Contamination and ecological risk assessment of toxic trace elements in the Xi River, an urban river of Shenyang city, China

Assessment of the accumulation level and ecological risk of heavy metals in surface sediments of Bong Mieu River, Quang Nam Province, Vietnam

This study assessed the accumulation levels and ecological risks associated with seven heavy metals (As, Pb, Cd, Hg, Cu, Cr, Zn) in the surface sediments of the Bong Mieu River in Quang Nam Province, Vietnam. The sampling encompassed 10 locations (S1-S10), considering areas both impacted and less impacted by gold mining activities. The findings revealed elevated levels of heavy metal pollution and associated ecological risks attributable to gold mining. Heavy metal content varied within specific ranges: As (70.6-341.2 mg/kg), Pb (216.3-504.1 mg/kg), Hg (0.138-0.252 mg/kg), Cd (0.91-1.51mg/kg), Cu (18.3-45.5 mg/kg), Cr (10.5-19.1 mg/kg), and Zn (49.3-84.1 mg/kg). Among these elements, Hg, Cu, Cr, Zn, and Cd adhered to the acceptable limits of VNTR 43:2017/MONRE (VNTR 43:2017/MONRE: National Technical Regulation/Ministry of Natural Resources and Environment of Vietnam). However, As and Pb content at all locations exceeded these limits significantly, with As being 4.1-20 times higher and Pb 2.3-5.5 times higher. The pollution of Pb and As was attributed to waste discharge from gold mining activities, which carry substantial amounts of these metals in various forms. The Igeo indicated heavy pollution of As and Pb in the sediments. Ecological risk factors were ranked as follows: E r i (As) > E r i (Pb) > E r i (Hg) > E r i (Cd) > E r i (Cu) > E r i (Cr) > E r i (Zn). The potential ecological risk (RI) due to combined heavy metal impact varied across locations, with S2 > S8 > S9 > S6 > S7 > S10 > S1 > S3 > S4 > S5, exhibiting low to moderate risk (RI values ranging from 73.4 to 252.8). The study area demonstrated high contamination levels for As and Pb, coupled with low to moderate potential ecological risks.

Indexical and statistical approaches to investigate the integrated origins of elements in the sediment of Teesta River, Bangladesh: sediment quality and ecological risk assessment

This study investigates ecological consequences from the combined provenance (natural and manmade) of fifteen metal(oid)s (Na, Al, K, Ti, Cr, Mn, Co, Zn, As, Rb, Sb, Cs, Ba, Th, and U) from a major Indo-Bangla transboundary river (Teesta). Instrumental neutron activation analysis has been performed to calculate the elemental concentration for a total of thirty sediment samples which accumulated from the upper, middle and downstream section of the Teesta River. In comparison with the crustal origin Rb, Th, and U were 1.5-2.8 times elevated. Elements from upstream and midstream sediments showed greater spatial variability than those from downstream sediments in terms of Na, Rb, Sb, Th, and U. Statistical approaches suggested the dominance of geogenic sources (Na, K, Al, Ti, Co, and Ba) of elements over anthropogenic sources (Cr and Zn). Alkali feldspar and aluminosilicates release lithophilic minerals into the sediments under the redox condition (U/Th = 0.18). Site-specific ecotoxicological indices advocated that some specific locations are highly hazardous relative to Cr and Zn. From SQG-based guidelines, Cr showed higher potential toxicity in some upstream locations relative to Zn, Mn, and As. In order to attain the knowledge limitation of northern transboundary rivers from Bangladesh, this study of origin and relative environmental impact will be beneficial for policy makers.

Bayesian-Based Approaches to Exploring the Long-Term Alteration in Trace Metals of Surface Water and Its Driving Forces

