Accumulation and risk assessment of heavy metals in water, sediments, and aquatic organisms in rural rivers in the Taihu Lake region, China

Bioavailable fractions of heavy metals in the road dust during infrastructure construction at urban Coimbatore and its potential health implications, India

Over the past two decades the Global South is witnessing unprecedented economic transformation and Asian Cities in particular have a remarkable upsurge. Coimbatore, an industrial city in Southern India with an estimated population of 2 million (in 2022) is witnessing a rapid transition in terms of infrastructure development. In this context, the present study attempts to assess the particulate matter (PM10 and PM2.5) emissions at road network construction sites and the heavy metal fractionation in the road dust/sediment samples with a core focus to quantify the bioavailable fraction of metals (Fe, Cu, Cr, Cd, Pb and Ni) and its source apportionment in the road side dust/sediment samples. About 60 composite road dust/sediment samples were collected for heavy metal fractionation analysis in the six arterial roads that undergo core developments like construction of road over bridges, additional road incorporation and street expansions. PM monitoring revealed that 24 h average PM2.5 (47 µg/m3) and PM10 (69 µg/m3) concentrations at many construction sites exceeded 24 h average recommended by WHO guidelines [PM2.5 (15 µg/m3) and PM10 (45 µg/m3), respectively]. The bioavailable fractions of Fe, Cu, Cr and Cd are notably higher in the roadside sediment samples at road construction sites. Health Risk assessment, such as carcinogenic risks (Children-4.41 × 10-2, Adult-3.598 × 10-6) and non-carcinogenic risks, inferred substantial risks at high intensity construction sites with statistical analyses, including PCA and cluster analysis, indicating considerable anthropogenic influences in the heavy metal fractions.

Occurrence, distribution, source apportionment, ecological and health risk assessment of heavy metals in water, sediment, fish and prawn from Ojo River in Lagos, Nigeria

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

Characterization and application of Fe-modified biochar alleviating Cr(VI) stress in pak choi seedling cultivated in Cr-polluted hydroponics

Chromium (Cr) is one of the common environmental pollutants, which causes severe health hazards on human health and environmental security. In this study, we characterized two biochars, a raw biochar (RBC) and a Fe-modified biochar (MBC) made from poplar wood chips and determined the effect of the two biochars on remediation of hexavalent chromium (Cr(VI)) in hydroponic system by monitoring Pak choi growth. Results showed the surface area, pore number and pore volume were significantly higher in MBC than in PBC, but the pore size was larger in PBC than in MBC. When compared to the control, low concentrations of Cr(VI) (≤2 mg L-1) promoted the growth and biomass production of Pak choi by 10-78%. In contrast, the high concentrations of Cr(VI) (≥4 mg L-1) showed a significantly reduction of the growth and biomass production of Pak choi by 10-28%. Fe-modified biochar (MBC) had a more significant impact than RBC on the remediation of Cr in the Cr(VI) pollution and improved growth and biomass production of Pak choi to a greater extent. Our study indicated that MBC has a better effect on degrading Cr(VI) pollution. The findings provide scientific basis and reference for the remediation of heavy metals in aquatic ecosystems by using biochar.

Ecological risk assessment of heavy metals in riverine sediments of rural area driven by urbanization

Rural revitalization denotes the gathering of large populations in rural areas and the subsequent gradual urbanization. Rural environments have been deteriorated by heavy metals (HMs) over the last few years. Without the existence of large-scale industries, the accumulation of HMs in sediments due to population aggregation in rural environments needs to be scientifically confirmed. Therefore, in this study we first understand the sediment pollution in rural environments in China and across the globe, and subsequently investigate HMs in sediments in rural micro water. The study area, Sichuan Province, China, was divided into two areas, namely, sparsely populated areas (SPA) and densely populated areas (DPA). Eight typical HMs (As, Zn, Ni, Hg, Cd, Cr, Cu, and Pb) were selected to target in riverine sediments, and the content and spatial distribution characteristics were analyzed. The results indicate that As, Hg, Cd, and Pb concentrations in sediments were higher than background values (BVs), with high concentration sample sites located in the DPA. In addition, the geo-accumulation index (Igeo), pollution load index (PLI) and potential ecological risk index (RI) were used to quantitatively evaluate the pollution characteristics of HMs in sediments, revealing that the sediments exhibited high As and Hg pollution in the DPA (PLI = 1.09). In general, mild (RI = 48.76) and moderate (RI = 154.92) HM pollution was observed in the sediments of the SPA and DPA, respectively, based on the high PLI (> 1.0) and RI (> 150) values. Correlation analysis and principal component analysis (PCA) indicate that the Cd in the sediment generally originated from geogenic sources, while the other elements (Zn, As, Cu, Cr, Hg, Ni and Pb) were primarily linked to anthropogenic sources. Finally, the results demonstrate that population aggregation will lead to the enrichment of HMs.

Assessment of trace metal bioaccumulation on the shells of edible gastropod Chicoreus ramosus and Hemifusus pugilinus

The current study aimed to examine how some gastropods absorbed trace metals (Chicoreus ramosus and Hemifusus pugilinus). The existence of 17 elements, including aluminium, arsenic, boron, calcium, cadmium, cobalt, chromium, copper, iron, potassium, lithium, manganese, sodium, nickel, phosphorus, lead, and zinc (Al, As, B, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mn, Na, Ni, P, Pb, and Zn), was confirmed by inductively coupled plasma-mass spectroscopy (ICP-MS) analysis of trace metals. According to the ICP-MS results, C. ramosus (Al: 1.97 ± 0.2 µg/g, Fe: 1.93 ± 0.2 µg/g, and As: 1.52 ± 0.4 µg/g) and H. pugilinus (Al: 1.85 ± 0.7 µg/g, Fe: 1.68 ± 0.6 µg/g, and As: 1.37 ± 0.6 µg/g) both had significant amounts of aluminium, iron, and arsenic, respectively. Zinc concentrations of 0.58 to 0.7 μg/g (C. ramosus) and 0.67 to 0.2 μg/g were recorded (H. pugilinus). The elemental composition of the surface of the sample was confirmed by scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX) micrographs, which also showed the degree of trace metal absorption in the chosen gastropod species.

