Geochemical baseline establishment and pollution source determination of heavy metals in lake sediments: A case study in Lihu Lake, China

Non-negligible roles of upstream rivers in determining the antibiotic resistance genes community in an interconnected river-lake system (Dongting lake, China)

Emergence and spread of antibiotic resistance genes (ARGs) in lakes have been considered as a global health threat. However, a thorough understanding of the distribution patterns and ecological processes that shape the ARGs profile in interconnected river-lake systems remains largely unexplored. In this study, we collected paired water and sediment samples from a typical interconnected river-lake system, Dongting Lake in China, during both wet and dry seasons. Using high-throughput quantitative PCR, we investigated the spatial and temporal distribution of ARGs and the factors that influence them. A total of 8 major antibiotic classes and 10 mobile genetic elements were detected across the Dongting Lake basin. The unique hydrological characteristics of this interconnected river-lake system result in a relatively stable abundance of ARGs across different seasons and interfaces. During the wet season, deterministic processes dominated the assembly of ARGs, allowing environmental factors, such as heavy metals, to serve as main driving forces of ARGs distribution. When the dry season arrived, variations in hydrological conditions and changes in ARGs sources caused stochastic processes to dominate the assembly of ARGs. Our findings provide valuable insights for understanding the ecological processes of ARGs in interconnected river-lake systems, emphasizing the necessity of upstream restoration and clarifying river-lake relationships to mitigate ARGs dissemination.

Quantification of heavy metal contamination and source in urban water sediments using a statistically determined geochemical baseline

Geochemical baselines (GBs) play a crucial role in discerning natural variability from anthropogenic impacts on elemental composition within the environment. However, their applicability in quantifying the contribution of pollution sources to heavy metal contamination in sediments remains understudied. This research aimed to assess the degree of contamination and local pollution source attribution by leveraging geochemical baselines derived from statistical techniques, specifically the relative cumulative frequency (RCF) and 2σ-iterative (2σ-I) methods. In the urban water systems of Ma'anshan City, the major iron ore centre in eastern China, we observed concentration ranges of Cr, Cu, Ni, Pb and Zn in 36 sediment samples ranging from 66.89 to 352.08 mg/kg, 22.01 to 133.37 mg/kg, 22.66 to 50.80 mg/kg, 14.66to 264.37 mg/kg and 73.30 to 2707.46 mg/kg, respectively. RCF and 2σ-I techniques yielded similar GBs with no significant differences (p > 0.05). The geo-accumulation index and contamination factor analysis showed a sediment heavy metal accumulation rank of Zn > Pb > Cr > Cu > Ni. The contribution percentage of pollution sources varied with land functional type of watershed. For industry-influenced sediments, the contribution of local sources to Cr, Cu, Pb and Zn was significant, with shares of 43%-88%. Overall, this study highlights the valuable insights provided by GBs for effective management of urban aquatic environments.

Geochemical baseline establishment and accumulation characteristics of soil heavy metals in Sabaochaqu watershed at the source of Yangtze River, Qinghai-Tibet Plateau

The establishment of soil geochemical baseline and heavy metal pollution assessment in the Qinghai-Tibet Plateau is of great significance for guiding environmental management in the high-cold and high-altitude regions. A total of 126 topsoil samples (0-20 cm) were collected and the contents of Cu, Pb, Zn, Ni, Cr, Cd, As and Hg were determined in the Sabaochaqu basin of the Tuotuo River, the source of the Yangtze River, in the Tibetan Plateau. The baseline values of 8 heavy metals were determined by mathematical statistics, iterative 2times standard deviation method, cumulative frequency and reference element standardization, and the soil heavy metal pollution in the study area was assessed by enrichment factor method and pollution index method. The results showed that the average contents of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn were 31.84, 0.29, 66.07, 17.35, 0.021, 27.86, 49.35 and 88.56 mg/kg, respectively. Baseline values were 22.24, 0.217, 64.16, 15.69, 0.0191, 26.46, 34.91, and 68.62 mg/kg, respectively. There is a great difference between the baseline value of soil heavy metals in study area and the Xizang soil background value, especially the baseline value of Cd was 2.68 times of its background value. The results of the pollution evaluation based on the baseline values showed that the 8 heavy metals were slightly enriched, and the overall pollution status was light pollution, and measures should be taken to control and manage them. The research results can provide a reference value for the evaluation of soil heavy metal pollution in the source region of the Yangtze River, and also provide a theoretical basis for the construction of soil heavy metal baseline values in similar high-cold and high-altitude regions.

The environmental capacity of rare heavy metal calculation in the Qinghai‒Tibet Plateau region via multifractal analysis

Accurate assessments of the soil environmental capacity are important for evaluating heavy metal pollution levels, facilitating effective prevention and control measures against such pollution. However, due to the lack of risk screening values for certain key elements, such as Rb, Sn, and Th, the assessment of the soil environmental capacity is not comprehensive. Therefore, in this study, the Menyuan-Huangzhong area of Qinghai Province was selected as the research area, and local background and risk values were established via multifractal analysis, thereby systematically examining the environmental capacity. The findings indicated that within the study area, the static environmental capacity values of 15 elements could be ranked as follows: Ba, Cu, Zn, Cr, Rb, Ni, La, Pb, Th, As, U, Sn, Tl, Cd, and Hg. In general, the residual capacity distribution of the various elements varied across the study area, with lower values primarily found in the northern and central regions and higher values obtained in the northwestern and southwestern regions. Between 2018 and 2068, there was a notable and rapid decline in the dynamic environmental capacity of Hg, Cu, and Cd in the study area. In the Menyuan-Huangzhong area of Qinghai, the average comprehensive soil environmental capacity index reached 0.91, indicating a moderate environmental capacity and slight associated health risks. The findings of this study could serve as a valuable reference for soil heavy metal pollution assessment, early warning, and management in this area; enhance the study of soil environmental capacity methods; and provide a theoretical foundation for subsequent research.

Comprehensive review on toxic heavy metals in the aquatic system: sources, identification, treatment strategies, and health risk assessment

Heavy metal pollution in water sources has become a major worldwide environmental issue, posing a threat to aquatic ecosystems and human health. The pollution of the aquatic environment is increasing as a result of industrialization, climate change, and urban development. The sources of heavy metal pollution in water include mining waste, leachates from landfills, municipal and industrial wastewater, urban runoff, and natural events such as volcanism, weathering, and rock abrasion. Heavy metal ions are toxic and potentially carcinogenic. They can also buildup in biological systems and cause bioaccumulation even at low levels of exposure, heavy metals can cause harm to organs such as the nervous system, liver and lungs, kidneys and stomach, skin, and reproductive systems. There were various approaches tried to purify water and maintain water quality. The main purpose of this article was to investigate the occurrence and fate of the dangerous contaminants (Heavy metal and metalloids) found in domestic and industrial effluents. This effluent mixes with other water streams and is used for agricultural activities and other domestic activities further complicating the issue. It also discussed conventional and non-conventional treatment methods for heavy metals from aquatic environments. Conclusively, a pollution assessment of heavy metals and a human health risk assessment of heavy metals in water resources have been explained. In addition, there have been efforts to focus on heavy metal sequestration from industrial waste streams and to create a scientific framework for reducing heavy metal discharges into the aquatic environment.

Application of the partial least square regression method in determining the natural background of soil heavy metals: A case study in the Songhua River basin, China

The "background" is an essential index for identifying anthropogenic inputs and potential ecological risks of soil heavy metals. However, the lithology of bedrock can cause significant spatial variation in the natural background of soil elements, posing considerable difficulties in estimating background values. In this study, an attempt was made to calculate the natural background through regression analysis of soil chemical composition, and reasonably evaluate the impact of lithology. A total of 1771 surface soil samples were collected from the Songhua River Basin, China, for chemical composition analysis, and the partial least square regression (PLSR) method was employed to establish the relationship between heavy metals (As, Hg, Cr, Cd, Pb, Cu, Zn, and Ni) and soil chemical composition/environmental parameters (SiO2, Al2O3, TFe2O3, MgO, CaO, K2O, Na2O, La, Y, Zr, V, Sc, Sr, Li and pH). The result shows that As, Cr, Pb, Cu, Zn, and Ni have significant linear relationships with soil chemical composition. Each of these six heavy metals obtained 1771 regression background values; some were higher than the uniform background value obtained from the boxplot, while others were lower. The regression background values recognized not only subtle anthropogenic inputs and potential ecological risks in low-background regions but also spurious contamination in high-background areas. All these indicate that the PLSR method can effectively improve the determination accuracy of the natural background of soil heavy metals. More attention should be paid to the serious anthropogenic inputs appearing in some places of the study area.

