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1.
Artigo em Inglês | MEDLINE | ID: mdl-31970638

RESUMO

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

2.
Artigo em Inglês | MEDLINE | ID: mdl-31744075

RESUMO

Simultaneous ecological and health risk assessments of potentially toxic elements in soils and sediments can provide substantial information on their environmental influence at the river-basin scale. Herein, soil and sediment samples were collected from the Guishui River basin to evaluate the pollution situation and the ecological and health risk of potentially toxic elements. Various indexes were utilized for quantitatively assessing their health risks. Pollution assessment by geo-accumulation index showed that Cd had "uncontaminated to moderately polluted" status in the soils and sediments. Potential ecological risk index showed that the Guishui River basin was at low risk in general, but Cd was classified as "moderate or considerable ecological risk" both in the soils and sediments. Health risk assessment calculated human exposure from soils and indicated that both non-carcinogenic and carcinogenic risks of the selected potentially toxic elements were lower than the acceptable levels. Health risks posed by potentially toxic elements bio-accumulated in fish, stemming from sediment resuspension, were also assessed. Non-carcinogenic hazard index indicated no adverse health effects on humans via exposure to sediments; however, in general, Cr contributed largely to health risks among the selected potentially toxic elements. Therefore, special attention needs to be paid to the Guishui River basin in the future.

3.
Sci Total Environ ; 689: 1030-1036, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31466143

RESUMO

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 206Pb/207Pb in DHTR SS-AA (1.107 ±â€¯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 (206Pb/207Pb and 208Pb/207Pb) 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.

4.
Sci Total Environ ; 694: 133624, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31401511

RESUMO

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 (Igeo), 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 Igeo. Moreover, the pollution and migration of Cu in urban soils are problematic as evidenced by the Igeo and RAC assessments. Release ability of Cu was assessed using parameters of DIFS model (i.e., bioavailability concentrations (CE), resupply ability (R), response time (Tc), desorption rate (k-1), and sorption rate (k1)). Residential areas showed high CE values for Cu, while the resupply ability was low. Furthermore, considering the influences of R, Tc, k-1, and k1, membership function value was used to re-calculate the order of CE 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.

5.
Sci Total Environ ; 672: 192-200, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-30954818

RESUMO

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.

6.
Sci Total Environ ; 664: 37-44, 2019 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-30743129

RESUMO

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.

7.
Sci Total Environ ; 660: 1338-1345, 2019 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-30743928

RESUMO

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 (Igeo) 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 Igeo 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.

8.
Sci Total Environ ; 660: 1433-1440, 2019 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-30743936

RESUMO

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 (GBCSb), 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 ±â€¯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, GBCSb (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 GBCSb 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.

9.
Materials (Basel) ; 12(3)2019 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-30744086

RESUMO

An embedded piezoelectric transducer was developed for monitoring the corrosion process of reinforcement bars in concrete based on the piezoelectric impedance technique. The electrochemical method was employed to accelerate the corrosion process of the reinforcement bar with relative mass loss of 0.5⁻10%, and the resistance spectra of the piezoelectric transducers were investigated to assess the corrosion process. The results show that the corrosion process of the reinforcement bar has significant influence on the resistance spectra of the piezoelectric transducers. Statistical parameters were used to intuitively evaluate the corrosion evolution based on variations of the resistance spectra. The corrosion process of reinforcement bar in concrete can be classified into three periods; that is, the initial period when the relative mass loss is less than 2%, the developing period at a relative mass loss of 2⁻4%, and the rapid corrosion period when the relative mass loss is higher than 4%.

10.
Sci Total Environ ; 666: 139-146, 2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-30798224

RESUMO

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.


Assuntos
Água Potável/análise , Exposição Ambiental , Rios , Oligoelementos/análise , Qualidade da Água , China , Humanos , Medição de Risco , Oligoelementos/efeitos adversos
11.
Sci Total Environ ; 653: 1161-1167, 2019 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-30759556

RESUMO

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 NH4NO3 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.

12.
Sci Total Environ ; 651(Pt 2): 1983-1991, 2019 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-30321721

RESUMO

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.

13.
Sci Total Environ ; 648: 197-205, 2019 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-30118935

RESUMO

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.

14.
Sci Total Environ ; 646: 1546-1553, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30235639

RESUMO

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/CTotal-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, CDGT-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.

15.
Ecotoxicol Environ Saf ; 164: 226-233, 2018 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-30118956

RESUMO

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.


Assuntos
Sedimentos Geológicos/química , Lagos/química , Chumbo/análise , Metais Pesados/análise , Poluentes Químicos da Água/análise , China , Monitoramento Ambiental , Medição de Risco
16.
Ecotoxicol Environ Saf ; 160: 184-190, 2018 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-29804015

RESUMO

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.


