Distribution and risk assessment of trace metals in sediments from Yangtze River estuary and Hangzhou Bay, China

Elemental geochemical evidence for the river-derived sources of trace metals in surface sediments from Hangzhou Bay, East China Sea

Coastal estuaries are often heavily subject to riverine influences by the inputs of sediment from terrestrial sources. Hangzhou Bay (HZB) is threatened by the riverine derived trace metals from two large rivers of Qiantang River (QTR) and Yangtze River (YZR). However, previous studies mainly focused on the incidental transport from the largest river in China (YZR) and failed to simultaneously evaluate the contributions of these two rivers, especially the directly flowing river of QTR, by their trace elemental geochemical composition and distribution. Herein, a comprehensive study identified the river-derived sources of multiple trace metals in surface sediments which transported from both of the rivers. The sampling stations were separated into three regions of YZR, HZB, and QTR based on their spatial distributions of sediment grain size and components. The significant variations for most of the trace metals concentrations, except for Cd, Th, and U, were found among three regions (χ2 ≥ 8.22, p ≤ 0.016). The highest concentrations in HZB were mainly resulted from the grain size effect (68.82% of the total variance), while the highest concentrations of Sr, Cd, and Ba in YZR and Zr and Hf in QTR were attributed to the anthropogenic source (11.90%) and mineral composition (6.21%) of river basins. After normalized the diversity of multiple trace metals concentrations and the influence of grain size by ratios of Igeo and EFLi, three regions were effectively distinguished. It was indicated that As, Cd, and Sb were enriched in the sediments of rivers by anthropogenic source (EFLi > 1.5 and/or Igeo > 1). The results evidenced that, after removing the influence of grain size, elemental geochemical composition of the surface sediments confidently identified the river-derived anthropogenic sources of the enriched trace metals from two major rivers, and largely from YZR.

Potential risk assessment and occurrence characteristic of heavy metals based on artificial neural network model along the Yangtze River Estuary, China

Pollution from heavy metals in estuaries poses potential risks to the aquatic environment and public health. The complexity of the estuarine water environment limits the accurate understanding of its pollution prediction. Field observations were conducted at seven sampling sites along the Yangtze River Estuary (YRE) during summer, autumn, and winter 2021 to analyze the concentrations of seven heavy metals (As, Cd, Cr, Pb, Cu, Ni, Zn) in water and surface sediments. The order of heavy metal concentrations in water samples from highest to lowest was Zn > As > Cu > Ni > Cr > Pb > Cd, while that in surface sediments samples was Zn > Cr > As > Ni > Pb > Cu > Cd. Human health risk assessment of the heavy metals in water samples indicated a chronic and carcinogenic risk associated with As. The risks of heavy metals in surface sediments were evaluated using the geo-accumulation index (Igeo) and potential ecological risk index (RI). Among the seven heavy metals, As and Cd were highly polluted, with Cd being the main contributor to potential ecological risks. Principal component analysis (PCA) was employed to identify the sources of the different heavy metals, revealing that As originated primarily from anthropogenic emissions, while Cd was primarily from atmospheric deposition. To further analyze the influence of water quality indicators on heavy metal pollution, an artificial neural network (ANN) model was utilized. A modified model was proposed, incorporating biochemical parameters to predict the level of heavy metal pollution, achieving an accuracy of 95.1%. This accuracy was 22.5% higher than that of the traditional model and particularly effective in predicting the maximum 20% of values. Results in this paper highlight the pollution of As and Cd along the YRE, and the proposed model provides valuable information for estimating heavy metal pollution in estuarine water environments, facilitating pollution prevention efforts.