Applying new regional background concentration criteria to assess heavy metal contamination in deep-sea sediments at an ocean dumping site, Republic of Korea

It is crucial to establish appropriate background concentrations to discern heavy metal pollution in the marine environment. In this study, we analyzed heavy metals in deep-sea sediment cores to determine regional background concentrations at the East-Sea Byeong Ocean dumping site. The vertical profiles of heavy metals were categorized into three groups based on their contamination characteristics, and regional background levels for 12 metals were determined using pre-1900 averages. The enrichment factor, contamination factor, and pollution load index, calculated using regional background concentrations, indicated significant contamination by Cr, Co, Cu, Zn, Cd, Hg, and Pb during the ocean dumping period. These results differ from those obtained using global average concentrations. This underscores the importance of considering regional characteristics to minimize the risk of misinterpreting anthropogenic impacts. The approach based on local information is considered useful when sediment quality guidelines are absent or inapplicable.

Differentiating environmental scenarios to establish geochemical baseline values for heavy metals in soil: A case study of Hainan Island, China

Soil heavy metal distributions exhibit regional heterogeneity due to the complex characteristics of parent materials and soil formation processes, emphasizing the need for appropriate regional standards prior to assessing soil risks. This study focuses on Hainan Island and employs the Multi-purpose Regional Geochemical Survey dataset to establish heavy metal geochemical baseline and background values for soil using an iterative method. Geographical detector analysis reveals that parent materials are the primary factor influencing heavy metal distribution, followed by soil types and land use. Heavy metal geochemical baseline values are established for the island's three environments and administrative regions. Notably, a universal geochemical baseline value cannot adequately represent regional variations in heavy metal distribution, with parent materials playing a crucial role in various scenarios. Locally applicable values based on parent material are the most representative for Hainan Island. This study provides a reference framework for developing region-specific environmental baseline values for soil heavy metal assessments.

Distribution, sources, and risk analysis of heavy metals in sediments of Xiaoqing River basin, Shandong province, China

The accumulation of heavy metals in river sediment poses a major threat to ecological safety. The Xiaoqing River originates in western Jinan, with higher population density and per capita gross domestic product (GDP) in its basin compared to the Shandong province average. This study analyzed the spatial characteristics, ecological risk, human health risk, and contamination sources of heavy metals by collecting sediment samples from Xiaoqing River. We use the methods such as geo-accumulation index (Igeo), ecological risk assessment based on the interval number sorting method, and health risk assessment to evaluate the risk of heavy metals in sediments. The research finding suggests heavy metals including Pb, As, Ni, and Cr are low ecological risks, while Hg and Cd have reached high and extreme ecological risks. Correlation analysis and principal component analysis were used to analyze the correlation and sources of different heavy metals. The six heavy metals were categorized into three groups. Factor 1, comprising Hg, Cr, and Pb, was identified as a mixed source with a contribution rate of 37.76%. Factor 2 is an agricultural source and comprises Ni, Cd, and As with a contribution rate of 27.05%. Factor 3 includes Pb and Ni contributing to 15.30% as a natural source. This study offers valuable insights for the prevention of heavy metal pollution, as well as promoting sustainable urban development.

Coastal sediment heavy metal(loid) pollution under multifaceted anthropogenic stress: Insights based on geochemical baselines and source-related risks

Contamination and risk assessments generally ignore the potential bias in results caused by the variation of background values at different spatial scales due to the spatial heterogeneity of sediments. This study aims to perform quantitative source-ecological risk assessment via establishing geochemical baselines values (GBVs) of heavy metal(loid)s (HMs) in Daya Bay, China. Cumulative frequency distribution (CFD) curves determined the GBVs of 12.44 (Cu), 30.88 (Pb), 69.89 (Zn), 0.06 (Cd), 47.85 (Cr), 6.80 (As), and 0.056 mg kg-1 (Hg), which were comparable to the background values of Guangdong Province surface soils, and implied a potential terrestrial origin of the coastal sediments. Principal component analysis (PCA) and positive matrix factorization (PMF) identified three sources (F1: natural processes; F2: anthropogenic impacts; F3: specific sources) with contributions of 51.7%, 29.2%, and 19.1%, respectively. The source-specific risk assessment revealed an ecological risk contribution potential of 73.8% for the mixed anthropogenic sources (F2 + F3) and only 26.2% for natural processes. Cd and Hg were the priority management of metallic elements, occupying 63.5% and 72.5% of the contribution weights of F2 and F3, respectively, which showed multi-level pollution potentials and ecological risk levels. The spatial distribution patterns demonstrated the hotspot features of HM pollution, and priority concerns should be given to the management of marine traffic and industrial point source pollution in Daya Bay. The results of the study provide a scientific approach and perspective for pollution treatment and risk management in the coastal environment.

Non-Negligible Ecological Risks of Urban Wetlands Caused by Cd and Hg on the Qinghai-Tibet Plateau, China

The Huangshui National Wetland Park (HNWP) is a unique national wetland park in a city on the Qinghai-Tibetan Plateau, containing three zones: Haihu, Beichuan, and Ninghu. In this study, a total of 54 soil samples (18 sampling points with depths of 0-10 cm, 10-20 cm, and 20-30 cm) were collected in these three zones, and the contents of heavy metals (Cr, Cd, Cu, Hg, Ni, Pb, Zn, and As) of each sample were determined. The ecological risk of eight kinds of heavy metals was evaluated by using the geo-accumulation index (Igeo), and the ecological risk-controlling effect of the Xining urban wetlands on heavy metals was explored by comparative analysis, and the possible sources of heavy metals in the soil were analyzed via correlation analysis and principal component analysis (PCA). The results revealed that the total heavy metal concentration order was Haihu > Beichuan > Ninghu zone. As and Cu presented vertical accumulation characteristics in the surface and lower horizon, respectively. Cr, Cd, Hg, Ni, Pb, and Zn accumulated downwards along the depth. On the spatial scale, the enrichments of Cd and Hg brought non-negligible ecological risks in plateau urban wetlands. The results of PCA indicated that soil heavy metals mainly came from compound sources of domestic and atmospheric influences, traffic pollution sources, and industrial pollution sources. The study has revealed that human activities have inevitable negative impacts on wetland ecosystems, while the HNWP provides a significant weakening effect on heavy metal pollution.

Metal-mining-induced sediment pollution presents a potential ecological risk and threat to human health across China: A meta-analysis

Aquatic sediment polluted by potentially toxic elements (PTEs) from mining activities represents a potential health "time bomb" for humans and the local ecology, but the integrated analysis of pollution and hazards of PTEs in sediment around typical metal mines in China is limited. Presently, the associated pollution status, spatial distribution, and ecological and health hazards of Cd, Cu, Zn, Pb, Cr, and As were investigated through index evaluation, spatial analysis, health risk assessment models, and Monte Carlo simulation. Overall, the sediment exhibited varying degrees of PTE contamination; notably, the level of Cd was 104.85 times higher than its background value, and it became the most enriched element in the surveyed sediment, followed in descending order by Cu, As, Zn, Pb, and Cr. Nationally, over 64.5% of metal-mining-affected sediment presented a very high ecological risk, contributed mostly by Cd (43.2%-98.7%) followed by As, Pb, and Cu; the risk contributed by both Cr and Zn was found to be negligible. The adverse health risk posed to children by most sediment was 1.72 and 6.46 times higher than that posed to adults for cancerous and noncancerous risks, respectively. The potential noncarcinogenic risks were mainly caused by As, which contributed over 78.9% of the Hazard Index values, then followed by Pb (>9.3%). For both children and adults, the carcinogenic risk of PTEs decreased in the following order: As > Cd > Cr > Pb. The investigated sediment was found seriously affected by nearby metal mines, especially those in regions with long-term and large-scale nonferrous-metal-mining activities. This study could provide a reference for policymakers to develop control strategies for PTE pollution in sediment around mining areas.

