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Abstract In this study, we estimated the toxicity risks from river sediments that were affected by multiple pollutants in the Haihe River Basin. We used a range of methods to determine the concentrations, bioavailability, and toxicity of a range of metals and contaminants in sediments and sediment porewater and then assessed the ecological risks and toxicity using various multivariate statistical approaches. We found that more than 70% of the samples were toxic. The concentrations of non-ionic ammonia (0.168–9.295 mg L−1) were generally high in the sediment porewater, while the concentrations of bioavailable chromium (Cr) and polycyclic aromatic hydrocarbons (PAHs) were also high in the porewater samples from NW01 and NW02, respectively. We used the toxic unit (TU) approach, based on the bioavailable pollutant concentrations, to determine the toxicity of PAHs, heavy metals, and non-ionic ammonia in river sediments and sediment porewater. We found that non-ionic ammonia was the main source of toxicity for Daphnia magna , and that Cr and zinc were toxic for Pseudokirchneriella subcapitata and Chironomus dilutus. By combining various indexes, we identified the main contributors to the toxicity in sediments collected from rivers affected by multiple pollutants. Graphical abstract fx1 Highlights • The river sediment showed high acute toxicity, especially for C. dilutus. • Cr, Zn, and non-ionic ammonia were the main contributors to biotoxicity. • Ammonia and metals require more attention for remediation progress in studied area. • Toxic units based on bioavailable contaminations could effectly predict observed toxicity. [ABSTRACT FROM AUTHOR]

Soil heavy metal contents were measured in newly submerged areas of the Danjiangkou Reservoir, China. We aimed to determine the heavy metal distribution in this area and the associated ecological risk. Most of these heavy metal contents (except Pb and Mn) suggest enrichment compared with the background values of soils from Henan Province, especially As and Cd with mean geo-accumulation index ( I geo ) values of 0.84 and 0.54. The spatial analysis results indicated that the highest heavy metal contents were distributed in the arable soils above 160 m elevation, whereas low heavy metal contents were observed under other land-use types above 160 m elevation. According to I geo and EF values, Cd was the major heavy metal contaminant in the newly submerged area, Cr, Pb and Mn mainly originated from natural geochemical sources. In contrast, Ni, Cd, As, Cu, and Zn mainly originated from anthropogenic sources. Evaluation using the potential ecological risk (PER) method indicated that PER of individual elements were low in the studied soils, and the comprehensive PER index was at a moderate level, indicating heavy metals in the soils of newly submerged areas may not threaten the water quality of Danjiangkou Reservoir, especially in winter. [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

The concentration partitioning between the sediment particle and the interstitial water phase plays an important role in controlling the toxicity of heavy metals in aquatic systems. The aim of this study was to assess the sediment quality in a polluted area of the Ziya River, Northern China. The contamination potential and bioavailability of six metals were determined from the concentrations of total metals and the bioavailable fractions. The results showed that the concentrations of Cr, Cu, Ni, Zn, and Pb exceeded the probable effect concentration at several sites. The high geoaccumulation indices showed that the sediments were seriously contaminated by Cd. The ratio of acid-volatile sulfide (AVS) to simultaneously extracted metal (SEM) was higher than 1, which indicated that the availability of metals in sediments was low. The risk assessment of interstitial waters confirmed that there was little chance of release of metals associated with acid-volatile sulfide into the water column. Values of the interstitial water criteria toxicity unit indicated that none of the concentrations of the studied metals exceeded the corresponding water quality thresholds of the US Environmental Protection Agency. Positive matrix factorization showed that the major sources of metals were related to anthropogenic activities. Further, if assessments are based on total heavy metal concentrations, the toxicity of heavy metals in sediment may be overestimated. [ABSTRACT FROM AUTHOR]

