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The periodic anti-seasonal inundation of the Three Gorges Reservoir (TGR) leads to changes in the molecular composition of dissolved organic matter (DOM) in riparian soils, further impacting the geochemical processes and ecological risk of heavy metals. However, the intrinsic driving mechanisms of DOM influencing the cadmium (Cd), a major pollutant in riparian soils in TGR, at the molecular level remain unclear. In this study, the DOM molecular composition, labile Cd in riparian soils and the key driving mechanism before and after flooding were explored using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), the diffusive gradients in thin films (DGT) and partial least squares path modeling (PLS-PM). A spectral analysis revealed that after flooding, the relative abundance of terrestrial humic-like substances decreased whereas that of microbial humic-like substances increased. Furthermore, FT-ICR MS analysis revealed that the relative abundance of lignin, the main molecular components of DOM in riparian soils, increased after flooding. The linkage of DOM with the concentration and kinetic processes of labile Cd indicated that the higher aromaticity and unsaturation, larger molecular weight, and higher humification level of DOM promoted the mobility of labile Cd from the soil solid phase to the liquid phase. In particular, our findings indicated that at the molecular level, the most significant factor influencing the mobility of labile Cd was lignin, which was primarily governed by the complexation of lignin with labile Cd. The complexation mechanism between lignin and labile Cd resulted in increased ecotoxicological risk of labile Cd after flooding, while the overall ecotoxicological risk was low in riparian soils in TGR. This study provides better insight into the geochemical cycling and fate of toxic elements in reservoir ecosystems under the change of hydrological regime., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Since the completion of Three Gorges Dam, the water-level-fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR) experiences the periodic anti-seasonal inundation. However, knowledge for mechanisms of mobilization and transformation of arsenic (As) in WLFZ soils of the TGR remains scarce. To address this gap, a combination of field observation and simulated flooding experiments attempts to illustrate the As mobilization, the transformation between As(V) and As(III), and the factors driving these processes. The study revealed that anti-seasonal inundation (with a temperature at 13 ℃) mitigated As release from submerged soils. Interestingly, the total As and ratio of As(III) (the more toxic form of As) concentrations in porewater at 13 ℃ was lower, and the prevalence of As(III) occurred later than those at 32 °C (imitate the seasonal inundation condition). The results indicated that the As reduction and the corresponding toxic risks in submerged soils were alleviated under anti-seasonal inundation. The study proposes the reduction of As-bearing manganese (Mn) mineral assemblages and competitive adsorption of dissolved organic carbon (DOC) as primary mechanisms for As mobilization. Furthermore, microorganism-mediated detoxification/reduction processes involving DOC, nitrogen, and Mn (oxyhydr)oxides were identified as central pathways for As(III) enrichment under anti-seasonal inundation. This study enhances understandings of the biogeochemical processes and fate of As in WLFZ soils influenced by artificial regulation of the reservoir., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The construction and operation of the Three Gorges Dam occluded sediment transportation in the Yangtze River. However, the sources, transport processes, and environmental impacts of these sediments on the Three Gorges Reservoir (TGR) remain unclear. Here, we used rare earth elements (REEs) to trace the transport pathways of sediments in the TGR, China. Geochemical characteristics including the chemical composition and fractionation, temporal and spatial distribution, and potential sources of REEs were also evaluated in this study. The individual REEs concentration in the TGR sediments followed the Oddo-Harkins rule, with the mean REEs value of 207.33 μg/g. REEs concentrations in the midstream were higher than those in the upstream and downstream of the TGR. Statistical analysis showed that water impoundment phase had no significant influence on the distribution of REEs. TGR sediments are mainly derived from terrigenous detrital particulates, characterized by a distinctive enrichment in light REEs, with its percentage higher than 90 % of the total REEs. The significant positive correlation among the REEs confirmed that they are co-existed and shared the similar sources. Multiple provenance analysis approaches using discriminant function analyses, provenance indices, and La/Yb-La/Sm-Gd/Yb ternary diagrams further indicated that the REEs in sediments originated from the weathering of mudstone in the basin of TGR. After periodic water level fluctuation for more than six years, the chemical compositions of REEs in TGR sediments slightly differed from those of the Yangtze River sediments before TGR construction, but were similar to those of the downstream of the Yangtze River. Therefore, this study indicated that the construction and operation of the TGR changed the chemical compositions and the origin of the sediments in the Yangtze River, which can provide useful insights into the transport pathways of TGR sediments and their impacts on the fluvial environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Sediments act as sinks of microplastics (MPs) derived from terrestrial ecosystems. However, the fate and transport of MPs at the zone of sediment-overlying water in reservoir environment are poorly understood. Here, the MPs distribution patterns in surface sediments of the Three Gorges Reservoir (TGR) and dominant mechanisms responsible for the sinking of MPs at the zone of sediment-overlying water were comprehensively investigated. The predominant occurrence of small microplastics (<300 µm, SMPs) in surface sediments of the TGR was found, with buoyant polyethene (PE) was dominant polymer types. Interestingly, the high abundance of SMPs in sediments correlated well with the Ca 2+ /Mg 2+ in overlying water, suggesting that divalent cations in overlying water may enhance the preferential deposition of SMPs. Simulation sinking experiments under the presence of Microcystis aeruginosa and two divalent cations using different-sized PE MPs demonstrated that the greater deposition of SMPs was mainly the result of the formation of biogenic calcite on the surface of MPs rather than magnesium minerals, which provides stronger ballasting effects for SMPs than for large MPs. This study first highlights that the impact of biomineralization on preferential sinking of SMPs and enhances the understanding of the transport behaviour of MPs in aquatic environment., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Characterizing the chemical properties, morphologies, size, and quantities of microplastics (MPs) in water samples with high precision is critically important for understanding the environmental behaviors of MPs. Traditional detection methods, such as Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy point-by-point detection, provide worthy reference techniques but are time- and labor-consuming. We established a super time-saving and high-precision technique to characterize MPs using micro-Raman automatic particle identification (MR-API). Based on the identification of PS spheres, screen magnification, exposure time, and the number of scans are selected as crucial detection parameters for MR-API analysis, which highly affect the precision of the results. Detecting particles down to 1 μm requires magnification of the mosaic until the scale showed 200 μm. The recommended setting parameters were 83.33 or 100 ms exposure time, 20 scans, 7 mW laser power, and 1 μm image pixel size, suitable for polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE), polyvinyl chloride (PVC), and polyamide (PA) particles detection. With the complete procedure of MR-API measurements, the recovery of MPs was 61.67-90.00 %. To validate the feasibility of the MR-API, the method was used to detect samples of known plastic types (mask leachates) and unknown plastic types (urban lake). A total of 4540 particles in the sample of mask leachates consuming 35 h 50 min 43 s, and 0.92 ± 0.49 % of particles were identified as MPs. The urban river sample efficiently identified PP, PET, PE, PVC, PS, EVA, and VC/VAC