Source apportionment and source-specific risk evaluation of potential toxic elements in oasis agricultural soils of Tarim River Basin

As rapidly developing area of intensive agriculture during the past half century, the oases in the source region of the Tarim River have encountered serious environmental challenges. Therefore, a comparative analysis of soil pollution characteristics and source-specific risks in different oases is an important measure to prevent and control soil pollution and provide guidance for extensive resource management in this area. In this study, the concentration of potential toxic elements (PTEs) was analyzed by collecting soil samples from the four oases in the source region of the Tarim River. The cumulative frequency curve method, pollution index method, positive matrix factorization (PMF) model, geographical detector method and health risk assessment model were used to analyze the pollution status and source-specific risk of potential toxic elements in different oases. The results showed that Cd was the most prominent PTE in the oasis agricultural soil in the source region of the Tarim River. Especially in Hotan Oasis, where 81.25% of the soil samples were moderately contaminated and 18.75% were highly contaminated with Cd. The PTEs in the Hotan Oasis corresponded to a moderate level of risk to the ecological environment, and the noncarcinogenic risk of soil PTEs in the four oases to local children exceeded the threshold (TH > 1), while the carcinogenic risk to local residents was acceptable (1E-06 < TCR < 1E-04). The research results suggested that the Hotan Oasis should be the key area for soil pollution control in the source region of the Tarim River, and agricultural activities and natural sources, industrial sources, and atmospheric dust fall are the priority sources that should be controlled in the Aksu Oasis, Kashgar Oasis and Yarkant River Oasis, respectively. The results of this study provide important decision-making support for the protection and management of regional agricultural soil and the environment.

Distribution and ecological risk assessment of heavy metals in sediments of Dajiuhu Lake Wetland in Shennongjia, China

The rapid development of modern society has resulted in discharge of large, heavy metal quantities into wetlands that have been continuously accumulating, causing severe pollution. Dajiuhu, located in the Shennongjia Forest District of Hubei Province in China, is a wetland of significant value internationally, serving as a model wetland ecosystem with heightened scientific research value. In this study, 27 surface sediment samples from nine sub-lakes in Dajiuhu were collected in August 2020. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the sediments were determined. The heavy metal occurrence and speciation characteristics were analyzed by an improved BCR (European Community Bureau of Reference) extraction method. Four methods were used to evaluate heavy metals' pollution degree and ecological risk. The possible source of heavy metals was inferred using correlation analysis and principal component analysis. The heavy metal content in the lake sediments of Dajiuhu wetland was from the highest to the lowest concentration as follows: Zn [Formula: see text] Cr [Formula: see text] Ni [Formula: see text] Pb [Formula: see text] Cu [Formula: see text] Cd. The average Cd content exceeded the national nature reserve threshold values, while the other heavy metals measured were below their respective threshold values. However, due to the occurrence of Pb and Cd in different forms, they still pose certain pollution and ecological risk to the lake wetlands. On the other hand, Zn, Cr, Ni, and Cu do not pose an ecological risk in the lakes of the Dajiuhu wetland. The spatial distribution of heavy metal content in the nine sub-lakes did vary significantly. Regarding the heavy metal sources in the lake sediments, Ni, Cr, and Cu originate from natural factors, and Cd and Pb have mainly anthropogenic origins. In contrast, Zn has both natural and anthropogenic origins. This study provides further insights into the study of heavy metal pollution in lake wetlands. It provides a framework and a direction for managing heavy metal pollution in the Dajiuhu wetland.

Sources and trends of trace elements and polycyclic aromatic hydrocarbons in a shallow lake in the Mediterranean area from sediment archives of the Anthropocene

In this study, the anthropogenic contamination in Trasimeno lake (Central Italy) was investigated using three sediment cores spanning over the last 150 years (Anthropocene) to identify the primary sources of pollution and quantify the level of contaminant enrichment in the basin. First, based on the relative cumulative frequency and linear regression methods, we obtained a geochemical baseline for the lake using the deeper parts of the sediment cores. The geochemical baseline allowed us to determine the values of trace elements enrichment factors. On this knowledge, as a second result, we were able to reconstruct the natural sources and the anthropogenic impact on the lake with a biennial resolution. This goal has been obtained by combining different inorganic and organic chemical proxies such as trace elements, polycyclic aromatic hydrocarbons, and lead isotope ratios and exploiting both principal component and factor analysis to associate chemical proxies to human-driven contamination processes. Five different groups of elements have been identified, one of which is of natural origin and four of anthropogenic origin. In particular, it was possible to identify the times and impacts of the industrial activities during the Second World War, which dispersed heavy metals in sediments. Moreover, we found evidence of the recent human activities that have characterized the surroundings of the basin, such as Pb inputs related to the use of gasoline and the enrichment of certain elements generally used in agricultural activities (such as P, Cu, and Mn) due to the development of this sector in the last 40 years.

Spatial-temporal variations and pollution risks of mercury in water and sediments of urban lakes in Guangzhou City, South China

This study aims to investigate the spatial and temporal characteristics, pollution degrees, and potential ecological risks of mercury (Hg) in urban lake waters and sediments in Guangzhou, where is a typical area of Hg emission and population-economic-industrial concentration in South China. In different districts of this city, the water from 15 lakes were collected continuously from June 2020 to May 2021, and the sediments from 9 lakes were collected in 2015 and 2021. The seasonal changes of Hg concentration (Hg-C) in the water were found to be high in winter and low in summer. The spatial distribution of Hg-C in sediments showed that it was high in urban central areas and low in suburbs. The Nemero index and geological accumulation index showed that there were uncontaminated of Hg in the collected lake water, and above moderately contaminated in the lake sediments in urban center, respectively. The Hg pollution potential ecological risk index showed that there was low risk in the collected water, high and extremely high risk in the lake sediments in urban center, respectively. The principal component analysis (PCA) and correlation analysis (CA) of Hg and meteorological factors showed that precipitation, temperature, and vapor pressure had negative effects on the seasonal changes of Hg-C in water, and air pressure and wind direction had positive effects. The PCA and CA of Hg and other geochemical elements showed that anthropogenic emissions may be the main sources of Hg in sediments, which was also supported by the data of population density, road density, and motor vehicles per 1000 people. This study provided a reference for urban lake pollution treatment, resident health, and ecological environment protection.

Enhanced dewaterability of lake dredged sediments by electrochemical oxidation of peroxydisulfate on BDD anode

Dredged sediments, as a product of mitigating endogenous pollution of rivers and lakes, cause severe environmental pollution without suitable disposal. To reduce dredged sediments, the electrochemical oxidation (EO) of peroxydisulfate (PS) on a boron-doped diamond (BDD) anode (EO/BDD-PS) was utilized to enhance the dewaterability of the dredged sediments. The soluble chemical oxygen demand increased in the EO/BDD-PS system, and more than 70.0% of the specific resistance to filtration was reduced by EO/BDD-PS within 20 min. The optimal conditions were determined to be as follows: current density, 30 mA cm^-2; PS dosage 4 g L^-1; and initial pH, 6.96. After treatment with EO/BDD-PS, the electronegativity of the sludge flocs was alleviated and the particle size increased from 7.61 to 10.64 μm. Furthermore, proteins and polysaccharides were degraded, and tightly bound extracellular polymeric substances (TB-EPS) and loosely bound EPS (LB-EPS) were effectively transported to soluble EPS (S-EPS). Furthermore, humification of organic matter occurred in S-EPS and LB-EPS when the dredged sediment was treated with EO/BDD-PS. Dominant hydroxyl radicals (•OH) and sulfate radicals (SO₄•^-) were generated in the EO/BDD-PS system. Moreover, the efficiency of the filtrate as an electrolyte decreased slightly after recycling five times. Therefore, this method may be economical for enhancing the dewaterability of dredged sediments.