A comprehensive analysis of heavy metal speciation, risk, and bioavailability in the sediments of three rivers in northern China (Shaocun River (SR), Wangyang River (WR), and Xiao River (XR)) was conducted. The results showed that higher pollution input resulting from urbanization and industrialization caused higher heavy metal contents and bioavailable proportion in the studied sediments. Total contents of all studied metals (Cr, Cu, Ni, Pb, and Zn) in the sediments of SR, WR, and XR were 270.31, 902.62, and 2367.46 mg/kg, respectively. The average percentages of bioavailable fractions were 31.16, 61.73, and 81.69 %, respectively. Cr, Ni, and Pb were all mainly observed in the B4 (residual) fraction in the studied sediments, with an average percentage of 42.03, 48.19, and 55.08 %, respectively. Cu was mainly observed in the B2 (reducible) fraction (40.53 %). Zn was mainly observed in the B1 (exchangeable/acid soluble/carbonate) fraction (36.01 %), resulting in medium or high risk associated with Zn in the sediments of SR, WR, and XR. Sedimentary heavy metal risk and bioavailability associated with regional urbanization and industrialization should be taken into consideration with respect to the health of aquatic ecosystems. [ABSTRACT FROM AUTHOR]

The distributions and mobilities of metals in pore water strongly influence the biogeochemical processes and bioavailabilities of metals at sediment-water interfaces. Heavy metal concentrations were measured in pore water samples from the Shaocun River (SR), the Wangyang River (WR), and the Xiao River (XR), tributaries of the Ziya River system, northern China. The aim was to assess heavy metal contamination in the system and the associated environmental risks. The mean Cd, Cr, Cu, Ni, Pb, and Zn concentrations in all three tributaries were 0.373, 57.1, 37.7, 20.4, 14.0, and 90.6 μg/L, respectively. The calculated Cd, Cr, Cu, Ni, Pb, and Zn diffusion fluxes in the rivers were −0.427 to 0.469, −71.8 to 42.5, 3.16 to 86.6, 5.29 to 14.0, 7.24 to 19.0, and −204 to 21.9 μg/(m day), respectively, showing that the pore water was a source of most of the metals to the water column. Only Cu and Pb in the XR and Cu in the WR exceeded the final chronic value recommended by the US Environmental Protection Agency, but the metals in the WR sediment could have caused toxic effects. These results are likely to be useful to the authorities responsible for sustainable river management. [ABSTRACT FROM AUTHOR]

A drastic decrease in the suspended sediment of Dongting Lake (DTL) has been observed due to Three Gorges Dam (TGD) impoundment operation since 2003. However, the relationship between sediment loads and metal fluxes has not been studied. This study comprehensively analyzed the content characteristics of seven metal(loid)s (As, Cd, Cr, Cu, Hg, Pb, and Zn) in the surface sediment of DTL from 2000 to 2019. The period of 2005–2009 corresponded to a metal(loid) enrichment stage in the sediment of DTL. The metal(loid) cumulative input of DTL from 2000 to 2019 reached 153 × 103 t, and the increasing rate was gradually diminished because of TGD operation, while the metal(loid) cumulative output reached 132 × 103 t. Undergoing an input-output state transition, the metal(loid) cumulative deposition of DTL in 2019 was only 42% of its peak in 2007. Especially, the metal(loid) fluxes of DTL all became negative for the first time in 2006. It is worth noting that Cd in DTL has shifted to a net export during the study period. Finally, the assessment results of pollution, risk, and toxicity indicated that metal(loid) effects on sediment quality were weakening in recent years. This study confirmed that DTL has shifted from metal(loid) deposition to export, providing new information for future DTL management options. [Display omitted] • Metal(loid) fluxes of Dongting Lake (DTL) were studied from 2000 to 2019. • Operation of Three Gorges Dam has changed DTL metal(loid) fluxes. • Metal(loid) annual output of DTL has exceeded their input in recent years. • The extent of metal(loid) pollution in the sediment of DTL was decreasing. • The pollution of Cd and Hg in the sediment of DTL remains to be a problem. [ABSTRACT FROM AUTHOR]