Trace metal pollution poses a serious threat to the aquatic ecosystem. Therefore, characterizing the long-term environmental behavior of trace metals and their driving forces is essential for guiding water quality management. Based on a long-term data set from 1990 to 2019, this study systematically conducted the spatiotemporal trend assessment, influential factor analysis, and source apportionment of trace elements in the rivers of the German Elbe River basin. Results show that the mean concentrations of the given elements in the last 30 years were found in the order of Fe (1179.5 ± 1221 μg·L^-1) ≫ Mn (209.6 ± 181.7 μg·L^-1) ≫ Zn (52.5 ± 166.2 μg·L^-1) ≫ Cu (5.3 ± 5.5 μg·L^-1) > Ni (4.4 ± 8.3 μg·L^-1) > Pb (3.3 ± 4.4 μg·L^-1) > As (2.9 ± 2.3 μg·L^-1) > Cr (1.8 ± 2.4 μg·L^-1) ≫ Cd (0.3 ± 1.1 μg·L^-1) > Hg (0.05 ± 0.12 μg·L^-1). Wavelet analyses show that river flow regimes and flooding dominated the periodic variations in metal pollution. Bayesian network suggests that the hydrochemical factors (i.e., TOC, TP, TN, pH, and EC) chemically influenced the metal mobility between water and sediments. Furthermore, the source apportionment computed by the Bayesian multivariate receptor model shows that the given element contamination was typically attributed to the geogenic sources (17.5, 95% confidence interval: 13.1-17.6%), urban and industrial sources (22.1, 18.0-27.2%), arable soil erosion (24.2, 16.4-31.5%), and historical anthropogenic activities (35.2, 32.8-43.3%). The results provided herein reveal that both the hydrochemical influence on metal mobility and the chronic disturbance from anthropogenic activities caused the long-term variation in trace metal pollution.

Heavy Metal Pollution and Health Risk Assessment of Vegetable-Soil Systems of Facilities Irrigated with Wastewater in Northern China

Soil pollution by heavy metals is a major concern in China and has received much attention in recent years. Aiming to investigate the status of heavy metal pollution and the safety of vegetables in the soil of wastewater-irrigated facilities, this study investigated the distribution and migration characteristics of heavy metals in vegetable−soil systems of facilities in a typical sewage irrigation area of the Xi River, Shenyang City, northern China. Health risks due to the fact of exposure to heavy metals in the vegetable soil of facilities and ingrown vegetables through different exposure pathways were evaluated. Spatial interpolation and a potential ecological risk assessment were applied to evaluate the soil quality. Bioaccumulation factors (BCFs) were used to analyze the absorption and transportation capacity of Cd, Cu, Pb, and Zn by different parts of different vegetables. The results showed that the average concentration of Cd exceeded the standard values by 1.82 times and accumulated by 11 times, suggesting that Cd poses the most severe pollution among the four metals in the soil of facilities in the Xi River sewage irrigation area. In the city, a significant accumulation of Cd in the soil was identified with different spatial distributions. Cd also contributed the most in terms of the estimated potential ecological risk index, while the impacts of the other three metals were relatively small. The concentrations of heavy metals were mostly lower than the limit set by the corresponding Chinese standards. Various BCFs were observed for the four metals in the order Cd > Zn > Cu > Pb. Vegetables also demonstrated different BCFs in the order of leaf vegetables > Rhizome vegetable > Solanaceae vegetable. The magnitude of the noncarcinogenic risk for all four heavy metals was less than one for all three exposure routes and did not cause significant noncarcinogenic health effects in humans. However, the carcinogenic risk of Cd from some vegetables via dietary intake was considered higher. Protection measures should be taken to implement better pollution control and land use planning.

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.

Assessment of metal mobility in sediment, commercial fish accumulation and impact on human health risk in a large shallow plateau lake in southwest of China

Sediment heavy metal pollution in the Dianchi Lake has been a long-term environmental problem of concern. This study investigated the lake sediment heavy metal contamination level, mobility, commercial fish metal accumulation and its impact on human health. The results show high As, Hg and Cd concentration in the sediment, while Pb and Cr contamination are insignificant. Sediment sequential extraction analysis shows that Hg in sediment has the highest portion of mobile fraction, followed by As, while the portion of mobile fractions of Cd, Pb and Cr in sediment is very low. The high concentrations of Hg and As in surface water and porewater were consistent with the chemical fraction composition of the two elements in sediment. Three major commercial fish species, Culterichthys erythropterus, Carassius auratus and Hypophthalmichthys molitrix, were collected for analysis of metal concentrations in their muscles. Among the same size of fish, C. auratus has the highest As concentration due to its bottom habitat and omnivorous feeding habits. On the other hand, C. erythropterus has the highest Hg concentration due to its relatively high trophic level position. The average THQ value of metals in fish tissue decrease in the order of As > Hg > Pb > Cd > Cr and the total THQ of average metal concentration in fish species decreased in the order of C. auratus > C. erythropterus > H. molitrix. Both THQ and total THQ is below 1, suggested no non-carcinogenic human health risk of fish consumption. However, TR of As in C. auratus was above 1.00E-04 threshold value, indicated potential carcinogenic human health risk. The results from this study indicate that although moderately to heavily contamination of Hg, As, and Cd occurred in Dianchi Lake sediment, only Hg and As tend to transport to surface water and accumulate in commercial fish due to their higher mobility in sediment.

