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Vanadium (V) is ubiquitously distributed in environmental media, imposing toxic hazards to organisms in biogeosphere. This review focuses on a comprehensive summary of the ecological and human health risks ascribed to V pollution, based on existing V toxicity relevant publications. Lower doses of V (< 2 mg/L) is beneficial to plant growth, however, V reduces plant biomass, induces toxic effects on plant morphology and adversely affects the absorption of essential plant elements at higher levels (≥ 2 mg/L). Oxidative stress induced by reactive oxygen species (ROS) produced under V stress may be the main reason for V toxicity to terrestrial and aquatic organisms. Although V contributes to high-efficient biological nitrogen fixation as a co-factor, V alters microbial community structures and drives its evolution. V can also accumulate in and harm human bodies. Knowledge gaps and further perspectives in aspects of V risks are thereby proposed, such as more toxic data reports for deriving V environmental quality criteria, elucidating the molecular mechanisms of detoxification and tolerance of organisms to V for bioremediation applications, and exploring the medical potential of V with the prevention of V toxicity to humans. This review advances our understanding of the toxic effects of V in the ecosystem and inspires future efforts on V management as well as application. [ABSTRACT FROM AUTHOR]

The problem of antibiotic contamination in the environment has attracted much attention in recent years. However, studies on antibiotic contamination in groundwater have only emerged in the last 15 years. In this study, we systematically reviewed the detection methods, distribution characteristics, risk, fate, and sources of antibiotics in groundwater in China, listed the concentrations of the main antibiotic types, and obtained the maximum concentrations by comparing the literature published in the last 10 years. The results show that 65 antibiotics were detected in groundwater in China, with sulfonamides and quinolones receiving the most attention. Antibiotic concentrations are influenced by hydrogeological conditions and seasonal variations, and the ecological risk in most areas is low to medium risk, which is relatively manageable. The highest concentrations found in most of the literatures were in the range of 10–1000 ng/L, but the maximum concentration can reach 47,444.5 ng/L, which requires extra attention. In addition, this study makes recommendations for improving groundwater monitoring surveys and protection measures to prevent the antibiotic contamination of groundwater more effectively. [ABSTRACT FROM AUTHOR]

Since the 1990s, sandstone-type uranium in the northern basin of China has become the main target for mining. Uranium mining can cause a series of impacts on the environment. A conceptual model of the geo-environment for sandstone-type uranium in northern China was described, which covers the changes in the geo-environmental characteristics in the natural state, in the mining process, during decommissioning and after treatment. Sandstone-type uranium is mainly distributed in the Songliao, Erlian, Ordos, Turpan–Hami and Ili Basins, which have arid climates and poor stratum permeability. Pitchblende is the main uranium-bearing mineral and is associated with iron, copper, coal, organic matter and other minerals. The mineral often has a low ore grade (0.01–1.0%) and high carbonate content (2–25%). Uranyl carbonate accounts for more than 90% of the total uranium in groundwater. The uranyl content is closely related to the TDS. The TDS of groundwater in the eastern and central ore belts is usually lower than 2 g/L, while in the western region, such as Xinjiang, it can exceed 10 g/L. In situ leaching (ISL) is the main mining method that results in groundwater pollution. Acid leaching leads to a pH decrease (<3), and heavy metals represented by U and Fe exceed the background values by hundreds of times, resulting in groundwater pollution. CO2 leaching is more environmentally friendly, and the excess ions are usually Ca2+, Mg2+, NO3− and HCO3−. Soil chemical anomalies originate mostly from wind erosion and precipitation leaching of decommissioned tailings. Uranium pollution is mainly concentrated within 20 cm of the surface, and the exceedance generally varies from two to 40 times. During ISL, a series of environmental measures will be taken to prevent pollution from being exposed to the surface. After treatment, the decommissioned uranium mines will likely have no impact on the surrounding environment. In the future, the protection of groundwater should be strengthened during production, and remediation methods based on electrokinetic, microbial and permeable reactive barrier (PRB) technology should be further researched. [ABSTRACT FROM AUTHOR]

Riverbank filtration (RBF) is an important part of the surface water–groundwater cycle, and it intercepts and retains many pollutants in rivers. However, RBF affects the biogeochemical process which enables aquifer sediments to release iron (Fe) and manganese (Mn). In this study, column experiments were performed to investigate the effects of ammonium ions and organic matter on Fe and Mn release from anaerobic RBF sediments. In addition, high-throughput sequencing technology was used to characterize the microbial community. The results showed that the ammonium ions (NH4+) and organic matter (COD) in groundwater promote the release of Fe and Mn from aquifer sediments. The trends of Fe and Mn release were similar during the leaching process. The maximum concentrations of Fe and Mn were 0.32 and 40 μg/L, respectively. The structural diversity and abundance of the microbial communities in the groundwater were closely related to the Fe/Mn content. Actinobacteriota, Proteobacteria, Acidobacteriota, Bacteroidota, and Chloroflexi were the dominant phyla, while Rhodococcus, Ochrobactrum, and Pseudarthrobacter were the dominant genera. These functional microbes are actively involved in the biogeochemical cycling of Fe, Mn, and N. In summary, contaminants and the microbial-community structure have dual effects on the release of Fe and Mn from RBF aquifers. [ABSTRACT FROM AUTHOR]