The Hai River Basin (HRB) is one of the most polluted river basins in China. The basin suffers from various types of pollutants including heavy metals and nutrients due to a high population density and rapid economic development in this area. We assessed the relationship between heavy metal accumulation by periphyton playing an important role in fluvial food webs and eutrophication in the HRB. The concentrations of the unicellular diatoms (type A), filamentous algae with diatoms (type B), and filamentous algae (type C) varied along the river, with type A dominating upstream, and types B then C increasing in concentration further downstream, and this was consistent with changes in the trophic status of the river. The mean heavy metal concentrations in the type A, B and C organisms were Cr: 18, 18 and 24 mg/kg, respectively, Ni: 9.2, 10 and 12 mg/kg, respectively, Cu: 8.4, 19 and 29 mg/kg, respectively, and Pb: 11, 9.8 and 7.1 mg/kg respectively. The bioconcentration factors showed that the abilities of the organisms to accumulate Cr, Ni and Pb decreased in the order type A, type B, then type C, but their abilities to accumulate Cu increased in that order. The Ni concentration was a good predictor of Cr, Cu and Pb accumulation by all three periphyton types. Our study shows that heavy metal accumulation by periphyton is associated with eutrophication in the rivers in the HRB. [ABSTRACT FROM AUTHOR]

Abstract: The Haihe Basin is in an area of high population density and rapid economic development, and is one of the most polluted river basins in China. Examination of heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) in overlying waters and surface sediments in rivers was conducted in the basin's seven watersheds. Cd concentrations of overlying river waters exceeded Chinese environmental quality standard values for surface water (>0.010mg/L) at 90% of stations. In surface river sediments, average concentrations of Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn in the basin were 0.364, 13.4, 81.9, 53.3, 435, 27.8, 20.0 and 256mg/kg, respectively. Cd, Zn and Cu were the most anthropogenically enriched elements, as indicated by enrichment factor (EF) values>1.5; EF values were highest for these metals in the Zi Ya He (ZYH) and Zhang Wei He (ZWH) watersheds. Cd in surface river sediments showed a high potential ecological risk (PER) in the ZYH and ZWH watersheds. The comprehensive PER due to all studied metals was high at many stations, especially in the ZYH and ZWH watersheds. The results indicate that heavy metal contamination in the rivers of the Haihe Basin should be considered when developing basin management strategies for protecting the aquatic environment. [Copyright &y& Elsevier]

Abstract: In this study, the source and risk associated with heavy metals in the estuarine sediments of Chaohu Lake Valley in East China were studied. The results demonstrated that most metal contents (Cd, Pb and Zn) increased continuously from 0.21, 8.05 and 73.76mg/kg in the substrate to 0.33, 17.20 and 100.22mg/kg in the surface sediments on average, respectively, in all ten estuaries evaluated. In addition, the high proportion of chemically reactive forms of Cd (18.10–33.60%) implied a moderately high risk, while the risk associated with Pb and Zn was moderate in most estuaries. Enrichment factor (EF) and cluster analysis (CA) were conducted to assess the metal sources. The EF values of Cd, Pb and Zn (4.96, 3.68 and 2.25, respectively) indicated that they had accumulated in the estuarine sediments. Additionally, CA suggested that their primary sources were anthropogenic, namely the extensive use of fertilizers. Therefore, heavy metal pollution due to agricultural intensification in Chaohu Lake Valley should be taken into account during the formation of valley management strategies for the water environment. [Copyright &y& Elsevier]

