Heavy metal pollution status in surface sediments of the coastal Bohai Bay

Contamination assessment of mercury, lead, cadmium and arsenic in surface sediments of Chabahar Bay

This study aimed to investigate heavy metals content of mercury (Hg), lead (Pb), cadmium (Cd) and arsenic (As) in surface sediments of Chabahar Bay. Sediment samples were taken from 13 stations and then analyzed. The concentration of Hg, Pb, Cd and As ranged between 0.06 and 0.14ppm, 8 and 23ppm, 0.05 and 0.9ppm and 5 and 22ppm, respectively. Arsenic content was more than ERL at some stations. Statistical analyses indicated critical importance of organic matter and mud in metal dispersion. Also, positive correlation of Al with Pb, Hg and Cd probably implies their terrestrial origination. Average enrichment factor of Hg, Pb, Cd and As were 2.67±0.95, 0.77±0.28, 6.56±9.9, and 7.53±3.44, respectively. Most stations were classified as moderately polluted and non-polluted sites.

Contamination and ecological risk assessment of trace elements in sediments of the rivers of Sundarban mangrove forest, Bangladesh

In this study, total concentrations of 16 trace elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Sb, Hg, Pb, Th and U) in sediments of the rivers of the Sundarban mangrove forest, after the catastrophic oil spill accident in the Sela river of Sundarban, were determined. The overall mean concentrations of V, Cr, Fe and Cd in surface sediments of the Sundarban are remarkably higher than available literature data of those elements. Trace element contamination assessment, using different environmental contamination indices, reveals that As, Sb, Th and U are low to moderately contaminated while Cd is moderately to severely contaminated in the sediments of this area. The multivariate statistical analyses were applied to reveal the origin and behavior of the elements during their transport in the mangrove ecosystem. High Cr, Ni, Cu and As concentrations suggest the risk of potentially adverse biological effects in the ecosystem.

Indices of soil contamination by heavy metals - methodology of calculation for pollution assessment (minireview)

This article provides the assessment of heavy metal soil pollution with using the calculation of various pollution indices and contains also summarization of the sources of heavy metal soil pollution. Twenty described indices of the assessment of soil pollution consist of two groups: single indices and total complex indices of pollution or contamination with relevant classes of pollution. This minireview provides also the classification of pollution indices in terms of the complex assessment of soil quality. In addition, based on the comparison of metal concentrations in soil-selected sites of the world and used indices of pollution or contamination in soils, the concentration of heavy metal in contaminated soils varied widely, and pollution indices confirmed the significant contribution of soil pollution from anthropogenic activities mainly in urban and industrial areas.

Distributions and sources of heavy metals in sediments of the Bohai Sea, China: a review

This paper summarizes the recent research results from studies concerning heavy metals in the Bohai Sea in recent decades. The temporal and spatial variations and potential sources of the heavy metals in the surface sediments were analyzed. Based on these obtained data, the average concentrations in surface sediments collected in recent years (summarized 3171 samples) were 0.31, 87.0, 25.7, 25.8, 0.11, 16.9, 52.2, and 27.7 μg/g for Cd, Zn, Cu, Pb, Hg, As, Cr, and Ni, respectively. In the samples collected in the 1980s, the concentrations were 22.6, 21.3, 69.13, 0.26, and 57.5 μg/g (summarized 218 samples) for Cu, Pb, Zn, Cd, and Cr. The concentrations of Cu, Pb, Zn, and Cd increased slightly. Generally, higher concentrations were measured in the Bohai Bay and central Bohai Sea. The distribution patterns of heavy metals were significantly different between samples collected after the year of 2000 and those in the 1980s. In the 1980s and recent years, higher concentrations of Zn, Cd, and Pb were measured in the samples collected from Bohai Bay and Liaodong Bay, respectively. This indicated that the sources of heavy metals in Bohai Sea were changed significantly during the past decades.

Design of Research on Performance of a New Iridium Coordination Compound for the Detection of Hg2

Heavy metal pollution has become one of the most significant pollution problems encountered by our country in terms of environment protection. In addition to the significant effects of heavy metals on the human body and other organisms through water, food chain enrichment and other routes, heavy metals involved in daily necessities beyond the level limit could also affect people’s lives, so the detection of heavy metals is extremely important. Ir (III) coordination compound, considered to be one of the best phosphorescent sensing materials, is characterized by high luminous efficiency, easy modification of the ligand and so on, and it has potential applications in the field of heavy metal detection. This project aims to product a new Ir (III) functional coordination compound by designing a new auxiliary ligand and a main ligand with a sulfur identification unit, in order to systematically investigate the application of iridium coordination compound in the detection of the heavy metal Hg²⁺. With the introduction of the sulfur identification unit, selective sensing of Hg²⁺ could be achieved. Additionally, a new auxiliary ligand is also introduced to produce a functional iridium coordination compound with high quantum efficiency, and to diversify the application of iridium coordination compound in this field.

Identifying sources of metal exposure in organic and conventional dairy farming

In humans the main route of exposure to toxic metals is through the diet, and there is therefore a clear need for this source of contamination to be minimized, particularly in food of animal origin. For this purpose, the various sources of toxic metals in livestock farming (which vary depending on the production system) must be taken into account. The objectives of the present study were to establish the profile of metal exposure in dairy cattle in Spain and to determine, by chemometric (multivariate statistical) analysis, any differences between organic and conventional systems. Blood samples from 522 cows (341 from organic farms and 181 from conventional farms) were analysed by inductively coupled plasma mass spectrometry to determine the concentrations of 14 elements: As, Cd, Co, Cr, Cu, Fe, Hg, I, Mn, Mo, Ni, Pb, Se and Zn. In conventional systems the generally high and balanced trace element concentrations in the mineral-supplemented concentrate feed strongly determined the metal status of the cattle. However, in organic systems, soil ingestion was an important contributing factor. Our results demonstrate that general information about the effects of mineral supplementation in conventional farming cannot be directly extrapolated to organic farming and special attention should be given to the contribution of ingestion of soil during grazing and/or ingestion of soil contaminated forage.

Quantification of the limitation of Langmuir model used in adsorption research on sediments via site energy heterogeneity

The Langmuir model has been extensively introduced into the field of environmental adsorption, while some studies showed that it was difficult for the model to describe the adsorption of sediments. The purpose of this paper is to recognize the applicability of the Langmuir model used in the adsorption of contaminants onto sediments quantitatively through the relationship between the error of Langmuir (δ) and site energy heterogeneity (σ). The formula for calculating δ in sediments was developed based on the heterogeneity parameters (m, n). The data was extracted from papers discussing about the adsorption of pollutants on natural sediments. It was further used to investigate the error of Langmuir and the effect on the error from the site energy heterogeneity. The results indicate that the Langmuir model can be applied in sediments when each one of the conditions below is satisfied, (1) m and n lie in the area which signifies that the relative error is less than 10%, (2) the site energy heterogeneity of sediment is under 5.668. These findings are vital for the proper choice of models fitting the adsorption process of sediments.