Multiple Risk Assessment of Heavy Metals in Surface Water and Sediment in Taihu Lake, China

Taihu Lake is the third-largest freshwater lake in eastern China. The contamination of heavy metals (HMs) in Taihu Lake resulting from rapid economic development and population growth has raised significant concerns in recent years. In this study, the contents and spatial distributions of eight typical HMs (Hg, Cr(VI), As, Cd, Cu, Ni, Pb, and Zn) in the fresh surface water and sediments from Taihu Lake were investigated. The potential ecological and health risks posed by HMs were evaluated using multiple assessment methods. Risk quotients were used to assess the ecological risks of HMs, and chronic risk quotients of Cu, Ni, and Pb (>1.0) were found in the surface water of Taihu Lake. According to the geo-accumulation index (I_geo) and pollution load index (PLI) values, the lake sediments exhibited moderate risks of Cd and Hg. In general, the sediments were moderately contaminated by HMs based on the average risk index (RI < 300). Spatially, a high ecological risk posed by the HMs existed in the sediments of northern Taihu Lake (RI > 300), while the sediments in the southwestern and eastern regions had moderate risk levels. The non-carcinogenic risk levels of Hg, Cd, Cu, and Zn were acceptable based on the exposure characteristics of residents living around Taihu Lake. The carcinogenic risk levels of Cr(VI), As, Pb, and Ni through drinking water were acceptable. However, the ingestion of Cr(VI), As, and Ni through drinking water and fish consumption may pose certain health risks. Therefore, the levels of toxic metals, in particular, Cr(VI), As, and Ni, in edible organisms should be monitored periodically and controlled to alleviate the potential carcinogenic risks through food ingestion. Our work provides valuable information concerning the ecological risk distribution of HMs in Taihu Lake, which is essential for protecting the safety of aquatic organisms and human health and minimizing HM pollution in the lake.

Analysis and potential ecological risk assessment of heavy metals in surface sediments of the freshwater ecosystem in Zhenjiang City, China

Heavy metals contamination in freshwater ecosystems has drawn attention worldwide. It is necessary to investigate heavy metals content and assess their ecological risk in order to protect the aquatic ecosystems. In this study, we collected surface sediment samples from the freshwater ecosystem of the city of Zhenjiang, in China, in both winter and summer. Then, we analyzed the seasonal and spatial distribution patterns of lead (Pb), chromium (Cr), cadmium (Cd), zinc (Zn), and copper (Cu). The contamination factor (CF), enrichment factor (EF), geo-accumulation index (Igeo), and potential ecological risk (Eri) were jointly used to assess the pollution degree and the ecological risk posed to the freshwater ecosystem by the aforementioned elements. Multivariate statistical analysis, including Pearson’s correlation and principal component analysis and cluster analysis, were used to identify potential sources of the investigated metals in this research area. Study results showed that: (1) the average concentrations values were 1.81 mg/kg and 1.15 mg/kg for Cd, 55.3 mg/kg and 62.2 mg/kg for Cu, 88.0 mg/kg and 52.5 mg/kg for Cr, 27.3 mg/kg and 22.8 mg/kg for Pb, 87.0 mg/kg and 271 mg/kg for Zn, in winter and summer, respectively. Amongst the investigated elements, the average concentrations of Cd, Cu, Cr, and Pb, were above the local background values in winter, whereas, Cd, Cu and Zn concentrations were higher than the background values in Zhenjiang; (2) The CF and EF indicated that Cd had a high contamination degree and a significant enrichment compare to others investigated metals in the surface sediment of in this research area. (3) Cd posed moderate, considerable, or very high ecological risks in different sites, while the other elements (i.e., Cu, Cr, Pb, and Zn) presented a low degree of ecological risk. (4) Multivariate statistical analyses results indicated Pb, Cu, and Zn had similar geochemical characteristics, while, Cd and Cr had significant differences with the above elements. Therefore, Pb, Cu, and Zn probably originate from the same sources, while Cd and Cr might have mixed sources, including both natural sources and human activities. Overall, more attention should be paid to Cd for risk assessment in the current study area. The findings of this study provide fundamental information for the evaluation and management of the heavy metals investigated in the freshwater ecosystem of Zhenjiang.

Research on the geochemical background values and evolution rules of lake sediments for heavy metals and nutrients in the Eastern China Plain from 1937 to 2017

For the first time, background quality guidelines have been developed for lake sediments along the Yangtze River. Evolution Rules of watershed environment in Eastern China were analyzed in 1937-2017. These methods of ¹³⁷Cs and ²¹⁰Pb radionuclide, 75% cumulative frequency, and background method were applied to calculate the sediment geochemical backgrounds (GB). The average GB values of Cu, Zn, Cd, Pb, Cr, total carbon (TC), total nitrogen (TN) and total phosphorus (TP) are 45.14 mg/kg, 86.99 mg/kg, 0.29 mg/kg, 33.71 mg/kg, 110.90 mg/kg, 17.20 mg/g, 1.60 mg/g, and 665.78 mg/kg, respectively. The radionuclide methods indicated that the sediment rate of 34 cm corresponding to 1963 is 0.63 cm yr^-1. The risk and accumulation of the sediment metals and nutrients in Yangtze Plain were uncontaminated levels before 1960, raised since 1980, and increased significantly in 2000. The Cd, TC, and TN in lake sediment were at low to moderate pollution, and few lakes are at high pollution. Sediment background values of the plain are different from soil background values in China and Consensus-Based Sediment Quality Guidelines in Europe/America. Results of sediment quality guidelines provide an important guidance for pollution prevention, environmental management, and risk assessment, especially the formulation of environmental laws.

Assessment of traces metals in sediment from Ebolowa Municipal Lake basin (central-africa): potential risk and provenance

This study focused on assessing contamination levels of heavy metal elements (Cr, Co, Ni, Zn, Cu, Mo, Cd, and Pb) in surface sediments for the Ebolowa Municipal Lake (EML) basin in Southern Cameroon and identifying possible pollution sources. Twenty-one samples from the EML and its tributaries (Mfoumou and Bengo'o) were subjected to geochemical analysis by inductively coupled plasma-mass spectrometry (ICP-MS). The results obtained from these analyses allowed us to calculate the Contamination factor (CF), enrichment factor (EF), geo-accumulation index (Igeo), Potential Ecological Risk Factor (Er), Pollution Load Index (PLI), and Potentiel Ecological Risk Index (RI). Multivariate statistics completed these analyses. The concentrations in mg/kg are as follows: Cr (96.46) > Zn (55.94) > Cu(34.01) > Ni(30.77) > Co(16.14) > Pb(10.58) > Mo (0.61) > Cd (0.14). However, these concentrations are higher in the sites subjected to the most anthropogenic pressure (EML and Mfoumou). The pollution indexes are between: 0.29 ≤ CF ≤ 2.76, -28.10 ≤ Igeo≤0.13, 0.14 ≤ EF ≤ 2.19. PLI values ˂ 1 in all sites. Er has high values for Cd (21.43–42.85) and low values for the other elements. RI ˂ 100 values for all elements and on all sites. Pearson's correlation matrix and the Hierarchical Classification Ascending (HCA) illustrate two sources of inputs. The spatial distribution of TME seems to be impacted by autochthonous inputs of domestic effluents and parameters such as particle size and organic matter content. The pollution index values illustrate low to moderate contamination and pollution in Cr, Ni, Co, Cd, and Cu. The Er values illustrate a moderate ecological risk for Cd. The RI values indicate a low ecological risk for all sites. High values are mainly associated with poor domestic waste management, non-compliant automotive buildings and agricultural activities.

Boundary Determination of Lake-Type Wetland Park Based on GIS Multifactor Analysis

One key carrier for wetland resource protection is wetland park, the main form of which includes lake-type wetland park. To determine the management and control boundary of lake-type wetland parks scientifically and reasonably is of great significance to the sustainable protection and utilization of wetland resources. From the perspective of landscape architecture, and landscape ecology, this paper studies the boundary determination of Changdang Lake National Wetland Park (the Park) based on satellite remote sensing information technology and GIS technology and in virtue of Analytic Hierarchy Process (AHP). In this study, 12 subindicators were selected from three levels including visual control, human geography, and ecological control. The weight of each indicator was determined by AHP, and then the influencing factors were transformed into graphic data by using GIS technology. Finally, the Park's boundary was determined by factor superposition analysis based on the weight. The research shows that the newly defined management and control boundary are about 340 sq.km, which effectively integrates the human and natural ecological resources around the lake area, makes the development of the surrounding areas harmonious, ensures the integrity of the lake area ecosystem, and facilitates the sustainable development of wetland resources.