This study was conducted to assess heavy metals in the overlying water and sediments of Luhun Reservoir, Henan Province, China, which is positioned downstream from a molybdenum (Mo) mining area. The pollution indexes indicated that deposition of all metals may have been affected by the mining area. The single element pollution factor (P i) of Mo was the highest among all heavy metals, with a mean value of 2.05. However, the sediments were subject to long-term accumulation of metals, particularly Mo, Cd, Pb, and Zn, which originated from anthropogenic sources. The mean individual element potential ecological risk index values for Cd were above 385, while the mean value comprehensive potential ecological risk index was 465, which indicates a high ecological risk. Moreover, the enriched heavy metals had different spatial distributions in the Luhun Reservoir sediments. Finally, Pearson correlation analysis indicated that the Pb was mainly affected by different anthropogenic sources and had no relationship with other metals, which suggests that the influence of mining area on heavy metal concentrations in the reservoir is difficult to disentangle. • Heavy metal pollution was assessed in a downstream reservoir of mining area. • Mo was the main pollutant in the overlying water of the reservoir. • Many metals in the sediments of the reservoir have a long-term accumulation. • Heavy metal risk resulting from mining should be of great concern. [ABSTRACT FROM AUTHOR]

Food security and human health can be seriously affected by heavy metal and metalloid (HM) pollution of soil. In this study, the risks posed by HMs and microbial community responses to HM pollution of agricultural soil in southwestern China were investigated. The C, N, P, and S (nutrients) concentrations were 12040.7–15912.7, 1298.06–1832.01, 750.91–2050.35, and 269.17–2115.52 mg/kg, respectively. The As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn concentrations were 3.11–8.20, 1.85–6.56, 22.83–43.96, 11.21–23.30, 0.08–0.81, 11.02–22.97, 24.07–42.96, and 193.63–698.39 mg/kg, respectively. Interpolation analysis indicated that the nutrient and HM concentrations varied spatially rather strongly. The concentrations of all of the elements were higher in soil from the northern sampling sites than in soil from the other sites. HMs in soil were found to pose high levels of risk (RI 898.85, i.e., >600). Cd contributed more than the other HMs to the risk assessment values (Er Cd 293.72–1031.94), so was the most serious contaminant. Microbial diversity decreased over time in soil with high HM concentrations (plot S2) and was lower than in soil with low HM concentrations (plot S8). The nutrient and HM concentrations correlated with the microbial community characteristics. Proteobacteria, Acidobacteria, and Chloroflexi were (in decreasing order) the dominant bacterial phyla. We speculate that these phyla may be strongly resistant to HMs. The fourth most common phylum was Actinobacteria. Bacteria in this phylum could be used as biological indicators of the HM pollution status. Soil micro-ecosystems can self-regulate. HM stress will affect the evolution of soil microorganisms and relevant functional genes. The spatiotemporal variability in the microbial community responses to HMs and the spatial analysis and ecological risk assessment results will be useful reference data for the remediation of HM-polluted soil. • Cd is the main priority pollutant and poses the strongest risks. • Plots with higher Cd concentrations had less microbial diversity. • The dominant Proteobacteria and Acidobacteria were resistant to heavy metals. • Heavy metal stress affects soil microorganism evolution and relevant functional genes. [ABSTRACT FROM AUTHOR]

It is important to understand the potential bioavailability of heavy metals in the sediments of land-freshwater interfaces (between terrestrial and aquatic ecosystems). Therefore, we evaluated the pollution of Cr, Ni, Cu, Zn, As, and Cd in land-freshwater interface sediments/soils according to total concentrations, and used sequential extraction method to measure different fractions of Cd. Then, the diffusive gradients in thin films (DGT) technique was employed to study the potential bioavailability of metals. Results showed that the concentrations of exchangeable and weak acid soluble fraction and oxidizable fraction were higher in ecotone area, and the values of reducible fraction and residual fraction were higher in deep water area. There existed significant positive correlations between [Cd]-DGT (concentration of Cd measured by DGT) and EXC-Cd (exchangeable and weak acid soluble fraction of Cd) (r 2 = 0.65), but the significant negative correlation was found between [Cd]-DGT and RES-Cd (Residual fraction of Cd) (r 2 = 0.52). DGT technique is a feasible method to measure potential bioavailability of heavy metals for risk assessment in the sediments/soils of land-freshwater interfaces. [ABSTRACT FROM AUTHOR]

