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Spatio-temporal dynamics, drivers and potential sources of heavy metal pollution in riparian soils along a 600 kilometre stream gradient in Central China
... Metal contamination and migration of contaminants in the soil, together with hydrologic processes, are possible threats to the environment. These trace metals are continually accumulating in the riparian soils, sediments, and plants through biogeochemical processes, eventually exceeding the regional background concentration and leading to heavy metals pollution of the riparian zone [11,12]. Therefore, the riparian zone in the river system is subjected to growing pressure as a result of the hydroelectric development and reservoir impoundment [13]. ...
... However, the results differ from the study by Tang et al. [54], which demonstrated that the heavy metal concentrations in the riparian soils of TGR generally follow a slight decreasing trend with an increase in elevation. Ye et al. [12] reported that the riparian soil of TGR was moderately contaminated by As and Pb according to several indices, and dam operation and local human activity affect heavy metal distribution in the riparian zone. The latest case study from Nuozhadu Reservoir, reported that the concentrations of Cu and Ni in the WLFZ soils increased noticeably with the increasing elevations, while Cr and Zn tended to decrease with increasing elevations [56]. ...
... Dam operation and local anthropological activities affect the heavy metals distribution in the riparian zone [12]. Changes in the flooding duration owing to reservoir operation leads to heavy metal accumulation in both the sediments and soil of the riparian zone [11,57]. ...
The cascade hydropower development in the Lancang River has significantly modified the hydrologic regime and is consequently responsible for many local environmental changes. The influence of the altered hydrological regime on heavy metals accumulation in the soils of the riparian zone was evaluated for the Xiaowan Reservoir (XWR). Specifically, this study focused on investigating the trace metals As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn and their concentrations in the riparian soils. Furthermore, this research aimed to examine the contamination levels of heavy metals by employing the geoaccumulation index (Igeo) and the ecological risk index (RI), respectively. Additionally, the relationship between heavy metals and water level fluctuations as caused by the dam operation was explored. The results showed that heavy metals deposits occurred in relatively low levels in the riparian soils of XWR, even though several of these metals were revealed to occur in higher concentrations than the local background value. The Igeo assessment indicated that the riparian soils exhibited slight pollution by Hg at the Zhujie wharf (ZJW) and Cr at the transect of the Heihui River (HHR), and moderate contamination by As at ZJW. Moreover, the RI revealed that As in riparian soils is moderately hazardous while Hg poses a high risk at ZJW. The polluted water and sediments from upstream and upland of the riparian zone may be contributing to the changed concentrations of heavy metal in the riparian soils. The present study inferred that the WLFs due to reservoir impoundment play a vital role in the accumulation of trace metals in the riparian zone. However, more exhaustive investigations are necessary for verification.
... Reservoir hydro-fluctuation belts may be affected by the presence of certain trace elements in the Three Gorges Dam, China (Sang et al., 2019;Zhang et al., 2022). Studies have reported accumulation of soil-associated P, Zn, Cd, Cr, and As in RHB in the case of low water level Ye et al., 2019a;Ye et al., 2020). Other studies have shown a significant and positive correlation of selected trace elements in soils and organisms (Xiang et al., 2018). ...
... The conventional risk assessment approach is generally linked with uncertainty. Nearly all risk assessment methods including single-factor pollution index, geo-accumulation index, enrichment factor, and toxic risk index in RHB were estimated using one-point value (Tang et al., 2014;Ye et al., 2019a;Zhang et al., 2022). The deterministic approach enhanced the uncertainty of estimations, possibly overestimating or underestimating the actual risks, while the probability distribution decreased the uncertainty of estimations (Gu et al., 2021). ...
... A molybdenum-antimony anti-spectrophotometric method was used to quantify both TP and AP in the extract. The concentrations of Cu, Cr, and Zn were determined using an inductively coupled plasma mass spectrometry (PerkinElmer NexION 350) following digestion using concentrated acids (HF+HNO 3 +HClO 4 ) (Ye et al., 2019a;Ye et al., 2020). The national standard material (GBW07445) was used as a quality control sample. ...
To examine the role of dam impoundment in elevating the levels of soil‐associated phosphorus (P) and trace elements in reservoir hydro‐fluctuation belts (RHB), soil samples in RHB and adjacent uplands (non‐flooded area, NFA) in the Three Gorges Reservoir, China, were collected and analyzed. Concentrations of available P, copper (Cu), chromium (Cr), and zinc (Zn) were found to be higher in RHB than in NFA (p < .05), whereas organic carbon was comparable in RHB and NFA (p > .05). The elevated levels of Cu, Cr, and Zn in RHB were probably associated the repeated drying–rewetting cycles created by the dam impoundment. The 95th percentile of the single‐factor pollution index and geo‐accumulation index in RHB were 1.29 and −0.21 for Zn, 3.21 and 1.15 for Cu and 3.37 and 1.17 for Cr. Elevated pollution potential of soil‐associated Zn, Cu, and Cr existed in RHB of the Three Gorges Reservoir.
Core Ideas Dam impoundments decreased total C and total N concentrations in reservoir flooded soils.
Cu, Zn, and Cr concentrated in the reservoir flood areas.
Variability of Cu, Zn, and Cr was captured in single‐factor pollution index and geo‐accumulation index
... HM accumulation in the soils of the WLFZ has been one of the major environmental concerns with respect to the TGR . Investigations highlighted that Cd, Cu, and Pb are among the most commonly detected HMs with relatively higher environmental risks in the surface soils of the WLZF in the TGR (Lin et al. 2012;Pei et al. 2018;Tang et al. 2015;Wang et al. 2017a;Ye et al. 2011Ye et al. , 2019aZhang et al. 2019). These researches regarding the distribution and occurrence of HMs in the riparian soil focused on the mainstream WLFZ of the TGR. ...
... mg/kg, and 31.20-74.53 mg/kg (Table 2), respectively, which were comparable to what have been reported in the riparian soils of the main WLFZ in the TGR (Pei et al. 2018;Tang et al. 2015;Ye et al. 2019a). Enrichments of Cd, Cu, and Pb in the soils of (Chen et al. 2015). ...
... The soil of 160 m asl altitude was subjected to fewer anthropogenic disturbances and the inundation might lead to the desorption of HMs to the reservoir water, which were responsible for the lower concentrations of Cd and Cu in the soil of 160 m asl altitude. In particular, the major source of Pb in the soil of the WLFZ has been identified to be the traffic exhaust and industrial discharge in the reservoir water (Gao et al. 2016;Ye et al. 2019a) so that the sorption of soluble Pb or the deposition of particle-associated Pb to the soil of the WLFZ was the major reason for the higher Pb content than that in the upland soil. However, a distinct "C-shape" vertical distribution pattern was observed for the three HMs at the lower altitude of 151 m asl in the WLFZ with significantly higher (P < 0.05) concentrations of Cu and Pb across soil profiles. ...
Purpose
This study aimed to relate the altitudinal and vertical distributions and occurrences of major heavy metals (HMs) to soil physicochemical properties in the riparian soils subject to periodic and intense wet–dry cycles
Materials and methods
Cadmium (Cd), copper (Cu), and lead (Pb) and their chemical fractions were investigated in the riparian soil (0–40 cm) of the upland and within the water-level-fluctuation zone (WLFZ) at two tributary backwaters of the Three Gorges Reservoir (TGR) in China. Selected soil basic properties and pore structures determining the distribution of HMs and their fractions were identified using correlation and redundancy analysis
Results and discussions
Cd showed moderate–strong contamination and prevailed in non-residual fraction (>73.2%) in the riparian soil of the tributary backwaters in the TGR. In contrast, Cu and Pb exhibited slight contamination and prevailing in residual fraction (>50.3%). Enrichment of HMs in the lower end relatively flat WLFZ where flow rate decreased abruptly and dramatically was observed. Cd exhibited the largest coefficient of variation (CV, up to 0.263) across soil profiles while Cu showed a relatively homogeneous profile distribution in the riparian soil. Soil organic matter (SOM), cation exchange capacity (CEC), and pH were identified to be the primary factors determining the distributions of Cd, Cu, Pb, and their chemical fractions, respectively, in the riparian soil with a high macroporosity. Nevertheless, soil porosity was the dominant factor (>65.0%) determining the distributions of all the three HMs and their fractions in the non-drainable micropore-dominated riparian soil
Conclusions
Soil basic property and pore structure variations due to periodic hydrodynamic disturbances from reservoir operation are closely related to the redistribution of HMs in the riparian soil. The coupling of these two variations is strongly suggested to assist reliable evaluation of various contaminants, including but not limited to HMs, regarding their spatial redistributions and mobilization potentials in the vadose zone at larger scales in response to climate change.
... After the formation of this WLFZ, the vegetation diversity in the area sharply decreased, the ecological barrier was damaged, and the environmental problems became increasingly prominent, directly threatening the long-term stable operation of the Three Gorges Project and the sustainable development of the reservoir economy [11]. Due to the vulnerability and sensitivity of this region, there has been global concern regarding its ecological structure, functions, and potential environmental challenges, with heavy metal pollution becoming a research hotspot [6,24,25]. Large-scale and long-term studies have found that since the establishment of the TGD, the concentrations of As, Cr, Pb, and Cu in the soil of the WLFZ have continuously increased, with heavy metal levels in the upper Yangtze River often exceeding those in the lower reaches. In many cases, these levels surpass the acceptable pollution thresholds set by various indices [26]. ...
... Although heavy metals typically exist at low levels in the environment, their high toxicity leads to accumulation over time, eventually exceeding toxicity thresholds. Once they enter the food chain and food web, they can have severe toxic effects on living organisms, impacting the entire ecosystem [6][7][8]. Awareness of the environmental and health problems caused by heavy metals is increasing, particularly concerning pollution in ecologically sensitive areas [9,10]. Phytoremediation is a cost-effective and eco-friendly strategy that has gained increasing attention in recent years [28,29]. ...
The water-level-fluctuation zone of a reservoir is an important connection between land and water; due to counter-seasonal rhythmic water level changes, this area is more sensitive and vulnerable, whereas the assessment and management of heavy metal pollution are still elusive. This study selected the water-level-fluctuation zone in the hinterland of the Three Gorges Reservoir. Through a quadrats investigation, the soil pollution status of seven heavy metals and the composition of herbaceous plants were identified, and the potential of the dominant species for phytoremediation was assessed. The results showed that the overall pollution was at the alert level (PN = 0.97) and a low ecological risk level (RI = 123.12). And the study area was primarily contaminated by a mixed source of traffic, agriculture, and industry. A total of 17 dominant species were calculated using importance values. Most dominant species had better phytoremediation potential for Cd and Cu. None of the 17 dominant species were hyperaccumulators, but they could still play an important role in phytoremediation due to their high adaptability to specific environments. The results have guiding significance for the management and remediation of soil heavy metal pollution in global reservoir areas, further promoting global ecological security and sustainable development.
... The decreased velocity within the permanent backwater area favors the deposition of sediments transported from the upstream during flooding season (Liro 2016(Liro , 2019Naganna and Deka 2018). Additionally, the low-gradient of alluvial channel and the widened river valleys from Zhongxian to Yunyang facilitate sediment deposition (Steiger and Gurnell 2003;Miller et al. 2013;Ye et al. 2019). Consequently, relatively more magnetite/maghemite particles from the Jinshajiang River accumulated in the lower section of the WLFZ in this middle reach during the summer flooding season. ...
... In the lower reach of the TGR, extending from Fengjie to Wushan, the increased contribution of fine SP/SD magnetic particles within WLFZ is primarily caused by intense soil erosion of nearby side slopes, where contain a significant amount of SP/SD particles in soils (Fig. 6). The steeper topography and higher altitudes in the lower reach of the TGR possibly contribute to this pattern (Ye et al. 2019). The slow water velocity in this typical permanent backwater area possibly plays a role as well. ...
Purpose
Iron-bearing magnetic minerals in the sediments of the water-level fluctuation zone (WLFZ) in large reservoirs play critical roles in the burial and release of organic carbon and pollutants. This study aims to reveal the spatial distribution of magnetic minerals across different elevations and reaches within the WLFZ of the Three Gorges Reservoir (TGR), the largest reservoir in the world, and their links to sediment provenance and hydrodynamic conditions. This study will provide a fundamental basis for future investigations in the roles of magnetic minerals in the circulation processes of pollutants and organic carbon within the WLFZ of fluvial-reservoir systems.
Materials and methods
~ 300 sediment samples and nearby side-slope soils were collected from various altitudes within the WLFZ at ten different sites of the TGR. The magnetic properties of these sediments and soils were examined using environmental magnetism. Additionally, previously reported data on magnetic properties of suspended sediments from upstream rivers flowing into the TGR were assembled. Nearby side-slope soils and suspended samples were used to represent magnetic properties of potential sources for the sediments within the WLFZ.
Results and discussion
Our findings reveal that magnetite/maghemite and hematite particles dominate the sediments within the WLFZ of the TGR. Relatively higher concentration of hematite particles in the upper part (> 165 m) of WLFZ mainly originates from or are nearby side-slope soils, whereas higher concentration of magnetite/maghemite particles in the lower part of WLFZ is primarily due to sediment supply from upstream of the Yangtze River. The dominance of coarser magnetite/maghemite within the WLFZ of the upper reach of the TGR, from Jiangjin district to Fuling district, is due to strong water flow velocity. An increase in the concentration of nanosized fine-grained magnetic particles within the WLFZ of the middle and lower reaches of the TGR can be attributed to a combination of reduced water dynamics and intense regional soil erosion of nearby side slopes.
Conclusions
Our findings indicate that the concentration and grain size of magnetic minerals exhibit spatial variations within the WLFZ of reservoirs under the influences of sediment provenance and hydrodynamics. These findings provide fundamental insights on future exploration into the crucial roles of iron-bearing magnetic minerals in the accumulation, migration, and transformation of pollutants and organic carbon within the WLFZ of reservoirs and their response to changes in sediment sources and water dynamics.