Spatiotemporal variations of heavy metal historical accumulation records and their influencing mechanisms in the Yangtze River Estuary

Complex transformations of heavy metals in the mega-river-estuary continuum limit our understanding of their pollution history. This study investigated sedimentary compositions of heavy metals, major elements, total organic carbon, grain size, and radionuclides to study spatiotemporal variations in heavy metal accumulation patterns and their controlling mechanisms in four sediment cores (E1-E4) from the Yangtze River Estuary (YRE). Results show that only E3 in the distal YRE front mirrors well the heavy metal pollution history due to its continuous deposition in a stable sedimentary environment, while E1 and E2 record the influence of riverine and estuarine projects and processes apparently. E1 in the proximal YRE front registers intense human disturbance through sediment dredging and dumping activities to produce a thick layer of abnormal low 210Pbex and minor heavy metal concentrations. E2 in the intermediate YRE front demonstrates the recently increasing influence of reduced sediment discharge by its upcore coarsening trend with decreased heavy metal concentrations. Flood and storm events left different imprints in core sediments of E2 and E3 by their coarse stratal units with fewer heavy metal concentrations. The source analysis indicates that heavy metals in estuarine sediments mainly come from natural processes but are significantly affected by human activities. A direct linkage of the heavy metal accumulation history with the socioeconomic development in recent decades is found by a comparison study of core data from the tidal river to the estuary, albeit with a remarkable spatiotemporal difference, which is jointly determined by grain size, offshore distance, hydrodynamic condition, depositional status, and sedimentation rate besides estuarine processes. This warns us to carefully interpret the heavy metal history from single or sparse core data in a mega estuary system with intense natural forces and human disturbances analogous to the YRE.

Multivariate statistical analysis of potentially toxic elements in the sediments of Quanzhou Bay, China: Spatial relationships, ecological toxicity and sources identification

In this paper, the spatial distribution, pollution degree, ecological toxicity and possible sources of seven potentially toxic elements (PTEs) collected from the surface sediments of Quanzhou Bay (QZB) were analyzed by obtaining concentration measurements. The results indicated that the areas with high Cu, Pb, Zn and Hg concentrations were mainly located in the Luoyang River estuary, while the areas with high contents of Cd and As appeared in the Luoyang River estuary area and in the southern part of QZB, respectively. The contamination indices showed that the Cd pollution degree was slight to serious, while other elements were slightly enriched. The calculation results of the potential ecological risk index (RI) and toxic risk index (TRI) indicated that Cd was the main element posing ecological risk among the PTEs of sediments in QZB, followed by Hg. Moreover, in approximately 30% of the surveyed sites, PTEs exhibited low toxicity to aquatic ecosystems. Finally, the self-organizing map (SOM) and positive matrix factorization (PMF) model were used to determine the PTEs sources. Natural sources, industrial emissions, and the combustion of fossil fuels were three main sources for PTEs in the surface sediments of QZB. This study provides a reference for assessing sediment pollution and managing marine pollution in QZB.

Microplastics in Seawater, Sediment, and Organisms from Hangzhou Bay

Microplastics (MPs) are widely present in global oceans, and can pose a threat to marine organisms. This study examined the abundance and characteristics of MPs in seawater, sediment, and organism samples collected from Hangzhou Bay. Abundance of MPs in seawater (n = 26) and sediment (n = 26) were 0.77-9.6 items/m³ and 44-208 items/kg dw, respectively. Size of MPs in sediment (mean 2.5 mm, range 0.21-5.3 mm) was significantly (p < 0.05) larger than that in seawater (1.1 mm, 0.13-4.9 mm). Fiber was consistently the predominant shape of MPs in seawater and sediment. The major polymer composition of MPs was polyethylene (PE; mean 47 %) in seawater, but textile cellulose (60 %) was the main polymer type of MPs in sediment. Average abundance of MPs in marine organisms (n = 388) ranged from 0.064 (zooplankton) to 2.9 (Harpodon nehereus) items/ind, with the mean size of 0.19-1.4 mm. MP abundance in marine organisms was not significantly correlated with their trophic level. Fiber was always the predominant shape of MPs in different marine organisms, contributing mean 67 (fish)-93 % (zooplankton) of total MPs. MPs in crustacean (mean 58 %), shellfish (64 %), and cephalopod (29 %) were dominated by textile cellulose. Whereas, PE (mean 44 %) and polypropylene (43 %) were the major polymer compositions of MPs in fish and zooplankton, respectively. To our knowledge, this is the most comprehensive study investigating the occurrence of MPs in environmental matrixes from Hangzhou Bay, which contributes to the better understanding of environmental behaviors of MPs in estuarine sea environment.