Systematic Assessment of Health Risk from Metals in Surface Sediment of the Xiangjiang River, China

The common empirical screening method is limited to a preliminary screen target from vast elements for human health risk assessments. Here, an element screening procedure was developed for assessing the human health risk of the elements in the sediment of the Xiangjiang River. Ninety-six surface sediment samples from eight sampling stations were collected and 27 elements of each sample were investigated. Thirteen of the 27 elements were screened for human health risk assessments through the three-run selections by calculating anthropogenic factors, building element maps, and the removal of unnecessary elements. Pb posed the greatest health risk and exhibited a potential noncarcinogenic risk for adults at the stations S4 and S5, although no visible noncarcinogenic and carcinogenic risk for adults and children in the Xiangjiang River. Our study also suggested that the chalcophile elements were associated with greater health risk, compared to the lithophile and siderophile ones.

Geochemical Footprint of Megacities on River Sediments: A Case Study of the Fourth Most Populous Area in India, Chennai

An intensive surface sediment survey was carried out over 24 locations from the upstream to downstream sections of two large rivers (Adyar and Cooum) in Chennai (India) during the February dry season of 2015. Trace element concentrations were assessed on a <63 µm fraction using the Geoaccumulation Index (Igeo) and the newly proposed Geochemical Urban Footprint Index (GUFI), which can be performed to determine the pollution status of any megacity river influenced by urban development. The sediment quality of Chennai’s rivers was also compared to worldwide megacity pollution using sediment quality guidelines (SQGs), and a new megacity pollution ranking was determined. The Igeo results indicate that the Chennai rivers studied are strongly to extremely polluted regarding trace element content of sediment. Silver (Ag), Cadmium (Cd) and Mercury (Hg) are the most significant tracers of urban contamination. Chromium (Cr) concentrations show an industrial contamination gradient in relation to levels of other trace elements (As, Cu, Ni, Pb, and Zn) at the Chennai megacity scale. The GUFI ranges from moderate to extreme contamination, particularly in the downstream stretches of the two rivers. This spatial trend is related to various point sources and identified at specific sampling stations, with a lack of identifiable buffer zones. According to the worldwide comparison of megacity pollution, Chennai is ranked in fifth position. The present position can be attributed to a number of explanations: a population explosion associated with the unplanned growth of the city and non-controlled point sources of pollution in Chennai’s waterways.

Concentration decline in response to source shift of trace metals in Elbe River, Germany: A long-term trend analysis during 1998-2016

Monitoring spatial and temporal chemical status of water bodies is crucial to assist environmental policy, identify the chemical fingerprints, and further reduce the source orientated pollutants. Elbe River is one of the major rivers affected by anthropogenic activities in vicinity countries. This study assessed the spatiotemporal changes in response to source shift of Cd, Cu, Ni, Pb, and Zn in the suspended particulate matter (SPM) at upstream, midstream, and downstream of the Elbe River reach in Saxony state, Germany. The average contents of trace metals in SPM was found in the order of Zn (676 mg/kg) » Pb (79 mg/kg) > Cu (74 mg/kg) > Ni (48 mg/kg) » Cd (3.2 mg/kg). According to the Mann-Kendall trend test, Cd, Cu, Pb, and Zn showed significant declines over 1998-2016. The results of source apportionment indicate industrial, urban, natural, and historical mining sources influencing the metal contents in the Elbe River of Saxony. The contributions of industrial and urban pollution decreased by 58.2% from 1998 to 2007 to 2008-2016. The contribution of the natural source was steady over the last two decades.