Heavy metal pollution in sediments of the largest reservoir (Three Gorges Reservoir) in China: a review

The Three Gorges Dam in China is the world's largest dam. Upon its completion in 2003, the Three Gorges Reservoir (TGR) became the largest reservoir in China and plays an important role in economic development and national drinking water safety. However, as a sink and source of heavy metals, there is a lack of continuous and comparative data on heavy metal pollution in sediments. This study reviewed all available literatures published on heavy metals in TGR sediments and further provided a comprehensive assessment of the pollution tendency of these heavy metals. The results showed that heavy metal concentrations in TGR sediments varied spatially and temporally. Temporal variations indicated that Hg in tributaries, as well as As, Cd, Cr, Cu, Ni, Pb, and Zn in the mainstream, exhibited a higher probability to exceed background values after the impoundment of TGR. Pollution assessments by contamination factor, geoaccumulation index, and potential ecological risk were similar. High Cd and Hg concentrations in both the mainstream and tributaries are a cause for much concern. However, sediment quality guidelines produced different results, as most previous studies adopted different sampling and measurement strategies. The data inconsistencies and lack of continuity regarding the reservoir confirm the need for a continuous monitoring network and the development of quality criteria relevant to the sediments of the TGR in the future.

Comprehensive analysis of mercury pollution in the surface riverine sediments in the Haihe Basin, China

The Haihe Basin extends over 318,000 km² or 3.3% of the total area of China, has a population of over 120 million, and is one of China's most polluted river basins. We investigated the pollution and risks from mercury (Hg) in surface riverine sediments of this basin and found that total Hg concentrations in surface sediments ranged from 0.001 to 1.05 mg/kg and averaged 0.054 mg/kg. Using the modified European Community Bureau of Reference standard method, we found that the exchangeable/acid-soluble, reducible, oxidizable, and residual fractions of Hg accounted for 9.86, 6.54, 11.0, and 72.6% of total Hg, respectively. The riverine sediments in the Da Qing He watershed had the highest anthropogenic enrichment of Hg (enrichment factor >1.5). There was a high potential ecological risk from Hg in the riverine sediments in the upper reaches of the Bei San He and Da Qing He watersheds, the middle reaches of the Luan He and Hei Long Gang watersheds, and the lower reaches of the Zi Ya He watershed. Comparison with risk assessment code showed that the riverine sediments in the Da Qing He, Luan He, and Tu-Hai Ma-Xia He watersheds represented a medium risk, with 16.6, 11.9, and 11.8% of Hg in the exchangeable/acid-soluble fraction, respectively.

Adsorption mechanism of chromium(III) using biosorbents of Jatropha curcas L

The removal of Cr³⁺ from water solutions by biosorbents from the rind, endosperm, and endosperm + episperm of the Jatropha curcas was evaluated. Adsorption tests were performed in batch systems for evaluating the influence of the solution's pH, adsorbent mass, contact time, initial Cr³⁺ concentrations, and solution temperature during the adsorption process. Kinetic, adsorption isotherm, and thermodynamic studies were performed to investigate the mechanisms that control adsorption. Ideal conditions for the adsorption process included pH of the solution of 5.5 and 8 g L^-1 adsorbent mass, within 60 min time contact between adsorbent and adsorbate. Maximum adsorption capacities by Langmuir model for rind, endosperm, and endosperm + episperm of the J. curcas were, respectively, 22.11, 18.20, and 22.88 mg g^-1, with the occurrence of chemosorption in mono and multilayers. Results show that the biosorbents obtained from J. curcas have a high potential to recuperate Cr³⁺ from contaminated water sources.

Level, source identification, and risk analysis of heavy metal in surface sediments from river-lake ecosystems in the Poyang Lake, China

The concentrations, sources, and risks of heavy metals (Fe, Al, Mn, Cr, Co, Ni, Cu, Zn, As, Cd, W, Pb, and Tl) in sediments in five river-lake ecosystems in the Poyang Lake region were studied. The concentrations of the heavy metals varied spatially, with most of the highest concentrations in the Raohe river-lake ecosystem (RH). All heavy metals except As, Cd, W, and Tl were enriched in sediments possessing high total organic carbon contents or in finer sediments. Based on enrichment factors and statistical methods, it was found that Cd in sediments in the Xiushui (XS), Ganjiang (GJ), Xinjiang (XJ) river-lake ecosystems, and RH; Mn in the XS, GJ, and RH; and W in the XS and GJ were greatly affected by anthropogenic inputs. Moreover, the origins of Cu, Zn, and As require more attention due to the high concentrations found. The high enrichment factor of Cd in the sediments indicated that this metal might cause significant pollution in the environment. The results of the modified potential ecological risk index revealed that the XS, GJ, RH, and XJ were at considerable ecological risk, while the sediments in the Fuhe river-lake ecosystem (FH) were at moderate ecological risk, with Cd contributing the highest proportion of risk. The hazard score fundamentally validated the modified potential ecological risk analysis and revealed a mean toxicity of 57.80% to the benthic organisms in the RH.

Distribution of heavy metals around the Barakah nuclear power plant in the United Arab Emirates

Inductively coupled plasma emission spectroscopy was used to measure the concentrations of heavy metals in 58 samples collected from the Barakah nuclear power plant (BNPP) area, UAE. The grain size distribution was symmetric, but the samples ranged from fine to coarse sand. The inverse relationship between grain size and heavy metal contaminations was validated. The pre-operational average heavy metal contaminations around the BNPP were 0.03, 0.40, 1.2, 2.05, 1.66, 1.6, 5.9, 7.3, 7, 8.8, 60, and 2521 ppm for Cd, Mo, Co, Cu, Pb, As, Zn, Ni, V, Cr, Mn, and Fe, respectively. The spatial distribution was more compact in the south compared to the north, with less severe contaminations in the east and west. The negative geoaccumulation indices suggest an uncontaminated area, and the BNPP has minor enrichments. All concentrations were significantly below the safe limits set by the Dutch guidelines. The levels of heavy metals reported in the UAE were lower than levels reported in countries around the world.

Trace metal pollution assessment in the surface sediments of nearshore area, off Calicut, southwest coast of India

Metal concentrations (Al, Cr, Ni, Cu, Zn, and Pb), grain size, and total organic carbon content in 29 surface sediment samples from the nearshore area off Calicut were analyzed to determine their distribution and pollution status. Surface sediments were dominantly silts with low percentage of clay and sand at nearshore and offshore areas. The mean metal concentrations were in the following order: Cr>Ni>Zn>Pb>Cu. The enrichment factor and geo-accumulation index of metals suggest that the surface sediments were not polluted by Zn and moderately polluted by Cu and Ni. By contrast, Cr and Pb showed significant enrichment levels. Results from a multivariate statistical analysis suggested that the spatial enrichment of these heavy metals was related to sediment type. Thus, the sediment distribution and their metal enrichment were mainly controlled by local hydrodynamic conditions that caused the winnowing of fine-grained sediments.