MPs using this method. The detected MPs size ranged from 8.3 to 5000 μm, saving 75.03 % and 58.38 % of the time compared to the conventional micro-FTIR and micro-Raman point-by-point methods, respectively. Therefore, this method is effective for detecting MPs in the environmental samples and has excellent prospects., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The Three Gorges Reservoir (TGR) has formed the water-level-fluctuation zone (WLFZ) due to reservoir regulation. However, as a sensitive zone in reservoir, little is known about the geochemical process and ecotoxicological risk of arsenic (As) in WLFZ soils under the anti-seasonal flow regulation. Hence, the anthropogenic contamination, mobility and ecotoxicological risks of As in WLFZ soils of the TGR were comprehensively assessed using the geochemical baseline concentration (GBC), chemical fractions, diffusive gradients in thin films (DGT) and toxicity data. The As concentrations in WLFZ soils showed a trend of increasing at the early stage of water impoundment and then stabilizing in recent years, which presented a low ecological risk of As according to the assessment by pollution indices. Based on GBC calculations, the average anthropogenic contribution of As was 13.95 %, indicating a slight influence of human activities. The distribution of labile As measured by DGT in WLFZ soils was mainly controlled by the Fe/Mn oxides, pH and organic matter. The DGT-induced fluxes in soils (DIFS) model further implied that resupply of As to soil solution was partially sustained by the soil solid phase, in which the resupply capacity was low and limited by the adsorption and desorption kinetics. In addition, the DGT was combined with toxicity data to obtain the risk quotient (RQ) and probabilistic risk assessment. The RQ value was lower than 1, indicating a low toxicity risk in WLFZ soils. Furthermore, the As in WLFZ soils had a low probability (5.97E-3 % and 7.77E-2 % in the mainstream and tributary, respectively) of toxic effects toward the aquatic biota. This study provides a comprehensive evaluation for the mobility and toxicity risk of As in WLFZ soils, which is beneficial to the prevention and control of heavy metals pollution in the riparian soils of lakes and reservoirs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The speciation of arsenic (As) determines its biogeochemistry and ecotoxicity in soils. However, the approach to in situ monitor labile As (III) and As (V) in soils still requires more exploration. In this study, we developed a method for simultaneously obtaining in-situ data on labile As (III) and As (V) in soils using diffusive gradients in thin films (DGT) and high performance liquid chromatography-inductively coupled plasma mass spectrometry. The Fe 2 O 3 ∙xH 2 O DGT sampler exhibited rapid and simultaneous accumulation of As (III) and As (V) in solutions within 90 min. The high efficiency of simultaneous elution of As (III) (~84 %) and As (V) (~97 %) was achieved using 0.8 % H 3 PO 4 as eluent at 90 °C for 80 min. The method detection limits for As (III) and As (V) were 0.01 and 0.005 μg/L, respectively. This method was applied to reveal the labile As (III) and As (V) in soils in the water level fluctuation zones of the Three Gorges Reservoir, which is the largest reservoir in China. The concentrations of As (III) and As (V) measured by DGT varied with different sampling sites, ranging from 0.01 μg/L to 1.20 μg/L and from 0.01 μg/L to 0.26 μg/L, respectively. The labile As (III) exhibited the higher resupply rate from soil solid phase to soil solution than labile As (V). This study helps to achieve simultaneous in-situ quantification of labile As (III) and As (V) in soils, and will improve the understanding of As mobilization and ecotoxicity in soils., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Photocatalytic oxygen activation is an excellent strategy for algae control in water. However, the fast recombination of photogenerated charge and slow rate of oxygen transfer limit the reactive oxygen species generation efficiency for algae inactivation. Herein, to solve above issues, magnetic field was introduced to the BiO 2-x /Bi 3 NbO 7 system to effectively covert oxygen into reactive radicals. The electrochemical experiment and DFT calculation results indicated the charge separation could be accelerated by the Lorentz force generated by the magnetic field, resulting in increase of electron concentration. Meanwhile, the value of volumetric gas-liquid mass transfer coefficient was increased by 59.79 % with magnetic field, thus more oxygen could be reduced to superoxide radical. Photocatalytic algae inactivation rate by BiO 2-x /Bi 3 NbO 7 with magnetic field could be increased by 2.07 times than that without magnet filed. This work further extends the strategy of using magnetic field to simultaneously facilitate the charge separation and oxygen transfer rate., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

Intimately coupled photocatalysis and biodegradation (ICPB) is an emerging technology that has potential applications in the degradation of bio-recalcitrant pollutants. However, the interaction principles between photocatalysts and biofilms in ICPB have not been well developed. This article covers a cooperative degradation scheme coupling photocatalysis and biodegradation for efficient degradation and mineralization of ciprofloxacin (CIP) using ICPB with B-doped Bi 3 O 4 Cl as the photocatalyst. In consequence, a removal rate of ∼95 % is reached after 40 d. The biofilms inside the ICPB carriers can mineralize the photocatalytic products, thus improving the removal rate of total organic carbon (TOC) by more than 20 %. Interior biofilms are not destroyed by CIP or photocatalysis, and they adapt to ICPB of CIP by enriching in Pseudoxanthomonas, Ferruginibacter, Clostridium, Stenotrophomonas and Comamonas and reconstructing their microbial communities using energy produced by the light-excited photoelectrons. Furthermore, this research gives new opinion into the degradation principles of the ICPB system., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

This study focuses on characterizing microplastics and non-microplastics released from surgical masks (SMs), N95 masks (N95), KN95 masks (KN95), and children's masks (CMs) after simulating sunlight aging. Based on micro-Raman spectrum analysis, it was found that the dominant particles released from masks were non-microplastics (66.76-98.85%). Unfortunately, CMs released the most microplastics, which is 8.92 times more than SMs. The predominant size range of microplastics was 30-500 µm, and the main polymer types were PP and PET. Compared with the whole SMs, the microplastic particles released from the cutting-SMs increased conspicuously, which is 12.15 times that of the whole SMs. The main components of non-microplastics include β-carotene, microcrystalline cellulose 102, and eight types of minerals. Furthermore, non-microplastics were mainly fibrous and fragmented in appearance, similar to the morphology of microplastics. After 15 days of UVA-aging, the fibers of the face layers had cracks to varying degrees. It was estimated that these four types of masks can release at least 31.5 trillion microplastics annually in China. Overall, this study demonstrated that the masks could release a large quantity of microplastics and non-microplastics to the environment after sunlight aging, deserving urgent attention in the future study., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Geochemical behaviors of trace metals in the sediment profiles are crucial for predicting the associated environmental risks in aquatic ecosystems. However, the comprehensive transport of trace metals under both equilibrium and dynamic conditions is still unclear under the changing hydrological regime. Here, the equilibrium partitioning behaviors and remobilization of five trace metals (Ni, Cu, Zn, As, and Pb) in sedimentary profiles within the tributaries of the Three Gorges Reservoir were explored by the partitioning coefficient (K d ), diffusive gradients in thin films (DGT), and DGT induced flux in sediments (DIFS) model. According to the K d values, As posed the highest migration ability among the trace metals in the sediment profiles under equilibrium circumstances. Similarly, the dynamic processes of trace metals simulated by the DIFS model also suggested that As displayed the highest desorption rate despite having the lowest labile pool size. Moreover, all trace metals were classified as the "partially sustained" case, while the supply abilities of As and other trace metals were limited by the diffusion and