Spatial distribution pattern of heavy metals in sediments of seasonal ice-covered lakes.

The heavy metal pollution in the sediments of tributaries directly affects the water quality of the Yangtze River. To investigate the distribution characteristics and pollution sources of heavy metals in the sediments of the incoming rivers in typical cities of the lower Yangtze River, the Nanjing section of the Yangtze River was selected as the study area. Sediment samples were collected from 16 monitoring points, and the monitoring data for As, Hg, Cr, Pb, Cd, Cu, and Zn were statistically analyzed. The potential ecological risk index method and the geo-accumulation index method were used to comprehensively evaluate the heavy metals in the sediments of the incoming rivers. Pearson correlation analysis and positive matrix factorization （PMF） were employed to analyze the sources of heavy metals in the sediments. The results indicated that the average values of seven heavy metals in the sediments of the incoming rivers were generally higher than those in the Yangtze River sediments, with all heavy metal coefficients of variation in the incoming river sediments exceeding 40%, indicating strong spatial heterogeneity. The primary heavy metal in the incoming river sediments in the Nanjing section of the Yangtze River was Cd, and the accumulation level and potential ecological risk of heavy metals in the Shitou River sediments were significantly higher than those in other incoming rivers. From upstream to downstream in the Nanjing section of the Yangtze River, the potential ecological risk index gradually increased, showing a spatial distribution characteristic of "lower upstream, higher downstream." When P < 0.01, Pearson correlation analysis indicated significant positive correlations among multiple heavy metals, suggesting that they may share common pollution sources. The results of the positive matrix factorization method （PMF） indicated that the main pollution sources of the incoming rivers included industrial pollution （26%）, agricultural pollution （29.7%）, and transportation （29.5%）, with the remaining 14.8% attributed to natural sources.

Spatial distribution, source apportionment and ecological risk assessment of heavy metals in the sediments of Haizhou Bay national ocean park, China

In order to understand the pollution characteristics, spatial distribution, potential sources, and ecological risk of heavy metals in the sediments of Tangxun Lake, the contents of heavy metals (As, Hg, Cd, Cr, Cu, Pb, Zn, and Ni) in the surface sediments of Tangxun Lake were analyzed, and the pollution status and potential ecological risk degree of heavy metals in the sediments were evaluated using the geo-accumulation index and potential ecological risk index. The potential sources of heavy metal pollutants were analyzed by correlation and principal component analysis. The results showed that except for Cr, the contents of other heavy metals were higher than their background values. The contents of Hg, Cd, Zn, and Cu were higher in the southwest and northeast corners of the lake, which may come from the combined pollution of sewage discharge, fisheries, and surrounding industrial and agricultural activities. The geo-accumulation index and potential ecological risk showed that Hg and Cd were in moderate pollution; Cu, Pb, and Zn were in non-light pollution; and As, Cr, and Ni were in non-pollution. Except for Hg and Cd, there were serious and serious potential ecological risks, and the other elements were at a low risk level. The heavy metals in the surface sediments of Tangxun Lake showed a high ecological risk level.