Impacts of metal contamination and eutrophication on dinoflagellate cyst assemblages along the Guangdong coast of southern China

Fifty-one surface sediment samples were collected from eleven sea areas along the Guangdong coast in southern China. Biogenic elements, metals and dinoflagellate cysts were analyzed. Twenty-one cyst taxa in 12 genera were identified. The cyst concentrations ranged between 14 and 250 cysts/g, with an average of 69 cysts/g. The low cyst production was caused by coarse sediments, high sedimentation rates, and high anthropogenic disturbances. Biogenic elements were comparable with those reported. However, the metal concentrations were far lower than the sediment quality guidelines. Both biogenic elements and metals were higher in the Mid Coast and lower in the Western Coast. Eutrophication slightly enhanced the productivity of autotrophic dinocysts, and cysts of Scrippsiella indicated eutrophication. Cd had inhibitory effects on cyst production. Alexandrium and Diplopsalis cysts were sensitive to metal contamination; however, Gyrodinium, Pheopolykrikos, and Lingulodinium cysts had high resistance to metal contamination.

Redox chemistry of nickel in soils and sediments: A review

Knowledge on the redox geochemistry of Ni is behind in comparison to other heavy metals. Hence, this article reviews the direct and indirect impact of redox potential (E_H) on mobilization and release dynamics of Ni in soils and sediments across the world. Nickel can show a different behavior in response to E_H. Mobilization of Ni increased at low E_H in various soils; however, oxic conditions can lead to an increased mobilization of Ni in other soils. Those differences occur because the mobilization of Ni is often indirectly affected by E_H, e.g. through E_H-dependent pH changes, co-precipitation with iron (Fe) and manganese (Mn) (hydr)oxides, complexation with soil organic carbon, similar position of Ni and magnesium (Mg) in the soil solid phase, and/or precipitation as sulphides. Dissolved concentrations of Ni showed a similar pattern like Fe and increased at low E_H in many soils, which might be explained by the reductive dissolution of Fe (hydr)oxides and the release of the co-precipitated/sorbed Ni. Few other studies indicated that Ni might be associated with Mn oxides rather than with Fe oxides. Additionally, the formation of soluble complexes with dissolved organic carbon may contribute to a mobilization of Ni at low E_H. Nickel and Mg are similarly affected by redox changes especially in serpentine soils. This review summarizes the recent knowledge about the redox chemistry of Ni and contributes thus to a better understanding of the potential mobilization, hazard, and eco-toxicity of Ni in frequently flooded soils and sediments as agricultural ecosystems.

Heavy metal distribution and contamination status in the sedimentary environment of Cochin estuary

Heavy metals (Fe, Mn, Cr, Zn, Ni, Pb, Cu, Co and Cd) in the surface sediments of Cochin estuary, Southwest coast of India were analyzed to understand the spatio-temporal variation and contamination status via six sampling campaigns. Pollution indices like enrichment factor, geoaccumulation index and pollution load index inferred that the sediments of the northern arm of the estuary exhibited severe trace metal accumulation. Numerical sediment quality guidelines were applied to assess adverse biological effects of the trace metals, suggesting that occasional biological effect may occur due to Cr, Cu, Ni and Pb. Correlations between metals, organic carbon, silt and clay suggested that both fine grained sediment and organic matter were important carriers for these metals. Multivariate statistics indicated that the sources of Cu and Ni resulted primarily from natural weathering processes, whereas enriched levels of Cd, Cr, Zn and Pb were mainly attributed to anthropogenic activities.

Toxic metal pollution in the Yellow Sea and Bohai Sea, China: distribution, controlling factors and potential risk

The Bohai Sea (BS) and Yellow Sea (YS), which are adjacent to the most urbanized and industrialized areas in China, are facing a variety of environmental problems. Two cruises were conducted to investigate the pollution status of toxic metals in BS and YS sediments. They generally presented a decreasing trend from near shore to offshore. In addition, two high concentration areas were observed in the central south YS and north of the Shandong Peninsula. The results of multiple regression analyses suggest that Hg is mainly controlled by anthropogenic loading, whereas for Cr, Cu, Ni, Pb and Zn, sediment properties, especially the Fe oxides content, play a more important role. For As and Cd, the contribution of anthropogenic loading and sediment properties are comparable. The risk assessment indicates that Hg, As, Cd and Ni should be listed as the primary contaminant metals in the BS and YS.

Modeling seasonal and spatial contamination of surface waters and upper sediments with trace metal elements across industrialized urban areas of the Seybouse watershed in North Africa

Industrialization and urbanization are the main sources of pollutions worldwide and particularly in developing countries. This study aims the determination of anthropogenic inputs with trace metals in aquatic ecosystems at the Plain of Annaba (NE Algeria), which is known as one of the largest industrial areas in Africa. Samples of surface waters and upper sediments were conducted in six stations: four in Meboudja wadi and two in Seybouse wadi. Contents of iron, copper, chromium, nickel, zinc, and manganese were measured by atomic absorption spectrophotometry, whereas Cd and Pb were determined using electrothermal atomic absorption spectrometry. Measurements of Hg were carried out using atomic fluorescence. Spatiotemporal variations of metal concentrations were tested using generalized linear models (GLM), whereas the influence of water pollution on sediment contamination was tested with generalized additive models (GAMs). Metal contents measured in surface water and sediments varied differently from upstream to downstream of the study wadis and between seasons. The results showed that the surface water was polluted with high levels of iron, nickel, chromium, lead, and cadmium. Values of the contamination index revealed that the surface sediments were contaminated by iron, chromium, lead, and cadmium. The GAMs indicated that water-phase metal concentrations had no significant effects on trace metal concentrations in the sediment. This suggests that seasonal metal concentrations in water phase, which are measured during the study period (2012) and are time-dependent, contribute increasingly and gradually over time-not immediately-to the accumulation of metals into the sediments. Therefore, the long-term accumulation of metals in the sediments resulted from the continuous discharges of metals in the water phase. The anthropogenic impacts are marked by high contaminations of Meboudja wadi particularly in downstream areas of the steel factory and the nearby industrial areas. The direct industrial discharges into the water and atmosphere (iron, lead, cadmium) as well as urban disposals and agricultural activities are at the origin of these contaminations.

Pollution characteristics and potential ecological risk assessment of metals in the sediments of Xiaoqing River, Jinan

The spatial-temporal changing characteristics and potential ecological risk combined with local policies and industrial status were analyzed. The metal contamination was studied by sediment quality guidelines (SQGs), potential ecological risk index (PERI), and geoaccumulation index (I _geo) of metals (Hg, Cr, Cd, As, Pb, and Cu) in the sediments of Xiaoqing River in Jinan from 1996 to 2014. Results showed that the concentrations of metals were in fluctuation and had a decreasing trend in the past 19 years, which was influenced by industry and policy. The concentrations of metals from upstream to downstream presented a change from low to high and then a gradual decrease which were mainly related to anthropogenic activities. The assessment suggested that Hg presented the highest levels of I _geo and was the largest contributor to RI, while Cd was the second contributor. This finding indicated that Hg and Cd had a strong effect on potential ecological risk. Damatou had the largest pollution level and potential ecological risk, whereas Mulizhuang was the least polluted area. SQGs indicated that Cd was below the TEC while it was the second contributor to potential ecological risk. Indeed, the pollution control of Xiaoqing River had a certain effect, but it needs long-term effective management measures and a strengthened source control. The suggestions of targeted management have been proposed in the paper.