the desorption kinetics, respectively. In addition, DGT-labile trace metals showed a diffusion trend from the sediment to the water column (except for Zn) at the sediment-water interface, indicating potential risks to water quality. Specifically, the equilibrium partitioning behaviors revealed the potential labile pool of trace metals in the solid phase, and the dynamic resupply process between the solid phase and porewater remained undetermined. In comparison, although DGT simulated the kinetic process of trace metals in the sediments, the labile pool of the trace metals could not be obtained. This study provided a holistic insight into the complementary trace metal behaviors under both equilibrium and dynamic conditions in the sediment and was beneficial to the water quality protection and internal pollution remediation in the aquatic environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Chromium (Cr) is a widespread pollutant with high toxicity and mobility. However, the diffusion-resupply kinetics of Cr(VI) between the solid phase and solution in the soils remain unclear. Here, we quantified the contributions of the soil solution and solid phase to the diffusion-resupply process of Cr(VI) in the contaminated soils using the diffusive gradients in thin-films (DGT) and DGT-induced fluxes in soils model. Based on the solution extraction result, Cr(VI) was the main available Cr species in the contaminated soils. Comparing the two diffusion-resupply stages of the kinetic process, the potential hazards due to the resupply from the solid phase can reach 10.71-50.66 %, although the soil solution accounted for the largest proportion of the effective concentration of Cr(VI) (49.34-89.29 %), which was ignored in the traditional equilibrium method. The kinetic parameters can be used to interpret the dynamic process. The resupply ability of the solid phase was closely related to the response time (T c ). The longer T c was consistent with the low desorption constant, indicating a kinetic limitation. The magnitude of the resupply from the solid phase was related to labile pool size of Cr(VI) and soil organic carbon content. This study established a new quantification method for assessing diffusion-resupply kinetics of Cr(VI) in the soil， indicating the underestimation of Cr(VI) risk based on the use of traditional equilibrium methods. Our data provided a scientific basis for ecological risk assessment, pollution prevention, surface- and groundwater control, and environmental governance in areas with Cr contaminated soil., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Urban rivers are potential sinks for microplastic (MP) contamination in the environment. However, the footprint of MPs in urban rivers is not well understood because it is influenced by natural and anthropogenic factors. This study focused on the occurrence, pollution risk, and potential sources of MPs in surface water and sediments before and after thawing in Shahe River, Beijing. The size distribution, morphological characteristics and polymer types of MPs were analyzed using a micro-Raman spectroscopy. The results showed that the average abundance of MP obviously increased after river thawing, from 1772 ± 1668 items·m -3 to 3877 ± 2517 items·m -3 in surface water and 4776 ± 4817 items·kg -1 to 14,004 ± 5371 items·kg -1 in sediments. The MP polymer types were more diverse after thawing. The main MP type in surface water changed from polyethylene terephthalate (PET) to polypropylene (PP). Moreover, PP was the most common type in sediments. Small-sized MPs (SMPs, 10-300 μm) were dominant in Shahe River, with the proportion increasing from 48.5% to 83.3% in surface water and from 84.3% to 94.4% in sediments after thawing. Although the MP pollution risk increased after thawing, it was still low in the Shahe River. Unfortunately, changes in polymer types caused by thawing and the emergence of toxic polymers increased the ecological risk in the urban river. These results revealed the information of MP contamination before and after thawing, and highlighted the barrier influence of river icing on the migration of MPs. Overall, the results presented a new perspective on the environmental behavior of microplastics in urban rivers, suggesting that the occurrence and dominance of SMPs and the emergence of toxic polymers in urban environmental media require close attention in the future., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Microplastics (MPs) in terrestrial aquatic ecosystems has received increasing attention. However, its footprints in reservoirs are poorly documented compared to those in rivers and lakes, especially for small-sized microplastics (<300 μm, SMPs). This study investigated the whole size spectrum of MPs contamination, classified by shape and polymer type, in surface waters and sediments at the Jiayan reservoir, one of the cascade reservoirs in the Upper Yangtze River in western China. High concentrations of MPs were detected in all surface water and sediment samples. The MPs abundances ranged from 1.10 × 10 4 to 6.17 × 10 4 items/m 3 (average 2.75 × 10 4  ± 2.33 × 10 4 items/m 3 ) in the surface water and 2.60 × 10 3 to 1.57 × 10 4 items/kg (average 6.90 × 10 3  ± 5.96 × 10 3 items/kg) in the sediment. The SMPs accounted for 80% of the total MPs particles, and were dominated by polyethylene (PE) fragment. Small-sized PE was the main contributor to the high abundance of MPs in the Jiayan reservoir. Neglecting SMPs not only leads to an underestimation of the degree of risk, but also causes misjudgment of the major morphology, components, and sources. The conditional fragmentation model analysis showed the stability of MPs increased from the fibers to fragments and fibers tend to disintegrate into smaller particles. Agricultural activities and atmospheric deposition were the main sources of MPs in the Jiayan reservoir. This study indicates that the reservoirs are presumably hotspots for MPs accumulation, and the fate of SMPs in the cascade reservoirs deserves more attention for further studies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

To overcome the interfacial problem between X-ray radiopaque ZrO 2 fillers and polymer resin in dental composites, monodispersed SiO 2 @ZrO 2 @SiO 2 (SZS) microspheres with narrow size distribution were prepared by a controlled sol-gel method. In the presence of SiO 2 coating layer over SiO 2 @ZrO 2 (SZ) microspheres, they were easily silanized same as SiO 2 microspheres. Ethoxylated bisphenol A dimethacrylate (EBPADMA) with a higher molecular weight and a lower viscosity was used as base resin monomer mixed with a low amount of diluent triethylene glycol dimethacrylate (TEGDMA). Additionally, the addition of a small amount of pore agent acetone dicarboxylic acid (ADCA) produced some voids, thereby effectively reducing the polymerization shrinkage of the resin. The prepared dental composites combining 52 wt% monodispersed silica microsphere, 20 wt% SZS microspheres, exhibited significantly enhanced capacity in radiopacity (higher than tooth enamel) and very low shrinkage (<0.1%). It also has better mechanical properties than resin composites filled with SiO 2 microspheres, and its strength can meet practical applications. The properties of the radiopaque dental composite were to be further tuned by varying the amount of SZS microspheres contents, and the radiopaque resin has an advantage over the commercial one in that it is clinically nondestructive., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

As the most widely used method for evaluating heavy metals (HMs) in soil or sediment, the enrichment factor (EF) is prone to bias and even yields misleading assessment results for HM pollution due to data uncertainties, lack of local background values and a failure to assess the comprehensive pollution of multiple HMs. Here, we developed an improved EF model integrating stochastic mathematical methods and geochemical baselines (GBs). First, GBs were obtained using the relative cumulative frequency distribution method. The probability that each HM belongs to each enrichment degree was then quantified based on the probability density function deduced from the maximum entropy method. Furthermore, we defined a synthetic index to reveal the probability that multiple HMs belongs to comprehensive enrichment degree considering the weight of each HM. Finally, the enrichment category for each HM and multiple HMs were determined following the first-order moment principle. The improved EF model was successfully applied to evaluate and predict the HM pollution in sediments collected from Poyang Lake, the largest freshwater lake in China. Slight enrichment (1.88) of multiple HMs was found in sediments from Poyang Lake, characterized by a pronounced probability (0.35) to deteriorate to the "moderate enrichment" category. Among the different HMs, Cd requires more attention considering its dominant contribution (0.51) to the comprehensive pollution and high probability (0.65) for deterioration. Otherwise, assessment results employing the improved EF model agree with the spatial patterns of HM concentrations based on spatial autocorrelation analysis and source apportionment using Pb isotopic signatures and principal component analysis. Compared with the conventional EF method, the assessment results of the improved EF model were more accurate, comprehensive and reliable. In conclusion, the improved EF model has a better capability of evaluating and predicting HM enrichment in sediments and can be helpful for optimizing control measures for HM pollution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