... Excessive accumulation of trace metals in riparian soils and river sediments is a challenging environmental issue due to their stability, persistence, and bioaccumulation in many river basins around the world [1,2]. In particular, the Pearl River Basin, which is located in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) of southern China, has relatively high concentrations of trace metals in soils and sediments compared to other areas in China [3,4]. ...
... To further assess the status of Pb and Cd pollution and distinguish between anthropogenic and natural sources, it is useful to calculate the nondimensional enrichment factors (EFs) of Pb and Cd, which are defined by the following equation [26]. EF = (Ci/CFe)sample/(Ci/CFe)background (2) where (Ci/CFe)sample is the ratio of the concentrations of Pb and Cd to that of Fe in samples, and (Ci/CFe)background is the background ratio of either Pb or Cd to Fe in Guangdong Province. ...
Pb and Cd accumulation in riparian soils and river sediments in river basins is a challenging pollution issue due to the persistence and bioaccumulation of these two trace metals. Understanding the migration characteristics and input sources of these metals is the key to preventing metal pollution. This study was conducted to explore the contents, geochemical fractionation, and input sources of Pb and Cd in riparian soils and river sediments from three lower reaches of the Pearl River Delta located in the Guangdong–Hong Kong–Macao Greater Bay Area. The total concentration of all Pb and Cd values exceeded the background values to varying degrees, and the exchangeable fraction of Cd in riparian soils and river sediments accounted for the largest proportion, while that of Pb was dominated by the residual fraction. Geoaccumulation index calculations showed that in the riparian soils, the average accumulation degree of Pb (0.52) in the Beijiang River (BJR) was the highest, while that of Cd (2.04) in the Xijiang River (XJR) was the highest. Unlike that in riparian soils, the maximum accumulation of Pb (0.76) and Cd (3.01) in river sediments both occurred in the BJR. Furthermore, the enrichment factor results also showed that Pb and Cd in the riparian soils and river sediments along the BJR were higher than those in the XJR and Dongjiang River (DJR). The relationship between enrichment factors and nonresidual fractions further proved that the enrichment factors of Cd were significantly correlated with the nonresidual fractions of Cd, which may imply various anthropogenic sources of Cd in the three reaches. Moreover, source identification based on principal component analysis (PCA) and Pb isotope ratio analysis indicated that riparian soils and river sediments have inconsistent pollution source structures. The PCA results showed that Pb and Cd were homologous inputs in the DJR, and there were significant differences only in the riparian soils and river sediments. Pb isotope tracing results further showed that the bedrock of high geological background from upstream may be the main reason for Cd accumulation in the XJR. However, the ultrahigh accumulation of Cd in the BJR is mainly caused by the input of the upstream mining and metallurgy industry. The control of upstream input sources will be the key to the prevention of trace metal pollution in these regions.
... Pesticide accumulations potentially disturb microbial activity and nitrogen cycle in riparian sediments (Chen et al. 2019). Anthropogenic activities upstream or on adjacent uplands cause heavy metal pollution in riparian zones (Ye et al. 2019). Polluted sediments due to river flooding contribute to the heavy metal contamination in riparian soils (Bai et al. 2012;Zhang et al. 2017). ...
... Polluted sediments due to river flooding contribute to the heavy metal contamination in riparian soils (Bai et al. 2012;Zhang et al. 2017). Industrial discharge, sewage, and agricultural run-off are the major anthropogenic sources of heavy metal pollution in riparian soils (Bai et al. 2016;Ye et al. 2019). Mining activities in riparian ecosystems can cause accumulation of heavy metals in floodplain (Graf et al. 1991). ...
Riparian zones are among the most valuable ecosystems on the earth. They act as the ecological engineers that improve river health through delivering a range of ecosystem functions. Stream bank stabilization, pollutant and sediment buffering, temperature regulation, provision of energy to river food webs and communities, groundwater recharge and provision of ecological corridors and habitat for wildlife, are among major ecosystem functions of riparian zones that play a great role in river health. Besides these ecosystem functions, riparian zones also provide various ecosystem goods and services for human well-being. But in the current scenario, riparian zones are under severe threat due to agricultural activities, urbanization, river flow alteration, overexploitation, climate change, pollution, and biological invasion. In the present and probable future scenarios of declining river health and global environmental changes, there is a pressing need of an integrated approach for managing riparian zones. This review article aims to advocate an integrated approach for riparian zone management based on various components such as riparian condition assessment, policy framework, stakeholder's participation, management practices, legislation, and awareness. Authors also discussed riparian zones in context of their concepts, features, functions, and threats.
... The issue of heavy metal pollution caused by metal mining activities and its environmental hazards has gained significant attention in the past few years. Soil serves as an important medium for the accumulation and enrichment of heavy metals (Ye et al., 2019). As a result, numerous studies have focused on evaluating heavy metal pollution in soil under the influence of lead-zinc mining. ...
... Soil is a natural resource that is vital to guarantee the sustainable development of agriculture, and an important object of ecological and environmental protection (Chen et al. 2019). Due to the rapid development of agriculture and industry in recent decades, soil toxic metal pollution has become one of the major environmental problems common to all countries in the world (García-Carmona et al. 2017;Solgi et al. 2012;Ye et al. 2019). Cadmium, lead and arsenic have become major pollutants in China's mining areas. ...
The problem of toxic metal pollution in the soil of mining areas accompanied by coal mining cannot be ignored. Taking the mining area of Wucaiwan in Xinjiang as the research subject, the content characteristics of soil toxic metals were sampled and analyzed. We calculated the rotation factor loading coefficients and further performed principal component analysis to resolve the sources of toxic toxic metals. We analyze the individual environmental capacity index and integrated environmental capacity index to reflect the environmental capacity level. The temporal change trend of soil environmental capacity was studied, and the correlation between environmental capacity, pH and organic carbon was explored. The results showed that (1) the average value of Cd content in the soil of the study area exceeded the background value, and the size of the total environmental capacity was ranked as Cr > Ni > Pb > Cu > Cd; (2) the size of the average individual environmental capacity index was ranked as Cu (1.15) > Cr (1.10) > Ni (1.04) > Pb (1.03) > Cd (0.96), and the comprehensive environmental capacity index was 1.06 (3) the cumulative contribution of the first three main components of soil toxic metals reached 91.55%, and the presumed sources were soil parent material, coal combustion and dustfall, respectively; (4) the correlation between the existing capacities of different toxic metals was strong, and the existing capacity of Pb was highly significantly and positively correlated with the organic carbon content.
... The strategic significance of the Yangtze River Basin lies in its crucial role as the economic and transportation epicentre of China (Luo et al., 2021;Ye et al., 2019;Zhang et al., 2021). Hosting over 40% of China's population and contributing more than 45% to the country's GDP (Gross Domestic Product), the basin stands as a linchpin in China's socioeconomic fabric. ...
Understanding the fine‐scale spatial distribution of heavy metal contamination is crucial for effective environmental capacity control and targeted treatment of polluted areas. This article presents the latest dataset on the occurrence of common heavy metals in the soils of the Yangtze River Basin. The dataset was compiled by reviewing peer‐reviewed literature published between 2000 and 2020. Rigorous quality control procedures were employed to ensure the accuracy of the data, including the extraction of detailed geographic locations and concentrations of heavy metals. The dataset includes 7867 records of heavy metal occurrences (Zn: 1045, Cu: 1140, Pb: 1261, Cr: 980, Cd: 1242, Ni: 649, As: 821, Hg: 729) in the soils of the Yangtze River Basin, distributed at four scale levels: province, prefecture, county, and township or finer. The results indicate that the distribution of heavy metal concentrations is relatively scattered, with higher concentrations in cities and regions with developed industry and agriculture. Cd has the highest exceedance rate (33.90%), indicating significant local contamination. Heavy metals, such as Zn at 11.96%, Ni at 12.63%, and As at 9.74%, also exceeded standard levels at certain sampling points. Cr had the lowest exceedance rate of 1.33%. This updated dataset provides essential information on the current status of heavy metals contamination in the soils of the Yangtze River Basin. It can be used for further ecological and health risk assessments and for developing strategies to remediate and prevent heavy metal contamination in the region.
... Concentrations of As (K-W test, p < 0.05), Cr (ANOVA, p < 0.01), and Cu (ANOVA, p < 0.05) showed significant differences across different months (Supplementary Figure S5). Short-term variations in heavy metal concentrations are typically closely associated with human activities (Vig et al., 2003;Ye et al., 2019). Heavy industrial activities are usually accompanied by substantial emissions of heavy metals (Jeong et al., 2021). ...
Bay ecosystems with unique economic and ecological value are more vulnerable to heavy metal pollution than other marine ecosystems. In South Korea, rapid economic development has exacerbated heavy metal pollution in bay environments. This study analyzed concentrations of seven heavy metals and the structure of macrobenthic community in Asan Bay. Five heavy metal indices (PLI, Pn, RI, TRI, and MERMQ) were used to assess ecological risk. Additionally, spearman correlation, biota–environment matching (BIO-ENV), and redundancy analysis (RDA) were utilized to determine the influence of heavy metals on macrobenthic communities. Although average concentrations of seven heavy metals were below sediment quality guidelines (SQGs), the average concentration of Cd was close to the threshold effects level (TEL). The nemerow pollution index (Pn) and the potential ecological risk index (RI) indicated that Cd was the primary heavy metal contributing to ecological risk. Spearman correlation, BIO-ENV, and RDA indicated that heavy metals were the main environmental factors influencing macrobenthic communities in Asan Bay. However, five heavy metal indices (PLI, Pn, RI, TRI, and MERMQ) did not show a response to the macrobenthic communities. Overall, low concentrations of heavy metals have a certain negative impact on macrobenthic communities in Asan Bay. This study can serve as an important reference for marine environmental protection and policy-making in Asan Bay.
... The open dumping without any treatment and material recovery leads to various detrimental effects on the environment and human health (Mukherjee et al. 2020;Yuvaraj et al. 2020;Nkoh et al. 2022). Among the various types of pollutants, soil contamination with toxic heavy metals (THMs) produced by various commercial and industrial activities has become a serious threat to the soil ecosystems (Ifon et al. 2019;Ye et al. 2019). Various industries including paper industries, textile industries, sago and tanneries generate a wide range of solid wastes majorly comprised of toxic pollutants especially THMs Woodford 2020). ...
... [24] The EF is given by standardizing the target metal with a reference metal with low occurrence variability, [25] such as Fe, Al, Mn, and Ti. [26][27][28][29] The EF can be derived using the following Equation (2). ...
Metals in soils exert toxic effects on soil quality and human health. In order to carry out metal contamination assessment and human health risk assessment of agricultural soils, a total of 662 cultivated soil samples were collected from two industrially oriented towns and three agriculturally oriented towns of Shifang City, Southwest China. Various indices were applied to analyze the pollution levels of soils caused by metals (Cr, Fe, Pb, Sr, Ti, V, Zn, and Zr). The relatively high values of the geo‐accumulation index ( I geo ) and the enrichment factor (EF) suggested that Sr, V, and Zn had cumulative trends in the soils. The average pollution load index (PLI) values of the industrial towns (1.19 and 0.99) were higher than those of the agricultural towns (0.92, 0.53, and 0.43), demonstrating the contribution of industrial activities to soil metal enrichment. The health risk assessment from the five towns indicated that Cr and V were the dominant contaminants in soils with high potential health risks. Dermal contact was the major pathway of the exposure of children and adults to Cr and V. This study improved the understanding of the pollution levels of metals in Shifang agricultural soils and put forward the necessity of minimizing the health risk of Cr and V in agricultural soil.
... The Yangtze River Basin is rich in mineral resources, with mineral species accounting for 80% of the proven mineral species in China. With the rapid development of industry in the Yangtze River Basin, more than 400,000 chemical industries are distributed along the Yangtze River (Ye et al., 2019). Abundant mineral resources would lead to the increase of the background value of heavy metals in soils, and frequent exploitation of mineral resources and industrial activities would lead to the aggravation of heavy metal pollution in nearby soils. ...
Supporting ecological protection and restoration has been at the heart of China’s ambitious Yangtze River conservation strategy. Knowledge of the current status of heavy metal distribution is important for planning remediation practices and allocation to waste treatment facilities. Through an extensive and systematic review of literatures, this study depicts the up-to-date spatial distribution and characteristics of typical heavy metals in soils of the Yangtze River Basin, China. A total of 7,694 geo-referenced records of heavy metal in soils of the Yangtze River Basin were compiled from the literatures published between 2000 and 2020. The results show the spatially-heterogeneous concentrations of Zn, Cu, Pb, Cr, Ni, As, Hg and Cd. The degree of heavy metal pollution was relatively higher in the middle reaches, while it was relatively lower in the upstream and downstream. According to the limits set by the state to ensure agricultural production and maintain human health, the average concentration of Cd greatly exceeded its limit. Overall, a certain number of heavily polluted areas were found to occur in regions with frequent human economic activities, posing potential health risks. The carcinogenic and non-carcinogenic risks of children are 1.4 times and 1.6 times higher than those of adults, respectively, and the heavy metal with the highest risk to human health was Cr. This study provides an important basis for the field of soil pollution prevention and control in the Yangtze River Basin. It updates the current understanding of the spatial pattern of major pollutants in a large ecologically protected region in China, which is conducive to the precise prevention and control of public health risks.
... It has been reported that higher concentrations of some heavy metals such as As, Zn, Cu, Ni, and Cr are highly correlated between agricultural activities and residential areas (Chen et al., 2021;Mohammadi et al., 2022). Furthermore, although the concentration of heavy metals in the river environment is related to human activity in riparian zones, the hydrological and depositional conditions can affect the physiochemical characteristics of the sediment (Bing et al., 2016;Ye et al., 2019). The reason for this is that hydrological conditions determine the distribution of sediment size and sorption capacity in the river environment (Feng et al., 2016). ...