Pollution, toxicity, and ecological risk of heavy metals in surface river sediments of a large basin undergoing rapid economic development

A comprehensive and detailed investigation of heavy metal pollution, toxicity, and ecological risk assessment was conducted for the surface river sediments of the Haihe Basin in China based on 220 sampling sites selected in 2013. The average concentrations of Cr, Cu, Ni, Pb, and Zn in the sediments were 129 mg/kg, 63.4 mg/kg, 36.6 mg/kg, 50.0 mg/kg, and 202 mg/kg, respectively. As indicated by the geoaccumulation and pollution load indices, most surface river sediments of the Haihe Basin were contaminated with the investigated metals, especially in the junction region of the Zi Ya He and Hei Long Gang watersheds. The 5 heavy metals in the sediments all had anthropogenic sources, and the enrichment degrees followed the order Cu > Pb > Zn > Cr > Ni, with mean enrichment factors of 3.27, 2.77, 2.58, 1.81, and 1.44, respectively. According to the mean index of comprehensive potential ecological risk (38.9), the studied sediments of the Haihe Basin showed low potential ecological risk, but the sediments were potentially biologically toxic based on the mean probable effect concentration quotient (0.547), which may be the result of speciation of the 5 metals in the sediments. The results indicate that heavy metal pollution should be considered during the development of ecological restoration strategies in the Haihe Basin. Environ Toxicol Chem 2017;36:1149-1155. © 2016 SETAC.

Heavy metal concentrations and speciation in riverine sediments and the risks posed in three urban belts in the Haihe Basin

Heavy metal (Cr, Cu, Ni, Pb, and Zn) pollution and the risks posed by the heavy metals in riverine sediments in a mountainous urban-belt area (MB), a mountain-plain urban-belt area (MPB), and a plain urban-belt area (PB) in the Haihe Basin, China, were assessed. The enrichment factors indicated that the sediments were more polluted with Cu and Zn than with the other metals, especially in the MPB. The sediments in the MPB were strongly affected by Cu and Zn inputs from anthropogenic sources. The risk assessment codes and individual contamination factors showed that Zn was mobile and posed ecological risks, the exchangeable fractions being 21.1%, 21.2%, and 19.2% of the total Zn concentrations in the samples from the MB, MPB, and PB, respectively. Cr, Cu, and Zn in the sediments from the MPB were potentially highly bioavailable because the non-residual fractions were 56.2%, 54.9%, and 56.5%, respectively, of the total concentrations. The potential risks posed by the heavy metals (determined from the chemical fractions of the heavy metals) in the different areas generally decreased in the order MPB > MB > PB. Pictorial representation of cluster analysis results showed that urbanization development level could cause Cr and Zn pollution in the urban riverine sediments to become more severe.

Trace element concentrations in reef associated sediments of Koswari Island, Gulf of Mannar biosphere reserve, southeast coast of India

Extensive field work was conducted in order to assess the sediment pollution level and potential ecological risk on coral reef ecosystem. Thirty three surface sample was collected using grid sampling technique. The calcium carbonate and organic matter were primarily controlled by the distribution of coral rubbles and seagrass meadows. The concentration of trace elements is higher than the crustal average in few locations and the same result was derived from index calculations. However, the significant concentration of lead was observed throughout the study area. The elevated level of lead is probably due to coal incinerating power plants, and confluence of urban runoff from the nearby coastal areas. Based on the sediment pollution index, the majority of the sediments belongs to highly polluted to dangerously polluted category. The ecological risk indicates that the sediments are under low risk to moderate risk category and this result was proved by correlation analysis.

Metal concentration in the tourist beaches of South Durban: An industrial hub of South Africa

South Durban basin of South Africa has witnessed tremendous urban, industrial expansion and mass tourism impacts exerting significant pressure over marine environments. 43 sediment samples from 7 different beaches (Bluff beach; Ansteys beach; Brighton beach; Cutting beach; Isipingo beach; Tiger Rocks beach; Amanzimtoti beach) were analyzed for acid leachable metals (ALMs) Fe, Mg, Mn, Cr, Cu, Mo, Ni, Co, Pb, Cd, Zn and Hg. The metal concentrations found in all the beaches were higher than the background reference values (avg. in μgg^-1) for Cr (223-352), Cu (27.67-42.10), Mo (3.11-4.70), Ni (93-118), Co (45.52-52.44), Zn (31.26-57.01) and Hg (1.13-2.36) suggesting the influence of industrial effluents and harbor activities in this region. Calculated geochemical indexes revealed that extreme contamination of Cr and Hg in all the beach sediments and high Cr and Ni levels poses adverse biological effects.

Toxic elements in the stream sediments of an urbanized basin, Eastern China: urbanization greatly elevates their adverse biological effects

The concentration of toxic elements (Hg, Cd, Cr, Cu, Pb, Zn, Ni and As) was measured in the sediments of the Qinhuai River in Eastern China along a rural to urban gradient. Multiple approaches were undertaken to evaluate the degree of enrichment and adverse biological effects of these elements. The results showed that the concentration of Hg, Cd, Zn, Cu and Pb increased exponentially from the agricultural headwater to the urbanized downstream, which reflects a severe anthropogenic influence. In addition, area-specific references, such as the local soil background (LSB) and upper continental crust (UCC) derived from the Yangtze craton, were more applicable for evaluating the enrichment of toxic elements in the Qinhuai River than was global UCC. In addition, Cd and Hg had the highest enrichment factor values (EF, with averages of 9.18 and 7.14, respectively); Zn, Pb and Cu had moderate EFs (averages from 1.52 to 2.40), while the average EFs of Ni, Cr and As were approximately equal to 1. Based on consensus-based sediment quality guidelines (SQGs), the contamination characteristics of all of the samples studied were associated with low to moderate priority of adverse biological effects (ABEs) in the rural upstream area, while it was associated with a high to moderate priority of ABEs in the urban sections of the Qinhuai River. Our results suggest that the adverse biological effects of elevated levels of toxic elements were strongly related to the degree of anthropogenic pollution.