Ecological Risk Assessment of Trace Metal in Pacific Sector of Arctic Ocean and Bering Strait Surface Sediments

The arctic region is a remote area with relatively few anthropogenic inputs, but there is increasing concern over toxic trace metal contamination in the Arctic Ocean. In this study, distribution characteristics of eight trace metals in the surface sediment of the Pacific Sector of the Arctic Ocean and Bering Strait are analyzed. The geochemical baseline value of each metal element is explored using the relative cumulative frequency curve method; the enrichment factor (EF), geo-accumulation index (I_geo) and potential ecological risk index (RI) are applied to assess the ecological risk level of the trace metals. According to the results, Cu, As and Hg had a little more content variation, and their contents in some areas were significantly higher than the previous reports. EF values show an obvious enrichment of element As, followed by Cr element with the moderate enrichment; the enrichment of the other six elements are not related to human activity. The I_geo value shows a moderately contaminated to heavily contaminated level of As and a moderately contaminated level of Cr. According to the potential ecological risk indexes in each site, most sites are at a low ecological risk level except five sites with RI/baseline values exceeding 150 which are at a moderate ecological risk level.

Bioaccumulation and potential human health risks of metals in commercially important fishes and shellfishes from Hangzhou Bay, China

Hangzhou Bay is facing severe anthropogenic perturbation because of its geographic position. We studied species-specific bioaccumulation of metals in commercially important fishes and shellfishes, and calculated the potential human health hazards through their consumption, which has not been reported earlier from this area. The hierarchy of metal concentration in organisms was in the decreasing order of Zn (10.32 ± 7.13) > Cu (2.40 ± 2.66) > As (0.42 ± 0.26) > Cr (0.11 ± 0.08) > Cd (0.07 ± 0.07) > Pb (0.05 ± 0.02) > Hg (0.012 ± 0.009). Except for Cd and As concentrations in fishes, metal concentrations have not exceeded the national and international guideline values. P. laevis and P. trituberculatus were the most bioaccumulative of the species studied. According to the non-carcinogenic risk assessment, children were more susceptible to metal contamination than adults. The carcinogenic risk (CR) values indicated that children were likely to experience carcinogenic threats for taking cancer-causing agents As and Cd through fish consumption. In terms of organisms, intake of two crab species, P. trituberculatus and E. sinensis, as well as the oyster species P. laevis, could be detrimental to consumers.

Effects of Human Activities on the Spatial Distribution, Ecological Risk and Sources of PTEs in Coastal Sediments

Potentially toxic elements (PTEs) have attracted substantial attention because of their widespread sources, long residue time and easy accumulation. PTEs in the surface sediments of inshore waters are strongly affected by human activities because these waters are a zone of interaction between the ocean and land. In the present study, to explore the environmental geochemical behaviour and source of PTEs in the surface sediments of coastal waters, the contents and spatial distributions of copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), chromium (Cr), mercury (Hg) and arsenic (As) in different regions of Xiamen Bay were investigated. The data were processed by multivariate statistical methods, and the distribution characteristics of PTEs in the surface sediments of Xiamen Bay were analysed. In addition, the pollution load index (PLI), geo-accumulation index (Igeo) and potential ecological index(RI) were used to evaluate the pollution degree and potential risk in the surface sediments of Xiamen Bay, and the positive matrix factorisation (PMF) model was used to analyse the source. The results show that Zn had the highest mean concentration, followed by Pb, Cr, Cu, As, Cd and Hg, among the seven PTEs. The mean contents of Pb, Zn, Cd, Cu and Hg, and especially Hg and Cd, were higher than the corresponding environmental background values. The average PLI value indicated that the Xiamen Bay sediment was moderately contaminated by PTEs. The Igeo results showed that Xiamen Bay was moderately to strongly polluted by Cd and Hg. The proportions of samples with low, medium and strong risk levels were 11.63%, 74.42%, and 13.95% in surface sediments, respectively. PMF models showed that the input of chemical fertilizer and medication, anthropogenic atmospheric components and terrestrial detritus were the main sources of PTEs in the surface sediment of Xiamen Bay.