The study investigates the occurrence and bioaccumulationof heavy metals in water, sediment,fish, and prawn from the Ojo River with a view to identify the source of origin and the associated ecological and human health risks. The result shows that heavy metal concentrations in water [As = 0.010, Cd = 0.001, Cr = 0.041, Cu = 0.019, Co = 0.050, Fe = 0.099, Pb = 0.006, Ni = 0.003, and Zn = 0.452(mg/L)]were within theacceptable limits. The heavy metals in the sediment [As = 0.050, Cd = 0.287, Cr = 0.509, Cu = 0.207, Co = 0.086, Fe = 33.093, Pb = 0.548, Ni = 0.153 and Zn = 4.249 (mg/kg)]were within their respective background levels orearth's crust and theTEL and PEL standardlimits. The bioaccumulation ofheavy metals in fish and prawntissues are in this hierarchical form: Fe > Zn > Cu > Cr > Ni > Co > Pb > Ar > Cd and Fe > Zn > Cu > Cr > Pb > Ar > Ni > Co > Cd, respectively. The bioaccumulation factors of heavy metals in fishranged from 0.893 - 16.611 and 1.056 - 49.204 in prawn, which were higher than the biota-sedimentation factors (BSAF) values, inferring that the fish and prawns of this study ingested heavy metals highly from watercolumn. The aggregated BSAF scores (fish = 5.584 and prawn = 9.137) showed that these organisms are good concentrators of heavy metals in sediments. The water quality index and other pollution indices (Singlepollutionindex, Heavymetal assessment index, and Heavy metalpollutionindex) demonstrates slightlycleanwater, with a moderate level of contamination. The HI values of heavy metals in water, fish, and prawn were lower than 1, implying non-carcinogenic risk in children or adults. The ADD and EDI values of the metals were within their respective oral reference doses (RfD). The TCR values showed that exposure to water, either by ingestion or dermal absorption and the consumption of P. obscura and M. vollenhovenii from the Ojo River would not induce cancer risks in people, though As, Cr, Cd, and Pb showed carcinogenic potentials. The sediment contamination indices such as CF, mCd, EF, and Igeo showed a moderate level of pollution. The ecological risk values (NMPI, mCd = 0.068, PLI = 0.016, and R.I = 86.651) of heavy metals implies "no-moderate risk" except for Cd, which showed high risk. The ecotoxicologicalparameters, m-PEL-Q (0.024) and m-ERM-Q (0.016) denotes low contamination and no probability of acute toxicity. The CV analysis showed high dispersions and variabilities in the distributions of the heavy metals in water. Other source analyses (Pearson's correlation matrix, PCA, and HCA) showed that both natural processes and anthropogenic activities are responsible for the occurrence of heavy metals in water and sediment from the Ojo River.

Heavy metal distributions in water, sediments, and freshwater shellfish collected from Liuyang River in China have been investigated. The concentrations of heavy metals including Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, and Pb were determined by ICP-MS. The distribution pattern of heavy metals in sediments was different from that in water. Large coefficients of variation of heavy metal concentrations were observed in water due to the susceptibility to discharge fluctuation and seasonal variation. Multivariate statistical analysis such as Pearson's correlation analysis, hierarchical cluster analysis (HCA), and principal component analysis (PCA) were employed to identify the possible sources of heavy metals in sediments. These heavy metals were categorized into three distinct groups, one was derived from natural existence and two were associated with anthropogenic activities. Five shellfish species including three species of gastropod mollusks (Parafossarulus eximius, Semisulcospira cancellata, and Pomacea canaliculata) and two species of bivalve mollusks (Corbicula fluminea and Anodonta woodiana) were collected and investigated. The distribution pattern of heavy metals in shellfish species was visualized by the nonmetric multidimensional scaling (NMDS) plot. The metal pollution index (MPI) values for the shellfish species were in the descending order of C. fluminea > A. woodiana > S. cancellata > P. eximius > P. canaliculata.

In order to understand the spatial distribution and sources of heavy metals in surface sediments of MaoMing city and to reasonably evaluate the ecological risk of heavy metals in sediments of the study area, the contents of heavy metals (As, Hg, Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) in surface sediments of eight rivers and three reservoirs were detected, and the risks of heavy metals were assessed using the geo-accumulation index (Igeo), potential ecological disk index (RI), and potential adverse biological impacts (ΣTUs). The sources of heavy metals were analyzed via correlation, principal component analysis (PCA), and positive matrix factorization (PMF). The results showed that the ω(Zn) (147.56 mg·kg-1) and ω(Hg) (0.20 mg·kg-1) were 3.72 and 2.25 times the background value, respectively, and the spatial distributions of Cd, Co, Cu, Mn, Ni, and Zn were in the order of northern>central>western>southeast. The geo-accumulation index results showed that Zn was at a moderate pollution level, 76.6% of the sampling sites of Hg were at a light-heavy pollution level, and other heavy metals were at a non-light pollution level. The results of potential ecological risk and potential adverse biological impacts indicated that the potential ecological risk index and toxicity effect of Gaozhou Reservoir were higher than those of other rivers, and Hg was the major contributor to heavy metal pollution. The three factors extracted from principal component analysis and positive matrix factorization represented natural sources, agricultural sources, and industrial sources, respectively. Therefore, in order to reduce the health hazards caused by heavy metals in sediments, a prevention and control system for the Hg element should be established.