... The increase in metal(loid) concentrations due to anthropogenic sources might cause various negative effects on ecological and human health (Tshalakatumbay et al. 2015;Lindsay et al. 2017;Li et al. 2018). It is thought that the metal(loid)s of Cu, Cd, and Hg might cause chronic diseases after long-term exposure (Han et al. 2017;Ye et al. 2019;Yuan et al. 2021a, b). Metal(loid)s can cause anthropogenic and natural pollution. ...
Heavy metal accumulation in aquatic environments is a global problem as it affects the quality of sediments and aquatic life. Therefore, this study examines the geochemical composition of heavy metals and their relationships, as well as their sources by applying multivariate statistical techniques to the geochemical content of the soil in the Gumusler Dam in central Turkey. The area is dominated by Paleozoic to Quaternary-aged igneous and metamorphic rocks. Average concentrations of all the major elements in terms of their abundance in descending order are as follows: SiO2, CaO, Al2O3, Fe2O3, MgO, K2O, TiO2, MnO, and Na2O. This suggests that SiO2 is the dominant major element in the soils. The contents of heavy metals have been found to vary in the following order: Strong positive correlations have been found among the following major elements: SiO2, CaO, MgO, TiO2, Ni, Rb, Pb, Zn, and As. According to the result of the principal component analysis using the extraction criterion, six factors were found to have an eigenvalue > 1, and they were found to explain 81.854% of the total variance of the dataset. All these factors reveal that the lithogenic effect and base metal mineralization are the two main sources of heavy metals in the sediments. Also, the results of the factor analysis were confirmed by hierarchical cluster analysis, which also yielded four clusters with similar element clusters. Regression analysis also confirmed that the host rocks and base metal mineralization in the area directly affect the sediment geochemistry in the dam.
... Because of its high corrosion resistance and high thermal conductivity, Cu is an essential component of vehicle braking systems and automotive radiators 64 . The wear of automobile parts will cause copper to enter the surrounding environment, so It is also often used as the identification element of the source of traffic 65,66 . Maximilian et al. 67 found that Zn can also be a marker element for mobile sources. ...
Studying the pollution status, spatial distribution characteristics, and sources of heavy metals in farmland soil in Anxin County will provide a method basis for the next step of soil remediation. This study investigates the contents of Zn, Cu, Pb, Cd, and Ni in wheat grains and soil samples. Moreover, different methods are used to evaluate soil heavy metal pollution. The results show that the soil in the study area is weakly alkaline. Cu, Zn, and Ni contents in the ground are lower than the risk screening values for soil contamination of agricultural land. In comparison, Cd and Pb contents are higher than the screening value of soil pollution risk of agricultural land, and the proportion of points lower than the control value of soil pollution risk of agricultural land are 64.58% and 16.67%, respectively. The farmland with high Cd and Pb content is mainly distributed near roads and factories and concentrated primarily on 0-20 cm topsoil. The Cd content in wheat grains meets the standard, but 4.17% of the samples are close to 0.1 mg kg−1 (more than 0.09 mg kg−1). The Pb content of 50% of the wheat grain samples exceeds the lead limit in the standard. The evaluation results of the single factor pollution index and geoaccumulation index show that the pollution degree of heavy metals in the soil is Cd > Pb > Cu > Zn > Ni. The potential ecological risk index in the study area is 288.83, and the soil heavy metal pollution is at a moderate-considerable ecological risk level. The average value of Cd's single-factor environmental risk index is 233.51, which belongs to the high environmental risk and is the main influencing factor. Cd and Pb in soil are significantly disturbed by the production activities of heavy metal processing enterprises around the farmland. It is speculated that there are two primary sources of soil heavy metal pollution in the study area. Cd, Pb, Zn, and Cu are mainly industrial and mobile sources, and Ni is primarily agricultural and natural sources.
... different types of pollutants (Yi et al., 2019), particularly the accumulation of heavy metals (HMs) in the soil. HMs based contamination of the soil influences the macro and micro-flora of soil (Isangedighi and David, 2019;Ye et al., 2019). These metals enter the soil through anthropogenic activities e.g. ...
Heavy metal (HM) contamination of the soil through anthropogenic activities influences the living systems and drastically impacts food chain. This study examined the application of silver nanoparticles (AgNPs) in two genotypes (G1 and G2) of Mung bean (Vigna radiata) for ameliorating the Pb toxicity. Different doses of Pb (0, 25, 50 μM) were differentially tackled by AgNPs with the aim of ameliorating the plant attributes. Both genotypes displayed statistically significant quantitative and qualitative modulations for Pb tolerance. In G2, the most prominent increase in plant height (43.79%), fresh biomass (49.56%) and total chlorophyll (20%) was observed at L2 (AgNPs 10 mg/L) in comparison with the control. Overall, photosynthetic rate was increased by 26% in G2 at L6 (AgNPs 25 mg/L + Pb 25 μM). In addition, the results presented 78.5% increase in water use efficiency of G2 while G1 experienced a maximum internal CO2 concentration (209.8%) at L8 (Pb 50 μM). AgNPs triggered balanced uptake of minerals and improved growth of Vigna genotypes. 50 μM Pb was most hazardous and caused maximum reduction in growth of Vigna plants along with a significant suppression in photosynthetic activity, increase in MDA (199.7%) in G1 and H2O2 (292.8%) in G2. In comparison to control, maximum superoxide dismutase (376%), peroxidase (659.8%) and catalase (9.3%) activity was observed in G2 at L11. The application of AgNPs substantially enhanced plant growth and helped them in surviving well in absence as well as presence of Pb. G2 genotype exhibited substantial tolerance capability and revealed less impairment in the studied attributes than G1 and treatment of AgNPs i.e. 25 mg/L was the best level that yielded best results in both genotypes. The results demonstrate that AgNPs mediate response(s) of plants under Pb stress and particularly contributed to HM tolerance of plants and thus showing great promise for use in phytoremediation.
... Jin et al. (2019) stated that Cr increased mainly due to natural resources in children's playgrounds, while the increase in Pb was due to traffic activities. Ye et al. (2019) determined that the main identifiable anthropogenic sources of heavy metals are traffic exhaust, sources associated with organic matter output (for example, sewage). Jiang et al. (2020) determined that four sources contribute to heavy metal accumulation in soils in Jiedong District: agricultural practices (23.08%), industrial activities (29.10%), natural resources (22.87%), and traffic emissions (24.95%). ...
As in the whole world, environmental problems have increased with the increase in residential areas in Turkey, and this situation has brought many problems, especially environmental pollution. Among the components of environmental pollution, heavy metals are the most dangerous and important in terms of human and environmental health. Especially Pb and Cr are among the most toxic and deadly heavy metals, and the concentrations of these heavy metals in the environment are constantly increasing. Soil is one of the elements most affected by the increase in pollution. Soils are both a nutrition and living environment for plants and one of the most important components of the environment. In addition, topsoil is one of the most important indicators of the level of air pollution. This study aimed to determine and map the Pb and Cr pollution in the city center of Ankara, the capital and the second-largest city of Turkey, with the help of topsoils. Within the scope of the study, Ankara city center was divided into sub-regions with different characteristics, and Pb and Cr analyzes were performed by taking topsoil samples from 50 points representing these regions. Then, the changes in Pb and Cr concentrations on a regional basis were statistically evaluated, the data were transferred to Geographic Information Systems (GIS) using ArcGIS 10.7 software, then modeled with the kriging method, one of the interpolation methods, and pollution maps were created. As a result of the study, it has been determined that the Cr concentration is generally higher in the northwest-southeast axis of the study area, decreases as one goes to the northeast and southwest, and the region with the highest Pb concentration is located in the center of the study area, that is, in the west of the town of Sincan.
... Additionally, rotation and fallow measures should be taken for the cultivated land that is seriously polluted and difficult to repair. For the land that is not suitable for agriculture, land use should be adjusted according to the law, and the prohibited production areas of agricultural products should be divided [43]. (3) In accordance with the "concentration into a piece, dynamic adjustment, and no reduction in the total amount" principle, a "deposit" system for the treatment of heavy metal pollution in the cultivated soil was formulated, and the county government set up a fund management committee. ...
In China, the environmental capacity problem of heavy metals has long been hidden in the Pearl River Basin creating a contradiction between the economic development and environmental health. Thus, this research calculated the environmental capacity of heavy metals in the agricultural land of the urban agglomeration in the Pearl River Basin, evaluated the health risk warning capacity using a comprehensive index. The results showed that the static capacity order of heavy metals in the study area was As > Pb > Zn > Cr > Hg > Cu > Ni > Cd. The dynamic capacity showed an upward trend, and it fluctuated in some cities. The remaining capacity of Cr and Ni was relatively poor, and the comprehensive soil quality index of the Pearl River Basin was 0.64. The pollution level was of grade IV, which belongs to the medium capacity, but the soil pollution risk still existed, which threaten the health of local resident. In this regard, this study also put forward some countermeasures for pollution control. Thus, studying the soil heavy metal environmental capacity can provide a reference for heavy metal pollution control and health risk early warning in the Pearl River Basin.
... With an area of 1084 km 2 , the TGR region (106 • 50'~111 • 50 ′ E, 29 • 16'~31 • 25 ′ N) has a total length of 665 km (Ye et al., 2019a). In this study, 16 paired surface sediment samples (n = 32, 0~5 cm) were collected using a pre-cleaned stainless-steel sampler (5 cm diameter and 30 cm length) in the WLFZ along the main stream of the TGR in March 2018 and September 2018, respectively. ...
Sixteen paired surface sediment samples (0–5 cm, n = 32) covering upstream to downstream of water-level-fluctuation zone of Three Gorges Reservoir, China were collected in March 2018 (following six months of submergence) and September 2018 (after six months of exposure). Seventeen per- and poly-fluoroalkyl substances (PFASs) were quantified to evaluate contamination characteristics, apportion source categories and estimate mass inventory and loadings. The concentration of ΣPFASs ranged from 0.26 to 0.82 ng g⁻¹ at high water-level (HWL) and 0.46–1.53 ng g⁻¹ at low water-level (LWL). Perfluorooctanoic acid (PFOA, mean: 0.32 ng g⁻¹) and perfluorooctane sulfonate (PFOS, mean: 0.12 ng g⁻¹) dominated, accounting 44.9% and 16.3% of the total PFASs, respectively. The distribution of PFASs was more influenced by anthropogenic activities than physicochemical parameters of the sediments. Positive matrix factorization (PMF) identified PFOA-based products was the major sources (40.1% and 38.6%, respectively). Besides, the direct sources of PFOA-, PFOS-, PFNA-and PFBA-based products played the predominant role, while the indirect degradation of precursors contributed relatively little. The sediment (0–5 cm) mass inventory of PFASs at LWL (57.5 kg) was higher than HWL (39.3 kg). The annual mass loadings of the total PFASs, PFOA, PFOS, perfluoroundecanoic acid (PFUdA) and perfluorononanoic acid (PFNA) from the upstream to the middle-lower reaches of Yangtze River were 27.4 kg, 11.1 kg, 4.63 kg, 2.89 kg and 2.57 kg, respectively. This study could provide the basic datasets of PFASs in surface sediments of the TGR, and also indicate an important transport of PFASs from upstream to the lower reaches, which should be further studied as well.
... Past studies noted that heavy metals derived from anthropogenic sources were high in the largest rivers and reservoirs in the world (Romano et al. 2018;Ghorab 2018; Three Gorges Reservoir (TGR) is known as the world's largest hydropower reservoir, located in the upper reach of the Yangtze river in China, is paid global attention as the China's vital water resource in power generation, flood control, transportation, irrigation, etc. Li et al. 2013). Hence, the reservoir area was undergone rapid development activities, industries, population and settlements expansion, which led to severe heavy metal pollution in terms of water, sediments, and soil in the reservoir (Zhu et al. 2019;Ye et al. 2019;Zhaoyong et al. 2015). Industrial and residential discharge, sewage, pesticides, and fertilizer are often released into the TGR water (Zhou et al. 2020;Bing et al. 2016). ...
Heavy metal (HM) toxicity, ecological risk, and pollution sources were analyzed using the pollution indexing and statistical methods in the Three Gorges Reservoir (TGR). The average concentration of HM increased in the order of Cr < Ni < As < Cd < Cu < Mn < Pb < Zn < Al < Fe during the recharge period and Cd < Cr < Ni < As < Cu < Pb < Mn < Zn < Al < Fe during the discharge period. Significant spatial variations of Pb, Zn, Cd, As, Mn, Ni, Cr, and Cu were observed at the upstream and downstream sampling sites. Pb sharply increased during the recharge period, ranges (6.93 –148.62 μg/L) and exceeded WHO and USPEA standards limit. HPI, HEI, Cd, WPI indicated low pollution and moderate pollution with the strong influence of Pb and Cd in the discharge and recharging period, respectively. HTML values are below the permissible toxicity load except for Pb. The Pb toxicity removal percentage is 56.47%, suggesting that the lead’s toxicity level is high in TGR and requires the removal process. Ecological risk index values indicated that pollution is low in TGR. The potential ecological risk indexes (RI) of 9.07 and 31.60 were obtained for the discharge and recharge period, respectively, indicating low potential ecological risk from heavy metals in TGR. However, RI values revealed that (Pb, Cd, As Cr Ni, Cu Zn, and Mn) were the most ecological risk HMs in TGR. A significant ecological risk of Pb and Cd distribution was observed across the TGR. Multivariate statistical results found that Pb, Cd, Zn, Mn, Ni, As, Cr, Cu mainly originate from industrial wastewater, mining, metals processing, and agricultural runoff. Fe and Al were mainly from bedrock weathering. Pb, Cd, Zn HMs are a threat to the reservoir ecosystem. This study delivered a current status of HM pollution, toxicity, ecological risk, and pollution sources, indicating a vital insight into HM pollution and water security management in the Three Gorges Reservoir.