Characteristics of Heavy Metals in Seawater and Sediments from Daya Bay (South China): Environmental Fates, Source Apportionment and Ecological Risks

In this study, the spatiotemporal distributions, potential sources, and ecological risks of Hg, Cr, and As in seawater, and Hg, As, Zn, Cd, Pb, and Cu in sediments from Daya Bay were investigated. The five-year average concentrations of Hg, Cr, and As in seawater were 0.020 μg/L, 0.79 μg/L, and 2.08 μg/L, respectively. The five-year average concentrations of Hg, As, Zn, Cd, Pb, and Cu in surface sediments were 0.04 mg/kg, 7.34 mg/kg, 63.81 mg/kg, 0.23 mg/kg, 25.60 mg/kg, and 11.78 mg/kg, respectively. Annual variations in Hg, Cr, and As in seawater exhibited different trends. HMs in sediments, such as As, Zn, Pb, and Cu, exhibited similar annual variations, whereas Hg and Cd exhibited different annual variations. The spatial distribution of metal species in seawater and sediments showed significant variability, and the concentrations decreased gradually from the coast to the open sea. The comprehensive potential ecological hazard index (RI) of HMs in sediments indicated a relatively high risk, especially for Hg and Cd contamination. The geoaccumulation indices (Igeo) of As, Zn, Pb, and Cu suggested that these metals did not pollute Daya Bay, whereas those of Cd and Hg indicated mild and moderate pollution. The environmental fates of HMs were discussed based on Pearson correlation analysis, revealing that concentrations of HMs were greatly affected by parameters, such as pH, salinity, dissolved oxygen (DO), and total organic carbon (TOC). Principal component and factor analyses indicated that Hg, Cr, As, and dissolved inorganic nitrogen (DIN) in water originated from similar sources, including domestic sewage and wastewater from fishing ports, runoffs, and outlets. For sediments, it was proposed that Cu, Zn, As, Pb, and TOC exhibited similar sources, including cage culture and waste discharge from outlets. Meanwhile, Hg and Cd originated from other point sources, such as a harbor. The study suggests that sustainable management and economic development be integrated to control pollutant emissions in Daya Bay.

Assessment of cadmium pollution and subsequent ecological and health risks in Jiaozhou Bay of the Yellow Sea

Million tons of cadmium (Cd) are annually discharged into China's coastal regions, creating a persistent hazard to marine organisms and human health. This study assessed Cd residues in the Yellow Sea's semi-enclosed Jiaozhou Bay (JZB), finding concentrations of 0.05-0.94 μg/L in seawater and 0.03-0.18 mg/kg in sediment. For marine organisms, mollusks had the highest Cd concentration (0.44 ± 0.09 mg/kg), followed by crustaceans (0.26 ± 0.08 mg/kg) and fish (0.10 ± 0.02 mg/kg). Cd was clearly accumulated by mollusks, with biota-sediment accumulation factor (BSAF) values >1 and biota-water accumulation factor (BWAF) values >1000. Stable nitrogen isotope (δ¹⁵N) analysis showed that Cd underwent biomagnification in mollusks, but was significantly bio-diluted with increasing trophic level among other marine organisms. In general, Cd contamination levels were low in the JZB's seawater and sediment, and fish was estimated to be certainly polluted due to strict safety limitations on seafood in China. Current Cd residues mean that few aquatic species (<< 5%) would be affected by acute exposure, and ~ 10% of the species would be affected by chronic exposure. Based on target hazard quotients (THQ) and estimated weekly intakes (EWIs), urban residents around the JZB would experience higher health risks in comparison with rural residents due to higher seafood consumption rates, especially from mollusk consumption. Therefore, urban households in the area should increase their fish consumption rate and reduce that of mollusks.