B is a potentially toxic element, and its potential ecological influences in aquatic environments have gained increasing attention in recent years, especially in reservoir ecosystems. As the largest freshwater reservoir in China, the estimation of B's ecological risks in the Three Gorges Reservoir (TGR) is critical for national drinking water safety. However, the lack of a toxicity coefficient (T c ) for B limits its ecological risk assessment (E r ) in aquatic environments, especially for sediments. In this study, the T c of B was carefully calculated, considering toxicological, sedimentological, and ecological ranking factors. The E r for B was then assessed for surface sediments collected from the TGR. Enrichment factors (EFs) were also used to identify the influence of human activities on B. The results show that the average concentrations of B in mainstream and tributary sediments were 53.98 mg/kg and 90.88 mg/kg, respectively, slightly higher than sediment background B values in China (48 mg/kg). Additionally, EFs showed that the tributary sediments were moderately enriched in B. The EF 1.5 value was higher than zero, indicating that the anthropogenic influence in tributary sediments than in mainstream sediments. Moreover, chemical speciation of B in TGR sediments was mainly attributed to the residual fraction, indicating weak migration of B in sediments. Furthermore, after calculating T c according to the principles of E r , it was found that it is more scientific to assign the T c of B in sediments a value of 2. Based on this T c value, the E r in the TGR was assessed and it revealed that B in TGR sediments had low ecological risk. The scientific calculation of the T c provides an important parameter for B ecological risk assessments in aquatic environments in the future., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The pollution of potentially toxic elements (PTEs) in Baiyangdian Lake (BYDL), the largest shallow lake in northern China, has been focused on since the construction of the Xiong'an New Area. However, research on the bioavailability and diffusive flux of PTEs in BYDL sediments has been still limited. Herein, sediment samples were collected from BYDL to systematically evaluate the pollution risk, bioavailability, and diffusion flux of PTEs using multiple methods, including the pollution indexes, risk assessment code, bioavailable metal index, the sequential extraction, and diffusive gradients in thin-films (DGT). The results showed that the average concentrations of PTEs (except for Cd) were similar to the local background. The spatial distribution of PTEs showed that their contents were higher in northern sediments than in southern sediments, and risk assessment results suggest that Cd is the priority pollutant in the BYDL. Most PTEs in the sediments were mainly present in the residue fractions; however, Cd was mainly present in the non-residue fraction. Further analysis of the Cd content and chemical fraction showed that Cd was not only abundant in the northern sediments, but also that the non-residual fraction of Cd was significantly higher than in the southern sediments. The diffusive fluxes of PTEs in the northern sediments were also investigated in comparison with their chemical fractions. Results suggest that Cd has the potential to diffuse from the sediment into the overlying water. Additionally, upon combining the DGT and chemical fractions analyses, it was found that the PTEs which mainly in non-residual fraction tend to diffuse upwards into the overlying water. But, the release tendency of PTEs does not fully depend on their non-residual content. Overall, PTEs did not significantly contaminate BYDL sediments; nevertheless, the potential ecological risk of Cd should be considered., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Trivalent chromium has historically been considered as an environmentally benign micronutrient due to its low mobility; however, its kinetic process in soil remains poorly understood. Here, the labile fraction and kinetics of Cr(III) in contaminated soils were explored using diffusive gradients in thin films (DGT) and the DGT-induced fluxes model. In contrast to the low mobility of Cr(III) in soils reported by the classic equilibrium partitioning method, we observed steady resupply from the solid phase through a dynamic process, wherein Cr(III) in the soils were maintained by an intermediate resupply rate with the R values at their maximum (R max ). The resupply of Cr(III) was influenced by the kinetic parameters and soil properties: (i) the resupply ability (R-R diff ) was influenced by pH and response time (T c ); (ii) R max , was controlled by pH, T c , and the desorption rate (k - 1 ); (iii) k - 1 was influenced by pH and soil texture. This study presents the new information regarding the kinetics of Cr(III) in soils and demonstrates that Cr(III) is steadily resupplied by soil, which is not captured by equilibrium-based methods, furthering our insight of the geochemical behavior of Cr(III). This information was essential for understanding the toxicity of Cr and improving remediation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Cascade reservoirs facilitate the effective use of water resources and help to alleviate existing problems of water shortage in drought-prone regions. However, the geochemical behavior and controlling mechanisms of trace metals in response to the operation of cascade reservoirs are relatively unknown. Here, trace metals (As, Cr, Cu, Li, Ni, Pb and Zn) from thirty sediment cores from cascade reservoirs (Panjiakou and Daheiting Reservoirs) in China were evaluated. Multiple methods including geochemical baseline, geostatistical analysis, factor analysis (FA), and positive matrix factorization (PMF), were combined to assess pollution status, identify and quantify potential anthropogenic sources, and determine the influence of hydrodynamic conditions on trace metals distribution. The results indicate that minor enrichment of trace metals appeared in both cascade reservoirs. However, trace metal concentrations exhibited spatial heterogeneity between two cascade reservoirs, and diverse hotspots of different metals were unexpectedly observed. This can be explained by the following three aspects: (1) Metal hotspots were detected upstream of the cascade dams via geostatistical analysis and FA, particularly for naturally sourced metals (As and Li) where dam interception resulted in higher concentrations in the upstream reservoir. (2) PMF analysis identified agricultural, industrial, and natural sources to account for 23.44%, 41.61%, and 34.95%, respectively, to the metal concentrations in the downstream reservoir. Anthropogenic emissions were the dominant factors influencing the spatial variability of Cu, Pb, and Zn between the cascade reservoirs, with higher concentrations observed in the downstream reservoir. (3) The hydrological regime also influenced the redistribution of human-derived metals, where slower flow velocities at river bends resulted in higher deposition of metal-bearing particles. This study shed light on the spatial distribution of trace metals in response to the construction and operation of cascade reservoirs, and it suggests that trace metal hotspots should be monitored to prevent potential contamination in sediments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Toxicity, bioavailability, and mobility of a metal depend on its speciation rather than its total concentration. In this discussion, we emphasize the need for field-based metal speciation analysis methods, given the flaws of traditional techniques. We express a science-based opinion