Occurrence, speciation and transportation of heavy metals in 9 coastal rivers from watershed of Laizhou Bay, China

The occurrence, speciation and transport of heavy metals in 9 coastal rivers from watershed of Laizhou Bay were investigated. The largest dissolved concentrations of Cd, Cu and Zn in water were 6.26, 2755.00, 2076.00 μg/L, respectively, much higher than several drinking water guidelines. The greatest concentrations of Cu, Zn, Cr, Ni, Pb and Cd in sediments were 1462, 1602, 196, 67.2, 63.5 and 1.41 mg/kg, dw, respectively. Correlation and principal component analysis was also conducted to determine the extent between the concentrations of metals in water and sediment, as well as relevant parameters. Throughout the river stretch, most of Cr Zn, Cr, Ni and Pb bound to residual fraction, however, Cd was preferentially bound to the exchangeable phase. Among the 9 rivers, Yellow river account for 72.5%, 67.5%, 55.4%, 59.4%, 79.4% and 85.5% for Cr, Ni, Cu, Zn. Cd and Pb, respectively. The combined potential ecological risk indexes were used to evaluate potential risks. The majority of sampling sites from watershed of Laizhou Bay have moderate ecological risk from metals. The government should pay more attention to the ecological risk of river ecosystem which flow to Laizhou Bay.

Preliminary assessment of metal distribution in the surface sediments along the coastline of the southern Caspian Sea

In the present study, the concentrations of metals in sediments along the coastline of the southern Caspian Sea were investigated. For this purpose, sediments were collected from 13 sampling sites in the southern Caspian Sea. The samples were then analyzed by inductively coupled plasma-optical emission spectrometry. Results showed that compound oxides may be responsible for the distribution of metals in the sediments of the southern Caspian Sea. According to mean effects range-median quotient, 61.5% of the studied sites from the southern Caspian Sea had a 21% probability of metal toxicity. On the basis of the enrichment factor, all metals were in the category of deficiency to minimal enrichment. Pollution load index showed that the other sampling sites had no pollution.

Environmental changes in Jiaozhou Bay of northern China during the past 90years using metals and biogenic elements in sediments

Metals and biogenic elements were analyzed from surface sediments and a 100cm core collected from Jiaozhou Bay in July 2009, to determine how the environment has changed over the past 90years due to increasing anthropogenic influences in this region. High concentrations of biogenic silica (BSi) represented the dominance of diatoms in the bay. Most metals were lower than the marine sediment quality guidelines; however, Hg, Zn, and Mn were at polluted levels. The vertical profiles of biogenic elements and metals in the sediment core suggest that the most significant environmental changes occurred since the 1990s, and three stages could be defined: (1) before 1950, characterized by low concentrations of biogenic elements and metals; (2) between 1950 and 1990, displaying an obvious increase of Hg and a slow increase of biogenic elements; (3) after 1990, reflected by a significant increase of total organic carbon (TOC), total nitrogen (TN), total phosphate (TP), and most metals, but a decrease of BSi. Correlation and principal component analyses indicated that most metals originated from lithogenic sources, industrial and domestic discharges as well as maricultural activities.

Heavy metals and nutrients (carbon, nitrogen, and phosphorus) in sediments: relationships to land uses, environmental risks, and management

Management of sediments in polluted rivers requires an inventory of sediment quantities as well as their nutrient and metal contents and the chemical forms of pollutants. We investigated the influence of three major land uses (i.e., orange plantation-OP, OP + residential + industrial-OPRI, and residential + industrial-RI) on the quality of surface sediments (0-20 cm below water/sediment interface) at the Sanyang Wetland (China). The total contents of metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) and nutrients (C, N, and P) as well as metal speciation in sediments were examined. GIS technology was used to estimate the volume of sediments needed to calculate the amounts of stored nutrients and metals in sediments. The surface sediments in the 3.2-km² study area contain more than 2800 Mg C, 200 Mg N, and 100 Mg P. OPRI and RI land uses contribute more total C, N, P, Zn, and Cd to sediments than OP land use. High contents of C, N, and P may provide options to recycle the sediments as fertilizer but must be used with caution due to high levels of metals. Total Cd in sediments is at an order of magnitude (up to 59 mg kg-1) higher than the Level III criterion in the Chinese Environmental Quality Standards for Soil. Sediments in all land uses have very high risks due to >50% exchangeable + carbonate-bound Zn, Ni, and Cd. It is suggested that toxicity tests be conducted to better assess the environmental risks associated with any potential use of sediments.

Source, distribution and ecotoxicological assessment of multielements in superficial sediments of a tropical turbid estuarine environment: A multivariate approach

The work examined the distribution, possible sources and ecotoxicological assessment of 51 trace elements covering 13 sampling stations in surface sediments of coastal regions of Sundarban mangrove wetland and adjacent Hugli river estuary. The element concentrations exhibited an increasing trend towards downstream of the estuary (except lanthanides) with maximum enrichment for 22 elements at Gangadharpur (Sundarban region). According to Sediment Quality Guidelines (SQGs), the concentrations of Cu, As, Cr and Cd exceeded the Effects-Range-Low values, while Ni at certain stations exceeded the Effects-Range-Medium suggesting adverse effects on the sediment-dwelling organisms. The geoaccumulation index revealed that the stations were unpolluted to moderately polluted. Risk Index (357.61) and Enrichment factor (11.42) depicted that Nimtala station (upstream) was at high ecological risk zone. The result of PCA endorsed that organic carbon and clay fraction play crucial role in accumulating the elements in sediments. This pilot study contributes to a better understanding of the geochemistry of this complex deltaic ecosystem.

Heavy metal contamination status and source apportionment in sediments of Songhua River Harbin region, Northeast China

The Songhua River represents one of the seven major river systems in China. It flows through Harbin city with 66 km long, locating in the northern China with a longer winter time. This paper aimed to study concentration distributions, stability, risk assessment, and source apportionment of heavy metals including chromium (Cr), cadmium (Cd), lead (Pb), mercury (Hg), arsenic (As), copper (Cu), zinc (Zn), and nickel (Ni) in 11 selected sections of the Songhua River Harbin region. Results showed that Cr, Cd, Pb, Hg, and As exceeded their respective geochemical background values in sediments of most monitoring sections. Compared with other important rivers and lakes in China, Cr, Hg, Cd, and As pollutions in surface sediments were above medium level. Further analysis of chemical speciation indicated that Cr and As in surface sediments were relatively stable while Pb and Cd were easily bioavailable. Correlation analysis revealed sources of these metals except As might be identical. Pollution levels and ecological risks of heavy metals in surface sediments presented higher in the mainstream region (45° 47.0' N ~ 45° 53.3' N, 126° 37.0' E ~ 126° 42.1' E). Source apportionment found Hejiagou and Ashi River were the main contributors to metal pollution of this region. Thus, anthropogenic activities along the Hejiagou and Ashi River should be restricted in order to protect the Songhua River Harbin region from metal contamination.