In vitro genotoxic and mutagenic effects of water samples from Sapucaia and Esteio streams (Brazil) under the influence of different anthropogenic activities

Pollution of aquatic ecosystems is associated with the discharge of mainly industrial and urban effluents, which may cause damage to public health. This study aims to evaluate the cytotoxic, genotoxic, and mutagenic potential of surface water samples under the influence of different anthropogenic effluents in a human-derived liver cell line (HepG2). Samples were collected in Esteio and Sapucaia streams (Rio Grande do Sul; Brazil), which flow into the Sinos River, a source of water supply for more than one million people. Physicochemical and microbiological analyses were performed as well as an analysis of inorganic elements using the PIXE technique (Particle-Induced X-Ray Emission). The presence of pharmaceutical compounds and caffeine was evaluated by gas chromatography coupled to mass spectrometry. The cytotoxicity, genotoxicity, and mutagenicity of the samples were evaluated in HepG2 cells by cell viability assays, alkaline Comet Assay and Cytokinesis-block micronucleus (CBMN) assay. We verified alterations in the physicochemical and microbiological parameters and detected caffeine, diethyltoluamide, and different inorganic elements that corresponded to elements from domestic and industrial effluents and agricultural runoff. Although the samples in the concentration used were not cytotoxic, water samples from all sites induced DNA damage. However, it is difficult to attribute these damages to a specific substance since the factors are a complex mixture of different compounds. Despite this, it is observed that both urban and industrial contributions had a similar effect in the cells evaluated. Such results demonstrate the need to perform biomonitoring of surface waters under anthropogenic influence, especially those that flow into rivers that are a source of public supply water. We also highlight the need for research into emerging pollutants in these aquatic environments.

Ecological Risk Evaluation and Source Identification of Heavy Metal Pollution in Urban Village Soil Based on XRF Technique

The rapid urbanization in China has resulted in significant differences between urban and rural areas. The emergence of urban villages is inevitable in this context, for which complex problems regarding land use, industrial management and ecological environment have arisen. This study performed a case study on a typical urban village, by assessing heavy metal pollution and ecological risk in soil. It detected a total of 80 basic units through portable X-ray fluorescence (XRF) instrument. A total of 25 high-risk contaminated points were selected, sampled and analyzed in laboratory as confirmation. The results showed the mean concentrations of Pb, Cu, Zn and Ni in soil were significantly higher than background values. Pb, Zn and Ni showed obvious pairwise correlation, and the high-value zones could be attributed to automobile traffic and industrial activities. In addition, the pollution problem is complicated by a combination of agricultural activities, the absence of clear division between different functional zones, as well as a general lack of environmental awareness. All of these lead to increased ecological risk and are a serios threaten to public health.

Distribution of heavy metals in surface soil near a coal power production unit: potential risk to ecology and human health

Coal thermal power plants are the dominant factor in producing various hazardous elements in surrounding surface soil, resulting in a significant human health hazard. In the current study, the seasonal (pre- and post-monsoon) concentration of As, Cd, Co, Cr, Cu, Fe, Li, Mg, Mn, Ni, Pb, and Zn in surface soil around coal power production unit was analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). The possible health risks throughout multiple exposure routes, i.e., ingestion, dermal, and inhalation were estimated for adult and children. Furthermore, geo-accumulation index (Igeo), enrichment factor (EF), pollution factor (CF), ecological risk index, and pollution load index (PLI) were applied to interpret the environmental pollution in the study area. The geospatial distribution pattern was computed to understand the trace and hazardous element distribution in the surface soil. As a result, the concentration of Fe (mg/kg) in pre-monsoon (15,620) and post-monsoon (27,180), Ni (mg/kg) in pre-monsoon (19.8), and post-monsoon (81.7) was found above the standard limits of soil prescribed by the WHO and FAO. Enrichment factor was observed between 0.95-6948 (pre-monsoon) and 0.53-116.09 (post-monsoon). The ecological risk index was found moderate to considerable for As and Cd metals during both seasons. In addition, the average PLI value was observed high for both seasons indicating the contamination of the study area with heavy metals. Moreover, Igeo values for Fe, Mg, and As were found relatively high. Conversely, health risks to the human population were found within the USEPA acceptable limits.

Distribution and Ecotoxicological Risk Assessment of Heavy Metals in Streams of Amanos Mountains from Southern Turkey

Assessing the potential ecological risks of chemical pollutants like heavy metals is a key tool of a sustainable environment. With this goal, ecotoxicological significant metal (Al, As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, and Zn) levels of the water (n = 32) and sediment (n = 32) samples of streams [rural (8 points) and urban (8 points) sides] on Amanos Mountains were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) and ecotoxicological risk assessment was performed through the potential ecological risk index (RI). The study region with intense urban activities has also ecological importance with regards to wildlife. It is located on the migration route of birds, hosts loggerhead and green sea turtles, Mediterranean seals, and some terrestrial species like mountain gazelle and striped hyena. All calculated RI values were below the potential risk limits and the ecotoxicological risk was observed to be very low. Metal levels should be monitored periodically, and necessary measures should be taken before the reflection of the increase to be determined by the risk assessment on the ecosystem.

Magnetic properties and its application in the prediction of potentially toxic elements in aquatic products by machine learning

Magnetic measurement was provided to substitute for time-consuming conventional methods for determination of potentially toxic elements. Both the concentrations of 12 elements and 9 magnetic parameters were determined in 700 muscle tissue samples from the snail Bellamya aeruginosa, shrimp species Exopalaemon modestus and Macrobrachium nipponense, and fish species Hemisalanx prognathous Regan, Coilia ectenes taihuensis, and Culer alburnus Basilewsky collected from Chaohu Lake during different hydrological periods. Spherical and irregular iron oxide particles were observed in the muscle tissues of the studied aquatic products. A field survey of the exposure parameters in humans, such as per capita intake dose of local aquatic products, found no evidence that consumption of the tested species poses a potential health risk. Redundancy analysis revealed different degrees of correlation between the magnetic parameters and concentrations of elements in aquatic products. Back-propagation artificial neural network (BP-ANN) and support vector machine (SVM) models were applied to predict elemental concentrations in aquatic products, using magnetic parameters as input. SVM models performed well in predicting the presence of Cr and Ni, with R and index of agreement values of >0.8 in both training and validation stages as well as relatively low errors. The BP-ANN and SVM models both performed relatively poorly in predicting the presence of Cd and Zn in aquatic products, with R values between 0.333 and 0.718 for Cd and between 0.454 and 0.664 for Zn in training and validation stages. For most of the elements, a better R value was obtained with the SVM than with BP-ANN model. The R of Co, Cr, Cu, Ni, and Ti in the training and validation stages of snail in the SVM model were >0.8. This study is a first step in developing a novel approach allowing the rapid monitoring of potentially toxic elements concentrations in aquatic products.

