白鹭栖息区域（都昌县多宝乡洞子李村、鄱阳县珠湖乡瓢里山、进贤县前坊镇西湖李家）的环境样品（水样、土壤以及小白鹭食物）与小白鹭羽毛和蛋壳样本，分析其中Pb、Cu、Zn、Cd、V、Cr、Ni和As 8种重金属元素含量，判定鄱阳湖湿地环境中重金属污染状况及生物富集特征。研究表明，环境样品中土壤样品中的重金属含量符合国家Ⅱ类土壤标准，鄱阳湖水样重金属含量在Ⅰ类地表水标准范围之内，仅小白鹭食物（小鱼虾：小河虾、小鲫鱼、小八须鱼等）中的重金属含量高于国家食品标准。小白鹭对环境中重金属污染物的富集表现为：除3个采样点小白鹭羽毛中Cr元素，瓢里山与青岚湖采样点小白鹭蛋壳中Cu元素对其食物的富集系数>1，构成富集外，其他重金属元素均不构成富集，但小白鹭羽毛和蛋壳中的各重金属元素对水样的富集系数为14628～8 00610，富集程度较高。而水体样品中的各重金属在小白鹭食物样品中均存在富集，系数高达51716～14 21937     

Evaluation of the concentration of HCH, DDT, HCB, PCB and PAH in the sediments along the lower stretch of Hugli estuary, West Bengal, northeast India

Detailed analyses of persistent organic pollutants (POPs) such as hexachlorocyclohexane (HCH) isomers (HCHs), dichlorodiphenyltrichloro ethane (DDT) and its metabolites (DDTs), hexachlorobenzene (HCB) and congeners of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the coastal estuarine environment of West Bengal, northeast India allowed the evaluation of the contamination status, distribution and possible pollution sources. HCH, DDT, HCB, PCB and PAH were identified compounds in all the samples, whereas the concentrations of chlorinated pesticides (trans-eptachlorepoxide, dieldrin, endrin, metaoxychlor and mirex) were below the detection limits and were not of great concern. The pesticides did demonstrate markedly different distributions reflecting different agricultural and domestic usage in the region. The range of concentrations of HCH, HCB, DDT and PCBs in the sediments were 0.11-0.40, <0.05-0.98, 0.18-1.93 and 0.18-2.33 ng/g dry wt, respectively. Overall elevated levels of HCB, DDT and PCB were recorded at Babughat, a very closely located site of the metropolitan megacity Calcutta. Fluoranthene (flu) and pyrene (py), the dominant 4-ring PAHs, also showed an abrupt elevated concentrations at Babughat with values of 214 and 144 ng/g dry wt, respectively. Among the isomers and metabolites of HCH, DDT and PCB, alpha-HCH, pp'-DDT and PCB (101), PCB (118), PCB(153) and PCB (138) were found to be dominant. High ratios of metabolites of DDT to SigmaDDTs reveal recent use of DDT in this coastal environment. Fluoranthene, pyrene, 1,2-benzo(a)anthracene and chrysene formed the dominant congeners out of 19 identified PAHs. The sources of contamination are closely related to human activities such as domestic and industrial discharge, automobile exhausts, street runoff, slum sewage, agricultural chemicals and soil erosion due to deforestation as well as atmospheric transport. This study is compared to other coastal and estuarine environments in India and abroad. The baseline data can be used for regular ecological monitoring, considering the industrial and agricultural growth around this important estuarine ecosystem.     

水体悬移质对重金属吸附规律研究 ——以长江宜昌段为例

随着长江三峡工程的建设,上游来水的流速在坝区附近减缓,随江水而下的大量泥沙在此沉淀,将使坝下（长江中下游）水中的悬移质浓度降低、粒径改变 ,从而改变水环境容量。利用长江宜昌江段的周年悬移质样及水样,研究了悬移质对重金属（铜、锌、铅、镉及铬）的吸附特征。结果表明,悬移质对上述金属的吸附可用Freundlich型及Langmuir型等温式较好进行拟合;当较高浓度的金属污染物排入江水后,在吸附及沉淀的共同作用下,浓度明显降低;单位悬移质的吸附量随悬移质浓度降低而上升,但总吸附量降低,从而导致水中的金属污染物的平衡浓度升高。所得结果为预测水环境容量提供了依据。