Environmental capacity of heavy metals in intensive agricultural soils: Insights from geochemical baselines and source apportionment

Soil environmental capacity (EC) of heavy metals (HMs) can be used as an index to evaluate the pollution status of HMs and to provide basic data for HM remediation. However, the commonly used soil EC for HMs usually are prone to bias due to the lack of local background values (BVs) and the consideration of the contribution from various HM sources. Here, a modified method was proposed to estimate the soil EC by integrating the establishment of local BVs and the quantitative evaluation of contributions from HM sources in an intensive agricultural area of Shouguang city, China. The local BVs of HMs were established using the relative cumulative frequency distribution method. The source-specific EC was quantified based on the local BVs and the contributions of HM sources identified by receptor model and variable importance analysis. Results showed that the average BV values of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were 7.67, 0.10, 62.84, 21.17, 0.031, 28.38, 19.25, and 59.60 mg kg^-1, respectively, in the study area. The source-specific EC of Cd, Cu, Hg, and Zn were higher than their current EC, indicating an underestimation of soil capacity of HMs by the traditional method. The EC of HMs in these soils was generally medium indicated by their comprehensive EC index (PI) (PI >0.7), suggesting a low risk level of the targeted HMs. According to indexes such as the individual metal index (Pi) and enrichment factor (EF), special attention should be paid to Cd and Zn due to their low capacity (Pi <0.7) and high accumulation (EF > 2) in some points across this area. Altogether, our findings suggested that the modified method had a better capability for evaluating and predicting the enrichment status of soil HMs, which can be helpful for formulating the targeted measures to control HM pollution in such intensive agricultural areas.

Geochemical baseline establishment and pollution assessment of heavy metals in the largest coastal lagoon (Pinqing Lagoon) in China mainland

Establishing geochemical baselines and assessment of heavy metal pollution in lagoon sediments are critical for providing guidance to coastal zone environmental management. We analyzed heavy metals in high-resolution sediment cores from Pinqing Lagoon in South China, and defined the baselines of common pollution elements with a significant anthropogenic contribution. With these baselines, a spatiotemporal pollution assessment revealed Cu and Cd as the predominant pollution metals in both core and surface sediments, although the ecological risk level in the interior lagoon remained low during the past ~170 years. Surface sediment pollution status indicate a significant spatial difference. The findings from this typical coastal lagoon evidence a strong self-clean capacity attributable to the frequent water-mass-energy exchange between the lagoon and the sea. Furthermore, despite the significant impact by the sea, the geochemical baselines are close to the catchment soil backgrounds that can be defined using a paleolimnological approach.

Spatial-Temporal Variations, Ecological Risk Assessment, and Source Identification of Heavy Metals in the Sediments of a Shallow Eutrophic Lake, China

The contamination of heavy metals (Pb, Cr, Hg, Cd, Ni, Cu, Zn, As, and Sb) in the sediments were investigated in Lake Yangcheng, a eutrophic lake in China. Results showed that the average concentrations of each metal in the surface sediments generally exceeded their corresponding background values. Higher values were observed in deeper zones, supporting the retention and accumulation of heavy metals in the core sediments. The spatial distributions of metal averages, pollution load index (PLI), and combined ecological risk index (RI) revealed that ecological risks were highest in the west lake, followed by middle lake, and were lowest in the east section. For the temporal variations of metal contents, the highest concentration was usually observed in the winter. However, the seasonal dynamics of Hg showed a different pattern with higher values in the autumn and lower values in the winter. According to contamination factor (CF), the Hg and Sb contaminations were considerable, while the other metals were moderate contamination. In terms of geoaccumulation index (I_geo) values, sediments were moderately–heavily polluted by Sb and moderately polluted by Hg, Cd, and Ni. Meanwhile, Hg exhibited a considerable health risk, while Cd and Sb were moderate risks, based on single ecological risk index (Er) values. Significant positive correlations among heavy metals and principal component analysis (PCA) indicated that anthropogenic activities were major sources. The source of Sb might be different from other metals, with industrial discharge as the main loading. This study highlighted the urgency of taking measures to prevent Hg, Sb, and Cd pollutions in Lake Yangcheng, especially the west region of this lake.

Spatial-temporal variation, ecological risk, and source identification of nutrients and heavy metals in sediments in the peri-urban riverine system

A great deal of attention has been directed to the toxicity, enrichment, and accumulation of urban river sediment pollution. To understand the spatial-temporal variation, ecological risk and source of nutrients, and heavy metals in sediments from the Weihe River, the concentrations of total nitrogen (TN), total phosphorus (TP), organic matter (OM), and 10 heavy metals (Cd, Sb, As, Co, Cu, Pb, Ni, Cr, Zn, and Mn) in sediments at 14 sampling sites along the river were investigated. The results showed that nutrients and heavy metals had an interannual decreasing trend, and that the high-value regions were concentrated in urban locations within the study area. Ecological risk assessment results showed that TN was between the security level (no toxic effect) and the lowest level (tolerable for organisms), TP was at the lowest level, and OM was within the security level, all mainly from external sources. The geoaccumulation index (I_geo) and enrichment factor (EF) of 10 heavy metals were all within the unpolluted level, while the pollution load index (PLI) of 12 sampling sites had reached the moderate pollution level. The results of Pearson correlation, principal component analysis, and cluster analysis showed that heavy metals originated mainly from industrial and domestic sources, geochemical environments, and agricultural activities, indicating that heavy metals in the Weihe River sediments were influenced significantly by anthropogenic activities. The results are expected to provide a scientific basis for the development and utilization of the Weihe River water resources.

The spatial-temporal evolution of heavy metal accumulation in the offshore sediments along the Shandong Peninsula over the last 100 years: Anthropogenic and natural impacts

The anthropogenic and natural impacts on the temporal and spatial variations of heavy metals in sediments under the Shandong Peninsula coastal current are still unclear. Here, the concentrations\burial fluxes of Cr, Cu, Zn, As, and Pb in three sediment cores retrieved from the Bohai Sea and the Yellow Sea along the Shandong Peninsula were analyzed to study the spatial-temporal variability of heavy metal accumulation over the last century. The results showed that the buried heavy metal fluxes were relatively low at the end of the Shandong Peninsula coastal current. The enrichment factor (EF) and geoaccumulation index (I_geo) indicated that those metals did not severely pollute the sediments except As that reached a moderate enrichment. Principal component analysis (PCA) revealed that Cr, Cu, Zn, and Pb were mainly derived from natural weathering and As was determined by anthropogenic contamination. The strength of the Shandong Peninsula coastal current, the Yellow River estuary location, and sediment discharge load significantly influenced the concentrations of natural-origin heavy metals by affecting sediment grain size and the source-sink process. The emission of pollutants from agricultural and industrial activities in the Shandong Peninsula region resulted in As enrichment since the 1950s. Moreover, the EF values of heavy metals in sediment cores from China's coastal seas showed apparent spatial variations of heavy metal pollution but had coherent temporal variability with China's economic development process. Heavy metals pollution has weakened in most coastal seas since the 2000s, likely due to the extensive industrial upgrading and the implementation of pollution control. These results have a reference significance for studying the evolution and source-sink process of the heavy metals in offshore sediments and tracing anthropogenic impacts in different periods.

Development of current ambient background threshold values for sediment quality parameters in U.S. lakes on a regional and statewide basis

For the first time, background threshold values have been developed for a large suite of sediment quality parameters from 969 lakes spanning the conterminous United States (U.S.). These values provide a statistical basis for estimating current ambient background, which refers to chemical and physical (e.g., grain size) concentrations derived from natural and/or widespread diffuse anthropogenic sources (e.g., nonpoint sources like atmospheric deposition and land runoff). Surficial sediment quality data, collected based on the randomized, probability-based sampling design of the 2017 National Lakes Assessment (NLA) study, were utilized for this effort. These data included 16 metal(loid)s, 25 polycyclic aromatic hydrocarbons (PAHs), 53 polychlorinated biphenyl (PCB) congeners, 27 legacy organochlorine pesticides and metabolites, total organic carbon (TOC), and grain size parameters. The data were analyzed based on different geographic areas, including: 10 U.S. Environmental Protection Agency (EPA) Regions, two major ecoregions bisecting the State of Minnesota (i.e., Temperate Plains and Upper Midwest), and for Minnesota. Hypothesis testing of 47 sediment quality parameters was performed on three geographic areas bisecting Minnesota, and there were many statistically significant (p < 0.05) differences between geographic pairs that included Minnesota. Background threshold values were calculated for parameters with >20% detects using 95% one-sided upper tolerance limit (UTL) with 95% coverage (UTL95-95) values. The UTL95-95 represents the value below which 95% of the population values are expected to fall with 95% confidence. These values were compared to matching sediment quality guidelines for the protection of benthic organisms, both with and without potential outliers removed. Applications and limitations of the UTL95-95 values are discussed. Jurisdictions within the continental U.S. could use these same publicly available sediment quality data to calculate UTL95-95 values for specific geographic areas, and other countries could design similar probabilistic field studies to determine current ambient background of sediment quality parameters in lake sediments.