At present, the methods widely applied to assess ecological risk of heavy metals are essentially single-point estimates in which exposure and toxicity data cannot be fully used and probabilities of adverse biological eff ects cannot be achieved. In this study, based on investigation of concentrations of six heavy metals (As, Hg, Pb, Cd, Cu, and Zn) in the surface seawater and sediment near the outlet of a zinc factory, located in Huludao City, Liaoning Province, China, a tiered approach consisting of several probabilistic options was used to refine ecological risk assessment for the individuals. A mixture of various heavy metals was detected in the surface seawater, and potential ecological risk index (PERI) was adopted to assess the potential ecological risk of heavy metals in the surface sediment. The results from all levels of aquatic ecological risk assessment in the tiered framework, ranging from comparison of single eff ects and exposure values to the use of distribution-based Hazard Quotient obtained through Monte Carlo simulation, are consistent with each other. Briefly, aquatic Zn and Cu posed a clear ecological risk, while Cd, Pb, Hg, and As in the water column posed potential risk. As expected, combined ecological risk of heavy metal mixture in the surface seawater was proved significantly higher than the risk caused by any individual heavy metal, calculated using the concept of total equivalent concentration. According to PERI, the severity of pollution by the six heavy metals in the surface sediment decreased in the following sequence: Cd>Hg>As>Pb>Cu>Zn, and the total heavy metals in the sediment posed a very high risk to the marine environment. This study provides a useful mathematical framework for ecological risk assessment of heavy metals.

Mangroves are often converted into gei wai ponds for aquaculture, but how such conversion affects the accumulation and behavior of heavy metals in sediments is not clear. The present study aims to quantify the concentration and speciation of heavy metals in sediments in different habitats, including gei wai pond, mangrove marsh dominated by Avicennia marina and bare mudflat, in a mangrove nature reserve in South China. The results showed that gei wai pond acidified the sediment and reduced its electronic conductivity and total organic carbon (TOC) when compared to A. marina marsh and mudflat. The concentrations of Cd, Cu, Zn and Pb at all sediment depths in gei wai pond were lower than the other habitats, indicating gei wai pond reduced the fertility and the ability to retain heavy metals in sediment. Gei wai pond sediment also had a lower heavy metal pollution problem according to multiple evaluation methods, including potential ecological risk coefficient, potential ecological risk index, geo-accumulation index, mean PEL quotients, pollution load index, mean ERM quotients and total toxic unit. Heavy metal speciation analysis showed that gei wai pond increased the transfer of the immobilized fraction of Cd and Cr to the mobilized one. According to the acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) analysis, the conversion of mangroves into gei wai pond reduced values of ([SEM] - [AVS])/foc, and the role of TOC in alleviating heavy metal toxicity in sediment. This study demonstrated the conversion of mangrove marsh into gei wai pond not only reduced the ecological purification capacity on heavy metal contamination, but also enhanced the transfer of heavy metals from gei wai pond sediment to nearby habitats.

The spatial and temporal distributions, contamination evaluation, and source apportionment of Cu, Zn, As, Pb, Cd, and Cr in the sediments of Hulun Lake were explored in this work. The pollution characteristics of six heavy metals were assessed by single factor pollution index (PI) and geo-accumulation index (Igeo). The sources of heavy metals in the surface sediments were analyzed by the positive definite matrix factorization (PMF) and Pearson correlation analysis. The sedimentary records of heavy metals in core sediments were reproduced by radioisotopes. The average concentrations of 6 heavy metals except Cd were lower than the corresponding background values. The spatial distributions of Cu, Zn, Cr, Cd and As were generally similar and showed higher abundances in the southwestern part of the lake. With the use and import of heavy metals, the concentration of heavy metals in core sediments increased with the fluctuation of years. The peak of heavy metal concentration was related to the high growth rate of gross domestic product in 2003-2008. The single factor pollution index and geo accumulation index results showed that the surface sediment was mainly polluted by Cd, followed by Zn and As. Natural parent material, agricultural activities and industrial activities were the main sources of heavy metal pollution in the sediments, accounting for 17.03%, 26.34%, and 56.63% of the total heavy metal accumulation, respectively. Pb was derived mainly from natural parent material. Cd and As were closely associated with agricultural activities. Cu and Zn were mainly attributed to industrial mining activities. Source apportionment of the ecological risks of heavy metals illustrated that industrial sources were the primary ecosystem risk sources (66.1%), followed by agricultural sources (23.75%) and natural sources (10.15%). The results will also provide reference data for future studies of heavy metals pollution in sediments from Hulun Lake and other lakes.