Phyllostachys pubescens (PP) biochars produced under a low oxygen pyrolysis atmosphere (oxygen content 1–4%) were prepared as sorbents for investigating the mechanisms of cadmium and lead sorption. A low-oxygen pyrolysis atmosphere increased biochar ash and specific surface area, promoting heavy metal precipitation and complexation. The maximum sorption capacity (Q m ) of Pb 2+ obtained from the Langmuir model was 67.4 mg·g −1 , while Q m of Cd 2+ was 14.7 mg·g −1 . The contribution of each mechanism varied with increasing oxygen content at a low pyrolysis temperature. Mineral precipitation with Pb 2+ was the predominant mechanism for Pb 2+ removal and the contribution proportion significantly increased from 17.2% to 71.7% as pyrolysis oxygen atmosphere increased from 0% to 4%. The results showed that cadmium sorption primarily involved coordination with π electrons, at 54.1–82.6% of the total adsorption capacity. The PP biochar shows potential for application in removing heavy metal contaminants, especially Pb 2+ . [ABSTRACT FROM AUTHOR]

Ultra-high content of heavy metals (UHHMs) poses a threat to soil health and agricultural products safety, in turn causing harm to human health through the food chain. Phytoremediation has proven to be an effective technique for restoration of soil contaminated with a single or several conventional content of heavy metals, whereas the effectiveness of phytoremediation for UHHMs-contaminated soil is unclear. In this study, we investigated the effectiveness of phytoremediation for UHHMs-contaminated soil and the role of soil microbes in the process of phytoremediation. Results showed that the Sedum alfredii grew well in UHHMs-contaminated soil, although the shoot height, biomass, and accumulation of heavy metals were slightly reduced due to the stress of UHHMs. Soil microbiome analysis demonstrated that both the number and diversity of microbes decreased in UHHMs-contaminated soil. However, the dominant species Patescibacteria proliferated to varying degrees under the exposure of various UHHMs. Patescibacteria is closely related to the functional genes regarding transport of various heavy metals. Given that Patescibacteria exhibits a strong migration ability in soil, it is likely involved in the transport of various heavy metals from the bulk soil to the rhizosphere. This enhanced the availability of heavy metals in the rhizosphere, which in turn improved the phytoremediation efficiency of the Sedum alfredii. This was further confirmed by structural equation modeling analysis and microbial phenotypes prediction. Findings suggest that using Sedum alfredii to remedy UHHMs-contaminated soil is feasible owing to the facilitation by soil microbes. • Sedum alfredii grew healthy in UHHMs-contaminated soil. • Phytoremediation efficiency was not significantly affected by UHHMs stress. • Patescibacteria proliferated greatly under UHHMs stress. • Patescibacteria was involved in the transport of heavy metals in soil. • Microbes in UHHMs-contaminated soil contained more mobile elements. [ABSTRACT FROM AUTHOR]

The pollution of Baiyangdian Lake (BYDL) has been of concern since the Xiongan New Area was established. To conduct ecological restoration of BYDL, the heavy metals (HMs) levels in sediments were assessed. Specifically, Surface sediments (0–10 cm) samples in BYDL were analyzed for Cd, Cr, Cu, Ni, Pb and Zn in October 2016 to evaluate the risk posed by trace metals, as well as their bioavailability and toxicity. The results demonstrated that HMs showed high pollution and risk levels in most sample sites as a result of Cd and Pb. Metals speciation analysis demonstrated that Cd, Cu, Pb and Zn were dominated by non-residual fractions that originated from anthropogenic sources and presented higher bioavailability. The risk assessment code indicated that Cd poses a medium level biological risk in BYDL, which reached 10.25% and 29.38%. The bioavailable metals index showed a strong correlation with acute toxicity (R 2  = 0.704), indicating bioavailable metals are an important reason for sediment acute toxicity. Canonical correspondence analysis demonstrated that HMs have a coercive effect on the distribution of benthic invertebrates. Overall, the results indicate that HMs pollution should be considered during the development of strategies for ecological restoration in BYDL. [ABSTRACT FROM AUTHOR]