Significant Decrease in Heavy Metals in Surface Sediment after Ten-Year Sustainable Development in Huaxi Reservoir Located in Guiyang, Southwestern China

In the Karst area of southwestern China, the heavy metals in the sediment of a reservoir are determined by both human activities and the high background values. Thus, this study explores the change of heavy metals in surface sediment after ten-year sustainable development in the upstream areas of a reservoir, Huaxi Reservoir, located in Guiyang of southwestern China, then evaluates the risk of these heavy metals to water environment systematically and finally identifies the sources in both 2019 and 2009. The results reveal that all of the measured heavy metals decrease dramatically and their spatial distributions change from the increase-decrease pattern to decrease-increase pattern, implying different locations of main source input. The risk indices based on the total or average content and relative or reference values have decreased to the lowest level. However, those indices calculated from the absolute content of each metalloid still show a low or a moderate risk because of the high background value, such as As and Cr. Moreover, although only one main source of heavy metals is identified in both 2019 and 2009, the risk from human activities still cannot be neglected because agricultural production and infrastructure construction would promote the weathering of soil and then these heavy metals from the soil will be brought into the reservoir with the rainfall-runoff process. The high background value of specific heavy metals, e.g., As and Cr would still exert some challenges to the water environment protections because the non-point source input of heavy metal cannot be controlled easily by promulgating a series of bans. These results provide important reference for creating the policies of water environment protection, especially in some Karst area of southwestern China that exhibits high background value of heavy metals.

Polybrominated Diphenyl Ethers and Heavy Metals in a Regulated E-Waste Recycling Site, Eastern China: Implications for Risk Management

Serious pollution of multiple chemicals in irregulated e-waste recycling sites (IR-sites) were extensively investigated. However, little is known about the pollution in regulated sites. This study investigated the occurrence of 21 polybrominated diphenyl ethers (PBDEs) and 10 metals in a regulated site, in Eastern China. The concentrations of PBDEs and Cd, Cu, Pb, Sb, and Zn in soils and sediments were 1-4 and 1-3 orders of magnitude lower than those reported in the IR-sites, respectively. However, these were generally comparable to those in the urban and industrial areas. In general, a moderate pollution of PBDEs and metals was present in the vegetables in this area. A health risk assessment model was used to calculate human exposure to metals in soils. The summed non-carcinogenic risks of metals and PBDEs in the investigated soils were 1.59-3.27 and 0.25-0.51 for children and adults, respectively. Arsenic contributed to 47% of the total risks and As risks in 71.4% of the total soil samples exceeded the acceptable level. These results suggested that the pollution from e-waste recycling could be substantially decreased by the regulated activities, relative to poorly controlled operations, but arsenic pollution from the regulated cycling should be further controlled.

Heavy Metal Contamination in an Industrially Affected River Catchment Basin: Assessment, Effects, and Mitigation

The concentrations of some heavy metals (Fe, Zn, Mn, Cu, Mo, Pb, Cd) were measured in river waters, macrozoobenthos, and fish (Kura scrapers) from one of the most developed mining areas in Armenia, the Debed River catchment basin. In order to assess heavy metal contamination and its hydro-ecological and health effects, the macrozoobenthos quantitative and qualitative parameters, geo-accumulation index, and hazard index were determined. Microalgal extraction experiments were conducted to assess the microalgal remediation efficiency for heavy metal removal from mining wastewaters. The results showed that the rivers in many sites were polluted with different heavy metals induced by mining activities, which adversely affected macrozoobenthos growth and caused human health risks in the case of waters used for drinking purposes. However, the river fish, particularly Kura scrapers, were determined to be safe for consumption by the local people, as per the conditions of the evaluated fish ingestion rate. The results have shown that microalgal remediation, particularly with Desmodesmus abundans M3456, can be used for the efficient removal ~(62–100%) of certain emerging contaminants (Mn, Pb, Cu, Zn, Cd) from mining wastewater discharged in the Debed catchment basin.

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.

Pollution and Ecological Risk Evaluation of Heavy Metals in the Soil and Sediment around the HTM Tailings Pond, Northeastern China

Tailings ponds are a main heavy metal pollution source in mining areas. In this study, the geo-accumulation index (Igeo) and the potential ecological risk index (RI) are used to evaluate the environmental impact of Hongtou Mountain (HTM) tailings pond on the surrounding area. Farmland soil, surface water, and sediment samples in the Hun River around the HTM tailings pond were collected. Heavy metal contents in the samples were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results show that Cu, Zn, and Cd content in the farmland soil and sediment around the lower reaches of the Hun River (HTM tailings pond section) are obviously higher than the upper reaches. The Igeo values show that the farmland soil near the outlet of the tailings pond is the most polluted area. Cu was classified as moderate-strongly pollution, Zn was moderately pollution, and Cd was strongly pollution. Cd is the major pollutant in farmland soil, the monomial ecological risk (Eri) for Cd is a very high potential ecological risk. The potential ecological risk of sediment in the dry season is more serious than in the raining season. In the dry season, the Igeo index shows strong pollution for Cu and Cd at the confluence of the Hun River and the tributary from the HTM tailings pond, and a moderate-strongly pollution for Zn. Whereas, the Eri index shows that the monomial ecological risk for Zn at H3 is low, and Cu is moderate. The potential ecological risk at H3 is high, and Cd is the main source of the ecological risk around the HTM tailings pond.

Spatial distribution and source analysis of heavy metals in soils influenced by industrial enterprise distribution: Case study in Jiangsu Province

Heavy metal pollution is frequent in China and has received increasing attention globally. This study investigated the influence of Chinese industrialization and urbanization on soil environmental quality. Soil samples from Jiangsu Province were collected, the Cd, Pb, Cr, Cu, Zn, Hg, and As contents were measured, and their spatial variability structure, spatial distribution pattern, and pollution degree were analyzed. The mean values of Hg, Cd, Pb, Cr, Cu, and As were all higher than the background values in Jiangsu Province. Cr and As levels represented moderate pollution, Cu, Zn, Cd, and Pb represented mild pollution, Cr and As represented slight pollution, and Hg was not a pollutant. Spatial distribution patterns were both zonal and concentrated in nature. High concentrations of heavy metals were distributed in developed cities and industrial parks along the Yangtze River. Soil heavy metal pollution showed a decreasing trend from south to north, consistent with the economic gradient. Industrialization had the greatest influence on the spatial heterogeneity of heavy metal pollution. Cr, Cu, Zn, and As were affected by both natural and anthropogenic sources, while Cd and Pb were mainly affected by the latter. Hg was mainly derived from industrial activities such as petrochemical production. There was spatial consistency between industrial enterprise distribution and soil heavy metal pollution with a tendency toward composite pollution accumulated by multiple elements in the soil surrounding industries.