... Its storage capacity and flood control capacities are 39.3 and 22.1 km 3 , respectively (Tang et al. 2016). The total length of the reservoir is 665 km, and the total submerged surface area is 1084 km 2 (Ye et al. 2019). This region is dominated by mountains (74%) and hills (22%), and belongs to the subtropical humid climate, with an annual temperature of 14.9-18.5 °C and annual precipitation of 1100-1400 mm (Li et al. 2019a, b, c). ...
The Three Gorges Reservoir (TGR) plays a crucial role in providing electricity for mega-cities across China. However, since the impoundment was completed in 2006, attention to environmental concerns has also been intensive. In order to determine the distribution, sources, and pollution status of trace elements in the water fluctuation zone of the TGR following ten years of repeated “submergence” and “exposure”, we systematically collected 16 paired surface sediment samples (n = 32) covering the entire main body of the TGR in March 2018 (following 6 months of submergence) and September 2018 (after 6 months of exposure), and quantitatively analyzed 13 elements (e.g., Mn, Fe, V, Cr, Ni, Cu, Zn, As, Sr, Y, Zr, Ba, and Pb) using X-ray fluorescence spectrophotometry (XRF). The results showed that, except for Sr, concentrations of trace metals following submergence were generally higher than those after exposure due to the less settling of suspended solids at the faster flow velocity during the drawdown period. Assessment using enrichment factors (EFs) and a geo-accumulation index (Igeo) both characterized a relatively serious anthropogenic pollution status of metals in the upper reaches of the TGR with respect to the middle-lower reaches. Source apportionment by positive matrix factorization (PMF) analysis indicated that agricultural activities (24.8 and 24.3%, respectively) and industrial emissions (24.5 and 22.9%, respectively) were the two major sources in these two periods, followed by natural sources, domestic sewage, and ore mining. Ecological risk assessment showed that metalloid arsenic (As) could be the main potential issue of risk to aquatic organisms and human health. A new source-specific risk assessment method (pRI) combined with PMF revealed that agricultural activities could be the major source of potential ecological risk and should be prioritized as the focus of metal/metalloid risk management in the TGR.
... Through both terrestrial and aquatic food chains, metal(loid)s can be absorbed by surrounding organisms and transferred to higher trophic levels, which causes potential harmful impacts on ecological and human health (Tshalakatumbay et al. 2015;Lindsay et al. 2017;Li et al. 2018a). It has been reported that chronic exposures to copper (Cu), cadmium (Cd), and mercury (Hg) could induce Wilson, Itai-itai, and Minamata diseases, respectively (Han et al. 2017;Ye et al. 2019). As a result, an improved understanding on the environmental cycling of metal(loid) contaminants is essential for food security, public health, and ecological sustainability. ...
PurposeThe construction of large dams submerges riparian soils within reservoirs. However, little is known about the influence of water submergence on metal(loid) solubilization from polluted soils. In this study, the spatial distribution and solubilization characteristics of soil-associated metal(loid)s within reservoirs along the middle Jinsha River were evaluated.Methods
Concentrations of soil-associated metal(loid)s were determined and principal component analysis was performed to evaluate the metal(loid) spatial distribution. Then, metal(loid) chemical fractions of highly contaminated soils were analyzed. Finally, ex situ experiments of metal(loid) solubilization were conducted under the influence of changing pH, suspended solid concentration (SSC), and oxidation-reduction potential (ORP) conditions as well as successive drought-wetting cycles.ResultsWithin the LY, AH, and LKK reservoirs, the soil-associated Ni and Cr originated from specific metal(loid) ores, and Cd and Cu remained from historical industrial pollution posed potential risks to water quality. Water submergence changed pH, SSC, and ORP conditions, which affected metal(loid) solubilization through dissolution-precipitation and sorption-desorption processes. The low SSC variables contributed to over 20% solubilization of total Cd, Cu, and As. Moreover, the neutral-alkaline conditions due to carbonate-dominated lithology limited metal(loid) release from soils. Finally, the decreased ORP promoted solubilization of metal(loid)s bound to Fe-Mn oxyhydroxides. Generally, the solubilization levels of metal(loid)s were dependent on the chemical fractions.Conclusion
Water submergence could induce potential solubilization of metal(loid)s, especially for Cd from historical industrial pollution. Thus, this study highlighted that the investigation on both spatial distribution and solubilization characteristics of metal(loid)s in riparian soils is important for future environmental management of reservoirs.
... This statement correlates with Li et al. [94] and Feng et al. [92]. Our results also confirm the theory of Ye et al. [95], that the spatiotemporal dynamics of heavy metals (Cd, Cu, Zn, and Pb) may be due to the physical and chemical properties of the soil. ...
This study assisted in identifying and preventing the increase in heavy metals in soil and winter wheat. Its accumulation can affect cultivated crops, quality and crop yields, and consumers’ health. Selected heavy metals were analyzed using the GTAAS method. They were undertaken on selected heavy metals content (Cd, Cu, Pb, and Zn) in arable soils at three sites in Slovakia and their accumulation in parts of cultivated winter wheat. Our study showed that the limit value of Cd in soil samples was exceeded in the monitored arable soils from 2017–2019. The average content values of Cu and Zn did not exceed the limit values, even in Pb values (except for the spring period). The analyses also showed that the heavy metals content for plants bioavailable in soil did not exceed the statutory critical values for Cd, Cu, and Zn’s average content values. However, Pb content exceeded permitted critical values. Heavy metals bioaccumulation (Zn, Cu) was within the limit values in wheat. Analyzed Cd content in wheat roots and Pb content were determined in all parts of wheat except grain. The study showed that grain from cultivated winter wheat in monitored arable soils is not a risk for consumers.
... Nutrients in sediment can be released into overlying waters and become a potential source of eutrophication; therefore, sediment is a crucial environmental sector to be considered in ecosystem protection . The studies on nutrient elements in water borne particulates (Müller et al. 2012;Koshikawa et al. 2007;Han et al. 2018), submerged sediment (Duan et al. 2008;Ran et al. 2016;Wu et al. 2016;Sun et al. 2018) and riparian sediment Ye et al. 2019;Zhang et al. 2019) in TGR have been conducted by several groups. Until now, most of the studies have focused on basic nutrient data collection, and the studies on seasonal influence are still scarce. ...
Permanently submerged sediment samples (SS) were collected in the center stream of eleven tributaries of Changjiang (Yangtze River) and at eight confluence zones in the Three Gorges Reservoir (TGR) in May and December of 2017. The work showed that aqua regia digestion is a simpler, more reliable and robust method compared to total digestion with hydrofluoric acid (HF) for the determination of trace metals (TMs) in sediment for risk assessment purpose. Our study revealed a remarkable accumulation of TMs at the confluence zones and a trend of their gradual increase toward this zone. The presence of iron and manganese (oxy)hydroxides combined with hydrodynamic conditions created by the Three Gorges Dam (TGD) and its operation are believed to play a crucial role. This work also found that concentrations of in May sediment were significantly higher than those in December, which could have been caused by both the cyclic hydrodynamic conditions and the warmer water. TOC and TP were both very low in the sediment. Although TN was 2 times higher than the Lowest Effect Level suggested by the Ontario Ministry of Environment, it is uncertain if it reflects a natural background level or due to anthropogenic activities. A critical discussion is made by comparing the conclusions obtained when using different TMs risk assessment models. Necessary precautions are highly recommended when performing this exercise. In this study, no significant risk from either TMs or nutrients was identified.
... From a sink perspective, Buttermore et al. (2018) attributed elevated Ni concentrations in bed sediments within agricultural watersheds in Puerto Rico to the use of nickel-based fungicides associated with banana plantations. Likewise, elevated concentrations of Cd, Cu and Zn were identified in bed sediments in agricultural portions of the Yangtze watershed (Ye et al. 2019). Additionally, the absence of riparian buffers has also been shown to play a role in sediment metal concentrations. ...
Tropical mountainous rivers transport a disproportionate amount of sediment to the global ocean. While these systems also deliver sediment-related pollutants (i.e., metals) to the coast, the potential accumulation of metal contaminants within these systems has been largely unexplored. This study analyzed the trace metal concentrations of fine riverbed sediment (< 0.63 µm) collected from Rio Loco, Rio Yauco and Rio Guamaní in Puerto Rico. A total of 17 samples were collected in June 2019 (~ 21 months following Hurricane Maria) from these watersheds. Metal concentrations (Al, Ba, Cd, Cu, Cr, Fe, Mn, Ni, Sb, Sn, U and Zn) were quantified with acid digestion and inductively coupled plasma mass spectrometry. Strong positive correlations were found between Cd, Pb, Sb and Sn (ravg > 0.60, p < 0.05) as well as between Ba, Cr and Ni (ravg > 0.81, p < 0.05). A comparison of land cover with metal concentrations revealed positive statistical relationships between Cu, Sb, Sn and Zn with developed land and Cr, Ni and U with agricultural land. Between 7 and 50% of the samples exhibited enrichment factor values indicative of moderate to significant levels of contamination (EF > 2) for each metal. Additionally, several metal concentrations exceeded the consensus-based threshold effect and probable effect values. Altogether, these data confirm that metals do accumulate in tropical mountainous watersheds and can be found at concentrations that impact freshwater ecosystems. These elevated metal concentrations coupled with periodic flushing events, regularly supported by hurricanes, suggest a threat to nearshore ecosystems such as coral reefs.
... The mobility of trace element such as As, Fe and Mn is highly dependent upon the concentration of dissolved organic carbon (DOC) due to its ability to change the redox conditions and microbial abundances. DOC concentrations in groundwater are higher in urban areas compared to natural or agricultural areas(McDonough et al. 2020).The processes of precipitation, mineral dissolution, adsorption/desorption, complexation/dissociation and oxidation/reduction control the mobility and availability of trace elements in the soil and groundwater(Leung and Jiao 2006;Sun et al. 2010 ;Ye et al. 2019). Many studies have focused on the presence and monitoring of trace elements in groundwater and drinking water. ...
Les eaux souterraines captées par les puits à grand diamètre dans la métropole de Cotonou (Sud du Bénin) sont tirées de l’aquifère du Quaternaire qui appartient au Bassin Sédimentaire Côtier. Cet aquifère côtier est particulièrement vulnérable non seulement de par son caractère superficiel et par l’influence des activités anthropiques mais aussi de par sa proximité avec les eaux salées du lac Nokoué et les mares contaminées. Les habitants des milieux défavorisés représentant environ 60% de la population de Cotonou sont les plus exposés face à l’utilisation quotidienne de cette ressource à des fins domestiques. Les campagnes de prélèvement spatio-temporel et les analyses physico-chimiques, isotopiques et bactériologiques, nous ont permis de décrire l’état actuel des eaux de l’aquifère peu profond, d’identifier les principaux facteurs et les périodes à risque de contamination des maladies hydriques notamment la leptospirose, une zoonose émergente méconnue à Cotonou. La nappe paraît principalement alimentée par les pluies locales. Mais l’utilisation conjointe des traceurs environnementaux (ions majeurs, ratio Cl/Br et isotopes stables), ont montré que cet aquifère peu profond est contaminé par les apports d'eau salée du lac Nokoué pendant la saison sèche, le lexiviat de déchets solides, d’eaux usées des fosses septiques et des fuites de latrines pendant la recharge par les pluies et aussi via les mares temporaires et permanentes. Même si l’interaction eau souterraine et les minéraux rocheux contribuent à la minéralisation, certains polluants anthropiques notamment les nitrates et les éléments traces (Mo, V, Zn et Al) peuvent parvenir à la nappe par lessivage ou être retenus par adsorption des sédiments sablo-argileux dans la Zone Non Saturée. D’autres comme le Fe et le Mn dépendent des conditions réductrices du milieu qui interviennent principalement au cours des processus de dénitrification et de dégradation de la matière organique. Les eaux contaminées de Cotonou se présentent donc comme un environnement favorable à la survie des leptospires en occurrence les mares obtenues après les précipitations du début de la saison des pluies. Le contact fréquent avec l'eau pendant la saison des pluies expose les habitants de Cotonou aux risques d'infections à la leptospirose. Les mesures de prévention des risques de contamination des maladies hydriques méritent sans doute une plus grande attention de la part des autorités sanitaires de la région côtière de l'Afrique de l'Ouest, en pleine expansion.
Soil toxic metals have strong spatial heterogeneity, and their sources vary among regions. Thus, this study integrated the Catreg and geographically weighted regression (GWR) models to quantitatively extract the main source proxies (numerical and categorical variables were analyzed simultaneously) for different toxic metals and analyze the spatial heterogeneity of the distributions of these sources. Pb, Cd and Hg were the predominant toxic metals in soil. Of the samples with Pb, Cd and Hg, 84.12 %, 68.03 % and 41.57 % exceeded the background values, and 5.36 %, 6.42 % and 5.43 % were moderately contaminated according to the geoaccmulation index, respectively. Industrial activities, with relative importance values of 17.82 %, 31.54 % and 26.51 % for Cd, Hg and Pb, respectively, were the predominant source of these metals especially, in their high-content cluster areas (central urban areas). Soil available phosphorus was another important factor (relative importance values of 13.03 %, 13.41 % and 25.55 % for Cd, Hg and Pb, respectively), and agricultural activities (especially the overuse of phosphoric fertilizers) were identified as an anthropogenic source of these toxic metals. Soil parent material had the greatest influence on As and Cr, with relative importance values of 19.88 % and 19.09 %, respectively, especially in their high-content accumulation area (the eastern coastal area), indicating that these toxic metals mainly come from natural sources. Slope had important impacts on toxic metal accumulation (relative importance values of 17.48 %, 21.22 %, 12.40 % and 16.13 % for Cd, Hg, Cr and As, respectively) by influencing industrial distribution and pollutant migration. By changing the soil adsorption capacity, soil organic matter (explaining 13.01 % of Pb) and soil pH (explaining 14.58 % of As and 12.40 % of Cr) strongly influenced toxic metal accumulation. This study highlights the benefits of the integrated Catreg-GWR model for analyzing multiple spatially heterogeneous environmental data types (numerical and categorical variables), providing a potential foundation for local pollution prevention.