Groundwater pollution in karst areas is often the result of the interaction of hydrogeological characteristics and human activities. In this study, a chimeric evaluation system of groundwater vulnerability and pollution load was constructed, and the groundwater contamination risk was intuitively displayed using a risk map. The study area is located in Qiannan, a typical karst area in Southwest China. Groundwater vulnerability was mainly calculated using the PLEIK model. Pollution source load evaluation was evaluated using the classification method. The groundwater pollution status was evaluated by the CCME WQI method. The results show that the groundwater vulnerability in the research area was mainly at a medium level. The areas with high pollution load values were mainly distributed in industrial parks and other pollution-source-gathering areas. The results of the water quality evaluation show that the groundwater quality in the study area was generally good. However, the impact of some pollution sources on the surrounding groundwater still cannot be ignored. The results reveal the risk level of groundwater pollution in typical karst areas and provide theoretical support for regional groundwater protection. [ABSTRACT FROM AUTHOR]

Accurate estimation of terrestrial water storage anomalies (TWSA) is crucial for the sustainable management of water resources and human living. In this study, long-term TWSA estimates are reconstructed by integration of multiple meteorological products and the water balance (WB) method at 0.5° × 0.5° resolution, generating a total of 12 combinations of different meteorological data. This scheme is applied to 10 river basins (RBs) within China and validated against GRACE observations and GLDAS simulations from 2003 to 2020. Results indicate that similar seasonal characteristics can be observed between different precipitation and evapotranspiration products with the average correlation coefficient and Nash–Sutcliffe efficiency coefficient metrics larger than 0.96 and 0.90, respectively. Three GRACE solutions indicate similar seasonal variations and long-term trends of TWSA over 10 RBs, with the correlation above 0.90. Similar performance can also be observed concerning the root mean square error and mean absolute error metrics. Nevertheless, WB-based TWSA estimates represent larger discrepancies compared to GRACE observations and GLDAS simulations. Specifically, the variation amplitude and long-term trend of WB-based results are much larger than that of the GRACE observations, which is mainly caused by the inaccuracy of remote sensing products and the neglect of anthropogenic activities. Comparable TWSA estimates independently computed from the WB method can only be achieved in 4 out of 10 RBs. This study can provide insightful suggestions for an enhanced understanding of TWSA estimates and improving the performance of the water balance method. [ABSTRACT FROM AUTHOR]

The concentrations of Cu, Zn, As, Pb, Cr, and Cd in soil were analyzed in a mining area in the Inner Mongolia Autonomous Region, China. The average metal concentrations in the soil samples were 204.07 mg/kg, 88.15 mg/kg, 14.47 mg/kg 88.52 mg/kg, 56.45 mg/kg, and 0.235 mg/kg, respectively. Based on the evaluation standards, background values of the soil heavy metals, multiple soil pollution assessment indices, such as the single factor index (Pi), the geological accumulation index (Igeo), the Nemerow index (Pn), the ecological risk index (ER), and the health risk index (HI) were applied to evaluate the soil environmental risks in the study area. It was found that in different soil layer depths (0–10 cm, 10–30 cm, and 30–50 cm), the evaluation result of each index showed that there were significant spatial differences in soil pollution levels, and the focus of different indices differed greatly from each other. The Pi put 18.14% of the area at high risk of soil contamination levels, due to the fact that this index highlights the Cu pollution factor more than other indices and relatively amplifies hazards in some high-risk areas. While the Pn indicated that 61.36% of the study area was at a safe level of soil contamination, it can underestimate the regional soil heavy metal pollution risk. In order to scientifically carry out soil-pollution-risk prevention and control, it is necessary to comprehensively compare and analyze the information disclosed by different indices. [ABSTRACT FROM AUTHOR]

Although riverbank filtration (RBF) has been widely applied in China, the managers do not pay enough attention to the inevitable clogging issues during continuous RBF operation. The RBF site, which is located near the Lalin River, northeastern China, was selected as the study area, and the laboratory column experiments were used to simulate the RBF process and further investigate the physical and chemical clogging. The removal of turbidity (59.4–95.1%), COD (21.9–71.7%), NH4+ (10.9–39.4%), Fe (18.5–64.8%), and Mn (19.8–71.7%) demonstrated the water quality improvement by RBF. Whereas, the significant decrease in permeability (39.6–88.2%) also indicated that the clogging issues could not be ignored during RBF. Among them, the physical clogging-dominated area, chemical clogging-dominated area, and the transition zone were located at 0–12.5%, 37.5–100%, and 12.5–37.5% of the infiltration pathway, respectively. Moreover, the concentration of suspended particle materials, mean size of riverbed sediments, and aquifer media are the major impact factors for physical clogging; the precipitation of soluble constituents and redox reaction and other hydrochemical processes were the major impact factors for chemical clogging. The conclusion of this study can contribute to managers alleviating the clogging issues and improving the effectiveness of the sustainable operation in the local RBF system. [ABSTRACT FROM AUTHOR]