Profiles and potential health risks of heavy metals in soil and crops from the watershed of Xi River in Northeast China

Heavy metal soil contamination is a major environmental concern in China and has drawn significant public attention in recent years. The present study assessed the human health risk of four heavy metals (cadmium, lead, mercury, and zinc) through soil exposure and dietary intake in the watershed of Xi River, west of Shenyang, Liaoning Province, northeast China. Concentrations of Cd, Pb, Hg, and Zn were determined in 411 soil samples and 59 crop samples collected from this area. The health risks of heavy metal exposure via soil ingestion, inhalation, dermal contact, and dietary intake of crops were further estimated; total hazard index values were 1.15, 1.33, and 2.03 for the adult male, adult female, and children, respectively, and the total cancer risk was 3.7 × 10^-3 for the local residents. Among the four investigated heavy metals, Cd was the primary pollutant posing health risks. The estimated non-carcinogenic and carcinogenic risks posed by the studied heavy metals were above the acceptable levels proposed by the U.S. EPA. Dietary intake of contaminated crops was identified as the predominant pathway for human heavy metal exposure in this area, suggesting that soil heavy metals can cause more harm when transported to the food chain. Overall, our findings suggest that the Xi River watershed is unsuitable for growing agricultural products, and more effective controls should be taken to curb future heavy metal pollution in the area.

Contamination and ecological risks of toxic metals in the Hai River, China

Contamination of trace metals in urban rivers is a global problem. The objective of this study was to investigate the contamination and ecological risks of trace metals in the Hai River, which receives substantial effluents from the Beijing-Tianjin region. A total of 43 surface water and sediment samples were collected and analyzed for physiochemical properties and toxic elements. The concentrations of Cd, Cr, Ni, Pb, Cu and Zn in the river water met the Chinese environmental quality grade I standards for surface water. The average total concentrations of Zn, Cr, V, Cu, Pb, Ni, Co, Sc and Cd in the sediments were 144.2, 77.5, 70.1, 46.1, 40.1, 29.6, 12.4, 9.9 and 0.26 mg/kg, respectively. The enrichment of Cd, Cr, Cu, Pb and Zn in the sediments was influenced by anthropogenic activity, as indicated by the enrichment factor (EF) and multivariate analysis. The concentrations of Co and Cr in the sediments were predominantly in residual fractions, while relatively higher amounts of Cd, Pb, Zn and Cu were in non-residual fractions. There was a significant correlation between concentrations of Cd, Co, Cr, Cu, Pb and Zn in non-residual fractions and their corresponding EF values (P < 0.01). This result further demonstrated that anthropogenic inputs were an important contributor to metal enrichment. The high bioavailability of Cd and poor bioavailability of Co and Cr in the sediments were demonstrated by the single extraction procedure. The significant correlation between concentrations of Cd, Cu, Pb and Zn in non-residual fractions and their concentrations in EDTA-extractable fractions was established (P < 0.01). This result indicates that single-step EDTA extraction may represent a useful procedure for assessing the bioavailability of Cd, Cu, Pb and Zn in riverine sediments. The ecological risks of the metals studied in the Hai River sediments were at a low level, dominated by the risks imposed by Cd.

Transcriptomic Profiles in Zebrafish Liver Permit the Discrimination of Surface Water with Pollution Gradient and Different Discharges

The present study aims to evaluate the potential of transcriptomic profiles in evaluating the impacts of complex mixtures of pollutants at environmentally relevant concentrations on aquatic vertebrates. The changes in gene expression were determined using microarray in the liver of male zebrafish (Danio rerio) exposed to surface water collected from selected locations on the Hun River, China. The numbers of differentially expressed genes (DEGs) in each treatment ranged from 728 to 3292, which were positively correlated with chemical oxygen demand (COD). Predominant transcriptomic responses included peroxisome proliferator-activated receptors (PPAR) signaling and steroid biosynthesis. Key pathways in immune system were also affected. Notably, two human diseases related pathways, insulin resistance and Salmonella infection were enriched. Clustering analysis and principle component analysis with DEGs differentiated the upstream and downstream site of Shenyang City, and the mainstream and the tributary sites near the junction. Comparison the gene expression profiles of zebrafish exposed to river surface water with those to individual chemicals found higher similarity of the river water with estradiol than several other organic pollutants and metals. Results suggested that the transcriptomic profiles of zebrafish is promising in differentiating surface water with pollution gradient and different discharges and in providing valuable information to support discharge management.