Previous investigations on heavy metals in the
water–sediment compartment focused on their spatial distribution, and the influence of sediment pH and organic matter (OM) on metal environmental occurrences. However, there are limited studies on the effects of physicochemical properties on the migration and transformation of heavy metals in the water–sediment compartments. This study investigated the relationship between the physicochemical properties of sediments and the distribution and chemical speciation of heavy metals, and the potential environmental risk of heavy metals in water and sediment using Risk Assessment Code (RAC) values and the Tessier five-step extraction method. Adsorption and desorption experiments showed that the sediment had weak adsorption and the strongest desorption capacity for Cd. Results of the pH, OM, surface element content, and X-ray diffraction (XRD) patterns suggested that cadmium (Cd) was more likely to partition into the water phase from the sediment during the flooding and water storage periods. When pH was 7–8 and OM content was 3.6–5.9%, the sediment–water distribution coefficient of Cd was low due to its large ionic radius, and the surface adsorption sites were saturated by other elements. These studies can provide a theoretical basis for the management and pollution control of the Three Gorges Reservoir.
Lead (Pb) toxicity is a major problem in agricultural soil that negatively affects plant growth and development. Glycine betaine (GB) is an effective compatible solute that resists abiotic stress and plays an important role to mitigate various stresses. The present study is the first of its kind on the application of GB to mitigate Pb toxicity on barley cultivars. To elucidate the role of GB in mitigating Pb toxicity of three concentrations (15 mM, 25 mM, and 35 mM) in two barley varieties (BH-959 and BH-946) with and without foliar application of GB (2 mM) was examined. The study found that increasing Pb concentration significantly (p<0.05) reduced the level of primary metabolites viz. photosynthetic pigments, protein, and carbohydrates in both cultivars upto 42.4%, 38.4% and 39% respectively. However malondialdehyde content, proline content, and antioxidant enzyme activity (SOD, CAT, and POX) were found to increased significantly (p<0.05) as compared to control treatment upto 83.4%, 83.2% and 51% respectively. In contrast, the application of GB led to significantly (p<0.05) improved physio-biochemical parameters as well as antioxidant enzyme activity (53%) and reduced oxidative stress along with malondialdehyde content (14.42%) in both varieties. An increment in these parameters revealed that exogenous application of GB (2 mM) significantly improves Pb (up to 35 mM) toxicity in barley plants and its use may be beneficial for crops susceptible to Pb toxicity to improve growth and yield.
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 fraction, diffusive gradients in thin films (DGT) and toxicity data. The As concentration 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.
The effects of initial soil moisture on colloid-associated transport are still poorly understood given the well-recognized significance of colloid-facilitated transport of strongly-sorbing contaminants. In this study, Cd leaching was sequentially conducted in an intact soil column under three initial moisture conditions (near saturation, field capacity and dryness). Soil colloids were always the dominant carriers for Cd. However, upon the lowering of initial soil moisture, increased transport of colloids (96.2→101.0→168.2 mg) was observed, surprisingly, along with decreased transport of colloid-associated Cd (C-Cd) (23.9→10.7→8.2 µg) and enrichment factor (248.4→105.9→48.8 mg/kg) of Cd on colloids, resulting from pH reduction which increased Cd desorption and colloid size increase and/or ζ-potential decrease that showed lower affinity for Cd. Correlation, redundancy analysis and structural equation modelling revealed the dominantly positive role of colloids, EC plus cations (Ca2+ and Mg2+) in the release of C-Cd and dissolved Cd (D-Cd), respectively, under initial moistures of near saturation and field capacity. Under initially dry conditions, soil water potential showed dominantly negative effects on the transport of both C-Cd and D-Cd. These findings highlighted the critical role of initial moisture conditions in modulating colloid-facilitated Cd mobilisation, providing insights into the environmental risk assessment of heavy metals in other leaching scenarios.
We examined the topsoil heavy metal concentration of four different urban functional areas (UFAs) in Nanjing, China: a heavy traffic area (HA), an industrial area (IA), a leisure area (LA), and a farmland area (FA). The purpose of the study is as follows: (i) to determine which heavy metal(s) were the primary pollutant(s) in the study area and the contamination status of five heavy metals (Cr, Ni, Cu, Zn and Pb) in the urban topsoil of Nanjing city, (ii) to assess the comprehensive pollution risk of heavy metals in UFAs using two methods: the ecological risk index and the fuzzy comprehensive evaluation based on Analytical Hierarchy Process (AHP). X-ray fluorescence (PXRF) was used to measure the soil heavy metal content, the potential ecological risk method was implemented to evaluate the risk level of each UFA, and the fuzzy comprehensive evaluation method was applied to assess the pollution degree of heavy metals in UFAs. PXRF analysis showed that Cr was the primary metal pollutant in the study area. There were also significant enrichments of Cu, Zn and Pb in collected soil samples. The four UFAs were ranked IA > HA > LA > FA in terms of the potential heavy metal ecological risk; the distribution pattern determined by the fuzzy comprehensive evaluation model followed the same order. Overall, 84.70%, 12.98% and 2.32% of the 647 sites were classified as class I (clean), class II (lightly polluted), and class III (heavily polluted), respectively, suggesting that most soil in Nanjing was clean. Based on the calculated weight matrices of the potential ecological risk results, the major pollutants were Cr and Zn. This investigation highlighted that most of the soil in the study area is clean, but certain sites are polluted to some degree, especially in the IA. The study area showed an overall moderate ecological risk for heavy metal pollutants, with Cu and Pb posing the greatest risk.
Accumulation of the pollutants in the sediment along the surface water may negatively affect on the riparian zones and ecological risk dimension. In order to reveal this problem, in the present study, detailed metal monitoring of sediments and riparian soils was performed seasonally with ICP-OES analysis. Pollution levels, changes, and potential sources were determined statistically. Ecological statuses are detailed. Contamination factor (CF), Enrichment factor (EF), Index of geo-accumulation (Igeo), pollution index (PI), and modified pollution index (MPI) potential and modified ecological risk indexes were analyzed. Although no significant seasonal differences were observed, almost all metals in the sediments and riparian soils spatially differed. Cr (11.4 to 136), Co (7.7 to 21.52), Cu (11.4 to 76.6), and Ni (14.06 to 128.2) as mg/kg from the upstream to the downstream increased significantly and gradually accumulated. The riskiest metals in the sediment and riparian soil in terms of basin river health are Cu, Co, Ni. Risk values were found heavily polluted (PI > 3 and MPI > 10), and the risk indexes (RI) are well above the "desired environment without the risk". RI was found to be more than 50, and modified risk indices exceeded 200 at many points. The transport of pollution in surface water has been revealed in the sediment and adverse effects on the riparian zone and ecological system. Considering sediment and riparian soil together, pollutant-based and holistic ecological risk assessments are necessary to determine river health.
The establishment of hydroelectric dams can lead to major changes in hydrology for habitats within the reservoir drawdown zones. The Three Gorges Dam (TGD) in China is the world’s largest hydroelectric facility, with a reservoir covering 1080 km2 and a drawdown zone covering 350 km2. Since the TGD’s establishment in 2008, the formerly terrestrial habitats within the dam’s drawdown zone have effectively been converted to riparian habitats. A strong understanding of ecological dynamics in these novel habitats is critical to their ongoing management. Given the major contribution of insects to ecosystem function and biodiversity, we surveyed riparian insect communities semi‐annually from 2011 to 2018 across a 600 km network of eighteen sites in the TGD’s drawdown zone. During this period the total abundance of insects increased 4.4–fold, and the composition of insect communities shifted significantly, with Diptera increasingly dominant in later years. Insect abundance trajectories were coupled with concomitant changes in local climate and soil chemistry, which have in turn been brought on by the novel hydrological regime in the drawdown zone. Revegetation efforts had limited impacts on riparian insect abundances. Overall, riparian insect communities have undergone marked shifts since the TGD started operating. We cannot explicitly attribute these effects to the TGD’s establishment, but our results indicate that they might have been shaped by – or are at least coupled with – the profound changes in hydrological conditions associated with the TGD’s establishment.
In Taipu River, after being transformed from a drainage channel to a drinking water supply river in 1995, heavy metals that have accumulated in sediments have become an environmental issue. Herein, we collected sediments of Taipu River in 2018, 2020, and 2021 and analyzed the distribution of Sb, As, Cd, Cu, Pb, Cr, and Zn to identify their sources. The results revealed that the mean concentrations of heavy metals were above the background values, except for Cr and As. During the non-flood season, the midstream of Taipu River becomes a heavy metal hotspot, with their concentrations 2–5 times higher than those in upstream sediment. There were significant correlations (r = 0.79–0.99) among drainage, precipitation and flow rate, which indicated that drainage caused by both the opening of Taipu Gate and precipitation control the flow rate and, then, possibly influenced the distribution of heavy metals. Moreover, three sources (industrial sources, particle deposition sources, and natural sources) were characterized as the determinants for the accumulation of heavy metal by the Positive Matrix Factorization model, with the contribution rates of 41.7%, 32.9%, and 25.4%, respectively. It is recommended that the influence of hydrological conditions and industrial activities should be a key consideration when developing regulations for the management of heavy metals in rivers.
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 (Kd), diffusive gradients in thin films (DGT), and DGT induced flux in sediments (DIFS) model. According to the Kd 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.
The concept of green site remediation calls for a model that can consider environmental impacts in the selection of site remediation alternatives. In this study, an integrated life cycle assessment (LCA)-fuzzy synthetic evaluation (FSE) model is developed to help practitioners select the optimal site remediation plan by incorporating life cycle impacts into the comprehensive suitability evaluation. The LCA module quantifies environmental and economic impacts using ReCiPe and Input-Output LCA methods, respectively. The impacts are evaluated along with other suitability considerations, presented in 32 indicators under ten criteria, by practitioners through a questionnaire survey. FSE is used to process the collected subjective judgments and generate a suitability index for informed selection. The integrated model is applied to a case study of an abandoned chemical industrial site contaminated by various organic chemicals and mercury. Four remediation alternatives, designed as the combined uses of ex-situ thermal desorption, in-situ thermal desorption, and in-situ containment, are evaluated. The LCA results show that the alternative with extensive use (treating 93.8 % of the contaminated soil) of in-situ thermal desorption is associated with the highest environmental and economic impacts, followed by the alternative with less extensive use (6.2 %) of in-situ thermal desorption. The FSE results show that the economic, technical, and environmental impact considerations are the top three important criteria. The integrated LCA-FSE results indicate that the alternative with mixed use of ex-situ thermal desorption and in-situ containment could be the optimal plan. Excluding LCA results could alter the suitability ranks of the alternatives.
Water-level-fluctuation zone (WLFZ) is a sensitive zone influencing the transformation between sink to source for heavy metals (HMs), which suffers from cyclic inundation and exposure during different hydrological regimes. To better understand the geochemical cycling of HMs in the WLFZ, we performed temporal analysis and transport quantification of HMs in the world’s largest freshwater WLFZ: Three Gorges Reservoir (TGR), China. From 2002 to 2020, HM contents in WLFZ soils fluctuated and gradually stabilized. In 2020, selective remobilization of HMs was observed, which were mainly influenced by four environmental factors: Fe and Mn oxides, soil pH, dissolved organic carbon, and soil mobility-resupply ability. Multiple models were developed to quantify the HM fluxes in 2019 and 2020 induced by soil erosion, runoff, and leaching. In 2020, HMs liberated in the TGR region catchment increased from 13.35 (2019) to 36.61 gigagram (Gg), including 6.90 Gg of non-residual fraction and 1.34 Gg of labile metals. Otherwise, metal fluxes of WLFZ soils into the TGR increased 1.96 times, which were attributed to integrated factors, including the increase of runoff, soil erosion, sediment load, and remobilization of HMs resulting from the catchment-wide flood in 2020. In particular, the runoff-induced labile metals only accounted for ∼ 10% of HM fluxes entering the TGR. We inferred that catchment-wide flood was an important control on HM transport in terrestrial and aquatic systems of the TGR region catchment. This study makes a novel contribution to the understanding of the transformation between sink to source of the WLFZ, and for targeted management of its ecological and environmental impact.
The properties and sources of soil heavy metals (Pb, Zn, Cu, Cd, As, Hg, Cr, and Ni) need to be comprehensively analyzed to take effective steps to control and reduce soil pollutants. In this research, 416 soil samples were collected on a large scale in China. Two receptor models (PCA/MLR and PMF) were utilized to identify pollutant sources and quantify the contributions. The means of soil heavy metals (Zn, Cu, As, Hg, Cr, and Ni) were lower than the corresponding screening values and intervention values. Cd was greater than the intervention value, while Pb was between the screening value and the intervention value. Source apportionments suggested that mine sources were the most polluted (64.28%), followed by traffic sources (38.98%), natural sources (11.41–39.58%), industrial sources (9.8–18.65%), and agricultural sources (2.79–14.51%). Compared to the PCA/MLR model, the PMF model had a better effect in evaluating soil heavy metal pollution. It gave corresponding weights according to the data concentration and its uncertainty, which made the result reasonable. The ecological risk assessment indicated that Cd posed a significant risk, while Hg caused a mild risk and the other six heavy metals posed a low risk. The spatial distribution of ecological risk suggested that severe risk points were mainly distributed in the central area, while high-risk points were distributed in the southern region. The SRI method was developed to link pollution sources and their potential ecological risks and indicated better applicability to the PMF model. The study findings could provide guidelines for monitoring the main sources and reducing the pollution of soil heavy metals.