With the ongoing development and utilization of nuclear energy, uranium pollution has become an increasingly serious issue. Although many adsorbents are able to remove hexavalent uranium (U(VI)) from aqueous solution, the development of a high capacity adsorbent exhibiting superior stability would be beneficial. Grafting poly(amidoxime) (PAO) onto reduced graphene oxide (rGO) provides suitable U(VI) adsorption performance but the PAO is prone to agglomeration. The present work used density functional theory calculations to predict that PAO would bond with pyrrolic N atoms in nitrogen-doped rGO (N-rGO). To confirm this, PAO-grafted rGO (PAO-rGO) and PAO-grafted N-rGO (PAO-N-rGO) were prepared and characterized and the successful grafting of PAO on N-rGO was demonstrated. Adsorption experiments demonstrated that PAO-N-rGO exhibit superb U(VI) adsorption performance compared with the original PAO-rGO under acidic conditions. As for competing metal ions, Cu2+, Al3+, and Ca2+ have a greater impact on U(VI) adsorption than Na+, Mg2+, and K+ both for PAO-rGO and PAO-N-rGO. The maximum adsorption capacities of PAO-rGO and PAO-N-rGO for U(VI) were calculated to be 1500.26 and 1545.95 mg g−1, respectively. The mechanism of nitrogen doping promoting uranium(VI) adsorption can be attributed to enhanced PAO grafting and improvement of adsorption performance of the rGO. This work demonstrates that nitrogen doping is a viable strategy for enhancing the U(VI) adsorption performance of PAO-rGO. [ABSTRACT FROM AUTHOR]

In order to elucidate the importance of biogeochemical interactions between NH4+ and aquifer media in groundwater runoff paths, a dynamic monitoring section in the riverbank zone, which is most sensitive to environmental characteristics and perpendicular to the flow direction of the Songhua River in northeastern China, was selected for field experiments in this study. The results indicated that the NH4+ concentration decreased gradually along the groundwater runoff path under exploitation conditions. The NH4+ concentrations of J1, J2, and J3 decreased by 8%, 18%, and 22%, respectively, as compared to the starting concentration of 1.3 mg/L. Adsorption of NH4+ by aquifer media at different depths is a monolayer adsorption process in accordance with pseudo-second-order kinetic equation. The maximum reduction of NH4+ from the aquifer media from top to bottom was 76%, 67%, 56%, and 42%, respectively. The function and activity of dominant functional bacteria have characteristics of coevolution with the NH4+ transformation process. The main genera in the fluctuation zone are Pseudomonas (8.83%) and Acinetobacter (4.37%), which mainly transform NH4+ by heterotrophic nitrification–aerobic denitrification (HN–AD). The main genera in the saturated zone are Flavobacterium (32.60%) and Sphingobium (3.54%), which mainly transform NH4+ by anaerobic denitrification. The spatial variations of species and abundance for NH4+ transformation functional bacteria decrease by 2.74% and 3.47%, respectively, along groundwater runoff paths. In the vertical and horizontal directions of groundwater runoff, the percentage of adsorption in NH4+ transformation gradually decreased and the percentage of biotransformation gradually increased. The adsorption processes in the O2/NO3− reduction, Fe/Mn reduction, and SO42− reduction zones were 20.7%, 3.6%, and 1.0%, respectively. The corresponding proportions of the biotransformation process were 79.3%, 96.4%, and 99.0%. This research is critical for elucidating the bio-geochemical interaction between NH4+ and aquifer media along the course of groundwater runoff in order to offer a scientific basis for the prevention and management of groundwater nitrogen pollution. [ABSTRACT FROM AUTHOR]