that the diffusive gradients in thin-films (DGT) is a promising and powerful technique for performing in-situ measurement of metal species or speciation in different environmental samples. Several limitations and challenges in further application of DGT are also highlighted in this discussion., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Urbanization and urban construction lead to entensive environmental deterioration. Trace metals in urban soils pose a threat to urban water bodies and local populations. However, the release ability of labile metals and their release risk in urban soils remains unclear. Here, soils were collected from different functional zones in the Pingshan District (PSD) of Shenzhen. Based on results of soil properties, total contents of trace metals, geochemical index (I geo ), and risk assessment code (RAC), diffusive gradients in thin films (DGT) and DGT-induced fluxes in soil (DIFS) model were further used to assess the release risk of trace metals in urban soils. The results showed that the average total concentrations of trace metals (As, Cr, Cu, Pb, and V) were higher than the local soil background values, implying that trace metals accumulated in urban soils. However, the distributions of labile metals determined by DGT were not similar to those of total metal concentrations. Except for As, urban soils from PSD sites exhibited "uncontaminated to moderately contaminated" levels based on the average values of I geo . Moreover, the pollution and migration of Cu in urban soils are problematic as evidenced by the I geo and RAC assessments. Release ability of Cu was assessed using parameters of DIFS model (i.e., bioavailability concentrations (C E ), resupply ability (R), response time (T c ), desorption rate (k -1 ), and sorption rate (k 1 )). Residential areas showed high C E values for Cu, while the resupply ability was low. Furthermore, considering the influences of R, T c , k -1 , and k 1 , membership function value was used to re-calculate the order of C E in urban soils. The final results suggested that the agricultural zone exhibited the highest release risk among soils from various functional zones. Therefore, DGT and DIFS model should be effective tools to assess the release risk of trace metals in urban soils., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Sediments act as crucial sink and source for metal contamination in aquatic environment of reservoir systems. However, the high complexity and heterogeneity of sediments make it difficult to trace the sources of metals in reservoir sediments. As a toxic metal, how to trace anthropogenic Pb sources in sediments is important for the water quality safety, especially in reservoir. Herein, 98 sediment samples collected from the connected Panjiakou Reservoir (PJKR) and Daheiting Reservoir (DHTR) were analyzed. A novel approach for tracing anthropogenic Pb sources was established by combining the regional geochemical baseline (RGB) and Pb isotopic ratios. The results showed that the mean concentration of Pb in these two reservoirs was 44.59 mg/kg, and the RGB value of Pb was 43.77 mg/kg. Pollution assessments using RGB and enrichment factor indicated that the influence of anthropogenic Pb is greater in DHTR sediments than in PJKR sediments. Based on the RGB model, samples influenced by anthropogenic activities (SS-AA) were screened and found in the DHTR. The anthropogenic Pb contribution in DHTR SS-AA was totally 35.29%. Moreover, the mean value of 206 Pb/ 207 Pb in DHTR SS-AA (1.107 ± 0.029) was slightly lower than those of natural inputs, indicating there was a small amount of anthropogenic Pb input in DHTR. The anthropogenic Pb sources were further identified using Pb isotopic ratios ( 206 Pb/ 207 Pb and 208 Pb/ 207 Pb) for DHTR SS-AA. Their apportionments were calculated with the help of the RGB model. The results showed that iron mining (20.42%) and coal combustion (14.87%) were the two main anthropogenic Pb sources. Aerosol deposition was likely the main pathway for coal combustion input. The results confirm that the proposed method of combining RGB and Pb isotopic ratios was a good attempt to trace the anthropogenic Pb sources in reservoir sediments., (Copyright © 2019 Elsevier B.V. All rights reserved.)

As one of the largest man-made reservoir, the Three Gorges Reservoir (TGR) brings great uncertainty and challenges regarding trace metal (e.g., Cu) remobilization in the sediment. Therefore, in this study, sediment cores were collected from the mainstream of the Yangtze River and its three tributaries in the TGR, with a focus on evaluating the Cu remobilization risk and release dynamics using conventional methods, diffusive gradients in thin films (DGT), and the DGT-induced fluxes in sediments (DIFS) model. The results showed that although total Cu concentrations were slightly higher than background values, Cu was mainly observed in the unreactive residual fraction. Additionally, assessment of sediment quality guidelines and the risk assessment code indicated low Cu contamination risk for all sampling sites. However, the results of DGT measurements at the sediment-water interface showed efflux of Cu from sediment to the overlying water at most sites, except for the upstream of the Meixi River and the mainstream of the Yangtze River. Interestingly, diffusion fluxes at the three tributaries displayed an increase trend from the upper to lower reaches. The DIFS model simulation further implied that the highest resupply capacity and desorption rate occurred in the Zhuyi River and the upstream of the Meixi River. In fact, the accumulation of Cu from the upper to the lower reaches of the Zhuyi River significantly elevated the Cu resupply capacity. Thus, more attention should be paid to Cu mobilization in the TGR, especially in the Zhuyi River and the upstream of the Meixi River., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Water quality is among the most important environmental issues related to sustainable development in China, especially to ensure national drinking water safety. Here, we investigated the concentrations of 19 trace elements in major drinking water sources from five major river basins in China: Yangtze River Basin, Yellow River Basin, Huai River Basin, Hai River Basin, and Liao River Basin. Water quality, human health risk, and probabilistic health risk were evaluated using statistical analysis, as well as the water quality index (WQI), hazard quotient, hazard index (HI), carcinogenic risk (CR), and Monte-Carlo simulation. The distributions of the trace element concentrations differed somewhat among the five river basins. Regardless, the concentrations of all trace metals were within the permissible drinking water quality limits set by China, WHO, and US EPA and Chinese surface water standards (Grade I). Based on the low WQI values, all five river basins were categorized as having "excellent" water quality. In the non-carcinogenic risk assessment, the HI values for both adults and children were within the safe limit (<1.0), indicating no adverse health effects on the human body via daily oral intake and dermal absorption. By contrast, the CR values for As exceeded the Chinese limit of 1.0 × 10 -6 , with a higher risk for adults, via ingestion as the main exposure pathway. Sensitivity analysis identified exposure duration and ingestion rate as the most sensitive variables affecting the probabilistic risk for adults, while As concentration and exposure duration were the most sensitive variables for children. Overall, the findings indicate that As in drinking water may pose a detrimental health risk to the exposed population; therefore, regulation and management should focus on As monitoring and evaluation in the major river basins of China., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The release of pollutants in soils owing to rainfall is a major challenge related to urbanization. Here, urban soils from different functional zones were collected to evaluate the release risk and estimate their annual release amounts of trace metals (Co and Ni) using multiple techniques, including diffusive gradients in thin-films (DGT), DGT-induced fluxes in sediments (DIFS) model, and Fourier-transform infrared (FTIR) spectroscopy. The results indicate that the average concentration of Co (6.55 mg kg -1 ) was slightly lower than that of the local soil background, whereas for Ni, the trend was reversed. Risk assessments based on total concentrations show that the soil samples were uncontaminated with Co while uncontaminated to moderately contaminated with Ni. However, the mobility coefficients indicate that Co posed low to medium