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.

Toxic elements in the stream sediments of an urbanized basin, Eastern China: urbanization greatly elevates their adverse biological effects

The concentration of toxic elements (Hg, Cd, Cr, Cu, Pb, Zn, Ni and As) was measured in the sediments of the Qinhuai River in Eastern China along a rural to urban gradient. Multiple approaches were undertaken to evaluate the degree of enrichment and adverse biological effects of these elements. The results showed that the concentration of Hg, Cd, Zn, Cu and Pb increased exponentially from the agricultural headwater to the urbanized downstream, which reflects a severe anthropogenic influence. In addition, area-specific references, such as the local soil background (LSB) and upper continental crust (UCC) derived from the Yangtze craton, were more applicable for evaluating the enrichment of toxic elements in the Qinhuai River than was global UCC. In addition, Cd and Hg had the highest enrichment factor values (EF, with averages of 9.18 and 7.14, respectively); Zn, Pb and Cu had moderate EFs (averages from 1.52 to 2.40), while the average EFs of Ni, Cr and As were approximately equal to 1. Based on consensus-based sediment quality guidelines (SQGs), the contamination characteristics of all of the samples studied were associated with low to moderate priority of adverse biological effects (ABEs) in the rural upstream area, while it was associated with a high to moderate priority of ABEs in the urban sections of the Qinhuai River. Our results suggest that the adverse biological effects of elevated levels of toxic elements were strongly related to the degree of anthropogenic pollution.

Assessment of metal contamination in the Hun River, China, and evaluation of the fish Zacco platypus and the snail Radix swinhoei as potential biomonitors

The Hun River is a major tributary of the Liao River in the northeast area of China and provides drinking water for 23 million local residents. This study was designed to assess the severity of metal contamination in the Hun River and the potential use of indigenous organisms (the fish Zacco platypus and the snail Radix swinhoei) as biomonitors of metal contamination. Water, sediment, and the native fish and snails were collected at four sampling sites that differed in their physicochemical characteristics and their contamination levels. The samples were analyzed for Cd, Cr, Cu, Ni, Pb, and Zn by ICP-MS. The results showed that although the overall potential ecological risks of the metals were low at our sampling sites, Cd posed a noteworthy ecological risk. Strong correlations were obtained between Cd concentrations in the organisms and in the environment. The results indicated that Z. platypus and R. swinhoei can be useful biomonitoring species for assessing Cd contamination. Biomonitoring with the snail may be most effective when focused on the gonad/digestive tissue (because of the high metal accumulation there), but further work is needed to confirm this.

Heavy metals and metalloids in the surface sediments of the Xiangjiang River, Hunan, China: distribution, contamination, and ecological risk assessment

Here, we aim to determine the distribution, ecological risk and sources of heavy metals and metalloids in the surface sediments of the Xiangjiang River, Hunan Province, China. Sixty-four surface sediment samples were collected in 16 sites of the Xiangjiang River, and the concentrations of ten heavy metals and metalloids (Mn, Zn, Cr, V, Pb, Cu, As, Ni, Co, and Cd) in the sediment samples were investigated using an inductively coupled plasma mass spectrometer (ICP-MS) and an atomic fluorescence spectrophotometer (AFS), respectively. The results showed that the mean concentrations of the ten heavy metals and metalloids in the sediment samples followed the order Mn > Zn > Cr > V > Pb > Cu > As ≈ Ni >Co > Cd. The geoaccumulation index (I _geo), enrichment factor (EF), modified degree of contamination (mC_d), and potential ecological risk index (RI) revealed that Cd, followed by Pb, Zn, and Cu, caused severely contaminated and posed very highly potential ecological risk in the Xiangjiang River, especially in Shuikoushan of Hengyang, Xiawan of Zhuzhou, and Yijiawan of Xiangtan. The Pearson's correlation coefficient (PCC) analysis, principal component analysis (PCA), and hierarchical cluster analysis (HCA) indicated that the ten heavy metals and metalloids in the sampling sediments of the Xiangjiang River were classified into three groups: (1) Cd, Pb, Zn, and Cu which possibly originated from Shuikoushan, Xiawan, and Yijiawan clustering Pb-Zn mining and smelting industries; (2) Co, V, Ni, Cr, and Al from natural resources; and (3) Mn and As. Therefore, our results suggest that anthropogenic activities, especially mining and smelting, have caused severe contamination of Cd, Pb, Zn, and Cu and posed very high potential ecological risk in the Xiangjiang River.