Intense input of potential toxic elements (PTEs) from diffuse anthropogenic sources to agricultural alluvial soils has caused bias in the geochemical baseline value (GBV) established by current methods. This study intends to assess the extent of bias and establish the GBV for 9 PTEs based on their source contribution on the largest alluvial islands in China, the Chongming Islands. The results of total PTE concentrations in soil samples (n = 120) showed that the islands were influenced by PTEs from various diffuse sources. Source identification methods provided a common conclusion that Ni, Co and Cr were dominated by the Yangtze River sediment input and thus more enriched in “recent” alluvial soils which were generated by large-scale reclamation practices. Positive matrix factorization quantified that pesticides and mineral fertilizer contributed 84.3% of As and 63.6% of Cd, especially in “old” soils, while a large proportion of Cu, Sb, Pb and Zn came from atmospheric deposition. Accumulation of PTEs was enhanced by soil sorption phases including organic matter and clay. Because of this differentiation in source contribution, the GBV of As, Cd, Co and Ni established on “recent” soils are significantly different from those established on data from the whole area. Using this source-based GBVs, the geoaccumulation index method suggested that 37% and 25% of the sampling sites were contaminated by As and Cd, respectively. This study emphasized the importance of considering different sources contribution in GBV determination to avoid underestimation of enrichment of PTEs from intense human diffuse sources.
The heavy metals contamination in soil has attracted increasing attention. In this study, the main objective was to determine three heavy metals (Cd, Pb, and Cr) of soils contaminated by smelting waste, and to evaluate pollution risk. The Pb (15.48 mg/kg) and Cd (311.39 mg/kg) mean concentrations exceeded the national standard, while Cr (48.60 mg/kg) concentration did not exceed. The Heavy metal fractions analysis showed that three heavy metals were dominated by FeMn oxides fraction (Fe-Mn). The correlation and cluster analysis indicated that there was significant correlation between Cd and Pb (0.55< r < 0.96), while Cr was not correlation to Cd and Pb. The environmental pollution of heavy metals was assessed by the ratio of secondary phase and primary phase (RSP). The result showed that RSP values of Cd, Pb, and Cr range from 13.05–54.28, 16.11–4.97 and 1.61–52.33, which indicated soil was serious contaminated by them. These results showed that smelting waste discharge led to this smelter soil being seriously contaminated by multiple heavy metals which have a tendency to transport and accumulate into deep soil due to their high fractional transformation.
Soils in floodplains and riparian zones provide important ecosystem functions and services. These ecosystems belong to the most threatened ecosystems worldwide. Therefore, the management of floodplains has changed from river control to the restoration of rivers and floodplains. However, restoration activities can also negatively impact soils in these areas. Thus, a detailed knowledge of the soils is needed to prevent detrimental soil changes. The aim of this review is therefore to assess the kind and extent of soil information used in research on floodplains and riparian zones. This article is based on a quantitative literature search. Soil information of 100 research articles was collected. Soil properties were divided into physical, chemical, biological, and detailed soil classification. Some kind of soil information like classification is used in 97 articles, but often there is no complete description of the soils and only single parameters are described. Physical soil properties are mentioned in 76 articles, chemical soil properties in 56 articles, biological soil properties in 21 articles, and a detailed soil classification is provided in 32 articles. It is recommended to integrate at least a minimum data set on soil information in all research conducted in floodplains and riparian zones. This minimum data set comprises soil types, coarse fragments, texture and structure of the soil, bulk density, pH, soil organic matter, water content, rooting depth, and calcium carbonate content. Additionally, the nutrient and/or pollution status might be a useful parameter.
The alteration of hydrologic condition of Three Gorges Reservoir (TGR) after impoundment has caused numerous environmental changes. This study investigated the distribution, accumulation and potential sources of the seldom monitored trace elements (SMTEs) in sediments from three tributaries (ZY, MX and CT) and one mainstream (CJ) in TGR during different seasons. The average contents of most SMTEs excluding Sb in the winter were similar to that in the summer. For Sb, its average concentrations in the summer and winter were roughly six and three times higher than its background value, respectively. Contamination factor (CF) and geoaccumulation index (Igeo) demonstrated that most of the sediments were obviously contaminated by Sb. The enrichment factors (EF) of Ga and Sb were higher than 2.0, revealing the possible anthropogenic inputs; However, the EFs of other SMTEs were lower than 1.5, indicating the natural inputs. Correlation and principal component analysis suggested the most SMTEs were positively correlated with major elements (Cr, Mn, Cu, Zn, As, Cd and Pb) and clay contents, which implies that SMTEs had the same sources with these major metals, and the fine particles might be a major carrier for transporting SMTEs from the rivers to the TGR.
We reviewed the current ecological and environmental conditions within the water level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR).The WLFZ encountered several eco-environmental problems, including the loss of biodiversity, soil erosion, challenges for land use, non-point-source pollution, nutrient accumulation, and heavy metal pollution, which seriously affected the ecological integrity and water quality of the TGR. Our review revealed that vegetation restoration of the WLFZ may be an ideal system response to cope with the eco-environmental problems of the WLFZ. Further, riparian vegetation had potential in reducing soil erosion, preventing nutrient accumulation, and adsorbing heavy metal pollutants in the WLFZ. We also described remedial riparian vegetation engineering in the TGR WLFZ—both past and potential. Vegetation engineering will be critical for improving the eco-environmental conditions in the WLFZ, and for maintaining ecological integrity of the TGR. We provided recommendations for on-going remedial actions in the TGR WLFZ.
Soil profiles were collected in three salt marshes with different plant species (i.e. Phragmites australis, Tamarix chinensis and Suaeda salsa) in the Yellow River Delta (YRD) of China during three seasons (summer and fall of 2007 and the following spring of 2008) after the flow-sediment regulation regime. Total elemental contents of As, Cd, Cu, Pb and Zn were determined using inductively coupled plasma atomic absorption spectrometry to investigate temporal variations in trace elements in soil profiles of the three salt marshes, assess the enrichment levels and ecological risks of these trace elements in three sampling seasons and identify their influencing factors. Trace elements did not change significantly along soil profiles at each site in each sampling season. The highest value for each sampling site was observed in summer and the lowest one in fall. Soils in both P. australis and S. salsa wetlands tended to have higher trace element levels than those in T. chinensis wetland. Compared to other elements, both Cd and As had higher enrichment factors exceeding moderate enrichment levels. However, the toxic unit (TU) values of these trace elements did not exceed probable effect levels. Correlation analysis showed that these trace elements were closely linked to soil properties such as moisture, sulfur, salinity, soil organic matter, soil texture and pH values. Principal component analysis showed that the sampling season affected by the flow-sediment regulation regime was the dominant factor influencing the distribution patterns of these trace elements in soils, and plant community type was another important factor. The findings of this study could contribute to wetland conservation and management in coastal regions affected by the hydrological engineering.
Dam is an important way of water-resources utilization in large rivers. To date, more than 50 000 dams with various sizes have been constructed in the Yangtze River basin, with many other dams proposed to be constructed by 2020. Dam construction has played significant roles in flood control, irrigation, navigation, and energy supply; however, the enormous negative effects, such as landslides, ecological problems, and water quality decline, could surpass positive gains. Although a long and complicated evaluation process had been carried out and the countermeasures for numerous foreseen negative impacts of the Three Gorges Dam (TGD) had been implemented, many uncertainties and debating opinions on the benefits and costs of this project still exist. In this review, we synthesize the negative impacts that have occurred as a result of the TGD, including reservoir-triggered seismicity, landslides, water quality control, ecological problems, siltation, and sediment discharge decline to assure an environmentally friendly operation of the TGD and regional sustainable development in the Yangtze River basin, especially in the Three Gorges Reservoir region.
Measurements were made of the adsorption of cobalt, copper, manganese, nickel, lead, and zinc on nine synthetic manganese oxides and three synthetic iron oxides, to determine the mechanism by which lead accumulates in the manganese oxides in soils. Adsorption of lead by the manganese oxides was up to 40 times greater than that by the iron oxides, and lead was adsorbed more strongly than any of the other ions studied by all of the oxides except goethite. This is considered to be the reason for the accumulation of lead in the manganese oxides in soils. No evidence was found for the oxidation of lead, nor for the formation of specific lead-manganese minerals.
The aim of this work has been to penetrate one of many possible avenues towards a potential ecological risk index to be used as a diagnostic tool for water pollution control purposes, i.e. to sort out which lakes/basins and substances should be given special attention. The work is based on the thesis that a sedimentological risk index for toxic substances in limnic systems should at least,account for the following four requirements.
The water level fluctuation zone (WLFZ) in the Three Gorges Reservoir is located in the intersection of terrestrial and aquatic ecosystems, and assessing heavy metal pollution in the drown zone is critical for ecological remediation and water conservation. In this study, soils were collected in June and September 2009 in natural recovery area and revegetation area of the WLFZ, and geochemical approaches including geoaccumulation index (I
geo) and factor analysis and soil microbial community structure were applied to assess the spatial variability and evaluate the influence of revegetation on metals in the WLFZ. Geochemical approaches demonstrated the moderate pollutant of Cd, the slight pollutant of Hg, and four types of pollutant sources including industrial and domestic wastewater, natural rock weathering, traffic exhaust, and crustal materials in the WLFZ. Our results also demonstrated significantly lower concentrations for elements of As, Cd, Pb, Zn, and Mn in the revegetation area. Moreover, soil microbial community structure failed to monitor the heavy metal pollution in such a relatively clean area. Our results suggest that revegetation plays an important role in controlling heavy metal pollution in the WLFZ of the Three Gorges Reservoir, China.
Fertile soils in the River Neretva estuary were developed by fluvial sedimentation and deposition of the eroded soil material from the karst hills within the catchment. After extensive reclamation, two reclaimed land zones (fluvial terraces and lower-laying terraces) have been delineated, both used for agriculture. The main objectives of this study were to evaluate soil chemical and geochemical properties in reclaimed zones that differ mainly in topography, soil types and agricultural land use. The origin of the trace metals in the arable soils was studied using multivariate statistics, and interpolation maps of trace metals were produced using GIS and geostatistics. Soil trace metal concentrations do not exceed a threshold value established by the Croatian Government regulation, with exception of copper. Comparative analysis of the main soil properties and trace metal concentrations in the study area showed a pronounced spatial variation and differences between two reclaimed zones in soil organic matter content, bioavailable P and total concentrations of Cd and Cu. Factor analysis in the area of the lower-laying terraces showed grouping of bioavailable P and K, organic matter content and pH (negative loading) in the component associated mostly with the land use. In the area of the fluvial terraces, bioavailable P and total Cd were grouped in the same component that may be explained by the traditional small farm agriculture and overuse of mineral fertilizers. In the whole study area, processes of secondary salinization were determined, accompanied by the raised chloride and sodium concentration measured in the saturation soil extract.
Eutrophication due to non-point source (NPS) of nitrogen (N) and phosphorus (P) has become a serious pollution problem in many Chinese rivers. In this paper, the export coefficient model (ECM) was used to assess the influence of NPS on N and P loading to the Three Gorges Reservoir Area (TGRA) of Hubei Province, People's Republic of China. Data from the main non-point sources were analyzed from 1995 to 2007, including rural domestic wastes, distributed livestock farms, fertilizers and soil erosion. Additionally, the potential N and P loading from NPS originated from a variety of sources were estimated and analyzed from 1995 to 2007, including runoff from rural domestic waste, livestock farms, land use, and atmospheric deposition, using the ECM. These gave the temporal distributions of the potential NPS loads within the reservoir area. The results indicated that the potential total nitrogen (TN) load was much higher than the potential total phosphorus (TP) load. The calculated TN load was 2.83×10(4) tonnes, while the TP load was 2.14×10(3) tonnes in 2007, with a ratio of TN/TP of 13.23. Record shows that "algae blooms" occurred 8 times in TGRA that year. Therefore, there may be a correlation between the eutrophication potential in the inlet water of TGRA and the TN/TP ratio of potential NPS loads. These findings demonstrate that the export coefficient model could provide a simple and reliable approach to evaluate the potential N and P loading to the Three Gorges Reservoir Area of Hubei Province in the People's Republic of China and may be useful for the planning and management of the local agricultural watersheds.
This study investigated temporal heavy metal characteristics over the past 20 years and the spatial variation of heavy metal characteristics at the Manwan Reservoir tail, center, and head in the Lancang River, Yunnan Province, China. The following heavy metals were selected for analysis: Hg, Cd, Pb, Cu, Zn, As, Cr, Fe, and Mn. Multivariate statistical methods, including principal component analysis (PCA) and the Pearson correlation matrix were used to distinguish the main pollution factors and sources before and after dam construction. The results indicate that the average annual values of heavy metals were far lower than the recommended values of the surface water quality standards in China with the exception of Hg. The concentration of metals showed considerable variation by season, where higher levels of metals generally occurred in high flow periods. The results from PCA show that three significant components were extracted, explaining 76.25% of the total variance. The ANOVA results indicate that Pb, Fe, Mn, and Cr had significant spatial variation (P < 0.05) at the reservoir tail, center and head. The enrichment factor (EF) used to compare the accumulation effect of heavy metals indicated that there was no enrichment (EF < 1) of heavy metals with the exception of Mn, which showed minor enrichment (1 < EF < 3) between the reservoir center and head. The spatiotemporal variation and the accumulation effects of water heavy metals were not distinct due to the construction of the Manwan Reservoir.