Sediment pollution characteristics and in situ control in a deep drinking water reservoir

Sediment pollution characteristics, in situ sediment release potential, and in situ inhibition of sediment release were investigated in a drinking water reservoir. Results showed that organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) in sediments increased from the reservoir mouth to the main reservoir. Fraction analysis indicated that nitrogen in ion exchangeable form and NaOH-extractable P (Fe/Al-P) accounted for 43% and 26% of TN and TP in sediments of the main reservoir. The Risk Assessment Code for metal elements showed that Fe and Mn posed high to very high risk. The results of the in situ reactor experiment in the main reservoir showed the same trends as those observed in the natural state of the reservoir in 2011 and 2012; the maximum concentrations of total OC, TN, TP, Fe, and Mn reached 4.42mg/L, 3.33mg/L, 0.22mg/L, 2.56mg/L, and 0.61mg/L, respectively. An in situ sediment release inhibition technology, the water-lifting aerator, was utilized in the reservoir. The results of operating the water-lifting aerator indicated that sediment release was successfully inhibited and that OC, TN, TP, Fe, and Mn in surface sediment could be reduced by 13.25%, 15.23%, 14.10%, 5.32%, and 3.94%, respectively.

Distribution of Heavy Metals in Surface Sediments of the Bay of Bengal Coast

The concentrations of major (Si, Al, Ca, Fe, and K) and minor (Cd, Mn, Ni, Pb, U, Zn, Co, Cr, As, Cu, Rb, Sr, and Zr,) elements in the surficial sediments were studied in an attempt to establish their concentration in the Bengal coast. It was revealed that the majority of the trace elements have been introduced into the Bengal marine from the riverine inflows that are also affected by the impact of industrial, ship breaking yard, gas production plant, and urban wastes. The concentration of heavy metals was measured using Atomic Absorption Spectroscopy and Energy Dispersive X-ray fluorescence instruments. The highest concentrations for several trace elements were thus recorded which generally decrease with distance from the coast. It was observed that the heavy metal concentrations in the sediments generally met the criteria of international marine sediment quality. However, both the contamination factor and pollution load index values suggested the elevation of some metals' concentrations in the region. Constant monitoring of the Bengal coast water quality needs to be recorded with a view to minimizing the risk of health of the population and the detrimental impacts on the aquatic ecosystem.

Geochemical source, deposition, and environmental risk assessment of cadmium in surface and core sediments from the Bohai Sea, China

Geochemical sources, spatio-temporal distribution, and associated environmental risk of Cd in the Bohai Sea were investigated using data from 405 surface sediment samples and two sediment cores. Local point Cd sources, TOC content, and currents are the main controlling factors of Cd distribution. The contribution of Cd from river discharge surpasses that from atmospheric deposition. Sediment-quality guidelines, enrichment factors, and chemical fraction analysis were used to assess metal toxicity in the collected sediments. Results show that Bohai Sea sediments have a moderate Cd enrichment level. This enrichment poses a high risk due to the relatively high mobility and bioavailability of Cd despite measured levels below sediment-quality guidelines at most stations. Vertical profiles of Cd concentrations, Al-normalized enrichment factors, and excess burial fluxes combined with ²¹⁰Pb dating reveal the history of Cd pollution in the Bohai Sea over the last century. Data show Cd unvaried before the 1800s, a slight increase from the 1800s to the late 1950s, a decrease from the late 1960s to the 1970s, and an increase from the 1980s to 2001, including a relatively high value in 1998. Historic variation in Cd is closely associated with both natural and anthropogenic activities.

An investigation of the effects of elevated phosphorus in water on the release of heavy metals in sediments at a high resolution

Excessive phosphorus (P) input plays an important role on the release of heavy metals in sediments under the eutrophic environment. In this study, a microcosm experiment with 40-day incubation using homogenized sediments was performed to investigate this aspect at a millimeter resolution. Diffusive gradient in thin films (DGT) and dialysis (Peeper) techniques were employed to simultaneously measure labile and dissolved P, Pb, Cd, Zn, Co and Ni in sediments at a millimeter scale, respectively. The results showed that an increase of water P from 0.02mgL^-1 to 0.20 and 2.4mgL^-1 generally led to intensified decrease of DGT-labile metals from the 10th to 20th days after the onset of incubation. The decrease in dissolved metals in pore water also appeared on the 20th day. The degree of decrease in the five metals was in the order of Pb>Cd>Zn>Co>Ni, which has a negative correlation with the solubility constants (K_sp) of each metal-P precipitate. This indicated that the negative effect was caused by the precipitation of metal P. On the 40th day during incubation, the concentrations of DGT-labile metals had different increasing pattern compared to those on the 20th day. The extent of metal recovery was positively correlated with the change of desorption rate constant (k_-1) and negatively correlated with the change in the characteristic time (T_c) to reach equilibrium from DGT perturbation derived from DGT-induced fluxes in sediments (DIFS) modeling. This suggested that the recovery of metal lability from elevated water P was a result of the increased releases of metals from sediment solids.

Trace element concentrations, risks and their correlation with metallothionein genes polymorphism: A case study of narrow-ridged finless porpoises (Neophocaena asiaeorientalis) in the East China Sea

The concentration of trace elements (TEs) and their risk to narrow-ridged finless porpoises (Neophocaena asiaeorientalis) are still unclear. The present study determined the concentration of typical TEs in liver, kidney, and muscle tissues from porpoises in the East China Sea, assessed potential health risk of TEs to porpoises, and explored the relationship between TE concentration and metallothionein genes (MTs) polymorphism. It was found that Zn, Cu, Mn, Cd and Hg were highly accumulated in liver, and Cd was highly accumulated in kidney. The concentrations of Cr, As, Pb and Ni were very low in all three tissues. TE concentrations showed significant positive correlation with body length, and sexual variation. The levels of most TEs were higher in tissues of porpoises in Ningbo and Nantong than in Pingtan, which is likely related to the local environment pollution level. The risk assessment showed that porpoises from Nantong and Ningbo could face health risks due to Hg, As, Cd, Pb, and Cr exposure. Moreover, two polymorphic sites on the MT4 gene were found to be significantly associated with increased levels of Hg, Cd, Zn and Mn. Whether these two polymorphic sites are involved in expression of MTs, or other functional processes, needs further research.

Contamination, Fractionation and Biological Risk Related to Metals in Surface Sediments from the Largest Deep Freshwater Lake in China

The toxicity and mobility of metals in the environment are driven by their specific chemical forms and binding states. However, heavy metal fractionation in sediments from plateau deep lakes in China is rare. This study analyzed surface sediments collected from Fuxian Lake, the largest deep freshwater lake in China; parameters examined included total metal concentrations, chemical partitioning, and biological risk assessment. The average total concentrations (mg/kg) were 7.9 for Cd, 97.6 for Pb, 102.8 for Cr, 60.8 for Ni, 73.6 for Cu, and 112.9 for Zn; these levels were significantly higher than their corresponding background values. Cd was preferentially associated with the acid-soluble fraction; significant portions of the Pb, Cr, Ni, Cu, and Zn were mainly associated with the residual fractions. Overall, surface sediments of Fuxian Lake were associated with a 21% incidence of toxicity based on the mean effects range-median quotient. Cd was mainly at high or very high risk levels, and Cu and Zn were mainly at medium or high risk levels based on the risk assessment code (RAC).