Assuntos
Poluentes do Solo/análise , Abastecimento de Água , Zinco/análise , Pequim , Fracionamento Químico , Difusão , Monitoramento Ambiental/métodos
17.
Sci Total Environ ; 628-629: 241-248, 2018 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-29438933

RESUMO

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 ±â€¯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.

18.
Ecotoxicol Environ Saf ; 147: 342-348, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28858707

RESUMO

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.


Assuntos
Arsênico/análise , Monitoramento Ambiental/métodos , Sedimentos Geológicos/química , Molibdênio/análise , Tungstênio/análise , Poluentes Químicos da Água/análise , China , Estações do Ano , Oligoelementos/análise , Recursos Hídricos
19.
Chemosphere ; 195: 390-397, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29274578

RESUMO

The South-to-North Water Diversion Project has been initiated to address the problem of water shortages in north China. However, the environmental impact of this project is currently unclear, especially for the geochemical process of toxic trace metals in reservoir riparian soil following water submergence. The mobility of Ni in Miyun Reservoir riparian soil samples was investigated using diffusive gradients in thin films (DGT), considering five different land use types and three vertical elevations. The DGT-induced fluxes in soil (DIFS) model was applied to simulate the kinetics of Ni mobilization in the soil. The results showed that the average concentration of Ni was 36.58 mg/kg, which was slightly higher than the corresponding background values reported for both Beijing and China. Coincidentally, the highest concentrations of both total Ni and DGT-labile Ni (CDGT-Ni) were observed at the same site (recreational area), indicating that anthropogenic activities may have contributed to the release of Ni. Land use type and vertical elevation had no significant influence on CDGT-Ni. In addition, CDGT-Ni was positively correlated with reducible fraction, CDGT-Fe, CDGT-Mn, and TOC, indicating that Ni in the soils was adsorbed mainly on the Fe/Mn oxides and organic matter. Moreover, the low values of R (CDGT-Ni/Csol-Ni, R < 0.25) indicated that the replenishment of Ni from the solid phase was poor, and the rate of Ni desorption was considerably lower than its depletion rate, thus leaving only a small proportion of Ni was available.


Assuntos
Níquel/análise , Poluentes do Solo/análise , Solo/química , Oligoelementos/análise , Pequim , China , Monitoramento Ambiental/métodos , Atividades Humanas , Cinética , Níquel/química , Água
20.
Huan Jing Ke Xue ; 39(12): 5464-5472, 2018 Dec 08.
Artigo em Chinês | MEDLINE | ID: mdl-30628389

RESUMO

The Three Gorges Reservoir (TGR) has achieved the target of water storage of 175 m for eight consecutive years until October 2017. To study the temporal and spatial variation of nickel (Ni) in different water periods under 175 m operating conditions in the TGR area, probe the impact of a large-scale water conservancy project on the Ni enrichment, and establish the pollution evaluation system of Ni in the TGR area, we collected 173 surface sediment samples from the TGR area during four consecutive water periods from December 2015 to June 2017 and measured the Ni concentration by using inductively coupled plasma mass spectrometry (ICP-MS). The mean values of Ni in the four water periods are higher than the background value of Yangtze sediment and soil. At the spatial scale, the Ni content in the mainstream exhibits a clear upward trend from upstream to downstream and is lower than that of the tributary. The tributaries of the lower reaches shows a notably higher Ni content than the tributaries of the upper and middle reaches. At the temporal scale, the water period exerts an insignificant effect on the Ni content. The Ni content is relatively stable and shows a downward tendency at a 175 m water level. The regional geochemical baseline (RGB) value of Ni was obtained through building a geochemical baseline model in the area. The RGB values of Ni in sediments during four consecutive water periods are 47.0, 44.2, 42.9, and 41.9 mg·kg-1, respectively. The Ni contents in the middle and lower reaches of the mainstream and tributary are significantly affected by human activities. Moreover, the pollution evaluations based on global Ni background values, local background values, and geochemical baseline values as reference values were compared and the geoaccumulation index and potential ecological risk of Ni were determined to comprehensively assess its pollution risk. The assessment data indicate that Ni in the aquatic environment of the TGR area is almost uncontaminated and poses a low ecological risk, except for samples in regions around Fengdu County and Guizhou Town in the Zigui County along the mainstream, which were uncontaminated to moderately contaminated. Relative to global and regional background values, the pollution assessment results obtained using the RGB as a reference value are more scientific and better match the temporal and spatial variation of the study area.

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