Iron (Fe) is one of the most biochemically active and widely distributed elements and one of the most important elements for biota and human activities. Fe plays important roles in biological and chemical processes. Fe redox reactions in groundwater have been attracting increasing attention in the geochemistry and biogeochemistry fields. This study reviews recent research into Fe redox reactions and biogeochemical Fe enrichment processes, including reduction, biotic and abiotic oxidation, adsorption, and precipitation in groundwater. Fe biogeochemistry in groundwater and the water-bearing medium (aquifer) often involves transformation between Fe(II) and Fe(III) caused by the biochemical conditions of the groundwater system. Human activities and anthropogenic pollutants strongly affect these conditions. Generally speaking, acidification, anoxia and warming of groundwater environments, as well as the inputs of reducing pollutants, are beneficial to the migration of Fe into groundwater (Fe(III)→Fe(II)); conversely, it is beneficial to the migration of it into the media (Fe(II)→Fe(III)). This study describes recent progress and breakthroughs and assesses the biogeochemistry of Fe enrichment in groundwater, factors controlling Fe reactivity, and Fe biogeochemistry effects on the environment. This study also describes the implications of Fe biogeochemistry for managing Fe in groundwater, including the importance of Fe in groundwater monitoring and evaluation, and early groundwater pollution warnings. [ABSTRACT FROM AUTHOR]

Agricultural production may cause groundwater pollution. This study investigated the characteristics of shallow groundwater pollution in a typical black land agricultural production area in Northeastern China and the geochemical behavior of major pollutants. A total of 27 and 23 shallow groundwater samples were collected for measuring on-site parameters and major components in 2000 and 2014, respectively. The improved integrated approach was used to assess groundwater contamination. The results showed that the groundwater was slightly polluted by agricultural activities. The average concentrations of major ions of shallow groundwater were found to be in the following order: Ca2+ > Na+ > Mg2+ > K+ for cations and HCO3− > SO42− > Cl− > NO3− for anions. Percentages of 7.4% and 34.8% of the total groundwater sample in 2000 and 2014, respectively, indicated that the shallow groundwater quality has gradually worsened in the past few decades. The concentration of NO3− was a major factor that influenced the observed groundwater quality changes. Scientific and effective fertilization of rice cultivation is an effective way to avoid groundwater pollution, and the improved groundwater quality evaluation methods can further improve the standard of groundwater resource management effectively. [ABSTRACT FROM AUTHOR]

A field trial was conducted in Inner Mongolia to evaluate the stabilization effects of phyto-stabilization, biochar-stabilization, and their coupled stabilization for As, Cu, Pb, and Zn in soil. Stabilization plants (Achnatherum splendens, Puccinellia chinampoensis, and Chinese small iris) and biochar (wood charcoals and chelator-modified biochar) were introduced in the field trial. The acid-extractable fraction and residual fraction of the elements were extracted following a three-stage modified procedure to assess the stabilization effect. The results after 60 days showed that the coupled stabilization produced a better stabilization effect than biochar-/phyto- stabilization alone. Achnatherum splendens and Puccinellia chinampoensis were found to activate the target elements: the residual fraction proportion of As, Cu, Pb, and Zn decreased while the acid-extractable fraction proportion of Cu and Zn increased in the corresponding planting area. Neither type of biochar produced a notable stabilization effect. The residual fraction proportion of As (20.8–84.0%, 29.2–82%), Pb (31.6–39.3%, 32.1–48.9%), and Zn (30.0–36.2%, 30.1–41.4%) increased, while the acid-extractable fraction proportion remained nearly unchanged after treatment using Chinese small iris-straw biochar or Achnatherum splendens-straw biochar, respectively. The results indicate that phyto-stabilization or biochar-stabilization alone are not suitable, whereas the coupled stabilization approach is a more efficient choice. [ABSTRACT FROM AUTHOR]

The excessive input of heavy metals such as vanadium (V) into the environment has been one of the consequences of global industrial development. Excessive exposure to V can pose a potential threat to ecological safety and human health. Due to the heterogeneous composition and reactivity of the various elements in soils and sediments, quantitative analysis of the chemical speciation of V in different environmental samples is very complicated. The analysis of V chemical speciation can further reveal the bioavailability of V and accurately quantify its ecotoxicity. This is essential for assessing for exposure and for controlling ecological risks of V. Although the current investigation technologies for the chemical speciation of V have grown rapidly, the lack of comprehensive comparisons and systematic analyses of these types of technologies impedes a more comprehensive understanding of ecosystem safety and human health risks. In this review, we studied the chemical and physical extraction methods for V from multiple perspectives, such as technological, principle-based, and efficiency-based, and their application to the evaluation of V bioavailability. By sorting out the advantages and disadvantages of the current technologies, the future demand for the in situ detection of trace heavy metals such as V can be met and the accuracy of heavy metal bioavailability prediction can be improved, which will be conducive to development in the fields of environmental protection policy and risk management. [ABSTRACT FROM AUTHOR]