Long-term study of heavy metal pollution in the northern Hangzhou Bay of China: temporal and spatial distribution, contamination evaluation, and potential ecological risk

Coastal ecosystem is vulnerable to heavy metal contamination. The northern Hangzhou Bay is under intensifying impact of anthropogenic activities. To reveal the heavy metal pollution status in the coastal environment of the Hangzhou Bay, a long-term investigation into the heavy metal contamination during 2011 to 2016 was initiated. Seawater and sediment samples of 25 locations depending on the sewage outlet locations in the northern Hangzhou Bay were collected to analyze the concentrations and temporal and spatial distribution of Cu, Pb, Zn, Cd, Hg, and As. Pollution condition, ecological risk, and potential sources were additionally analyzed. Results show that the annual mean concentrations of Cu, Pb, Zn, Cd, Hg, and As were 2.13-4.59, 0.212-1.480, 7.81-20.34, 0.054-0.279, 0.026-0.090, and 1.08-2.57 μg/L in the seawater, and were 16.34-28.35, 16.25-26.33, 67.32-97.61, 0.084-0.185, 0.029-0.061, and 6.09-14.08 μg/L in the sediments. A decreasing trend in Cu, Pb, Zn, Cd, and Hg concentrations and an increasing trend in As of the seawater were observed. However, in the sediment, the heavy metals demonstrated a rising trend, except for Hg. The single-factor pollution index showed an increasing trend in Cd and As in the seawater, depicting an enhanced pollution of Cd and As, while in the sediments, Cu, Pb, and As were in pollution-free level (average Geo-accumulation index (I_geo) values below 0) in general, and only occasional slight pollution occurred in individual years, e.g., As with 0.403 in 2016. The mean I_geo values of Cd ranged from - 0.865 to 0.274 during 2011 to 2016, indicating that the pollution level of Cd was slight, but is likely to increase in the forthcoming years. The level of heavy metal contamination in sediments was low in 2011 (5.853) and 2012 (5.172), and moderate during 2013 to 2016 (in the range of 6.107 to 7.598), while the degree of potential ecological risk was low in the study period, except moderate in 2013 (125.107). The highest contamination degree and potential ecological risk appeared in 2013 (Cd = 7.598; RI = 125.107), while Cd and Hg contributed over 75% of the ecological risk. Overall, the results show low pollution level and low potential ecological risk in the northern Hangzhou Bay; however, more attention should be paid to the potential ecological risk due to Hg and Cd. Graphical abstract Spatial distribution of the heavy metal levels in the sediment of the coastal environment of the northern Hangzhou Bay on a long-term basis.

Evaluation of ecosystem health and potential human health hazards in the Hangzhou Bay and Qiantang Estuary region through multiple assessment approaches