Application of algae for heavy metal adsorption: A 20-year meta-analysis

The use of algae to adsorb heavy metals is an efficient and environmentally friendly treatment for contaminated water and has attracted widespread research attention. In this study, a meta-analysis of the heavy metal adsorption capacity of algae from five different phyla and the factors influencing these capacities was conducted. Phaeophyta was found to have a high heavy metal adsorption capacity, whereas Bacillariophyta had a relatively low adsorption capacity; Chlorophyta, Rhodophyta, and Cyanophyta had moderate adsorption capacities. Non-living algae were more effective in practical applications than living algae were. Algal biomass had a relatively high adsorption efficiency of 1-10 g/L, which did not increase significantly when algal concentration increased. The algal adsorption efficiency for initial heavy metal concentrations of 10-100 mg/L was higher than for concentrations of greater than 100 mg/L. The results further show that algal adsorption of heavy metals reached a maximum capacity of 80-90% within 20 min. Heavy metal adsorption by algae was not temperature-dependent, and it was more effective in moderately to weakly acidic environments (pH = 4-7.5). Considering these aspects for practical applications, algae from some phyla can effectively be used for heavy metal biosorption in contaminated water.

Application of diffusive gradients in thin films (DGT) and simultaneously extracted metals (SEM) for evaluating bioavailability of metal contaminants in the sediments of Taihu Lake, China

The toxicities of heavy metals in sediments are related to their bioavailability, which is critical for deriving reliable sediment quality guidelines. To evaluate the bioavailability of the metals (Cd, Cu, Ni, Pb and Zn), sediments were collected from Taihu Lake, one of the largest and most important freshwater lakes in China. Concentrations of simultaneously extracted metals (1-M HCl extraction, C_SEM) in the sediments, metals released from sediment to pore waters and accumulated by diffusive gradients in thin films (DGT, C_DGT), and dissolved metals in the overlying water (C_OLW) were measured separately. Sediment toxicity was assessed with tubificids (Monopylephorus limosus) and chironomids (Chironomus kiiensis and Chironomus tentans). Significant relationships existed between the total metal concentrations and C_SEM, C_DGT, and C_OLW measurements (r² = 0.43-0.95, n = 27, p < 0.001), with stronger relationships with C_SEM (r² = 0.91-0.95) than C_DGT (r² = 0.56-0.85) and C_OLW (r² = 0.43-0.71). Risk quotients were derived by dividing C_SEM by sediment quality guideline values (SQGVs), and by dividing both C_DGT and C_OLW by water quality criteria (WQC). Toxicity of the sediments to the three species was better explained by the C_SEM-based risk quotient than those derived from C_DGT and C_OLW. The study indicated that DGT piston probes deployed face down in sediments did not accumulate metals in proportion to the bioavailable metal fraction that caused toxicity to these freshwater benthic organisms, and that single measurements of metals in overlying waters are not adequate for predicting risks of toxicity from sediments. The measurement of C_SEM was determined to be effective for assessing the risk posed by the metals in the Taihu Lake sediments, but offered limited improvement over measurement of total metal concentrations.

Biota-sediment metal accumulation and human health risk assessment of freshwater bivalve Corbicula fluminea in Dongting Lake, China

In this study, we analyzed the concentrations of metals in sediments and Corbicula fluminea in China's Dongting Lake to assess the suitability of C. fluminea as an effective biomonitor of metal contamination in sediments and food safety. We analyzed the biota-accumulation capacity by calculating the biota-sediment accumulation factor (BSAF) and assessed the potential human health risk of metals exposure via consumption of C. fluminea using the target hazard quotient (THQ) and total target hazard quotient (TTHQ). The results showed that the average concentrations of As (31.93 mg kg^-1), Cd (5.54 mg kg^-1), Cr (105.50 mg kg^-1), Cu (32.53 mg kg^-1), and Zn (207.89 mg kg^-1) in sediments were higher than their respective standard set by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China. The sediment metals, which were mainly anthropogenic in origin, were at high levels and pose a relatively high ecological risk. Cadium (Cd) showed very high potential ecological risk levels and should be included in the prior pollutants list in the studied area. The mean levels of As (0.81 mg kg^-1) in C. fluminea were 1.62-times higher than that set by the National Health Commission of the People's Republic of China. BSAF values of the soft tissues of C. fluminea were between 0.05 and 2.14, with higher values for Cu (2.14), Cd (1.77), Zn (1.60), and Ni (1.27). Soft tissues of C. fluminea were able to reflect spatial differences in Sr within sediments around Dongting Lake. The results indicated that C. fluminea could be an potential biomonitor for sediment metals assessment in biomonitoring programs, especially for Cu, Cd, Zn, Ni, and Sr. The mean values for THQ and TTHQ of all the analyzed metals were below 1.0, indicating that the intake of metals via comsumption of C. fluminea does not result in an appreciable risk to human health.

Occurrence, speciation, and risks of trace metals in soils of greenhouse vegetable production from the vicinity of industrial areas in the Yangtze River Delta, China

The effect of industrial activities on trace metals in farmland of rapidly industrializing regions in developing countries has increasingly been a concern to the public. Here, soils were collected from 13 greenhouse vegetable production (GVP) farms or bases near industrial areas in the Yangtze River Delta of China to investigate the occurrence, speciation, and risks of Cr, Cu, Zn, Cd, Ni, and Pb in GVP soil. The results revealed that the main metal elements causing GVP soil pollution were Cd, Zn, Ni, and Cu, of which contamination levels were generally unpolluted to moderately polluted. Zinc pollution was mainly attributed to heavy fertilization, while Cd, Ni, and Cu pollution may be greatly ascribed to industrial effluents and coal combustion. Metal speciation studies showed that most of Cr, Ni, Cu, and Zn was present in residual fraction while more than half of Cd and Pb was present in non-residual fractions. Additionally, pollution of Cd, Cu, Ni, and Zn in GVP soil increased their corresponding mobile fractions. Risk assessment using potential ecological risk index and risk assessment code showed that Cd was the major risk contributor. Specifically, Cd generally posed moderate or considerable ecological risk as well as displayed medium or high mobility risk in GVP soil. Thus, great attention should be paid to the contribution of both industrial discharges and intensive farming to soil pollution by trace metals, especially Cd, because of its high mobility risk.

Changes in exoskeleton surface roughness and expression of chitinase genes in mud crab Macrophthalmus japonicus following heavy metal differences of estuary

Risk assessment of heavy metals is important for the health evaluation of inhabiting species in aquatic ecosystem. This study investigated whether chitin exoskeleton of mud crab Macrophthalmus japonicus is affected by heavy metals in estuary sediments in Korea. We compared heavy metal concentrations and analyzed the expression of M. japonicus chitinase genes, which play the crucial role in the formation of chitin exoskeleton. Concentrations of heavy metals were highly observed in crab body inhabiting Hampyeong among estuarine sites. High expressions of chitinase 1 were observed in crab gill and hepatopancreas from Myodo, which is the site with the lowest concentration of heavy metal in crab body. The surface roughness of the exoskeleton decreased with the increased concentration of heavy metals accumulated in the crab body. These results suggest that the total bioconcentration of heavy metals in crabs affected the expression of chitinase genes and changes in the exoskeleton surface roughness.