Distribution characteristics, risk assessment, and source analysis of heavy metals in typical lake sediments in Inner Mongolia, China

近年来太湖底泥重金属污染越来越受到各方关注.为了解太湖沿岸区底泥重金属污染状况，基于2018年太湖全湖污染底泥勘察项目中重金属监测数据，对梅梁湖、竺山湖、西部沿岸区、南部沿岸区、东太湖、贡湖6个太湖沿岸湖区浅层（0~30 cm深度区间）底泥中Hg、Cd、As、Pb、Cu、Zn、Cr、Ni 8种重金属元素含量进行分析，运用潜在生态风险指数法及空间插值分析方法对底泥重金属污染生态风险进行评价，并对底泥重金属来源进行初步分析.结果表明，太湖沿岸区浅层底泥中重金属分布具有明显的空间异质性，竺山湖、西部沿岸区、贡湖、梅梁湖等湖区重金属含量较高，南部沿岸区、东太湖重金属含量相对较低；各个湖区的Cd、Pb、Cu、Zn、Ni含量，竺山湖的Hg、As、Cr含量，贡湖的As、Cr含量，南部沿岸区的As含量以及梅梁湖的Cr含量均高于背景值；0~30 cm不同深度区间内底泥重金属含量越往表层相对越高.潜在生态风险指数法评价结果表明，0~30 cm深度区间内底泥重金属严重污染区域（重金属综合潜在生态风险指数RI≥300的区域）主要分布在西部沿岸区中部（茭渎港至乌溪港近岸侧）、竺山湖北部、贡湖北部（望虞河入河口附近），面积分别为104.54、10.80、6.89 km²，合计约122.23 km²；Cd和Hg是主要的重金属生态风险贡献因子、且毒性较强，西部沿岸区、贡湖主要表现为Cd污染，竺山湖主要表现为Cd、Hg复合污染，且西部沿岸区的Cd污染最为严重.重金属源分析结果表明，太湖沿岸区浅层底泥中Zn、Cu、Cr、Ni、Hg、Pb、As具有相似的来源，可能主要来自于工业污染，Cd可能主要来自于农业污染.研究结果可为太湖底泥重金属污染防治提供一定参考和基础数据支撑.;Lake Taihu is the third-largest lake in China, which is located at the junction of Shanghai City, Jiangsu Province and Zhejiang Province. Lake Taihu and Taihu Basin play a crucial role in the implementation of the national strategy of the integrated development of the Yangtze River Delta region. To characterize the pollution characteristics of heavy metals in shallow sediments in the coastal area of Lake Taihu, the monitoring test data for heavy metals of 230 sediment samples at 0-10 cm depth, 159 sediment samples at 10-20 cm depth, and 115 sediment samples at 20-30 cm depth were collected which were from the investigation project of polluted sediments in Lake Taihu in the year of 2018. The contents of eight heavy metal elements (Hg, Cd, As, Pb, Cu, Zn, Cr and Ni) in the samples which in Meiliang Bay, Zhushan Bay, Western Coastal Area of Lake Taihu, Southern Coastal Area of Lake Taihu, East Lake Taihu and Gonghu Bay were analyzed. The potential ecological risk index method and spatial interpolation analysis method were applied to evaluate the ecological risk of heavy metal pollution in sediments, and the sources of heavy metals in sediments were preliminarily analyzed. The results showed that the distribution of heavy metals in shallow sediments had evident spatial heterogeneity. The heavy metals' contents in Zhushan Bay, Western Coastal Area of Lake Taihu, Gonghu Bay and Meiliang Bay were higher than those in the Southern Coastal Area of Lake Taihu and Eastern Lake Taihu. The contents of Cd, Pb, Cu, Zn and Ni in each lake area, the contents of Hg, As and Cr in Zhushan Bay, the contents of As and Cr in Gonghu Bay, the content of As in the Southern Coastal Area of Lake Taihu, the content of Cr in Meiliang Bay were higher than the background value. The heavy metals contents in sediments in different depths of 0-30 cm had a rise from its bottom to its surface. The potential ecological risk assessment results presented that the seriously polluted area of heavy metals in sediments at 0-30 cm depth which heavy metals ecological risk index RI ≥ 300 were mainly distributed in the central part of the Western Coastal Area of Lake Taihu (the nearshore side from Jiaodu River to Wuxi River), the northern part of Zhushan Bay, the northern part of Gonghu Bay. The distribution area was 104.54 km², 10.80 m² and 6.89 m² respectively, with a total area of 122.23 km². Cd and Hg were the main heavy metal ecological risk contributors with strong toxicity. The Western Coastal Area of Lake Taihu and Gonghu Bay were mainly polluted by Cd, Zhushan Bay was mainly polluted by Cd and Hg. The Cd pollution in the Western Coastal Area of Lake Taihu was the most serious. The heavy metals source analysis results demonstrated that the Zn, Cu, Cr, Ni, Hg, Pb and As in shallow sediments in the coastal area of Lake Taihu have similar sources, which may mainly come from industrial pollution. Moreover, the Cd may come from agricultural pollution. The research results can provide references and basic data supports for the prevention and control of heavy metal pollution in the sediments of Lake Taihu.