Ecological Risk Due to Heavy Metal Contamination in Sediment and Water of Natural Wetlands with Tourist Influence in the Central Region of Peru

In this study, the quality of sediment and surface water in two natural wetlands, Paca and Tragadero, in the central region of Peru was evaluated using pollution indices, including the geoaccumulation index, pollutant load index, modified pollution degree, potential ecological risk index, and site rank index, for four heavy metals. Principal component analysis was used to identify potential metal contaminant sources. The determination of Fe, Zn, Pb, and As was performed by flame atomic absorption spectrophotometry. The average concentrations of metals in the sediments of both lagoons decreased in the order Fe > Zn > Pb > As. The analysis of the contamination indices determined that As and Pb are the elements that contribute the most to environmental degradation in both wetlands. There is a strong correlation between the values of potential ecological risk and the modified degree of contamination, revealing that the Paca wetland has a moderate degree of contamination and potential ecological risk, while Tragadero presents a high degree of contamination and considerable potential ecological risk. The application of the site rank index showed that more than 50% of the sampling sites have between high and severe contamination. The principal component analysis presented 79.2% of the total variance. Finally, the results of this study are essential in order to carry out preventive actions for environmental protection in these lake ecosystems of great importance for many activities, such as bird watching.

Effect of river-lake connectivity on heavy metal diffusion and source identification of heavy metals in the middle and lower reaches of the Yangtze River

Metal pollution poses a significant threat to ecological security and human health. Current research on the causes, sources and distribution of metal pollution in the Yangtze River plain is lacking. This study investigated the accumulation, risk, distribution, and sources of heavy metals in 62 lakes along the Yangtze River, and analyzed the relationship between river-lake connectivity, economic structure, population and metal diffusion. The mean concentrations of Cr, Cu, Hg, Zn, Cd, Pb and As in the surface sediments of these lakes were 90.8, 60.1, 0.06, 102, 0.89, 42.7, and 6.01 mg/kg, respectively. Most (99%) of the lake sediments were contaminated with Cd, and the lakes in the middle reach and southern bank of the Yangtze River had a higher ecological risk. Cr originated from the natural environment, whereas Zn, Cu, Pb, Cd and As were affected by human activities. The lakes disconnected from the Yangtze River had higher concentrations of Cu, Zn, Pb and As, while the lakes connected to the river had higher concentrations of Cd and Cr. This comprehensive analysis determined the pollution characteristics of heavy metals, illustrated the causes of non-point pollution in the Yangtze River plain, and showed that soil-water erosion is important in metal diffusion.

Geochemical Baseline Establishment and Source-Oriented Ecological Risk Assessment of Heavy Metals in Lime Concretion Black Soil from a Typical Agricultural Area

To accurately assess the potential ecological risk posed by heavy metals in lime concretion black soil and quantify the risk contributions from different sources, an investigation of 217 surface soil samples and 56 subsoil samples was performed in the southern part of Suzhou City. Geochemical baseline values of soil heavy metals (Cr, Zn, Pb, Ni, Hg, Cu, Cd, As, Mn and Co) in the study area were calculated as 53.6, 61.5, 19.8, 27.6, 0.08, 18.4, 0.13, 12.9, 416.1 and 11.0 mg/kg, respectively, by using reference metal normalization and cumulative frequency curve methods. Subsequently, four potential sources of soil heavy metals were identified by the positive matrix factorization. Finally, the potential ecological risks arising from the identified sources were determined by the integrated model of positive matrix factorization and Hakanson potential ecological risk index. Results showed that the ecological risk posed by soil heavy metals in the study area ranged from low to moderate level. Hg and Cd were the two largest risk contributors, supplying 36.0% and 30.3% of total risk value. The origin of heavy metals in the soils is mostly related to four sources including agricultural activities, natural dispersion, coal consumption and traffic pollution. Source apportionment of the potential ecological risks revealed that the dominant risk source in the study area was natural dispersion (42.0%), followed by coal related industries (26.5%), agricultural activities (20.4%) and traffic pollution (11.1%). This work gives a clear baseline information of the heavy metal accumulations in lime concretion black soil and provides a successful case study for the source-oriented ecological risk assessment.

Heavy metal contamination in surface sediments from lakes and their surrounding topsoils of China

Due to rapid urbanization, industrialization, agricultural development, and mining activities, soil heavy metal pollution has become a severe issue in China. To explore the regional heavy metal ecological risk of lake sediment and surrounding topsoil, we analyzed 237 lakes, with 1797 lake sediment sampling points and 1164 surrounding topsoil sampling points. Lower mean concentrations were detected for most heavy metals in soils than sediment (except for Hg). Cd and Hg in sediments and soils showed a more significant variation, with the coefficient of variation exceeding 110%. Linear regressions and Pearson's correlation analyses demonstrated that sediments and soils exhibited significant positive correlations. The principal heavy metals exceeding the Agricultural Soil Control Standard (ASCS) in sediments and soils were As and Cd, respectively. The Yunnan-Guizhou Plateau Lake Region (YGPLR) was the most seriously affected, exceeding the ASCS for Cd. The lakes with the most severe pollution were located in YGPLR impacted by the high background concentration of heavy metals in soil and mineral development activities. The Eastern Plain Lake Region, the Southeast Lake Region, and the Northeast Plain and Mountain Lake Region showed a clear anthropogenic impact. Lakes in the Inner Mongolia-Xinjiang Lake Region and the Tibetan Plateau Lake Region were estimated to have relatively low ecological risks due to their sparse population and slight environmental disturbance. The impact of geochemical factors on the ecological risk of heavy metals in lake sediments is more substantial than that of human activities at the regional scale.

Assessment of heavy metal content, distribution, and sources in Nansi Lake sediments, China

Much attention has been paid to the heavy metal contamination of lake sediments in rapidly developing regions. In this study, heavy metal (Cd, Cr, Co, Ni, Mn, Pb, As, Cu, and Zn) concentrations in sediment surface samples and cores from the Nansi Lake were investigated to ascertain the potential sources and environmental risks of heavy metals. The average concentration of heavy metals was 0.16-16.04 times background concentrations. The enrichment factor, Tomlinson pollution load index, geo accumulation index, positive definite matrix factor analysis (PMF), and potential ecological risk index were used to assess heavy metal concentrations and explore the evolution of heavy metal sources, and result indicated that Cd reached moderate pollution levels, which is the most polluted heavy metal in the history and present, while the remaining heavy metals are at low or no pollution levels. The contribution of Cd to RI exceeded 76%, which is the decisive factor in the ecological risk of Nansi Lake. The result of ecological risk showed that the risk level for most of Nansi Lake is medium, and some areas of Zhaoyang Lake and Weishan Lake reach high levels. The PMF results showed that there are four main factors influencing heavy metal concentrations in Nansi Lake sediments, including industrial sources, fertilizers, and herbicides used in agricultural production, traffic-related emissions, and mineral mining. Among these factors, industrial and mineral mining sources were found to be the most important, and the highest contribution rate occurred in the -10cm (1960s). Although the contribution of fertilizers and herbicides is lower than that of other sources, increasing trend should be a warning sign that Cd has reached a high ecological risk level in Nansi Lake sediments.