Bench‐scale experiments were conducted to investigate the effect of hydraulic loadings and influent concentration on the migration and biotransformation behaviour of three groundwater pollutants: ammonium (NH4+), iron (Fe2+) and manganese (Mn2+). Columns packed with aquifer media collected from a riverbank filtration (RBF) site in Harbin City, NE China were introduced synthetic groundwater (SGW) or real groundwater (RGW) were at two different constant flow rates and initial contaminant concentrations to determine the impact of system conditions on the fate of the target pollutants biotransformation. The results showed that the biotransformation rate of Fe2+ Mn2+ and NH4+ decreased by 8%, 39% and 15% under high flow rate (50 L d−1) compared to low flow rate (25 L d−1), which was consistent with the residence‐time effect. While the biotransformation rate of Fe2+ Mn2+ and NH4+ decreased by 7%, 14% and 9% under high influent concentration comparing with original groundwater. The 16S rRNA analysis of the aquifer media at different depths after experiments completion demonstrated that the relative abundance of major functional microbes iron‐oxidizing bacteria and manganese‐oxidizing bacteria under higher flow rate and higher influent concentration decreased 13%, 14% and 25%, 24%, respectively, whereas the ammonium‐oxidizing bacteria and nitrite‐oxidizing bacteria exhibited minimal change, compared to the lower flow rate. Above all results indicated that both high flow rate and high concentration inhibit the biotransformation of NH4+, Fe2+ and Mn2+. The biotransformation of Fe2+ and Mn2+ occurs primarily in the 0–40 cm and 20–60 cm depth intervals, respectively, whereas the NH4+ biotransformation appears to occur relatively uniformly throughout the whole 110 cm column. The biotransformation kinetics of NH4+ in RGW and SGW, Mn2+ in RGW at different depths accords with the first order kinetics model, while Fe2+ in RGW and SGW, Mn2+ in SGW presented more complicated biotransformation process. The results should improve understanding of the transport and fate of common groundwater pollutants in RBF and other groundwater recharge environments. [ABSTRACT FROM AUTHOR]

Purpose: From perspective of risk management and control, the ecological risk contributed from various sources can give direct risk information in selecting priority pollutants to control in river ecosystem restoration. However, studies combined receptor model with risk assessment to obtain ecological risk in every source category that is still limited. It is essential to quantitatively and spatially analyse the contributions of various sources to both the content and ecological risk in river system. Materials and methods: Ten trace metals in 47 sediment samples were collected in Le'an River, which is the main tributary of the largest freshwater lake in China, Poyang Lake and analysed by laboratory analysis. The potential ecological risk index (PERI) model was used to evaluate the ecological risk posed by sediment trace metals. The positive matrix factorization (PMF) was utilized to identify the source of sediment trace metal and apportion their contribution. The ecosystem risks of the sources were quantitatively analysed by combining PERI and PMF, termed PMF-PERI. In addition, we conducted a spatial dissimilarity analysis of the source contribution distributions. Results and discussion: The ecological risk assessment results showed that the metals Cd, Cu, and Hg may cause the main ecological hazards. Source apportionment of the trace metal concentrations indicated that the dominant source of trace metals in the sediment was human activities (55.83%), such as Pb-Zn mining and agricultural activities (30.33%), gold smelting (13.62%) and copper mining (11.89%). Source apportionment of the ecological risks posed by the trace metals indicated that natural sources were the main ecosystem risk sources (64.75%), followed by Pb-Zn mining and agricultural activities (14.65%), copper mining (10.67%) and gold smelting (9.93%). The results of spatial dissimilarity analysis indicated that the significant spatial variation in the contribution compositions was related to the locations of the sources and the river. Conclusions: The results of this study indicated that the emission reduction of agricultural activities should be given priority attention for protecting the watershed environment of the Le'an River. In addition, this study extends the use of risk assessment in receptor model source apportionment. [ABSTRACT FROM AUTHOR]

Based on the chemiluminescence (CL) phenomenon of peroxymonosulfate (PMS) and Tb(III) enhanced by its ligand in a micelle microenvironment, a fast and sensitive flow injection CL method for PMS detection was proposed and applied to the analysis of different samples and PMS decomposition. Under the optimized conditions, a linear range was obtained from 4.0 × 10–6 mol L–1 to 2.0 × 10–4 mol L–1 with a high correlation coefficient (r = 0.9997), detection limit of 5.0 × 10–7 mol L–1 (S/N = 3) and relative standard deviation of 2.4% for 1.0 × 10–5 mol L–1 PMS (n = 9). This was successfully applied to the determination of PMS in Virkon powder, tap water, and swimming pool water samples with satisfactory recoveries from 94.8% to 104.8%. In particular, the analytical frequency could be as fast as five samples per minute because there was no reaction step before analysis and the CL phenomenon was instantaneous. Therefore, this CL method has also been successfully applied to investigate the PMS decomposition profiles in carbon material (carbon nanotubes, carbon nanofibres, activated carbon and graphene oxide) catalysis systems, which followed pseudo‐first‐order kinetics with good correlation coefficients (r > 0.9305). Quenching experiments and electron spin resonance spectra verified that the CL phenomenon was due to the formation of singlet oxygen, and that hydroxyl and sulfate radicals might be important in the generation of singlet oxygen. Tb(III) is the luminescent emitter according to the characteristics emission bands of the fluorescence and CL spectra in different media. [ABSTRACT FROM AUTHOR]