Spatial distribution, enrichment, and source of environmentally important elements in Batticaloa lagoon, Sri Lanka

The present paper is the first documentation of distribution and contamination status of environmentally important elements of superficial sediments in the Batticaloa lagoon that is connected to the largest bay of the world. Surface sediment samples were collected from 34 sites covering all over the lagoon. Concentrations of elements such as As, Cr, Cu, Fe, Nb, Ni, Pb, Sc, Sr, Th, V, Y, Zn, and Zr were measured by X-ray florescence analysis. Geochemically, the lagoon has three different zones that were influenced mainly by fresh water sources, marine fronts, and intermediate mixing zones. The marine sediment quality standards indicate that Zr and Th values are exceeded throughout the lagoon. According to the freshwater sediment quality standards, Cr levels of all sampling sites exceed the threshold effect level (TEL) and 17 % of them are even above the probable effect level (PEL). Most sampling sites of the channel discharging areas show minor enrichment of Cu, Ni, and Zn with respect to the TEL. Contamination indices show that the lagoon mouth area is enriched with As. Statistical analysis implies that discharges from agricultural channel and marine fluxes of the lagoon effects on the spatial distribution of measured elements. Further research is required to understand the rate of contamination in the studied marine system.

Influence of introduced Sonneratia apetala on nutrients and heavy metals in intertidal sediments, South China

To investigate the influence of Sonneratia apetala on nutrients and heavy metals in intertidal sediments, sediment cores of S. apetala marsh and mudflat in Shenzhen Bay, China were analyzed. The results showed that S. apetala improved sediment nutrient properties due to increased total carbon (TC), total nitrogen (TN), and total sulfur (TS). The levels of heavy metals were higher in S. apetala site than in mudflat, including chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg). In S. apetala site, TC, TN, and TS were not positively correlated with Cr, Ni, As, Cd, and Pb, indicating their less important roles in trapping heavy metals. There were positive correlations among Ni, Cu, Zn, and Cd in both sites, suggesting similar anthropogenic source. Levels of As were higher than the probable effect level at both sites, indicating their toxicological importance. The geo-accumulation index and potential ecological risk index revealed higher metal contaminations in S. apetala site, especially for Cd, Hg, and As. Multivariate analysis implied that S. apetala alter the biogeochemical cycle of Cd and Cr to a certain extent. These findings indicate that S. apetala may improve soil nutrient properties and facilitate heavy metal accumulation in intertidal sediments.

Metal contamination and its ecological risk assessment in the surface sediments of Anzali wetland, Caspian Sea

In this study, the accumulation of metals, including Al, Fe, Zn, V, Ni, Cu, Cr, Cd, Co, As, and Pb, in sediments of Anzali wetland in the southwest region of the Caspian Sea was investigated. For this purpose, the sediments were collected from 17 sampling sites in Anzali wetland, Caspian Sea. The samples were then analyzed using inductively coupled plasma-optical emission spectrometry (ICP-OES). Pearson correlation coefficient showed significant and positive correlation between concentration of all metals (except As and Cd). Furthermore, the results implied that Al and Fe are probably responsible for the transportation of heavy metals into the sediments of Anzali wetland. According to mean effects range-median quotient (mean ERM quotient), the sediments from Anzali wetland had a 21% probability of toxicity.

Trace metals in a sediment core from the largest mariculture base of the eastern Guangdong coast, South China: Vertical distribution, speciation, and biological risk

A sediment core collected from Zhelin Bay, the biggest mariculture base of the eastern Guangdong Province, was analyzed for trace metal concentrations and chemical fractions. Average total concentrations (mg/kg) were 20.7±15.4 (Pb), 74.6±11.6 (Cr), 40.7±6.0 (Ni), 55.9±13.0 (Cu), and 169.0±11.9 (Zn), with the concentrations of Cr, Ni, Cu and Zn being significantly higher than their corresponding background values. We identified two vertical distribution patterns of the trace metals in the sediment core. In all sub-samples, Pb was mainly associated with the reducible fraction, whereas a major portion (62.2 to 95.2%) of Cr, Ni, Cu, and Zn was strongly associated with the residual fractions. Biological risk assessment based on the mean effects range-median quotient suggests that the Zhelin Bay sediment core has a 21% probability of being toxic.

Assessment of heavy metal contamination in the surface sediments: A reexamination into the offshore environment in China

The contents of Cu, Pb, Zn, Cd, Cr, Hg and As in the surface sediments of over 668 sites were monitored in a comprehensive program for assessing the degree of heavy-metal pollution and adverse biological effects of the offshore sediments in China. The contamination factor and geoaccumulation index indicated that As and Pb might be two of the most influential pollution loading in these metals. Cluster analysis separated 19 areas in China's near seas into 7 groups with different pollution characteristic, where the sediments along Zhejiang coast were the most highly-contaminated. Based on biological adverse effects index and sediment quality guideline for As, nearly half of sites in China's near seas induced slight adverse biological effects. With correlation analysis, self-organizing map and factor analysis, different sources as well as various adsorption mechanisms/anthropogenic factors were suggested to be important roles in altering the concentration of heavy metals in the sediments.

Vertical profile, contamination assessment, and source apportionment of heavy metals in sediment cores of Kaohsiung Harbor, Taiwan

Six sediment cores collected at the Kaohsiung Harbor of Taiwan were analyzed to evaluate their vertical profiles, enrichments, accumulations, and source apportionments of heavy metals. This was performed to investigate any potential ecological risks posed by heavy metals. Results indicated that the mean heavy metal content (mg kg^-1) in the six sediment cores was as follows: Hg (0.4-6.4), Cd (<0.05-2.4), Cr (18-820), Cu (16-760), Pb (31-140), and Zn (76-1900). The patterns of heavy metal content in the sediment cores differed substantially among the four river mouths. However, the vertical profiles of metals were relatively stable, indicating that wastewater has the constant characteristics and has been discharged into the rivers for a long period of time. Results of pollution assessment of enrichment factor, geo-accumulation index, and pollution load index revealed that river mouths experience severe enrichment, strong accumulation, and high contamination from the primary heavy metals. It was not consistent in the assessment results of mean effect range median quotient, potential ecological risk index, and total toxic unit method. Potential ecological risks caused by Hg in the sediments at Canon River and Love River mouths on aquatic organisms were extremely high. The estimates derived from the receptor modeling of multiple linear regression of the absolute principal component scores indicated that the contributions of the composite heavy metals derived from the Canon River and the Love River on the potential toxicity and risks to the water environment of Kaohsiung Harbor were highest, followed by those derived from Salt River and Jen-Gen River.