Causes of variations of trace and rare earth elements concentration in lakes bottom sediments in the Bory Tucholskie National Park, Poland

The objective of this study was to analyse spatial variability of the trace elements (TEs) and rare earth elements (REEs) concentration in lake bottom sediments in Bory Tucholskie National Park (BTNP); Poland. The following research questions were posed: which factors have a fundamental impact on the concentration and spatial variability of elements in bottom sediments, which of the elements can be considered as indicators of natural processes and which are related to anthropogenic sources. The research material was sediments samples collected from 19 lakes. The concentrations of 24 TEs and 14 REEs were determined. The analyses were carried out using the inductively coupled plasma mass spectrometry (ICP-QQQ). Cluster analysis and principal component analysis were used to determine the spatial variability of the TEs and REEs concentrations, indicate the elements that are the indicators of natural processes and identify potential anthropogenic sources of pollution. The geochemical background value (GBV) calculations were made using 13 different statistical methods. However, the contamination of bottom sediments was evaluated by means of the index of geo-accumulation, the enrichment factor, the pollution load index, and the metal pollution index. The BTNP area is unique because of its isolation from the inflow of pollutants from anthropogenic sources and a very stable land use structure over the last 200 years. This study shows high variability of TE and REE concentrations in lake sediments. The values of geochemical indices suggest low pollution of lakes bottom sediments. It was found that TEs originated mainly from geogenic sources. However, the concentrations of Li, Ni, Sc, Se, Be, Se, Ag, Re, Tl, Cd, Sb and U may be related to the impact of point sources found mainly in the Ostrowite Lake. Almost all REEs concentrations were strongly correlated and their presence was linked to with geochemical processes. The elements allowing to identify natural processes and anthropogenic pollution sources were Cr, Co, Cu, Ag, Cd, Zn, Bi, Re, Ba, Al and Rb in TEs group and Nd, Gd, Yb, Lu, Eu, Dy and Ce in REEs group. The analysis shows high spatial variability of TE and REE concentrations in lake sediments. The values of geochemical indices point to low pollution of lakes sediments. The anthropogenic sources only for two lakes had an impact on concentrations of selected TEs and REEs. The analyses allowed to identify elements among TEs and REEs documenting geochemical processes and those indicating anthropogenic sources of pollution.

Intensity analysis of chromium cycling in south Jiangsu region of China

Suzhou (SZ), Wuxi (WX) and Changzhou (CZ) (collectively called the SXC area) in southern Jiangsu Province surround Tai Lake on three sides and have an important impact on its ecology. The emission and circulation of Cr in the three cities were quantified according to the six categories (including industry production, agricultural livestock, vehicle exhaust, solid waste, atmospheric subsidence and runoff) to analyze its regional characteristics and source category characteristics and to build a Cr cycle diagram to evaluate the pollution situation. The results showed that the Cr emissions from solid waste were the highest and mostly came from industrial sludge, accounting for 76.4% of the total circulation. The Cr emissions from SZ and WX were significantly higher than those of CZ, accounting for 47.0% and 42.9% of the regional total. The Cr in the excrement of pigs and poultry, dry sedimentation and surface runoff exceeded 100 tons every year, which needed to be valued. The Cr concentration in the surface water, soil and atmosphere in SXC area all met with the highest national standards. Studies have shown that the sediments and benthic organisms in the west and north of Tai Lake were already in a low-pollution state, but which was overall acceptable. Through this study, Cr circulation was clarified in typical areas, which was convenient for the monitoring and management of heavy metal pollution in the areas surrounding Tai Lake.

Characterizing the anthropogenic-induced trace elements in an urban aquatic environment: A source apportionment and risk assessment with uncertainty consideration

The spatial distribution of water quality status, especially in water bodies near intensively urbanized areas, is tightly associated with patterns of human activities. For establishing a robust assessment of the sediment quality in an urban aquatic environment, the source apportionment and risk assessment of Cr, Mn, Ni, Cu, Zn, As, Cd, Hg, and Pb in sediments from an anthropogenic-influenced lake were carried out with considering uncertainties from the analysis methods, random errors in the sample population and the spatial sediment heterogeneity. The distribution analysis of the trace metals with inverse distance weighting-determined method showed that the pollutants were concentrated in the middle and southern areas of the lake. According to the self-organizing map and constrained positive matrix factorization receptor model, agricultural sources (24.8%), industrial and vehicular sources (42.5%), and geogenic natural sources (32.7%) were the primary contributors to the given metals. The geogenic natural had the largest random errors, but the overall result was reliable according to the uncertainty analysis. Furthermore, the stochastic contamination and ecological risk models identified a moderate/considerable contamination level and a moderate ecological risk to the urban aquatic ecosystem. With consideration of uncertainties from the spatial heterogeneity, the contamination level of Hg, and the ecological risk of Cd in had a 20-30% probability of the increase.

Microbial remediation for the removal of inorganic contaminants from treated wood: Recent trends and challenges

Owing to the seriousness of the ecological risk and human hazard of inorganic wood preservatives, their effective removal was gradually recognized. This paper details different types of wood preservatives, their perniciousness, and their potential removal alternatives, while the wood treatment process is briefly described. Among decontamination methods, microbial remediation is considered as an environmentally friendly approach with enormous potentialities over the conventional treatments. In the current review, the mechanism of bioremediation is summed up and recent advances, challenges, and future perspectives of microbial remediation are discussed. The removal of heavy metals from treated wood requires a combination of various technologies to obtain higher performance. Meanwhile, the decontaminated wood generated through bioremediation can be effectively reused.

Evaluation of potential ecological risk, possible sources and controlling factors of heavy metals in surface sediment of Caohai Wetland, China

Caohai, a plateau wetland in Southwest China, is a national nature reserve providing protection for a variety of threatened and endangered species of migrant birds (e.g., the black-necked crane Grus nigricollis). It has been experiencing the increasing environmental problems with heavy metals due to anthropogenic activities. However, the contamination of heavy metals in different habitats is unclear. Surface sediment samples from these habitats were thus collected to analyze the distribution characteristics, potential risk and possible sources for heavy metals (Cd, Hg, Pb, Zn, Ni, Cr, Cu, Be, and V). The results showed that all of Cd, Hg, Pb, Zn, Cr, and Ni concentrations exceeded the background values, and these elements (except Cr and Ni) presented comparatively high levels in habitat adjacent to urban in comparison with the other habitats. Based on the regression analysis, we found that metals with higher EFs (Cd, Hg, Pb, and Zn) were mainly controlled by anthropogenic loadings, while metals with lower EFs (Cr, Ni, Be, and V) were mainly associated with sediment properties (pH or NOM). In addition, the results from geo-accumulation index, Hakanson potential ecological risk assessment, and risk assessment code showed that Cd and Hg posed a medium to high environmental risk to the ecosystem, and the other heavy metals posed no or low risk. Therefore, to protect this wetland ecosystem and to supply a well habitat for migratory birds, greater efforts aimed at reducing anthropogenic discharges and remediating sediment contaminated with heavy metals should be pursued.

Metal Distribution and Sediment Quality Variation across Sediment Depths of a Subtropical Ramsar Declared Wetland

The study of wetlands is particularly important as these systems act as natural water purifiers and thus can act as sinks for contaminated particles. Wetland sediments are important as they provide an indication of potential contamination across temporal and spatial scales. The current study aimed to investigate the distributions of selected metals and nutrients in different sites in relation to sediment depth, and identify relationships among sediment metals. Significant differences in nutrient (i.e., N, P) and metal (i.e., K, Mg, Na, Fe, Cu, B) concentrations were found across study sites, whereas nutrients (i.e., N, P) and metals (i.e., Ca, Mg, Fe, Cu, Zn) were significantly different with sediment depths. When compared against Canadian sediment standards, most of the assessed metals were within the “no effect” level across the different sites and depths. The K, Ca, and Mg concentration showed extreme contamination across all sites and depths. The enrichment factor values for K, Ca, and Mg showed extremely high enrichment levels for all sites and sediment depths. The Na, Mn, Fe, Cu, Zn, and B concentration showed mostly background enrichment levels. All sediments across the different sites and sediment depths indicated deterioration of sediment quality. Pearson correlations suggest that most metals might have originated in a similar source as that of Mn and B, owing to a lack of significant differences. These results provide baseline information for the general management of the Nylsvley Wetland in relation to sediment metal pollution. The specific sources of metal contaminants also require further elucidation to further inform management efforts.