Various colloids are present in the natural groundwater environment, and colloids act on the processes involved when radionuclides leak from a repository in a high-level waste disposal site. This paper investigates the effect of colloidal silicate in natural groundwater environments on the migration behaviour of Sr(II). Three different experimental cases have been designed: (1) effect in the presence of colloidal silicate, (2) effect in the presence of a porous medium, and (3) effect in the presence of both colloidal silicate and porous medium (referred to as CS, PM, and PC, respectively). Batch experiments were used to study the effect of influencing factors on Sr(II) migration behaviour, such as the amount of CS, solid-to-liquid ratio, pH, contact time, and initial concentration of Sr(II). The experiments showed that the effect of PC on the migration behaviour of Sr(II) was greatest, and the presence of CS enhanced the sorption. The colloid amount, pH, and solid-to-liquid ratio significantly affected the migration behaviour. The more the colloids were added, the better the adsorption effect. The optimal pH and solid-to-liquid ratio were 6 and 20 : 1, respectively. The alkaline environment is more conductive to colloid sorption. When the solid-to-liquid ratio was 20 : 1, the sorption percentage of PC is 0.5 times larger than PM. Although the PC has a longer adsorption equilibrium time, the percentage of adsorption can be larger than that in the other two cases. The kinetics and isotherms of Sr(II) were best described by the pseudo-second-order and Langmuir models. It was inferred that strong chemical interactions and/or surface complexation contributed primarily to Sr(II) sorption, and the process was on the monolayer adsorption of the outer surface. These findings provide valuable information for the migration behaviour of strontium in groundwater environments of geological disposal site. At the same time, it provides information for the implementation of permeable reactive barrier technology to control the transport of radioactive Sr(II) and its species in natural surface and groundwater. [ABSTRACT FROM AUTHOR]

We explored the effect of the presence or absence of humic acid (HA) on the sorption behaviour of Sr onto soil. We examined three different experimental cases for Sr sorption: (1) sorption in the presence of only colloidal HA, (2) sorption in the presence of only soil and (3) sorption in the presence of both colloidal HA and soil (HS). A batch technique was used to study the influencing factors, including the amount of colloidal HA, solid content, pH, initial concentration of Sr and contact time. The experiments showed that the influencing factors significantly affected the sorption process. For example, in the case of soil and HS, the sorption percentage increased rapidly with increasing solid content at m/V < 20 g/L, changing from 8.35% and 37.54% to 49.09% and 77.03%, respectively. Moreover, scanning electron microscopy and Fourier transform infrared spectroscopy were used to characterize samples. The kinetics and isotherms of Sr were best described by the pseudo-second-order and Langmuir models, which indicated that the process was controlled by chemisorption and uniform monolayer sorption with constant energy on the outer surface. These findings provide valuable information for predicting strontium migration in radioactive waste disposal sites. [ABSTRACT FROM AUTHOR]

Palygorskite (PAL) was modified with sodium dodecyl sulfate (SDS) for the removal of Sr(II) from aqueous solutions. Analysis of the structural characteristics of PAL before and after modification showed that PAL was successfully modified with SDS. Sorption experiments were conducted in batch mode under optimum conditions to evaluate the effect of initial pH and co-existing ions on the removal of Sr(II) by SDS-modified PAL. The equilibrium sorption isotherm data for Sr(II) were analyzed using Freundlich and Langmuir isotherm sorption equations, and the data fitted well to the Freundlich isotherm model. Pseudo-first-order and pseudo-second-order kinetic models were examined, and the sorption of Sr(II) showed better agreement with the pseudo-second-order kinetic model (r2 > 0.99). The desorption experiments indicated that the SDS-modified PAL having sorbed Sr(II) does not release significant amounts of Sr(II) into the environment under natural conditions, thus avoiding secondary pollution. [ABSTRACT FROM AUTHOR]

Hydrogeochemical evolution of interactions between surface water and groundwater is crucial for guaranteeing water supply quality in a riverside water source area. This study focuses on the seasonal and spatial characteristics of hydrogeochemical evolution affected by groundwater exploitation in the Hulan water source area using hydrochemical analyses and stable isotope tracers. Results show that the concentrations of major ions and total dissolved solids (TDS) increase considerably during the dry season. A bicarbonate water type is primarily produced by the dissolution of calcite, dolomite and gypsum, as well as the cation exchange and human activities. Along the typical infiltration path, the proportions of surface water increase with proximity to the river from 8%‐63% during the wet season to 11%‐84% during the dry season, which are attributed to an increased hydraulic gradient by exploitation. The typical path is classified into two zones. The first is the intensive mixing zone (within 1 km) with increasing concentrations of major ions and TDS due to mixing effect. The second is the exploitation influence zone (1‐3.3 km) with increased concentrations of Ca2+, Mg2+, SO42−, and HCO3− during the dry season due to two reasons of seasonal variations in evaporation, stronger water‐rock interactions and mixing effects with increased surface water by exploitation. Article impact statement: The hydrogeochemical evolution of surface water‐groundwater interaction is crucial for water supply quality in water source areas. [ABSTRACT FROM AUTHOR]