Numerical sediment quality guidelines (SQGs) for freshwater ecosystems have previously been developed using a variety of approaches. Each approach has certain advantages and limitations which influence their application in the sediment quality assessment process. In an effort to focus on the agreement among these various published SQGs, consensus-based SQGs were developed for 28 chemicals of concern in freshwater sediments (i.e., metals, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and pesticides). For each contaminant of concern, two SQGs were developed from the published SQGs, including a threshold effect concentration (TEC) and a probable effect concentration (PEC). The resultant SQGs for each chemical were evaluated for reliability using matching sediment chemistry and toxicity data from field studies conducted throughout the United States. The results of this evaluation indicated that most of the TECs (i.e., 21 of 28) provide an accurate basis for predicting the absence of sediment toxicity. Similarly, most of the PECs (i.e., 16 of 28) provide an accurate basis for predicting sediment toxicity. Mean PEC quotients were calculated to evaluate the combined effects of multiple contaminants in sediment. Results of the evaluation indicate that the incidence of toxicity is highly correlated to the mean PEC quotient (R(2) = 0.98 for 347 samples). It was concluded that the consensus-based SQGs provide a reliable basis for assessing sediment quality conditions in freshwater ecosystems.
Though there are many studies of heavy metal contaminations of urban dusts in developed countries, little attention has been paid to this kind of study in developing countries, including China. Therefore, a series of investigations were performed to provide heavy metal signatures of urban dusts and to evaluate potential sources in Xi'an, Shaanxi Province. Sixty-five samples of urban dusts were collected in Xi'an. Then Ag, Cr, Cu, Mn, Pb and Zn concentrations were determined by using atomic absorption spectrophotometry, and As, Hg and Sb concentrations by atomic fluorescence spectroscopy. The results indicate that, in comparison with Chinese soil, urban dusts in Xi'an have elevated metal concentrations as a whole, except those of arsenic and manganese. These concentration levels are comparable to those in other studies. Correlation coefficient analysis, principal component analysis (PCA) and cluster analysis (CA) were performed and three main sources with corresponding cluster elements were identified: (1) Ag and Hg have commercial and domestic sources; (2) Cr, Cu, Pb, Sb and Zn are mainly derived from industrial sources, combined with traffic sources as well for Pb and Zn; (3) As and Mn come mainly from soil sources, and As also has an industrial source. Based on PCA and CA analyses, manganese was selected as the reference element, and heavy metal enrichment factors (Efs) were calculated, which in turn further confirms the source identification. Also, Efs give an insight of human influence degree of urban dusts.
The Three Gorges Reservoir, the world’s largest hydropower project, has operated stably for more than five years. To understand its water quality status, the nutrient and biochemical indexes, the total nitrogen (TN), the total phosphorus (TP), the potassium permanganate index (CODMn), the five-day biochemical oxygen demand (BOD5) and fecal coliform (F. coli), as well as the heavy metals (Cu, Hg, As, Cd, Zn and Pb) of samples collected from 10 sites during the time period of 2008 to 2013 were studied via using multiple analysis approaches. For each parameter, pictures of the spatial and temporal distributions were presented, and the reasons behind their variation trends were elaborated. Principal component analysis (PCA) was applied to identify the types of pollution. The Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI) was calculated to concisely mark the water quality. In addition, a human health risk assessment of the heavy metals in a representative site was conducted. The results showed that the water quality state in the Three Gorges Reservoir was intricate but stable and acceptable from 2008 to 2013. The TN, TP and Pb were considered to be the key pollution indexes. Enforcements to alleviate industrial and urban pollution, along with ship management, have worked. The decrease in heavy metal concentrations from upstream to downstream was associated with the self-purification of the reservoir. However, rural pollution became worse in those years. Improper agricultural activity was an important reason for this trend. For local residents, drinking water was generally safe, but cancer caused by As and Pb is a potential issue.
The concentrations and distribution characteristics of heavy metals in carp (Cyprinus carpio) collected from three main stem sections and seven typical tributaries of Three-Gorge Reservoir (TGR) were investigated after the 175 m impoundment. The concentrations of Cr, Cd, As, Pb, Ni, Cu and Zn in all samples were measured, and the Target Hazard Quotient (THQ) was used to assess the potential health risk to the local consumers. The results showed that Zn concentration was the highest (5.88 mg·kg-1 in average) in fish muscle, while Cd concentration was the lowest (0.013 mg·kg-1 in average). All heavy metal concentrations in carps were lower than the tolerance limits in the related standards. Pearson correlation matrix as well as cluster analyses were applied to identify inter-relationships of the heavy metals. Cluster analysis identified four clusters among the studied heavy metals based on their concentrations in fish samples. Significant positive correlation was found between Cr and Cu and between Pb and As. A significant positive correlation was also observed between Pb concentrations and fish sizes, indicating a bioaccumulation potential of Pb in fish. Comparing to fishes in other areas of Yangtze River Basin, the concentrations of heavy metals in carp from TGR were low, and there was no obvious increasing tendency after impoundment. Moreover, due to the enhanced sediment deposition along the reservoir flow, a decreasing trend of these heavy metals in carp was observed from upstream to downstream in the main stream of TGR. Based on the THQ analysis, we concluded that the seven heavy metals in fish tissue posed no obvious health risk to the general population consumption.
In order to investigate the heavy metals concentrations and their potential ecological risks of sediments in Three Gorges Reservoir during its impounding period, 24 sediment samples were collected from both the mainstream and tributaries for analyzing Cu, Pb, Zn, Cd, Ni, Cr, As and Hg. The index of geoaccumulation and the potential ecological risk index were then employed to evaluate the pollution degree of heavy metals in the sediments. The results indicate that the average contents of heavy metals in Three Gorges Reservoir: Cr is 86.31 mg·kg -1, Ni is 46.81 mg·kg -1, Cu is 76.03 mg·kg -1, Zn is 137.63 mg·kg -1, Cd is 0.75 mg·kg -1, Pb is 59.40 mg·kg -1, As is 18.07 mg·kg -1, Hg is 0.109 mg·kg -1, respectively. Average concentrations of heavy metals in sediments of Three Gorges Reservoir are relatively higher than those in sediment background of Yangtze River. The assessment by geoaccumulation index indicates that the pollution degree of heavy metals is: Cd>Pb>Cu>As>Zn>Ni>Hg>Cr. The assessment by potential ecological risk index show that the potential ecological risk intensity caused by heavy metals is: Cd>Hg>Cu>As>Pb>Cr>Zn, and Cd is the predominant element among them. In general, it is not significantly polluted during the impounding of Three Gorges Reservoir.
Phosphorus fate and transport in natural waters plays a crucial role in the ecology of rivers and reservoirs. In this paper, a coupled model of hydrodynamics, sediment transport, and phosphorus transport is established, in which the effects of sediment on phosphorus transport are considered in detail. Phosphorus adsorption is estimated using a mechanistic surface complexation model which is capable of simulating the adsorption characteristics under various aquatic chemistry conditions. The sediment dynamics are analyzed to evaluate the deposition and release of phosphorus at the bed surface. In addition, the aerobic layer and anaerobic layer of the sediments are distinguished to study the distribution of phosphorus between dissolved and particulate phases in the active sediment layer. The proposed model is applied to evaluate the effects of various operating rules on sediment and phosphorus retention in the Three Gorges Reservoir (TGR). Results show that the proposed model can reasonably reflect the phosphorus transport with sediment, and management scenarios that influence sediment retention will also influence the phosphorus balance in the TGR. However, modest operational changes which have only minor effects on sediment retention also have limited influence on the phosphorous balance.
The impoundment of the Three Gorges Reservoir (TGR) in China influences the quality of the water supply. Surface sediment samples from the TGR mainstream and three tributaries were collected. Acid volatile sulfide (AVS), simultaneously extractable metals (SEMs), and the fraction of organic carbon (foc) were used to assess the toxicity of heavy metals. Sediment quality guidelines (SQGs) were established using the equilibrium partitioning approach. The results showed that the surface sediments were found to be oxic or suboxic. AVS concentrations in sediments were relatively low, below SEM concentrations. The [SEM] - [AVS] model indicated that all sediments possibly have adverse effects on aquatic life. However, ([SEM] - [AVS])/foc predicted no adverse biological effects in some areas of the Meixi and Caotang Rivers, while adverse effects to aquatic life were uncertain for the other sediments. The partitioning coefficients, water quality criteria, and residual metals in the sediments were the main factors influencing the SQGs for the TGR, while the metals bound to AVS had a negligible effect. The normalized TGR SQGs were all much higher than the existing standards except for cadmium and copper. The differences might be attributed to the approaches used for derivation of SQGs and the physical and chemical characteristics of the sediments.
Suspended sediments from large and middle size Chinese estuaries, including the Yalujiang, Shuangtaizihe, Luanhe, Jiaojiang and Zhujiang, were analysed to understand trace metal transport in the coastal zone. The determinations of 13 major and trace elements plus organic carbon were made of total concentrations and were fully validated by certified reference materials (CRMs). The combination of the data sets with other Chinese estuaries, such as Changjiang and Huanghe, provides an overview of particulate trace metal geochemistry in this region. Trace metal levels in Chinese rivers are relatively low compared with those draining industrialized regions of Europe and North America. In the estuaries, most particulate elements illustrate stable distribution in the mixing zone until a salinity of 30, especially when absolute concentrations are normalized to aluminium, although the total suspended matter (TSM) is quite different in time and space. Using Al as a reference, it was estimated that 25–40% for Cu, and 5–20% for Pb could remain in labile part in the Jiaojiang, Shuangtaizihe and Zhujiang, whereas different features of labile elements were found in the Changjiang and Luanhe. The mean enrichment factor (EFm) increases with higher sewage to river runoff ratio (S/R) over the drainage basin and EFm for suspended matter is higher than that for bottom sediments. Finally, inputs of particulate trace metals to the coast are estimated based on the riverine sediment load and chemical compositions.
Multivariate statistical analysis and geochemical approaches were exploited for the assessment of the level of some heavy metals (Mn, Fe, Ni, Cu, Zn and Pb) in sediments from Sudanese harbors along the Red Sea coast. Principal component analysis, as a multivariate statistical analysis approach, was applied to identify contribution sources by heavy metals in sediments. While a single source (crustal) was recorded in the bulk sediments and coarse sediment grains (grain-size 1000–500 µm), two sources (crustal and anthropogenic) were recorded in fine sediment grains (grain-size < 500 µm). Furthermore, enrichment factor (EF), as a geochemical approach, appointed polluted sites by heavy metals in the study area. Based upon a previous study addressed the interpretation of EF values, minor to moderate anthropogenic enrichment were recorded in sediments from some sites in the study area. The main anthropogenic activities that believed to be the major sources of pollution by heavy metals in the study area are discharges from oil refinery, industry, shipping activity and domestic waste. Hierarchical cluster analysis (HCA), as another multivariate statistical analysis approach, was applied for the concentrations of heavy metals in bulk sediments to group sediments according to their mineralogical composition. The output of HCA is that sediments from the Port-Sudan harbor can be divided mainly into three areas — east, west and south. For the Sawakin harbor, no apparent trend for the spatial distribution of heavy metals in sediments was recorded.
Based on ten heavy metals collected twice annually at 59 sites from 1998 to 2004, enrichment factors (EFs), principal component
analysis (PCA) and multivariate linear regression of absolute principal component scores (MLR-APCS) were used in identification
and source apportionment of the anthropogenic heavy metals in marine sediment. EFs with Fe as a normalizer and local background
as reference values was properly tested and suitable in Hong Kong, and Zn, Ni, Pb, Cu, Cd, Hg and Cr mainly originated from
anthropogenic sources, while Al, Mn and Fe were derived from rocks weathering. Rotated PCA and GIS mapping further identified
two types of anthropogenic sources and their impacted regions: (1) electronic industrial pollution, riparian runoff and vehicle
exhaust impacted the entire Victoria Harbour, inner Tolo Harbour, Eastern Buffer, inner Deep Bay and Cheung Chau; and (2)
discharges from textile factories and paint, influenced Tsuen Wan Bay and Kwun Tong typhoon shelter and Rambler Channel. In
addition, MLR-APCS was successfully introduced to quantitatively determine the source contributions with uncertainties almost
less than 8%: the first anthropogenic sources were responsible for 50.0, 45.1, 86.6, 78.9 and 87.5% of the Zn, Pb, Cu, Cd
and Hg, respectively, whereas 49.9% of the Ni and 58.4% of the Cr came from the second anthropogenic sources.
Samples of fine-grained channel bed sediment and overbank floodplain deposits were collected along the main channels of the Rivers Aire (and its main tributary, the River Calder) and Swale, in Yorkshire, UK, in order to investigate downstream changes in the storage and deposition of heavy metals (Cr, Cu, Pb, Zn), total P and the sum of selected PCB congeners, and to estimate the total storage of these contaminants within the main channels and floodplains of these river systems. Downstream trends in the contaminant content of the <63 μm fraction of channel bed and floodplain sediment in the study rivers are controlled mainly by the location of the main sources of the contaminants, which varies between rivers. In the Rivers Aire and Calder, the contaminant content of the <63 μm fraction of channel bed and floodplain sediment generally increases in a downstream direction, reflecting the location of the main urban and industrialized areas in the middle and lower parts of the basin. In the River Swale, the concentrations of most of the contaminants examined are approximately constant along the length of the river, due to the relatively unpolluted nature of this river. However, the Pb and Zn content of fine channel bed sediment decreases downstream, due to the location of historic metal mines in the headwaters of this river, and the effect of downstream dilution with uncontaminated sediment. The magnitude and spatial variation of contaminant storage and deposition on channel beds and floodplains are also controlled by the amount of <63 μm sediment stored on the channel bed and deposited on the floodplain during overbank events. Consequently, contaminant deposition and storage are strongly influenced by the surface area of the floodplain and channel bed. Contaminant storage on the channel beds of the study rivers is, therefore, generally greatest in the middle and lower reaches of the rivers, since channel width increases downstream. Comparisons of the estimates of total storage of specific contaminants on the channel beds of the main channel systems of the study rivers with the annual contaminant flux at the catchment outlets indicate that channel storage represents <3% of the outlet flux and is, therefore, of limited importance in regulating that flux. Similar comparisons between the annual deposition flux of specific contaminants to the floodplains of the study rivers and the annual contaminant flux at the catchment outlet, emphasise the potential importance of floodplain deposition as a conveyance loss. In the case of the River Aire the floodplain deposition flux is equivalent to between ca. 2% (PCBs) and 36% (Pb) of the outlet flux. With the exception of PCBs, for which the value is ≌0, the equivalent values for the River Swale range between 18% (P) and 95% (Pb). The study emphasises that knowledge of the fine-grained sediment delivery system operating in a river basin is an essential prerequisite for understanding the transport and storage of sediment-associated contaminants in river systems and that conveyance losses associated with floodplain deposition exert an important control on downstream contaminant fluxes and the fate of such contaminants.