Trophic transfer of toxic elements in the estuarine invertebrate and fish food web of Daliao River, Liaodong Bay, China

In order to study element accumulation and trophic transfer in the food web, sixteen benthic invertebrate species and nine fish species were collected from the Daliao River estuary for analysis of toxic elements and nitrogen stable isotope in the muscle tissue. The concentrations ranged between 1.44-17.98, 0.01-9.30, 0.17-36.15, 0.7-145.4, 0.01-0.33, 0.14-14.88, 0.10-2.51, 0.02-0.14, and 19.3-221.1mgkg^-1 for As, Cd, Cu, Hg, Ni, Pb, Sb, and Zn, respectively. As, Cd, Cu, and Zn were significantly higher in the benthic invertebrates than in fish, whereas Hg and Sb were significantly lower. In addition, the benthic invertebrates were characterized by the highest bioaccumulation factor (BAF) for Cd, whereas the fish were characterized by the highest BAF for Hg. A significant decrease in Cd, Cr, Cu, and Ni levels, and a significant increase in Hg and Sb levels were observed with increasing trophic levels.

Spatial distribution and ecological risk assessment of phthalic acid esters and phenols in surface sediment from urban rivers in Northeast China

Concentration and spatial distribution of six phthalic acid esters (PAEs) and eight phenols in sediments of urban rivers, namely the Xi River (XR) and Pu River (PR) in Shenyang city, Northeast China were investigated and the ecological risk of these target pollutants was assessed based on the risk quotient (RQ) approach. Target PAEs and phenols were detected in most of sediment samples collected from the XR and PR. The concentrations of total PAEs in sediments varied from 22.4 to 369 μg/g dw in the XR and 3.71-46.9 μg/g dw in the PR. The levels of phenols ranged from 2.72 to 106 μg/g dw in the XR and 0.811-25.0 μg/g dw in the PR, respectively. The dominant pollutants in both XR and PR were DEHP, phenol and 4-methylphnol. The sampling locations XR1-3 in the XR suffered severe contamination from PAEs and phenols. The sites PR1 and PR6 were heavily polluted by phenols and PAEs, respectively. Almost all target PAEs and phenolic compounds in sediment of the XR exhibited medium or high ecological risk to organisms and the ecological risk in the PR mainly originated from PEAs, phenol and 4-methylphenol. These results would provide guidance for individual pollutant control and indicate that it is imperative to take some effective measures to reduce the pollution of those contaminants.

Removal of trace metals and improvement of dredged sediment dewaterability by bioleaching combined with Fenton-like reaction

Bioleaching by Aspergillus niger strain SY1 combined with Fenton-like reaction was optimized to improve trace metal removal and dewaterability of dredged sediments. The major optimized parameters were the duration of bioleaching and H₂O₂ dose in Fenton-like process (5 days and 2g H₂O₂/L, respectively). Bioleaching resulted in the removal of ≈90% of Cd, ≈60% of Zn and Cu, ≈20% of Pb, and in decrease of sediment pH from 6.6 to 2.5 due to organic acids produced by A. niger. After addition of H₂O₂, Fenton-like reaction was initiated and further metal removal occurred. Overall efficiency of the combined process comprised: (i) reduction of Cd content in sediment by 99.5%, Cu and Zn by >70% and Pb by 39% as a result of metal release bound in all mobilizable fractions; (ii) decrease of sediment capillary suction time (CST) from 98.2s to 10.1s (by 89.8%) and specific resistance to filtration (SRF) from 37.4×10(12)m/kg to 6.2×10(12)m/kg (by 83.8%), due to reducing amount of extracellular polymeric substances (EPS) by 68.7% and bound water content by 79.1%. The combined process was found to be an efficient method to remove trace metals and improve dewaterability of contaminated dredged sediments.