The issue of contaminated sites has been highlighted as an immediate priority in the 13th Five-Year Plan of China. Identification and prioritization of contaminated sites are of key importance for proposing effective strategies for the regional management of contaminated sites. In this study, three advanced multi-attribute methodologies, the risk-based priority methodology, the regional risk assessment methodology, and the dominance-based rough set approach (DRSA), were comparatively employed to screen contaminated sites in, Guangxi, Southwest of China. The results of the three prioritizations show that the highest ranking site identified by the three methods had great agreement. In regard to the screening attributers, while the risk-based prioritization methodology and regional risk assessment methodology allowed a high discrimination in the screening of contaminated sites associated with different attributes, such as farmland, residential areas, contaminant level, number of people, area, storage quality, site service life, and surrounding communities, the DRSA allowed the identification of contamination strength (CS) and contamination potential (CP). [ABSTRACT FROM AUTHOR]

Riverbank filtration (RBF) has been widely used throughout the world as an effective means to regulate surface water and groundwater resources and pretreat raw water for municipal water supply. The quality of the water from a riverside well field and the mixing ratios of surface water and groundwater is primarily impacted by the hydrodynamic processes in the RBF system. The RBF system is largely controlled by the water exploiting system in addition to the natural hydrologic condition of the river–aquifer system. As one of the most important design parameters of the riverside well field, the drawdown of groundwater level greatly determines the water head differences between the river water and groundwater as well as the field flow net, which subsequently impacts the mixing of river water and groundwater and water quality significantly. This study aimed to improve the understanding of the mixing process between the surface water and groundwater and estimate the impact of the RBF on the mixing ratio of surface water–groundwater and water quality quantitatively. A set of field pumping tests with various groundwater level drawdowns were carried out independently and successively at a riverside field with a single pumping well near the Songhua River in Northeast China in August 2017. During these tests, the water levels and hydrochemical parameters of the Songhua River, the adjacent aquifer, and the pumping well were monitored. The dynamic mixing process of the river water and groundwater and water quality under various drawdown conditions were analysed systematically using analytical methods. The results obtained from Dupuit method and the Mirror Image method in conjunction with the Hydrochemical Tracing method showed that the pumping water directly from the river water reached 60% ± 10% after a steady flow net was established. The larger the proportion of the pumping water captured from the river, the better quality of the pumping water was, because the quality of the river water (only limited to some water quality parameters monitored which were minority) was better than that of the groundwater. The results also showed that total Fe, TDS, total hardness, CODMn, and K+ were relatively sensitive to the changes of groundwater drawdown, and their concentrations decreased with an increase in the groundwater drawdown. It can be concluded that both the mixing ratio of the surface water and the groundwater and the water quality of the riverside well field can be regulated through adjusting the designed drawdown of the groundwater level, which is helpful for the design and the optimization of the riverside well water intake engineering. [ABSTRACT FROM AUTHOR]

A host of environmental consequences will result from global warming, but arguably, the effect on water resources is one of the most consequential. This paper synthesizes results of published modeling studies that examined the groundwater system and hydrologic cycle under the Representative Concentration Pathway (RCP) 8.5 scenario (CO2 at 936-ppm level at year 2100). Natural replenishment of groundwater occurs predominantly from infiltration of precipitation and surface impoundments. Therefore, the first stage of the study was to review a changed hydrologic cycle under RCP 8.5 in terms of influence from (1) precipitation, evapotranspiration, and soil moisture; (2) surface water and its interaction with groundwater; (3) extreme hydrologic events, and (4) teleconnection patterns. The general pattern of climate impact on groundwater resources follows the precipitation pattern with depletion in tropical and/or subtropical regions and with increase in the high-latitude regions of the Northern and Southern Hemispheres. However, regional variability also corresponds to the heterogenous impact of climate changes on regional distribution of precipitation and evapotranspiration, localized interaction between surface water and groundwater, and distances from the oceans with rising sea level. The decline of the water table in many areas may seriously reduce irrigated crop production and adversely impact groundwater-dependent ecosystems. Relatively fewer studies have been conducted on climate-change impacts on groundwater resources compared to surface-water systems, and the uncertainties on the recharge estimates are large. There appears to be an urgent need for including groundwater systems in climate impact assessment and in climate mitigation strategies. [ABSTRACT FROM AUTHOR]