risk, while Ni posed low risk. Hence, further investigation of DGT measurements and DIFS model show that the DGT-measured Co and Ni concentrations were lower than the corresponding concentrations in solution, leading to low R values and the partial resupply of Co and Ni from the solid phase. The FTIR spectra and elemental analysis suggest that because of the electrostatic attraction and complexation of the hydrosilicate minerals and organic matters, the metal resupply was restrained, resulting in them being only a partial resupply. Moreover, the mobility of Co was mainly controlled by the resupply ability, response time, and desorption rate; while for Ni, the particle concentration and porosity played important roles in determining mobility. In addition, the release amounts of the trace metals were quantified using the binary mixing equation. The estimated annual release amounts of Co and Ni in Pingshan District were 0.44-3.54 t and 1.93-16.47 t, respectively. This study provides an effective in-situ method for estimating the release amounts of trace metals in soils during rainfall combining DGT and DIFS model., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Lakes are essential water resources in China and their water quality is vital to the sustainability. However, the geochemical processes of trace elements, especially those of seldom-monitored trace elements, have not been adequately studied. Here, the regional geochemical baseline (RGB) of vanadium (V) was established using cumulative frequency and normalization methods. Then, the RGB was applied to quantitatively calculate the anthropogenic contribution rate in sediments of the Poyang Lake (PYL), which is the largest freshwater lake in China. The pollution level and ecological risk of V were evaluated using the geoaccumulation index (I geo ) and potential ecological risk index (EI) with respect to three different reference values, namely local soil background values (BV), the RGB, and the median value of V concentrations. The health risk of V accumulation in residents through fish consumption during sediment resuspension was assessed by combining the environmental impact assessment model and health risk assessment model. The mean concentration of V in PYL sediments was 94.37 mg/kg (33.80-148.53 mg/kg), which was slightly higher than the levels in stream sediments in China, but lower than the local BV. The calculated RGB was slightly higher than the average V content in PYL sediments, but similar to the local BV. The average anthropogenic contribution rate was calculated as 11.48%, demonstrating low anthropogenic influence. Moreover, the result of I geo and EI showed that V in PYL sediments was uncontaminated and posed a low ecological risk. In addition, based on the calculation by the two models, the human health risk result (target hazard quotient <1) indicated that the average human health risk from fish consumption due to sediment resuspension was negligible., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Toxic metals in the sediments of the Three Gorges Reservoir (TGR) in China are a conspicuous scientific issue. However, compared with the commonly monitored metals, the geochemical behavior and potential risk of antimony (Sb) in TGR sediments remains unclear. Here, sediment samples were collected from the entire TGR. Multiple assessment approaches (i.e., geochemical baseline concentration of Sb (GBC Sb ), grain size normalization, potential ecological risk, and health risk assessment) were used to evaluate the Sb status in sediments. The average Sb concentration was 1.14 ± 0.20 mg/kg, ranging from 1.10 to 1.19 mg/kg. The spatial distribution of Sb exhibited a tendency to accumulate from upstream to downstream. Normalization by fine grain size revealed that fine grain particles mainly influenced the Sb spatial distribution in TGR sediments. The temporal variation of Sb revealed that the mean content of Sb was higher in the dry season than in the wet season. Moreover, GBC Sb (1.10 mg/kg) was higher than the background value of Sb in Yangtze River sediments. Determination of the anthropogenic contribution rate gave a mean value of 11.43% using the GBC model, indicating that the main contribution of Sb in TGR sediments originated from natural sources. According to sediment loads during 2015 and 2016, the anthropogenic input deposited 2.74 and 3.32 t of sediments in 2015 and 2016, respectively. In addition, the assessment results of the potential ecological risk index based on GBC Sb suggested that Sb presented a low ecological risk in TGR sediments. Sb accumulation in fish caused by the sediment resuspension was calculated by the environmental impact assessment model. Further assessment of target hazard quotients demonstrated that Sb was at a safe level for fish consumption., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The toxicity and bioavailability of Cr depends on its speciation in the aquatic environment. Here, we developed a new method for simultaneously obtaining in-situ data on labile Cr(III) and Cr(VI) using diffusive gradients in thin films (DGT) and high-performance liquid chromatography hyphenated to inductively coupled plasma mass spectrometry (HPLC-ICP-MS). A Zr-oxide DGT was applied to accumulate both labile Cr(III) and Cr(VI). The elution of Cr species was carried out with 50 mM EDTA-2Na at pH 9.5 for 1.5 h. Agilent Bio WAX anion-exchange chromatography was used to separate Cr species in the slightly alkaline mobile phase containing 40 mM NH 4 NO 3 at pH 7.4. An ICP-MS was used to quantitatively measure Cr within 4.5 min. Method detection limits were 0.05 μg/L for Cr(III) and 0.02 μg/L for Cr(VI). Labile Cr(III) and Cr(VI) was accurately quantified in synthetic solutions for pH in the range of 5-8 and ionic strength ranging from 10 to 100 mmol L -1 . The method allows quantification of labile Cr(III) and Cr(VI) in natural water and was consistent with results of when a separate measurement method based on DGT was used. This study was an attempt at simultaneous in-situ quantification of labile Cr(III) and Cr(VI), and will facilitate in-situ labile Cr speciation analysis in the environment., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Arsenic (As) contamination in sediments has been reported worldwide. However, few studies have investigated As contamination on a national scale in China. This study aims to address this gap by analyzing the existing literature on As contamination and sediment samples collected from ten main river basins: the Songhua River Basin (SRB), Liao River Basin (LRB), Hai River Basin (HRB), Yellow River Basin (YRB), Huai River Basin (HuRB), Yangtze River Basin (YtRB), Pearl River Basin (PRB), Southeastern River Basin (SeRB), Southwestern River Basin (SwRB), and Northwestern River Basin (NwRB). Regional geochemical baseline (RGB) values of As in the sediments of river basins were calculated to estimate human contributions of As using normalization and cumulative frequency distribution curves. The established RGB values in the SRB, YtRB, and PRB were higher than the corresponding regional soil background (RSB), possibly because of the high intensity of human activities in the SRB, YtRB, and PRB. Taking RGB and RSB values as the background references, contamination assessment yielded important information on As contamination in China. With high As contributions from Yunnan province, the PRB suffered from the highest level of contamination, and the mean human contribution of As in the PRB was 64.4%. The contamination levels in the less developed southwestern regions were even higher than in some river basins in economically developed regions (e.g., YRB). In addition, As in the PRB and YtRB was found to be partially contributed by industrial wastewater discharge, and the response of As contamination in sediments to industrial wastewater discharge was analyzed. The temporal change (2004-2016) of As in sediments from the PRB, YtRB, and YRB corresponded well with that of As discharged in wastewater within the corresponding river basins. This study thus serves as a valuable foundation for policies focused on ameliorating As contamination in China., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Response of trace metals to the consecutive water level fluctuation in the Three Gorges Reservoir (TGR) sediments remains unclear. Here, we evaluated the influence of consecutive stages of water level fluctuation on trace metal pollution using multiple analytical approaches. The spatio-temporal distributions of trace metals in TGR sediments were investigated for five consecutive water impoundment stages from 2015 to 2017. Anthropogenic