Heavy metals in the riverbed surface sediment of the Yellow River, China

One hundred and eleven riverbed surface sediment (RSS) samples were collected to determine the heavy metal concentration throughout the Inner Mongolia reach of the Yellow River (IMYR), which has been subjected to rapid economic and industrial development over the past several decades. Comprehensive analysis of heavy metal contamination, including the enrichment factor, geo-accumulation index, contamination factor, pollution load index, risk index, principal component analysis (PCA), hierarchical cluster analysis (HCA), and Pearson correlation analysis, was performed. The results demonstrated that a low ecological risk with a moderate level of heavy metal contamination was present in the IMYR due to the risk index (RI) being less than 150 and the pollution load index (PLI) being above 1, and the averaged concentrations of Co, Cr, Cu, Mn, Ni, Ti, V, and Zn in the RSS, with standard deviations, were 144 ± 69, 77.91 ± 39.28, 22.95 ± 7.67, 596 ± 151, 28.50 ± 8.01, 3793 ± 487, 69.11 ± 18.44, and 50.19 ± 19.26 mg kg^-1, respectively. PCA, HCA, and Pearson correlation analysis revealed that most of the RSS was heavily contaminated with Zn, Ni, and Cu, due to the influence of anthropogenic activities; moderately contaminated with Ti, Mn, V and Cr because of the dual influence of anthropogenic activities and nature; and slightly to not contaminated with Co because it occurs mainly in the bordering desert areas. Graphic abstract ᅟ.

Polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the intertidal zone of Bohai Bay, Northeast China: Spatial distribution, composition, sources and ecological risk assessment

Polycyclic aromatic hydrocarbons (PAHs) can enter intertidal zones by various pathways and pose potential threats to intertidal ecosystem. We investigated distribution, composition, sources and risk assessment of PAHs in intertidal surface sediments of Bohai Bay. Total PAH concentrations ranged from 37.2ng·g^-1 to 206.6ng·g^-1, among which high values occurred near Nanpaishuihe River Estuary and Haihe River Estuary. The composition patterns of PAHs were characterized by the predominance of 3-ring and 4-ring PAHs, and acenaphthylene was the most dominant component. Diagnostic ratios and principal component analysis have confirmed that PAH contaminants originated from mixed sources, and the major was local combustion. The mean benzo(a)pyrene equivalent concentration of total PAHs in intertidal sediments was 15.67ng·g^-1, which was mostly contributed by seven carcinogenic PAHs. According to ecological risk assessment, negative effects related to acenaphthylene would occur occasionally in partial survey regions of the study.

Spatial variability of heavy metals in estuarine, mangrove and coastal ecosystems along Parangipettai, Southeast coast of India

An elaborate survey on the contamination of heavy metals was carried out in surface sediments of different ecosystems such as Vellar-Coleroon estuarine, Pichavaram mangrove and coastal region of Parangipettai, Southeast coast of India. The study was intended since, the coal based thermal power plant and oil refinery plant are proposed to set up along this coast and aquaculture industries and dredging activities are developing. The parameters such as soil texture, pH, total organic carbon (TOC) and heavy metal (Fe, Mn, Cu, Cd, Zn and Ni) concentrations were analyzed for the surface sediments during pre and postmonsoon seasons. Among the metals analyzed, Fe and Mn were found to have dominant as the levels were recorded as 11,804 μg g^-1 and 845.2 μg g^-1 respectively. A significant correlation was observed between total organic carbon (TOC) and heavy metals. In the mangrove ecosystem, the levels of heavy metals found to be maximum indicating that the rich organic matter acts as an efficient binding agent for metals. The overall finding of the present study indicated that the sediments from the entire Vellar-Coleroon estuarine and Pichavaram mangrove ecosystems were found moderately polluted with cadmium metal. The result of cluster analysis indicated disparity in accumulation of heavy metals in sediments of different ecosystems due to the variations in organic matter. The heavy metals were transported from land to coastal through flood during monsoon season reflecting the variations in their levels in different ecosystems at postmonsoon season.

Distribution, enrichment, and source identification of selected heavy metals in surface sediments of the Siran River, Mansehra, Pakistan

To assess the trace metal pollution in the Siran River, sediments were collected from 12 sites, from the left and right banks of the river in 2013. The concentrations, accumulation, distribution pattern, and pollution status of heavy metals in sediments were investigated using geoaccumulation index (I geo) and enrichment factor (EF). The toxic risk of heavy metals was assessed using interim sediment quality guidelines (ISQGs), portable effect level (PEL), threshold effect level (TEL), and toxic effect threshold (TET). I geo and EF values showed that sediments were loaded with Ni, Cd, Pb, and Co and no obvious variations were found among the left and right banks of the river. The EF and I geo values were found in order of Co > Pb > Ni > As > Cd > Cu > Zn > Fe and Cd > Co > Pb > Ni > As > Fe > Zn > Cu > Mn, respectively. Furthermore, multivariate statistical analysis like inter-metal correlation, cluster analysis (CA), and principal component analysis (PCA) results revealed that geogenic and anthropogenic activities were major sources of sediment contamination in the study area. These results indicated that more attention should be paid to the inner loads of sediment in order to achieve improvements in reservoir water quality after the control of external pollution.

Spatial distribution and pollution assessment of heavy metals in the surface sediments of the Bohai and Yellow Seas

A total of 141 surface sediments were collected and analyzed for their geochemistry, total organic carbon, and grain size to assess the heavy metal pollution in the Bohai and Yellow Seas. The enrichment factor (EF) and geoaccumulation index (Igeo) of Cu, Pb, Zn, Cr, Cd, Ni, As, and Hg were calculated to assess anthropogenic contamination, and the results suggest that moderate Pb, Cd, and As contamination occurs in the study area. Sediment quality guidelines were applied to assess the adverse biological effects of these metals. The spatial distribution of the mean Effects Range-Median quotient for the vast majority of the study area is between 0.1 and 0.5, indicating low impact and potential negative biological effects. Multivariate analysis indicates that Cu, Pb, Zn, Cr, and Ni resulted primarily from lithogenic sources, whereas As, Cd, and Hg were mainly attributed to anthropogenic sources.

Heavy metals in aquatic organisms of different trophic levels and their potential human health risk in Bohai Bay, China

Fourteen aquatic organism samples were collected from Bohai Bay, and concentrations of five heavy metals were measured to evaluate the pollution levels in aquatic organisms and the potential risk to human health. The concentrations of Zn and Cu were much higher than those of Cd, Cr, and Pb in all the organisms. In general, the heavy metal concentration levels were in the order phytoplankton < zooplankton < fish < shrimp < shellfish. Heavy metal concentrations in higher trophic-level aquatic organisms in Bohai Bay were compared to those in the organisms from other worldwide coastal waters. The concentration levels of most heavy metals were higher than the 75th percentile, except that Pb concentration was between the 25th and 50th percentiles. The calculated bioconcentration factors (BCF) of Cr, Cu, and Pb for phytoplankton were less than 100, indicating no accumulation in primary producers. The bioaccumulation factor (BAF) of Pb for zooplankton was the highest, indicating significant Pb accumulation in zooplankton. For higher trophic-level aquatic organisms, the order of BAF values was fish < shrimp < shellfish for most metals except for Pb. The human health risk assessment suggests that strict abatement measures of heavy metals must be taken to decrease the health risk caused by consuming aquatic products.