Anthropogenic pollution has become a major issue governing ecosystem and human health risks. The Hangzhou Bay and Qiantang Estuary region are facing unusual perturbation due to rapid development along the embayment in recent decades. This study evaluated the organic and inorganic pollutants in water, sediment, and from the muscles of higher trophic organisms (fish, crustacean, shellfish) during four different seasons (in 2018-2019) along the Qiantang Estuary and Hangzhou Bay region to assess the ecosystem health and potential hazard status. Dissolved inorganic phosphate and nitrogen were the major pollutants in this area, which led to severe eutrophication throughout the study period. Eutrophication signals coincided well with the phytoplankton abundance, which revels the control of nutrient enrichment on the spatio-temporal distribution of phytoplankton. Food availability, along with salinity and temperature, drives the zooplankton population distribution. Heavy metals were not the issue of water quality as their concentrations meet the national and international baseline standards. However, in the sediments, Copper (Cu) and Arsenic (As) concentrations were higher than the baseline value. Towards the northwestern part of the Qiantang Estuary, the overall potential risk index of sediment with higher Cadmium (Cd) and Mercury (Hg) depicted delicate condition with moderate risk for the sediment contamination. The As concentration in fishes was close to the baseline standards limit irrespective of low As values within water and sediments. The higher concentrations of Zinc (Zn) and As in shellfish muscles, whereas other metals were within the limit of baseline standard in all the organisms. However, the hazard analysis (Targeted hazard quotient, THQ) values for the seafood consumption to human health indicates the potentially threatening consequences of shellfish and crustacean consumption on human health.

Distribution and risk analysis of heavy metals in sediments from the Yangtze River Estuary, China

Sediments core within the Yangtze River Estuary was collected for metal and grain size analysis. The vertical distribution characteristics of eight metals along the core were investigated based on ¹³⁷Cs and ²¹⁰Pb radionuclide dating. The sediment was mainly composed of sand and silt. The metals concentrations were Al, 4.67-6.83; Fe, 2.3-3.94; Mn, 0.046-0.07; Cr, 69.5-103; Cu, 14.3-32.1; Zn, 47.3-96.7; Cd, 0.037-0.212; Pb, 13.7-23; Ni, 18.8-38.9 (mg·kg^-1, except Al, Fe, and Mn as %), respectively. Geoaccumulation indexes (I_geo) indicated that Cu, Zn, and Pb were of pollution-free level; Cd, Cr, and Ni were in a slight polluted level. Based on potential ecological risk factors (EI), Cd posed a moderate risk to the local environment. Correlation analysis showed that Fe, Al, and Mn had a close association with Cu, Zn, Pb, and Ni at p < 0.01. Clay was significantly correlated with other metals except Cr and Cd.

Factors controlling the accumulation and ecological risk of trace metal(loid)s in river sediments in agricultural field

There is an increasing concern of ecological risk from toxic trace metals in sediments to aquatic environment in agricultural field. However, the knowledge of factors that control the accumulation and risk of trace metals in such environment is limited. In this study, we conducted source apportionment of 9 trace metal(loid)s in river sediments on Chongming Islands, China, where there had been >120 years of agricultural practice. The influence from sediment properties on metal accumulation and mobility were also discussed. The results indicate that anthropogenic metal input generally elevated Cd, Sb, Pb and Zn concentrations as their average values were 3.3, 2.6, 1.6 and 1.6 times of the background respectively. Significantly high As (max = 28.2 mg/kg) and Cu (max = 145.6 mg/kg) were also found in some individual sites. Positive matrix factorization analysis suggests that atmospheric deposition contributed 53.5% and 54.7% of the total Sb and Pb respectively, while most anthropogenic Cd, Cu, As and Zn was agriculture-derived. Amorphous Fe, Mn and Al oxides and organic matter were the most important binding phases which favour trace metal accumulation. Fractionation information from BCR sequential extraction suggests high potential mobility of Cd (>37% in acid extractable fraction). Fe/Mn oxides bound As, Cd, Cu, Pb and Zn (reducible fraction), which comprised 15-26% of the total, increased the ecological risk in anoxic sediments. The potential ecological risk index and risk assessment code identified more than 74% of the sampling sites as high to extremely high ecological risk because of the high toxicity and mobility of Cd.