contributions and trace metal stocks in the TGR were quantitatively estimated using a combination of a regional geochemical baseline (RGB) and annual sediment load. Results showed that trace metals were accumulated after the construction and impoundment of the TGR. However, after the TGR operated normally for more than five years, trace metals concentrations stabilized in sediments. Trace metal concentrations in the mainstream were slightly higher than those in the tributaries. In the mainstream, metal concentrations in the upstream were lower than those in the midstream and downstream except for Cd. Anthropogenic contributions of trace metals ranged from 8.51 to 24.86% and were highest for Hg and Cd. The sediment load was the main factor influencing trace metal stock in TGR sediments. Although the total Cd stock amount was relatively low, its potential ecological effects are of great concern due to its high mobile fraction percentages and toxicity. The RGB-based geo-accumulation index and potential ecological risk index showed that TGR sediments were uncontaminated, and were subject to low ecological risk from trace metals. This result differs from traditional assessment results, indicating that previous assessments may overestimate the ecological risks of the trace metals in the TGR. The health risks posed by trace metals bio-accumulated in fish, stemming from sediment resuspension, were assessed using an environmental impact assessment model. Results suggested that residents should not experience significant health risks from the intake of individual metals through fish consumption., (Copyright © 2018 Elsevier B.V. All rights reserved.)

As the sole drinking water source for Beijing City, Cd has been previously assessed as the major contaminant in Miyun Reservoir (MYR) riparian soils. However, the potential release risk of Cd in such soils, and the labile-Cd release-resupply process from the soil solid phase to solution after water impoundment remain poorly understood. We established a geochemical baseline concentration (GBC) of Cd in MYR riparian soils, combined with the diffusive gradient in thin films (DGT) technique and DGT-induced fluxes in soil (DIFS) model, to reveal a dynamic release-resupply process and influencing factors of labile Cd in riparian soils. The results showed that Cd GBC in riparian soils was 0.12 mg/kg, which was higher than the Cd background value (BV) for Beijing. Using Cd GBC as BV to assess the Cd contaminant level, the geo-accumulation index showed that Cd in riparian soils was at the uncontaminated level. In addition, Cd in the soils belonged to the non-residual fraction using the Community Bureau of Reference method. Cd mobility coefficients (F1/C Total -Cd) of soils at low elevation had relatively high values, implying that Cd may be released during the initial impoundment of the MYR. Moreover, correlation analysis was used to found the major influencing factors between DGT-labile Cd and several parameters. The results showed that the DGT-labile Cd was positively correlated to the reducible and oxidizable fraction, C DGT -Fe, and total organic carbon, illustrating that the release of Cd from soils was controlled by Fe oxides and organic matter. The resupply ability (R values) and DIFS model parameters revealed that Cd in MYR soils belonged to the partially sustained case, and the slow desorption rate suggested that the release risk of Cd was low in the MYR riparian soils., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Source identification of trace metals in the water environment is important in understanding its environmental behavior and in the prevention and remediation of further pollution. Here, the regional geochemical baseline (RGB) and Pb isotopic ratios are combined to decipher the anthropogenic contribution rate, main anthropogenic source, and transport pathway of trace metals in sediments collected from the largest freshwater lake in northern China, Baiyangdian (BYD) Lake. The established RGB values of Cr, Ni, Cu, Zn, Cd, and Pb were 63.0, 27.8, 24.7, 46.1, 0.18, and 22.0 mg/kg, respectively, which were slightly different from the regional soil background values. Based on the RGB and actual concentrations of trace metals in the lake sediments, the calculated average anthropogenic contribution were lower than 20% except for Cd. Compared with the other trace metals, Cd was the element most impacted by anthropogenic input, which was mainly caused by the point source pollution in some sites. The risk assessment (geo-accumulation index and potential ecological risk) using the RGB as the regional background values showed that BYD sediments were uncontaminated by the trace metals, and at low ecological risk from the trace metals. The results of these two risk assessments further validated the assessment of the anthropogenic contribution by the RGB. In addition, Pb isotopic ratios result showed that coal combustion was the main potential source of anthropogenic Pb in the BYD sediments and atmospheric deposition was the main transport pathway. This study tried to combine the geochemical baseline and Pb isotopic composition to identify the anthropogenic input of trace metals in the sediments. It will provide a new insight into assessing the anthropogenic contributions, identifying the main anthropogenic sources, and transport pathways of trace metals in water environment., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The middle route of the South-to-North Water Diversion project alleviates drought in northern China, especially reducing water shortage pressure in Beijing. However, after submersion, the potential release risk of metals in newly submerged soils into the water in the receiving reservoir remains unclear. Here, we assess the labile Zn in the riparian soils of Miyun Reservoir (MYR) using the diffusive gradients in thin films (DGT), DGT-induced fluxes in soils (DIFS) model, and Community Bureau of Reference (BCR) sequential extraction. The results showed that the average Zn concentrations at three sampling sites (S2, S3, and S5) exceeded soil background value (74.8 mg/kg), indicative of Zn accumulation in the MYR. The concentrations of DGT-labile Zn varied within 39.7-62.4 μg/L (average: 56.7 μg/L), with the greatest value observed at 145 m at sampling site S3, attributed to anthropogenic activities in recreational areas. The DGT-labile Zn showed no correlation with classes of land, elevations, or soil properties. Sequential extraction results demonstrated that Zn predominantly existed in the residual fraction, but still showed a strong capability for resupply from the solid phase (R >1). The DIFS model simulation results showed that Zn underwent irreversible diffusion of intra-particle metals from the solid phase to the soil solution. Therefore, the potential release risk of labile Zn in riparian soils in MYR cannot be ignored, especially for areas experiencing human disturbance., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The mobility and transfer of trace metals in sediments are vital to understanding trace metals environmental behavior in water environment. However, as a predominant aquatic carcinogen, an effective method for assessing the release and deposition for Cr at the sediment-water interface (SWI) is still not clearly understood. Here we established a comprehensive methodology to evaluate the release risk of Cr at the SWI combining regional geochemical baseline (RGB) and diffusive gradients in thin films (DGT). Sediment cores and water samples were collected in the two tributaries and mainstream of the Three Gorges Reservoir, which is the world's largest man-made hydroelectric station. Results showed that the calculated Cr carcinogenic risks in surface water did not exceed US EPA maximum recommended level. The RGB of Cr (85.53 ± 14.44 mg/kg) were calculated and the differentials between Cr concentration and RGB in surface sediments showed the average anthropogenic contribution rate was 6.03% and the upstream of Meixi River (MX-S) and mainstream were influenced by anthropogenic activities. The net diffusive flux using DGT showed that Cr in the midstream of Caotang River and MX had the potential to move upwards into the overlying water. Furthermore, combining the results of differential (Cr concentration vs. RGB) and the net flux, MX-S was the only site with a risk of Cr release. To the best of our knowledge, this study is the first attempt to combine RGB and DGT to scientifically assess metal release at SWI and provided a new perspective to comprehensively assess metal pollution in water environment., (Copyright © 2018 Elsevier B.V. All rights reserved.)