Comparative studies on growth and Pb(II) removal from aqueous solution by Nostoc muscorum and Anabaena variabilis

Industrial wastewater containing heavy metals is a major environmental problem that needs to be treated. This study reported the ability of two fresh water algae cyanobacteria (Nostoc muscorum and Anabaena variabilis) to remove lead from aqueous solutions of four different initial concentrations (0-50 mg/L^-1) for 21 days under controlled laboratory conditions. Results obtained in this study showed a maximum removal of Pb(II) (97.8%) by N. muscorum at 15 mg/L^-1 initial metal concentration however the maximum removal by A. variabilis at the same concentration was 71.4% after 16 day of incubation. These N. muscorum appeared to be more efficient than A. variabilis for removing Pb(II). Algal growth, pigments in the algae cells were measured during incubation period. Lower concentrations of lead increased biomass, OD, chlorophyll a and carotenoids in both algae. On the other hand, higher concentrations of lead were inhibitory for growth.

Occurrence and risk assessment of heavy metals in water, sediment, and fish from Dongting Lake, China

In this study, 15 representative surface waters and sediments and seven typical fish were collected during the wet season in 2016 to explore the occurrence, chemical fractionation, and ecological risk of heavy metals (Cu, Zn, Pb, Cd, Cr, Hg, As, and Ni) in aquatic ecosystems of Dongting Lake in China. In surface water, the concentrations of all elements were lower than the third grade of the surface water quality standards (GB3838-2002). The highest concentrations of Zn, Pb, Cd, Ni, and Cu were found in the outlet of Dongting Lake, whereas As and Cr were highest in the Xiangjiang River Delta area. In surface sediments, the concentration decreased in the order of Zn > Cr > Pb > Cu > Ni > As>Cd > Hg; the highest concentration of all elements, except for Hg, was located in the Xiangjiang River Delta area; for chemical fractionation, Cr, Hg, Zn, As, Ni, and Cu were mainly residual fractionation; and Pb and Cd were mainly in a reducible state and fraction soluble in acid, respectively. In fish muscle, the concentrations of all elements were lower than relevant standards; the highest concentration appeared in fish living in the middle-lower and demersal layers. As for the feeding habits of fish, the average concentration decreased in the order of carnivorous > omnivorous > herbivorous fish. The potential ecological risk and the ratio of secondary phase to primary phase assessment showed that Cd and Hg had the highest ecological risk and that Cd and Pb had a high risk of secondary release. A health risk assessment showed that drinking water and fish for consumption in urban and rural areas around Dongting Lake were in the acceptable level.

Human exposure to trace elements in central Cambodia: Influence of seasonal hydrology and food-chain bioaccumulation behaviour

Exposure to mercury and other trace elements remains an important public health concern, worldwide. The present study involved a comprehensive field study to determine concentrations of fourteen trace elements (Al, As, Cr, Co, Cd, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and Zn) in surface water and different fish species from Tonlé Sap Lake in central Cambodia, during both the dry and wet seasons. Total arsenic (tAs) and Mn in surface water during the dry season exceeded WHO drinking water guidelines. Total mercury (tHg) concentrations (µg/g wet wt.) in fish during the wet season (GM = 0.055; CI₉₅ = 0.01-0.26) were approximately 15 times higher (P < 0.05) compared to those during the dry season (GM = 0.0035; CI₉₅ = 0.0004-0.033). Mean target hazard quotients (THQs) for inorganic arsenic (iAs), methyl mercury (MeHg), Mn and Pb were > 1, with estimated maximum values greatly exceeding 1. Mean THQs of Zn, Cd, Ni and Se were very near 1, with estimated maximum values exceeding 1. The MeHg THQ (min-max range: 0.16-9.09) during the wet season was 7 times higher than in the dry season (min-max range: 0.05-1.35). Concentrations of Hg and other trace elements varied widely between fish species. The findings suggest that exposure of some trace elements via water and food is of concern in this region. High consumption rates of fish and rice key factors related to trace element exposure. Seasonal hydrology and species-specific bioaccumulation behaviour in the Tonlé Sap Lake watershed also play an important role. The generated information will be useful to better mitigate trace element exposure in this region.

Trace metals dynamics under contrasted land uses: contribution of statistical, isotopic, and EXAFS approaches

Three sub-basins of the Seine River (France) under contrasted land uses (i.e., forested, agricultural, and urban) have been investigated in order to assess the origin and seasonal variation of trace metals, and evaluate their geochemical background and dynamics. Our results highlight a high anthropogenic impact on all elements for both the dissolved and particulate fractions. The main source for each element in the dissolved phase was determined and shows that transition and post-transition metals mainly originate from forested areas, while alkali and alkaline earth elements, metalloids, and halogens rather originate from agricultural land use. Conversely, for the particulate phase, most of the elements cannot be associated with a specific land use. Seasonal variation of elements was assessed according to the forested and agricultural land uses, and geochemical backgrounds were determined using average export rates, highlighting that the geochemical background for the forested land use is higher than the agricultural one for most of the elements. Finally, to confirm those results, Zn dynamics in the three characteristic sub-basins and between the different land uses was investigated using a combination of Zn speciation, Zn isotopic ratio, and Zn export rates.

Effect of copper on the accumulation and elimination kinetics of fluoroquinolones in the zebrafish (Danio rerio)

Fluoroquinolones (FQs) have attracted wide concerns due to their pseudo-persistent and universal presence in natural water. Here we exposed zebrafish separately to two FQs (enrofloxacin (ENR) and ofloxacin (OFL)) in different copper (Cu) concentrations for 20 days (d) in a flow-through system, followed by a 11 d depuration period in clean water to investigate compound specific bioaccumulation and tissue distribution. Two FQs could accumulate in zebrafish, and the high concentration was observed in liver. Moreover, the levels of FQs in different treatment groups were higher than the corresponding control fish group. The uptake rates (k₁), elimination rates (k₂), BCF value, and half-lives (t_1/2) of FQs ranged from 0.02 to 3.28 d^-1, 0.01 to 0.97 d^-1, 0.33 to 109.33, 9.90 to 69.31 d, respectively. With Cu exposure concentration's increasing, k₁ values in three tissues (liver, skin and gill) obviously decreased. The exposure concentration affected the BCF value significantly, but didn't change their relative compositions in liver, gill, skin, and muscle after long time exposure. BCF values of ENR were always a little bit higher than those of OFL in almost all the tissues (liver, skin and gill) in the low Cu concentration treatments, whereas, in the high Cu concentration treatments the bioconcentration factors (BCF) values of ENR were lower than the values of OFL. The exposure of Cu played an important role in the FQs bioconcentration and BCF. These results are meaningful for improved understanding and prediction of the behavior and fate of metallic and antibiotics in aqueous environments.