Source apportionment and source-oriented risk assessment of heavy metals in the sediments of an urban river-lake system

Heavy metal pollution in lakes has attracted concerns worldwide since long retention times in lakes allow metals to accumulate and may pose significant threat to ecosystem health. For designing targeted risk mitigation strategies, it is necessary to identify the source-specific risks of heavy metals in the environment. Although previous studies have addressed either risk assessment or source identification of heavy metals in the environment, few have attempted to establish a link between them. In the study, we perform a combination of source apportionment and risk assessment for characterizing the pollution sources and source-specific risks of heavy metals in the sediments of an urban river-lake system. To this end, positive matrix factorization (PMF) was employed to apportion the potential sources of heavy metals, combined with a support vector machine classifier and the referential source fingerprints of metals in the study area. Then, the apportionment results were incorporated into the environmental risk models to evaluate the ecological and human health risks posed by heavy metals from the identified pollution sources. Results showed the river-lake system was contaminated by Cd, Cu, Zn and other metals in varying degree. Particularly, the element of Cd presented moderate to heavy pollution level. In relative, the industrial activities were identified as the largest contributor (48.0%) of heavy metals in the river-lake sediments, mainly associating with electroplating and paper making, followed by the agricultural activities (27.3%) and mix source (24.7%). Overall, the non-carcinogenic and carcinogenic risks posed by the heavy metals were acceptable, however, the element of Cd showed moderate ecological effect. Further, source-oriented risk evaluation suggested industrial processes made higher contributions to the ecological risk of heavy metals in the river-lake system. The study will provide regulators help to update the information by adding apportionment analysis in the context of risk assessment to facilitate subsequent mitigation strategies.

Hydrodynamic impact on trace metals in sediments in the cascade reservoirs, North China

Cascade reservoirs facilitate the effective use of water resources and help to alleviate existing problems of water shortage in drought-prone regions. However, the geochemical behavior and controlling mechanisms of trace metals in response to the operation of cascade reservoirs are relatively unknown. Here, trace metals (As, Cr, Cu, Li, Ni, Pb and Zn) from thirty sediment cores from cascade reservoirs (Panjiakou and Daheiting Reservoirs) in China were evaluated. Multiple methods including geochemical baseline, geostatistical analysis, factor analysis (FA), and positive matrix factorization (PMF), were combined to assess pollution status, identify and quantify potential anthropogenic sources, and determine the influence of hydrodynamic conditions on trace metals distribution. The results indicate that minor enrichment of trace metals appeared in both cascade reservoirs. However, trace metal concentrations exhibited spatial heterogeneity between two cascade reservoirs, and diverse hotspots of different metals were unexpectedly observed. This can be explained by the following three aspects: (1) Metal hotspots were detected upstream of the cascade dams via geostatistical analysis and FA, particularly for naturally sourced metals (As and Li) where dam interception resulted in higher concentrations in the upstream reservoir. (2) PMF analysis identified agricultural, industrial, and natural sources to account for 23.44%, 41.61%, and 34.95%, respectively, to the metal concentrations in the downstream reservoir. Anthropogenic emissions were the dominant factors influencing the spatial variability of Cu, Pb, and Zn between the cascade reservoirs, with higher concentrations observed in the downstream reservoir. (3) The hydrological regime also influenced the redistribution of human-derived metals, where slower flow velocities at river bends resulted in higher deposition of metal-bearing particles. This study shed light on the spatial distribution of trace metals in response to the construction and operation of cascade reservoirs, and it suggests that trace metal hotspots should be monitored to prevent potential contamination in sediments.

Establishment of geochemical baseline and multiple assessment of vanadium pollution in sediment cores from the two cascade reservoirs, North China

Vanadium (V) is a potential toxic pollutant, and thus, V pollution in reservoir sediment should be scientifically evaluated because reservoirs are the main source of drinking water in China. However, the pollution assessment of V in reservoir sediment is often overestimated or underestimated due to the limitation for selecting local background values. In this study, the selection of the V background value in sediments was based on regional geochemical baseline (RGB) model. Multiple methods including geo-accumulation index (I_geo), potential ecological risk index (EI), and health risk assessment were applied to evaluate V pollution in sediment cores collected from the Panjiakou-Daheiting Reservoirs (PDR). The results show that the mean value of V concentrations in the PDR sediment cores was 92.86 mg/kg (57.69-141.19 mg/kg), which is higher than the soil background in Hebei Province and stream sediment values in China. V concentrations in the Panjiakou Reservoir were higher than those in the Daheiting Reservoir. The RGB value of V was 96.33 mg/kg in the PDR sediments. A comparison of the V concentrations and RGB values in the sampling sites indicated that half of these sites are impacted by anthropogenic inputs. Among the sites influenced by human activity, the average anthropogenic contribution was 9.9%, suggesting that majority of V in the PDR sediments originated from natural source. The pollution assessments of V were evaluated using I_geo and EI with RGB as the background value, and results indicated that the sediments in the PDR were not polluted with V. The environmental impact assessment model was also established for calculating V accumulation in fish due to sediment resuspension. Then, health risk assessment model was applied to further calculate the health risk to residents due to fish consumption. The evaluated target hazard quotient demonstrated that local fish consumption produced no adverse effect on human health during sediment disruption.

Trace metals in core sediments from a deep lake in eastern Turkey: Vertical concentration profiles, eco-environmental risks and possible sources

The contents of 12 trace metals (Hg, As, Pb, Cd, Ni, Cr, Zn, Cu, Co, Mn, Al and Fe) in two sediment cores (Hz11-P02 and Hz11-P09) from the Lake Hazar, one of the deepest natural lakes in Turkey, were examined to evaluate vertical concentration profiles, possible sources, pollution status and eco-environmental risks of these metals. The highest concentrations of Cd and As were detected in the upper part (0-10 cm depths) of core Hz11-P02, while Hg concentration was at a maximum in the upper part of core Hz11-P09. The concentrations of other metals except Cr were the highest in the bottom layer (depths below 100 cm) of both cores. Among trace metals (TMs), Cr, Ni, Al and Mn in core Hz11-P02 and Mn in core Hz11-P09 showed statistically significant correlations with core depth (p < 0.01). The mean concentrations of Hg, Pb, Cd, Cu, Zn, Co, Mn, Al and Fe in core Hz11-P02 were significantly higher than those in core Hz11-P09 (p < 0.01). Also, the mean enrichment factor, geoaccumulation index and contamination factor values of As, Cu, Cd, Zn, Pb and Hg were higher in core Hz11-P02. The ecological risk index (RI) values for core Hz11-P02 were between 150 and 300 in 40.3% of the samples, indicating "moderate ecological risk", whereas the RI values for core Hz11-P09 were <150 in 100% of the samples, indicating "low ecological risk". Factor, cluster and correlation analyses, and contamination indices indicated that As and Hg in core Hz11-P02 predominantly originated from anthropogenic sources, while 12 trace metals in core Hz11-P09 derived from natural sources.

Meta analysis of heavy metal pollution and sources in surface sediments of Lake Taihu, China

Heavy metal concentrations in Taihu Lake sediment from studies performed between 2000 and 2018 were analyzed and Monte Carlo uncertainty analysis of heavy metal geo-accumulation, potential ecological risk and toxicity data for Taihu Lake sediment was performed to allow heavy metal pollution of Taihu Lake sediment to be described clearly, objectively, and comprehensively. Five main conclusions were drawn. (1) Most attention should be paid to As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn pollution. (2) The geo-accumulation indices showed that Cd is the most important pollutant and that the probabilities of Taihu Lake sediment being moderately polluted, moderately-heavily polluted, and heavily polluted were found to be 53.6%, 34.9%, and 18.7%, respectively. (3) Cd is the main contributor to potential ecological risks and had cumulative low risk, moderate risk, and considerable risk probabilities of 63.0%, 27.0%, and 10.0%, respectively. (4) Toxicity unit evaluation results indicated that Pb is the main contributor of toxicity in Taihu Lake sediment and had cumulative low toxicity, moderate toxicity, and high toxicity probabilities of 53.0%, 36.8%, and 5.6%, respectively. (5) Positive matrix factorization model results indicated that industrial sources are the main suppliers of heavy metals to Taihu Lake sediment, contributing 64.9% of the heavy metals. The summarized results and conclusions will improve local government awareness of heavy metal pollution in Taihu Lake and will aid in the development of appropriate pollution control measures. The results will also provide reference data for future studies of heavy metal pollution in sediment from Taihu Lake and other lakes.