Source analysis and risk evaluation of heavy metal in the river sediment of polymetallic mining area: Taking the Tonglüshan skarn type Cu-Fe-Au deposit as an example, Hubei section of the Yangtze River Basin, China

The Le'an River is a main tributary of the Poyang Lake, which is the largest freshwater lake in China. The aim of this study is to research the distribution and potential ecological risks of heavy metals in the middle and lower reaches of the Le'an River, which is contaminated by nearby copper mines. Sediment and water samples were collected from 12 stations during the dry, wet, and normal season in 2016, respectively. The geo-accumulation index and potential ecological risk index were used to determine general pollution characteristics of trace metals in sediments. Results suggested that sediments in the Le'an River were considerably polluted by Cd, Pb, Cu, and Zn. Sediment concentrations of heavy metals showed significant spatial variations. The concentrations of heavy metals such as Cu, Zn, and Cd in water are higher in the dry season than in the normal and wet seasons. The distribution of heavy metals along the river is influenced by hydraulic conditions. The flow velocities in wet and normal seasons are positively correlated with the concentrations of heavy metals such as Cd, Pb, Cu, and Cr. There are seasonal differences in the distribution characteristics of heavy metals in surface sediments. In the dry season, the concentration of heavy metals in sediments is the highest in the middle reaches of rivers near mining areas, while during the wet and normal season, it reaches the highest value in the lower reach near the estuary. Except for Cd, whose major form of heavy metal in the sediment is in an exchanging state, the other heavy metals occur mainly in stable states. The assessment of the geo-accumulation index showed significant Cu, Cd, and Cr pollution. Among the heavy metals investigated, Cd was likely to result in more harmful effects.

Heavy metals in surface sediments of the Jialu River, China: Their relations to environmental factors

This study seeks to clarify the content characteristics, spatial distribution, potential sources and ecological risks of nitrogen, phosphorus and some heavy metals (As, Hg, Cd, Cr, Cu, Pb, Zn and Ni) in the sediments of Yueliang Lake. Nitrogen, phosphorus and heavy metals were analyzed in the surface and core sediments of Yueliang Lake. The present situation of heavy metal pollution and the degree of potential ecological risk in sediments was evaluated by the geo-accumulation index (Igeo) and potential ecological risk index (RI). The correlation (CA) and principal component analysis (PCA) methods were used to analyze the potential sources of the main pollutants among the heavy metals. The results show that the total nitrogen (TN = 2305 mg/kg) and total phosphorus (TP = 530 mg/kg) in the surface sediments of Yueliang Lake are at medium and low levels, respectively. The average content of organic matter was 2.17%, and the nutrient ratio was 6.90–11.92, which was significantly higher in the northwest than in the middle and east of Yueliang Lake, indicating that the organic matter was a mixture of endogenous aquatic plants and exogenous terrestrial plants in the sediments. From two evaluation indices (RI and Igeo) calculated using element contents, the heavy metals in the surface sediments were at a moderate ecological risk level. The level of Hg was moderately polluted, Pb and Cd were at the mildly polluted level, and Cu, Zn, As, Cr and Ni were at pollution-free levels. Except for Hg, the other elements in the core sediment are basically not polluting, and the whole is at the level of slight ecological risk. The sources of heavy metals in the sediments are roughly divided into three categories. The first category is natural sources, including Cr, Ni, As, Zn and Cu. The second category includes Cd and Hg and the main sources are highly related to energy development and agricultural activities. The third category is light Pb pollution caused by vehicular traffic and coal-related industrial activities. Therefore, the pollution problems caused by tourism development and agricultural activities should be considered in the future development of the Yueliang Lake area.