Evaluating a 5-year metal contamination remediation and the biomonitoring potential of a freshwater gastropod along the Xiangjiang River, China

Effective remediation of heavy metal pollution in aquatic systems is desired in many regions, but it requires integrative assessments of sediments, water, and biota that can serve as robust biomonitors. We assessed the effects of a 5-year metal contamination remediation along the Xiangjiang River, China, by comparing concentrations of trace metals in water and surface sediments between 2010-2011 and 2016. We also explored the trace metal biomonitoring potential of a freshwater gastropod (Bellamya aeruginosa). Metal concentrations in water (means and ranges) dropped over time to within permissible limits of drinking water guidelines set by China, USEPA, and WHO in 2016. Although sediment means and ranges of Cd, Pb, Zn, and Mn also diminished with remediation, those for Cr and Cu slightly increased, and all six metals retained concentrations higher than standards set by China. All metals in sediments could also be associated with anthropogenic inputs using a hierarchical clustering analysis, and they generate high potential ecological risks based on several indices, especially for Cd and As. The bio-sediment accumulation factors of all measured trace metals in gastropod soft tissues and shells were lower than 1.0, except for Ca. Trace metal contents in gastropods were positively correlated with those in water and surface sediments for As (soft tissues) and Cr (shells). Collectively, our results do not yet highlight strong beneficial effects of 5-year remediation and clearly illustrate the heavy metal pollution remaining in Xiangjiang River sediment. Additional physical, chemical, and biological measurements should be implemented to improve sediment quality. We further conclude that gastropod soft tissues and shells can be suitable biomonitors of spatial differences in some heavy metals found within river sediments (e.g., As, Cr).

Source identification and spatial distribution of metals in soils in a typical area of the lower Yellow River, eastern China

In this study, 234 soil samples were recently collected from Gaoqing County (a typical area of the lower Yellow River) to determine the contents of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Multivariate statistical analyses such as correlation analysis, principal components analysis, and one-way ANOVA were applied to identify the source of metals in the soil. Geostatistical methods were used to analyze the spatial structure and distribution of the metals. The results indicated that the mean contents of all metals exceeded the background value of the lower Yellow River, especially for As, Cu, and Hg (1.23, 1.20, and 1.29 times that of the BV, respectively), indicating that these metals were enriched in the study area to different degrees. The results derived from multivariate analysis suggested that As, Cd, Cr, Cu, Ni, Pb, and Zn were mainly controlled by the combination of human activities and soil parent material, and the human activities included industrial emissions, traffic emissions, and agricultural practices. In addition, Hg mainly originated from anthropogenic inputs, such as textile printing, plastics processing, and petrochemical engineering. The contents of metals in different types of land use and parent materials are clearly different. The mean content for eight elements in urban construction land was significantly higher than that of the other land use types; in addition to Hg, the mean content of the other elements was the highest in the lacustrine deposit. The elements of As, Cd, Cr, Cu, Ni, Pb, and Zn had similar hotspots in the urban area, indicating the significant human influence. In addition, these seven metals showed high values in the southeast lacustrine deposit area. The high-value areas of Hg were concentrated in the southwest and northeast study area, which were consistent with the spatial pattern of the industrial sites.

Heavy metal contamination in river water and sediments of the Swarnamukhi River Basin, India: risk assessment and environmental implications

The concentration of heavy metals was analyzed each of 20 river water, suspended sediments and bed sediments along the stretch of Swarnamukhi River Basin. River water is not contaminated with heavy metals except Fe and Mn. Contamination factor in sediments shows considerable to very high degree contamination with Cr, Cu, Pb and Zn. The sources of these metals could be residential wastes, sewer outfall, fertilizers, pesticides (M-45 + carbondine) and traffic activities apart from natural weathering of granitic rocks present in the basin area. Principal component analyses indicate the interaction between metals in different media. The comparison of metals (Cu, Pb and Zn) in bed sediments of Swarnamukhi River with the Indian and world averages indicates that the values obtained in the basin are above the Indian averages and far below to the world averages. Average shale values and sediment quality guidelines point toward the enrichment and contamination of Cu, Cr, Pb and Zn to several fold leading to eco-toxicological risks in basin.

Bioaccumulation of heavy metals in fish species from the Meiliang Bay, Taihu Lake, China

In the present study, the bioaccumulation of heavy metals (Cr, Cu, Cd, Pb) content were determined in freshwater edible fishes Cyprinus carpio Linnaeus and Pelteobagrus fluvidraco, which were caught from the Meiliang Bay, Taihu Lake, a large, shallow and eutrophic lake of China. The results showed that the Cr, Cu, Cd and Pb content in the edible parts of the two fish species were much lower than Chinese Food Health Criterion (1994). However, the results showed marked differences in the four analyzed metal content between the two species and different tissues as well as significant variations. Pb content were the highest in the liver of fishes, Cd contents were almost the same in all organs of fishes, Cr contents mainly enriched in the kidney and liver, Cu contents were the highest in gills, However, the total metal bioaccumulation were greatest in the liver, gills and the lowest in the muscle. Although the total accumulations were highest in P. fluvidraco compare then C.carpio. This investigation indicated that fish products in Meiliang Bay, Taihu Lake were still safe for human consumption, but the amount consumed should be controlled under the Chinese Food Health Criterion to avoid excessive intake of Pb. Further, this is the first report on seasonal distribution of heavy metals and proximate compositions of commercialized important edible fishes from Meiliang Bay, Taihu Lake, China.

Heavy metal pollution in immobile and mobile components of lentic ecosystems-a review

With growing population and urbanization, there is an increasing exploitation of natural resources, and this often results to environmental pollution. In this review, the levels of heavy metal in lentic compartments (water, sediment, fishes, and aquatic plants) over the past two decades (1997-2017) have been summarized to evaluate the current pollution status of this ecosystem. In all the compartments, the heavy metals dominated are zinc followed by iron. The major reason could be area mineralogy and lithogenic sources. Enormous quantity of metals like iron in estuarine sediment is a very natural incident due to the permanently reducing condition of organic substances. Contamination of cadmium, lead, and chromium was closely associated with anthropogenic origin. In addition, surrounding land use and atmospheric deposition could have been responsible for substantial pollution. The accumulation of heavy metals in fishes and aquatic plants is the result of time-dependent deposition in lentic ecosystems. Moreover, various potential risk assessment methods for heavy metals were discussed. This review concludes that natural phenomena dominate the accumulation of essential heavy metals in lentic ecosystems compared to anthropogenic sources. Amongst other recent reviews on heavy metals from other parts of the world, the present review is executed in such a way that it explains the presence of heavy metals not only in water environment, but also in the whole of the lentic system comprising sediment, fishes, and aquatic plants.