Microbial communities in floodplain soils are exposed to periodical flooding. A long-term submerged Eutric Gleysol (GLe), an intermediate flooded Eutric Fluvisol (FLe), and a short-time flooded Mollic Fluvisol (FLm) at the Elbe River (Germany) with similar organic carbon contents (Corg) between 8.1% and 8.9% were selected to test the quality of phospholipid fatty acids (PLFA), soil microbial carbon (Cmic), basal respiration (BR), metabolic quotient (qCO2), and Cmic/Corg ratio to characterize and discriminate these soils with microbial parameters.
The Three Gorges Project has been subject to intense debates regarding its benefits and costs. The environmental impacts of this huge project have been an important focus of these debates since the project planning stage. After the operation of the Three Gorges Dam at full capacity at the end of 2008, new environmental and ecological issues are emerging. This paper gives a brief description of the Three Gorges Project and its environmental impact assessment process, as well as major efforts to control environmental problems brought about by the project. From the long and complicated evaluation process, it is clear that there are large uncertainties and competing opinions regarding the benefits and costs, especially the ecological and environmental ones, of the project even after great research effort. Emphasis here is given to the environmental challenges including: (1) water quality control; (2) water and sediment regulation; (3) biodiversity conservation in the riparian and aquatic ecosystems; (4) environmentally friendly dam operation and regional sustainable development. Opportunities often grow out of the challenges. The Three Gorges Project provides opportunities for grand-scale experiments on the environmental, ecological, and socio-economic impacts of large dams. Local, national, and international concerted efforts and concrete actions should be directed to the mitigation and control of the negative impacts as well as securing the positive contributions of the project across scales Yes Yes
Soils were sampled in three types of wetlands from the young (A) and old (B) reclaimed regions of the Pearl River Estuary. They were analyzed for total concentrations of heavy metals to investigate their distributions and pollution levels in both regions. Results showed that most heavy metals in ditch and riparian wetlands did not significantly differ from those in reclaimed wetlands in A region, while significantly lower for Cd, Cu, Pb, and Zn in reclaimed wetlands in B region, suggesting higher effects of long-term reclamation. Iron, Cr and Cu were identified as metal pollutants of primary concern and had higher contributions to the total toxic units compared to other metals. Almost all metals exceeded their lowest effect levels and Fe and Cr even exceeded the severe effect levels. Multivariate analysis shows that Fe and Mn are controlled by parent rocks and other metals mainly originate from anthropogenic source.
Using canonical correspondence analysis (CCA), relationships were investigated between plant species composition and flooding characteristics, heavy metal contamination and soil properties in a lowland floodplain of the Rhine River. Floodplain elevation and yearly average flooding duration turned out to be more important for explaining variation in plant species composition than soil heavy metal contamination. Nevertheless, plant species richness and diversity showed a significant decrease with the level of contamination. As single heavy metal concentrations seemed mostly too low for causing phytotoxic effects in plants, this trend is possibly explained by additive effects of multiple contaminants or by the concomitant influences of contamination and non-chemical stressors like flooding. These results suggest that impacts of soil contamination on plants in floodplains could be larger than expected from mere soil concentrations. In general, these findings emphasize the relevance of analyzing effects of toxic substances in concert with the effects of other relevant stressors.
Surface water samples were collected from 42 sampling sites throughout the upper Han River during the time period of 2005-2006. The concentrations of trace metals were determined using inductively coupled plasma-atomic emission spectrometry (ICP-AES) for the seasonal variability and preliminary risk assessment. The results demonstrated that concentrations of 11 heavy metals showed significant seasonality and most variables exhibited higher levels in the rainy season. Principal component analysis (PCA) and factor analysis (FA) revealed that variables governing water quality in one season may not be important in another season. Risk of metals on human health was then evaluated using Hazard Quotient (HQ) and carcinogenic risk, and indicated that As with HQ >1 and carcinogenic risk >10(-4), was the most important pollutant leading to non-carcinogenic and carcinogenic concerns, in particular for children. The first five largest elements to chronic risks were As, Pb, V, Se and Sb, in the dry season, while they were As, V, Co, Pb and Sb in the rainy season. This assessment would help establish pollutant loading reduction goal and the total maximum daily loads, and consequently contribute to preserve public health in the Han River basin and develop water conservation strategy for the interbasin water transfer project.
In order to analyze and evaluate different trace metals on surface water of the Changjiang River, concentrations of dissolved trace metals (Cu, Ni, Fe, Co, Sc, Al, Zn, Pb, Cd, Se, As, Cr, and Hg), major elements (Ca and Mg), and nutrient (NO3- were measured. Samples were taken at 76 positions along Changjiang River in flood and dry seasons during 2007-2008. Spatial distributions identified two main large zones mainly influenced by mineral erosion (sites 1-22) and anthropogenic action (sites 23-76), respectively. Principal component analysis (PCA) and hierarchical cluster analysis were used to identify the variance distinguishing the origin of water. Four significant components were extracted by PCA, explaining 74.91% of total variable. Cu, Ni, Fe, Co, Sc, Al, Ca, and Mg were mainly associated with the weathering and erosion of various rocks and minerals, while an anthropogenic source was identified for Cd and As. Although erosion was one source of Pb and Zn, they were also input by atmospheric deposition and industrial pollutions. NO3- and Se were mainly associated with agriculture activities. However, Hg and Cr showed different sources. CA confirmed and completed the results obtained by PCA, classifying the data into two large groups representing different areas. Group 1 referred to the upper reaches which represented samples mainly corresponding to natural background areas. Group 2 referred to the middle and lower reaches including samples under anthropogenic influence. Meanwhile, group 2 was subdivided into three new groups, representing agricultural, industrial, and various artificial pollution sources, respectively.
In order to investigate the contamination levels of trace metals, surface water samples were collected from six regions along
Yangtze River in Nanjing Section. The concentrations of trace metals (As, B, Ba, Be, Cd, Cr, Cu, Fe, Pb, Li, Mn, Mo, Ni, Sb,
Se, Sn, Sr, V and Zn) were determined using inductively coupled plasma-atomic emission spectrometry (ICP-AES). Total concentrations
of the metals in the water samples ranged from 825.1 to 950.4 μg/L. The result was compared with international water quality
guidelines. Seven metals levels were above the permissible limit as prescribed by guidelines. A preliminary risk assessment
was then carried out to determine the human health risk via calculating Hazard Quotient and carcinogenic risk of the metals.
Hazard Quotients of all metals were lower than unity, except As. The carcinogenic risk of As and Cd was higher than 10−6, suggesting that those two metals have potential adverse effects on local residents.
Surface sediments (0-5 cm) from 59 stations within the Yangtze River intertidal zone (YRIZ) were sampled for metal contamination analysis in April and August 2005. The concentrations ranged (in mg kg(-1) dry weight): Al, 40,803-97,213; Fe, 20,538-49,627; Cd, 0.12-0.75; Cr, 36.9-173; Cu, 6.87-49.7; Mn, 413-1,112; Ni, 17.6-48.0; Pb, 18.3-44.1; and Zn, 47.6-154; respectively. Among the 59 sampling stations, enrichment factors (EF) indicate enrichment of Cd (52 stations), Cr (54 stations), Cu (5 stations), Ni (26 stations), Pb (5 stations) and Zn (5 stations). Geoaccumulation indexes (I(geo)) also suggest individual metal contamination in localized areas. This study indicates that Cd, Cr and Ni enrichment in the YRIZ sediment is widespread whereas Cu, Mn, Pb and Zn enrichment is localized or nonexistent. Factor and cluster analyses indicate that Cd is associated with total organic carbon whereas Cu, Cr, Ni, Pb and Zn have a close association with Mn.
The concentrations of metals, loss of ignition and nutrient (N, P) were determined in the bottom sediments of the Rybnik Reservoir (southern Poland). The mean concentrations of the metals in the bottom sediments were: Cd 25.8 microgram/g, Cu 451.7 microgram/g, Zn 1583.4 microgram/g, Ni 71.1 microgram/g, Pb 118.6 microgram/g, Cr 129.8 microgram/g, Fe 38782 microgram/g and Mn 2018.7 microgram/g. The bottom sediments are very heavily loaded with zinc, manganese, copper, nickel, phosphorus and lead (percentage enrichment factor), and cadmium, phosphorus and zinc (index of geoaccumulation). The increase of cadmium, lead, nickel and zinc concentrations was connected with the inflow of the contaminated water of the river Ruda and long-range transport. The contamination of the reservoir with copper and manganese resulted mainly from atmospheric precipitation. The variability of the bottom sediment loading with metals during the investigations was affected in the first place by changes in the concentration of iron, but also those elements whose concentrations in the bottom sediment were elevated compared to the concentrations in shale--cadmium, nickel and lead.
Surface sediments and sediment cores collected at the Pearl River Estuary (PRE) and its surrounding coastal area were analysed for total metal concentrations, chemical partitioning, and Pb isotopic compositions. The distribution of Cu, Cr, Pb, and Zn demonstrated a typical diffusion pattern from the land to the direction of the sea. Two hotspots of trace metal contamination were located at the mixed zone between freshwater and marine waters. The enrichment of metals in the sediments could be attributed to the deposition of the dissolved and particulate trace metals in the water column at the estuarine area. The similar Pb isotopic signatures of the sediments at the PRE and its surrounding coastal area offered strong evidence that the PRE was a major source of trace metals to the adjacent coastal area. Slightly lower (206)Pb/(207)Pb ratios in the coastal sediments may indicate other inputs of Pb in addition to the PRE sources, including the inputs from Hong Kong and other parts of the region.
Gola di Lago is a small (ca. 3 ha), minerotrophic peatland in Canton Ticino, southern Switzerland. Chemical analyses of peat show remarkable concentrations of As, Se, and U. Coring at regular intervals (19 sites) revealed several zones of pronounced accumulation, with As concentrations up to 350 mg kg(-1) (2000 mg kg(-1) on a mineral matter basis). Both Fe and S are also enriched at this depth, suggesting that redox-related transformations have affected all three elements. High concentrations of Se (up to 28 mg kg(-1)) and U (up to 470 mg kg(-1)) were also detected, representing on a mineral matter basis 350 and 2900 mg kg(-1), respectively. An intermittent stream entering the peatland contained up to 400 microg of As L(-1), but the permanent stream leaving the mire contains <2 microg L(-1). A three-dimensional map of the spatial distribution of As shows that the main source of As is the intermittent stream and not the basal, mineral sediment underlying the peatland. Arsenic is highly enriched not only in shallow peat layers at the interface between the stream and peatland today but also in deeper peat layers in the center of the mire, at what must have been the stream-peat interface in the past. By sequential extraction of fresh peat samples, 100% of the As could be extracted from a shallow sample but only 19% from a sample taken from the deeper layers. In both cases, most of the As was associated with the organic matter fraction (73% and 57% respectively). Although this peatland is an effective geochemical trap for As in the stream waters, the mechanisms of removal remain unclear.
The spread of contaminants in soil can be hindered by the soil stabilization technique. Contaminant immobilizing amendments decrease trace element leaching and their bioavailability by inducing various sorption processes: adsorption to mineral surfaces, formation of stable complexes with organic ligands, surface precipitation and ion exchange. Precipitation as salts and co-precipitation can also contribute to reducing contaminant mobility. The technique can be used in in situ and ex situ applications to reclaim and re-vegetate industrially devastated areas and mine-spoils, improve soil quality and reduce contaminant mobility by stabilizing agents and a beneficial use of industrial by-products. This study is an overview of data published during the last five years on the immobilization of one metalloid, As, and four heavy metals, Cr, Cu, Pb and Zn, in soils. The most extensively studied amendments for As immobilization are Fe containing materials. The immobilization of As occurs through adsorption on Fe oxides by replacing the surface hydroxyl groups with the As ions, as well as by the formation of amorphous Fe(III) arsenates and/or insoluble secondary oxidation minerals. Cr stabilization mainly deals with Cr reduction from its toxic and mobile hexavalent form Cr(VI) to stable in natural environments Cr(III). The reduction is accelerated in soil by the presence of organic matter and divalent iron. Clays, carbonates, phosphates and Fe oxides were the common amendments tested for Cu immobilization. The suggested mechanisms of Cu retention were precipitation of Cu carbonates and oxy-hydroxides, ion exchange and formation of ternary cation-anion complexes on the surface of Fe and Al oxy-hydroxides. Most of the studies on Pb stabilization were performed using various phosphorus-containing amendments, which reduce the Pb mobility by ionic exchange and precipitation of pyromorphite-type minerals. Zn can be successfully immobilized in soil by phosphorus amendments and clays.
The water used by 85% of the Asian population originates in Tibetan Plateau. During April and May of 2006, water samples were collected from four major Asian rivers in the Plateau (i.e. the Salween, Mekong, Yangtze River and Yarlung Tsangpo) and analyzed for Cu, Pb, Zn, Ag, Mo, Cd, Co, Cr, Ni, Li, Mn, Al, Fe, Mg and Hg. The results showed that elements such as Mg were rather high in Tibetan rivers, giving a mean electrical conductance of 36 mS/m. In a few locations, the results also showed relatively high concentrations of Al and Fe (>1mg/L). However, the concentrations of Cu, Zn, Ag, Cd, and Cr were generally low. Contamination with Pb was identified at a few locations in the Salween and Ni at a few sites in the Yangtze River.