As the largest man-made reservoir in China, the Three Gorges Reservoir (TGR) has significant influence on national drinking water safety. The geochemical behavior of trace elements at the sediment-water interface (SWI) is still unknown. The mobilization characteristics of trace elements (As, Mo and W)-determined by diffusive gradients in thin films (DGT)-were studied to quantitatively calculate the release trends in the SWI in three typical tributaries and the mainstream of the TGR in the summer. The results showed that concentrations of DGT-labile As, Mo and W in the overlying water and sediment cores showed significant variations in the ranges of 0.05-50.90, 0.30-1.63 and 0.01-0.42μgL -1 , respectively. The apparent net diffusive fluxes were significantly positive in most sampling sites (77.8% for As, 88.8% for Mo and 66.6% for W), suggesting that the sediment was the source of these three elements. It was noteworthy that the maximum net diffusive fluxes of As and W were found in the upstream of Meixi tributary, which may be attributed to anthropogenic activities. In addition, As, Mo and W may be incorporated in Fe and Mn oxyhydroxides and these three elements simultaneously remobilized with Fe and Mn., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The South-to-North Water Diversion Project, one of China's largest water diversion projects, has aroused widespread concerns about its potential ecological impacts, especially the potential release of trace metals from shoreline soils into Miyun Reservoir (MYR). Here, riparian soil samples from three elevations and four types of land use were collected. Soil particle size distributions, contents and chemical fractionations of trace metals and lead (Pb) isotopic compositions were analyzed. Results showed that soil texture was basically similar in four types of land use, being mainly composed of sand, with minor portions of clay and silt, while recreational land contained more abundant chromium (Cr), copper (Cu), zinc (Zn) and cadmium (Cd), suggesting a possible anthropogenic source for this soil pollution. The potential ecological risk assessment revealed considerable contamination of recreational land, with Cd being the predominant contaminant. Chemical fractionations showed that Cu, arsenic (As), Pb and Cd had potential release risks. Additionally, the 206 Pb/ 207 Pb and 208 Pb/ 207 Pb values of soils were similar to those of coal combustion. By combining principal component analysis (PCA) with Pb isotopic results, coal combustion was identified as the major anthropogenic source of Zn, Cr, Cu, Cd and Pb. Moreover, isotope ratios of Pb fell in the scope of aerosols, indicating that atmospheric deposition may be the primary input pathway of anthropogenic Zn, Cr, Cu, Cd and Pb. Therefore, controlling coal combustion should be a priority to reduce effectively the introduction of additional Zn, Cu, Cd, and Pb to the area in the future., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The environmental impact of the Three Gorges Reservoir (TGR) in China has raised widespread concern especially in relation to metal pollution. The diffusive gradient in thin films (DGT) technology was applied to investigate arsenic (As) remobilization in sediment cores collected from the main stream and a tributary in the TGR during July 2015. The results showed that the horizontal and vertical distributions of C DGT -As varied among the four sampling sites. For the same DGT probe, the horizontal distributions of C DGT -As (0-6mm, 6-12mm, 12-18mm) exhibited similarity in the overlying water and different tendencies in the sediment profiles; the vertical variations of C DGT -As showed different mobilization tendencies. Moreover, the mobility patterns of As in the sediment profile showed the diffusion potential of As from the deep sediment to the surface sediment and overlying water were in the order of MX-2< MX-1< CJ < MX-3. In addition, similar distribution characteristics and correlation analysis showed that the mechanisms of As mobility were associated with Fe and Mn. The results also showed that sulphide and As were simultaneous remobilization in the tributary sediment core in the TGR., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The pollution of agricultural soils with cadmium (Cd) has become a serious problem worldwide. The potato (Solanum tuberosum L.) was used to investigate how different concentrations of Cd (1, 5, and 25mgkg(-1)) affected the physiological parameters and the subcellular distribution of Cd in the potato. The analyses were conducted using scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX). The results suggest that the leaf is the organ with the highest accumulation of Cd. The malondialdehyde (MDA) content increased and the chlorophyll content decreased in response to high level of Cd. The SEM-EDX microanalysis revealed that Cd was primarily deposited in the spongy and palisade tissues of the leaf. Furthermore, Cd was also detected in the cortex and the adjacent phloem and was observed inside the intercellular space, the interior surface of the plasma membrane, and on the surface of the elliptical starch granules in the tubers of the potato. Although low concentrations of Cd migrated from the root to the tuber, the accumulation of Cd in the tuber exceeded the standard for food security. Therefore, the planting of potato plants in farmland containing Cd should be seriously evaluated because Cd-containing potatoes might present high health risk to humans., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The sorption behaviors of diuron (DIU), fluridone (FLU) and norflurazon (NOR) by a single-walled carbon nanotube (SWCNT) and three multi-walled carbon nanotubes (MWCNT) samples including MWCNT10 (<10nm, outer diameter), MWCNT20 (10-20 nm), and MWCNT40 (20-40 nm) were investigated. All adsorption isotherms were nonlinear and were well fitted with the Freundlich model and Dubinin Ashtakhov (DA) model. The linear relationships between the organic carbon (OC)-normalized saturated adsorption capacity (Q(0)(OC)) and surface area (SA) suggest that SA is presumably responsible for the adsorption of DIU and NOR on CNTs. While FLU, DIU, and NOR OC-normalized distribution coefficients (logK(OC)) of CNTs increased with increasing their hydrophobicity (logK(OW)) and the positive relationships between the logK(OW)-normalized logK(OC) (i.e., logK(OC)/logK(OW)) of FLU, DIU, and NOR and their hydrogen bonding ability indicate that the adsorption of FLU, DIU and NOR was mainly controlled by the hydrophobic interaction and hydrogen bonding. The higher logK(OC) or Q(0)(OC) values of MWCNT10 and SWCNT relative to other large MWCNTs and carbonaceous adsorbents suggest that MWCNT10 has the potential to serve as an adsorbent used to reduce the mobility of herbicides in agricultural and environmental applications., (Copyright © 2012 Elsevier B.V. All rights reserved.)