Studies on seasonal pollution of heavy metals in water, sediment, fish and oyster from the Meiliang Bay of Taihu Lake in China

The present study, seasonal pollution of heavy metals (Pb, Cd, Cr and Cu) in water, sediment, tissues of fish Carassius carassius and oyster Crassostrea gigas were determined at seven sampling sites from Meiliang Bay, Taihu Lake during one year calendar, 2016. The total heavy metal concentrations in water samples were higher in winter and summer than in spring and autumn season, whereas in sediment they were higher in winter and summer seasons, respectively. The trend of metal mean contents found in the fish and oyster were in decreasing order of Pb > Cu > Cr > Cd and Pb > Cu > Cr > Cd, respectively. The tissues of fish and oyster captured during winter and summer accumulated a higher significant different amount of metals relative to other season, which was attributed to a higher influx of agricultural waste, sewage and sludge by heavy rainfall and floods. In addition, the pollution load index (PLI) values were above one (>1), indicating an advanced decline of the sediment quality, and contamination factor (CF) confirmed that the sediment samples were moderate to high contamination by Pb and Cr. Thus, comparative studies with seasonal pollution of heavy metals in Meiliang Bay of Lake Taihu regions indicate considerable heavy metal enrichment in water, sediments as well as in various organs of fish and oyster. Finally, our results indicated that the metal concentration values increased statistically significant different related to season (p < 0.001). The determination of heavy metal stress biomarkers in fish along with seasonal variations may serve as a convenient approach during pollution bio-monitoring programme.

The average concentration function of dissolved copper in Hun River, Liaoning province, Northeastern China

Water samples were collected from Hun River to research the change in the concentration of dissolved copper and its distribution as well as accumulation during the dry season in 2013. The mean concentrations of dissolved copper in Hun River were 0.1057-0.1533 mg/l during the dry season. The results indicated that the most severe dissolved copper pollution were associated with the mining area, industrial area, and living area along the Hun River. The results also indicated that controlling the sources of copper pollution effectively reduced the concentration of dissolved copper in Hun River. The concentration function about time and spatial coordinate, average concentration function about time coordinate, average concentration function about spatial coordinate, and bounded mean oscillation space were used to evaluate the extent of copper pollution in Hun River. The error function, quartiles, and curve fitting tool were performed to determine the stations with high concentration of dissolved copper in Hun River. We furthermore obtained the upper and lower bounds of the error between two kinds of bounded mean oscillation spaces to explore the migration of copper pollution in Hun River. The results of the average concentration function and bounded mean oscillation space revealed that the long-term control measures of copper pollution and short-term control measures of copper pollution, the control of copper pollution in large watershed, and the control of copper pollution in small watershed in Hun River should be combined with each other. The strict policy and pollution control strategy should be implemented to ensure that the water of the Hun River meets the natural environment standard for the growth of aquatic life and human.

Effects of land use types on dissolved trace metal concentrations in the Le'an River Basin, China

Using land use types in multiple spatial scales (entire basin, buffer zones, and slopes) as well as statistical and spatial analysis, relationships between land use types and concentrations of dissolved trace metals were determined in the Le'an River Basin, China. The result showed that farmland and urban land were determined as the source of the pollutants, while forestland and grassland were identified as the sink of the pollutants. The temporal differences of relationships between land use types and concentrations of dissolved trace metals mainly due to the discrepancy of rainfall characteristics. Land use type close to river was a better indicator for the effectiveness of concentrations of trace metals, especially at scale of 0-200 m. Forestland and grassland on lower slopes greatly affected the water quality, and the former had no significant or weak influences on higher slopes. Urban land had the greater positive correlations with concentrations of dissolved trace metals on higher slopes, which are mainly due to frequent mining activity. Further analysis suggested that the buffer zones with low slope needed to be seriously taken into consideration for effective land use management in similar basin.

Ecological risk assessment of toxic organic pollutant and heavy metals in water and sediment from a landscape lake in Tianjin City, China

To estimate the ecological risk of toxic organic pollutant (formaldehyde) and heavy metals (mercury (Hg), arsenic (As), cadmium (Cd), and chromium (Cr)) in water and sediment from a landscape Lake in Tianjin City, an ecological risk assessment was performed. The risk quotient (RQ) method and the AQUATOX model were used to assess the ecological risk of formaldehyde in landscape water. Meanwhile, the RQ method and the potential ecological risk index method were used to assess the ecological risk of four heavy metals in water and sediment from the studied landscape lake, respectively. The results revealed that the maximum concentration of formaldehyde in landscape water was lower than the environmental quality standards of surface water in China. The maximum simulated concentrations of formaldehyde in phytoplankton and invertebrates were 3.15 and 22.91 μg/L, respectively, which were far less than its toxicity data values (1000 and 510 μg/L, respectively), suggesting that formaldehyde in landscape water was at a safe level for aquatic organisms. The RQ model indicated that the risks of phytoplankton and invertebrates were higher than that of fish posed by Hg and Cd in landscape water, and the risks from As and Cr were acceptable for all test organisms. Cd is the most important pollution factor among all heavy metals in sediment from studied landscape lake, and the pollution factor sequence of heavy metals was Hg > As > Cr > Cd. The values of risk index (RI) for four heavy metals in samples a and b were 43.48 and 72.66, which were much lower than the threshold value (150), suggesting that the ecological risk posed by heavy metals in sediment was negligible.

Distribution and risk assessment of metals and arsenic contamination in man-made ditch sediments with different land use types

Ditches are subjected to a large input of nutrients, trace metals, and arsenic and the enhancement of sedimentation due to human activities. However, the influence of different types of land uses on the distribution and associated environmental risk of metals and arsenic in the Red purple Sichuan Basin remains largely unclear, which is needed for water management. This study was carried out to characterize metal/metalloid status in ditch sediments from different land uses. A total of 68 surface sediment samples (0-5 cm) were collected from open ditches distributed in different land use types, i.e., cultivated ditches (CD), barren land ditches (BLD), roadside ditches (RSD), and residential ditches (RD), within the Sichuan Basin. Mean concentrations of Cr, Ni, Cu, Zn, Cd, Pb, and Mn in both RD and RSD were above the soil background values of Sichuan Basin, but Cd in ditch sediments of the basin posed considerable ecological risk to the environment. Overall, metals/metalloid (except Pb) decreased in the following order of RD > RSD > BLD > CD. Of the different land use types in the hilly region, residential and roadside land uses were likely to adverse effects on aquatic life. Multivariate statistical analysis showed that Mn, As, Cu, Ni, Zn, Fe, and Al were mainly influenced by natural weathering (erosion), while Pb might come from heavy vehicular traffic. The degree of contamination (Md), enrichment factor (EF), and the geo-accumulation index (Igeo) showed that Cd causes strong sediment pollution in the basin. Sediment quality guidelines SQG-Q values displayed that metals and arsenic created medium-low potential of adverse biological effects. These results provide baseline information on the metals and arsenic pollution in the Sichuan Basin. Awareness of land use type contributions to metals and arsenic requires that these man-made ditches be considered for their mitigation of pollutants in this region.