Development of a Sensitive Escherichia coli Bioreporter Without Antibiotic Markers for Detecting Bioavailable Copper in Water Environments

The whole-cell bioreporters based on the cop-operon sensing elements have been proven specifically useful in the assessment of bioavailable copper ions in water environments. In this study, a series of experiments was conducted to further improve the sensitivity and robustness of bioreporters. First, an Escherichia coli △copA△cueO△cusA mutant with three copper transport genes knocked out was constructed. Then, the copAp::gfpmut2 sensing element was inserted into the chromosome of E. coli △copA△cueO△cusA by gene knock-in method to obtain the bioreporter strain E. coli WMC-007. In optimized assay conditions, the linear detection range of Cu²⁺ was 0.025–5 mg/L (0.39–78.68 μM) after incubating E. coli WMC-007 in Luria–Bertani medium for 5 h. The limit of detection of Cu²⁺ was 0.0157 mg/L (0.25 μM). Moreover, fluorescence spectrometry and flow cytometry experiments showed more environmental robustness and lower background fluorescence signal than those of the sensor element based on plasmids. In addition, we found that the expression of GFPmut2 in E. coli WMC-007 was induced by free copper ions, rather than complex-bound copper, in a dose-dependent manner. Particularly, the addition of 40 mM 3-(N-Morpholino)propanesulfonic acid buffer to E. coli WMC-007 culture enabled accurate quantification of bioavailable copper content in aqueous solution samples within a pH range from 0.87 to 12.84. The copper recovery rate was about 95.88–113.40%. These results demonstrate potential applications of E. coli WMC-007 as a bioreporter to monitor copper contamination in acidic mine drainage, industrial wastewater, and drinking water. Since whole-cell bioreporters are relatively inexpensive and easy to operate, the combination of this method with other physicochemical techniques will in turn provide more specific information on the degree of toxicity in water environments.

Enrichment assessment of Sb and trace metals in sediments with significant variability of background concentration in detailed scale

Variability of background concentration of toxic trace metal(loid)s in sediments can often lead to under/over-report of contamination level, even in detailed scale. In this study, both surface (5-10 cm) and subsurface (> 10 cm) sediments were collected at many sites in a small lake (0.528 km²) with multi-function (irrigation, aquaculture, and watercourse) in an industrial area. Total concentration of trace metal(loid)s (Cd, Cr, Co, Cu, Ni, Sb, Pb, and Zn) and potential reference elements (Ti, Zr, Rb, and Li) were analyzed. The results showed that although the trace metal(loid)s were mainly lithogenic in subsurface sediments, the variability of baseline concentration was significant. For Sb, this variability was a result of alteration in hydrological parameters as well as sediment properties including Fe/Mn oxide contents, particle size distribution, and organic matter contents. Comparison of the normalized Sb concentration in samples from two sediment cores indicated that Ti is the best reference element for normalizing Sb to reduce the impact from particle size and natural source. Enrichment assessment using modified EFs (Ti as reference element) and I_geo index (measured baseline concentration) suggested that about 70% of the surface sediments were at least moderately polluted by Sb in the lake, as a result of recent anthropogenic input, mainly from nearby industries, e.g., concrete factory and textile factory. Modified EFs should be used, instead of I_geo index, when Sb enrichment was relatively low in sediment. The anomalies of Sb background concentration may need regulator attention when assessing the level of sediment contamination.

Biological risk assessment of heavy metals in sediments and health risk assessment in bivalve mollusks from Kaozhouyang Bay, South China

The concentrations of heavy metals (Cd, Pb, Cr, Ni, Cu, Zn, Hg and As) in surface sediments and bivalve mollusks in Kaozhouyang Bay were investigated. A biological risk analysis of the sediments indicated that ten sites (about 76.92% of the total number of sites) had a 21% incidence probability of toxicity. A health risk analysis of the bivalve mollusks indicated that Cu and As posed low risks to consumer health. On the basis of the target hazard quotient (THQ), adverse effects may occur based on total THQ (TTHQ). The highest TTHQ was found in the species, Ostrea rivularis, which had the highest capacity for the bioaccumulation (factor > 38) of Cd.