In Situ, High-Resolution Profiles of Labile Metals in Sediments of Lake Taihu

Characterizing labile metal distribution and biogeochemical behavior in sediments is crucial for understanding their contamination characteristics in lakes, for which in situ, high-resolution data is scare. The diffusive gradient in thin films (DGT) technique was used in-situ at five sites across Lake Taihu in the Yangtze River delta in China to characterize the distribution and mobility of eight labile metals (Fe, Mn, Zn, Ni, Cu, Pb, Co and Cd) in sediments at a 3 mm spatial resolution. The results showed a great spatial heterogeneity in the distributions of redox-sensitive labile Fe, Mn and Co in sediments, while other metals had much less marked structure, except for downward decreases of labile Pb, Ni, Zn and Cu in the surface sediment layers. Similar distributions were found between labile Mn and Co and among labile Ni, Cu and Zn, reflecting a close link between their geochemical behaviors. The relative mobility, defined as the ratio of metals accumulated by DGT to the total contents in a volume of sediments with a thickness of 10 mm close to the surface of DGT probe, was the greatest for Mn and Cd, followed by Zn, Ni, Cu and Co, while Pb and Fe had the lowest mobility; this order generally agreed with that defined by the modified BCR approach. Further analyses showed that the downward increases of pH values in surface sediment layer may decrease the lability of Pb, Ni, Zn and Cu as detected by DGT, while the remobilization of redox-insensitive metals in deep sediment layer may relate to Mn cycling through sulphide coprecipitation, reflected by several corresponding minima between these metals and Mn. These in situ data provided the possibility for a deep insight into the mechanisms involved in the remobilization of metals in freshwater sediments.

Concentrations, diffusive fluxes and toxicity of heavy metals in pore water of the Fuyang River, Haihe Basin

While the concentrations of heavy metals in pore water provide important information about their bioavailability, to date few studies have focused on this topic. In this study, pore water in river sediments collected from nine sampling sites (S1-S9) was examined to determine the concentrations, fluxes, and toxicity of heavy metals in the Fuyang River. The results showed that the average concentrations of Cr, Ni, Cu, As, Zn, and Pb in pore water were 17.06, 15.97, 20.93, 19.08, 43.72, and 0.56μgL(-1), respectively; these concentrations varied as the pore water depth increased. The diffusive fluxes of Cr, Ni, Cu, As, Zn, and Pb were in the following range: (-0.37) to 3.17, (-1.37) to 2.63, (-4.61) to 3.44, 0.17-6.02, (-180.26) to 7.51, and (-0.92) to (-0.29)μg(m(2)day)(-1), respectively. There was a potential risk of toxicity from Cu to aquatic organisms, as indicated by a value of the Interstitial Water Criteria Toxic Units that exceeded 1.0. Values of the Nemeraw Index were 2.06, 0.48, 0.11, 0.20, 1.11, 1.03, 0.99, 0.88, and 0.89 from S1 to S9, respectively. Only S1 was moderately polluted by heavy metals in pore water.

Spatial Evaluation of Heavy Metals Concentrations in the Surface Sediment of Taihu Lake

With regard to the size of China's freshwater lakes, Taihu Lake ranks third and it plays an important role in the supply of drinking water, flood prevention, farming and navigation, as well as in the travelling industry. The problem of environmental pollution has attracted widespread attention in recent years. In order to understand the levels, distribution and sources of heavy metals in sediments of Taihu Lake, random selection was carried out to obtain 59 samples of surface sediment from the entire lake and study the concentrations of Pb, Cd, Cu, Zn, Cr and Ni. Toxic units were also calculated to normalize the toxicities caused by various heavy metals. As a result, Cd and Cu in sediment were considered lower than the effect range low (ERL) at all regions where samples were gathered, while Pb and Ni were categorized into ERL-effect range median (ERM) at over 22% of the regions where samples were obtained. Nevertheless, all average concentrations of the samples were below the level of potential effect. According to the findings of this research, significant spatial heterogeneity existed in the above heavy metals. In conclusion, the distribution areas of heavy metals with higher concentrations were mainly the north bays, namely Zhushan Bay, Meiliang Bay as well as Gonghu Bay. The distribution areas of Cu, Zn, Cr and Ni with higher concentration also included the lake's central region, whereas the uniform distribution areas of those with lower concentrations were the lake's southeast region. In addition, it was most probable that the spatial distribution of heavy metals was determined by river inputs, whereas atmospheric precipitation caused by urban and traffic contamination also exerted considerable effects on the higher concentrations of Pb and Cd. Through evaluating the total amount of toxic units (ΣTU), it was found that higher toxicity existed primarily in the north bays and central region of the lake. If the heavy metals were sorted by the reduction of mean heavy metal toxic units in Taihu Lake in descending order, it would be Pb, Cr, Ni, Cd, Zn and Cu. Generally speaking, these result of analyses are conducive to alleviating the contamination of heavy metals in Taihu Lake.

Meta-Analysis of the Copper, Zinc, and Cadmium Absorption Capacities of Aquatic Plants in Heavy Metal-Polluted Water

The use of aquatic plants for phytoremediation is an important method for restoring polluted ecosystems. We sought to analyze the capacity of different aquatic plant species to absorb heavy metals and to summarize available relevant scientific data on this topic. We present a meta-analysis of Cu, Zn, and Cd absorption capacities of aquatic plants to provide a scientific basis for the selection of aquatic plants suitable for remediation of heavy-metal pollution. Plants from the Gramineae, Pontederiaceae, Ceratophyllaceae, Typhaceae and Haloragaceae showed relatively strong abilities to absorb these metals. The ability of a particular plant species to absorb a given metal was strongly correlated with its ability to absorb the other metals. However, the absorption abilities varied with the plant organ, with the following trend: roots > stems > leaves. The pH of the water and the life habits of aquatic plants (submerged and emerged) also affect the plant's ability to absorb elements. Acidic water aids the uptake of heavy metals by plants. The correlation observed between element concentrations in plants with different aquatic life habits suggested that the enrichment mechanism is related to the surface area of the plant exposed to water. We argue that this meta-analysis would aid the selection of aquatic plants suitable for heavy-metal absorption from polluted waters.