Evolution of shallow fluoride groundwater, in the Lower Liaohe River Plain in northeastern China, a typical coastal area, has been studied to assess the controls of geology, geochemistry and human activity on high-fluoride groundwater. A total of 212 shallow groundwater samples were collected. The range of the measured F– concentration was 0.11–4.9 mg/L with the mean value of 0.71 mg/L. Durov diagram classification, variation function calculation, thermodynamic calculation and factor analysis were used to analyze the distribution, origin and key influencing factors of high-fluoride groundwater. The distribution of high-fluoride samples was mainly concentrated in the southwestern and northeastern Lower Liaohe River Plain. The main origin of high fluoride in shallow groundwater was the lixiviation of fluorine-rich rocks in the northern plain and the alluvial fan of Da Linghe and Xiao Linghe Rivers. Additionally, through the migration and enrichment of fluoride in Xinmin, Linghai, a higher fluoride area was formed. The key influencing factors of fluoride groundwater was the fluoride lixiviation, regional hydraulic gradient, hydrochemical types and ion composition. Meanwhile, human pollution, evaporation and local irrigation were comparatively weak influencing factors. The process of calcite dissolution controlled the regional distribution of high fluoride in shallow groundwater. [ABSTRACT FROM AUTHOR]

Riverbank filtration is a natural water treatment technology that consists of extracting water from rivers by pumping wells located in the adjacent alluvial aquifer. It is vital to choose the most appropriate from multiple potential candidate sites, which is a complex procedure and seldom paid attention to. In this study, a method system including multicriteria evaluation indexes was developed with which the suitability of bank filtration along the Songhua River of China for developing riverside groundwater sources was assessed. The system was comprised of main suitability indexes for water quantity, water quality, interaction intensity between surface water and groundwater, and the exploitation condition of aquifer condition, weights of which were determined by specialist marking methods. Based on this assessment system, the suitability of the study area was divided into five grades. Results show that riversides along Lalin River, Hulan River, and the middle part of Songhua River are suitable for developing riverside groundwater sources. [ABSTRACT FROM AUTHOR]

To develop novel 99mTc labeled nitroimidazole imaging agents for imaging tumor hypoxia, 99mTc labeled ethylene diamine tetraacetic acid derivative of 4-nitroimidazole was reported by us earlier, which showed disadvantage of an unsatisfactory tumor-to-blood ratio. Therefore, 2-nitroimidazole was adopted as a pharmacophore to synthesize EDTA-2-EtNHNM, which was radiolabeled with 99mTc in high yield to achieve 99mTc-EDTA-2-EtNHNM. 99mTc-EDTA-2-EtNHNM was hydrophilic and exhibited good in vitro stability. Cellular experiment demonstrated its hypoxic selectivity while biodistribution results showed improved tumor-to-blood and tumor-to-muscle ratios. SPECT imaging studies of 99mTc-EDTA-2-EtNHNM indicated obvious accumulation in tumor, suggesting its potential to be a radiotracer for imaging tumor hypoxia. [ABSTRACT FROM AUTHOR]

Investigation of surface water and groundwater interaction (SW-GW interaction) provides basic information for regional water-resource protection, management, and development. In this survey of a 10-km-wide area along both sides of the Songhua River, northeast China, the hydrogeochemical responses to different SW-GW interactions were studied. Three types of SW-GW interactions were identified—“recharge”, “discharge”, and “flow-through”—according to the hydraulic connection between the surface water and groundwater. The single factor index, principal component analysis, and hierarchical cluster analysis of the hydrogeochemistry and pollutant data illuminated the hydrogeochemical response to the various SW-GW interactions. Clear SW-GW interactions along the Songhua River were revealed: (1) upstream in the study area, groundwater usually discharges into the surface water, (2) groundwater is recharged by surface water downstream, and (3) discharge and flow-through coexist in between. Statistical analysis indicated that the degree of hydrogeochemical response in different types of hydraulic connection varied, being clear in recharge and flow-through modes, and less obvious in discharge mode. During the interaction process, dilution, adsorption, redox reactions, nitrification, denitrification, and biodegradation contributed to the pollutant concentration and affected hydrogeochemical response in the hyporheic zone. [ABSTRACT FROM AUTHOR]

Pollution risk assessment of a groundwater resource area is instrumental in contributing to groundwater protection. This study considered the evaluation results of source apportionment by combining a principal component analysis (PCA) with a factor analysis (FA) to identify potential risk sources. The vulnerability was evaluated using a DRASTIC model as the main pollution pathway, and groundwater quality as a pollution receptor, in order to validate the risk of pollution in a typical groundwater resource area of northeastern China. Results showed that four principal potential pollution sources were point source pollution such as water-rock interaction, dissolution of iron and manganese bearing minerals due to geological processes, non-point source pollution of nitrogen such as agriculture fertilizers, and organic pollution resulting from domestic and industrial wastewater. A “high” and “relatively high” pollution risk occurred mainly at the northwestern and southeastern edges of the region, respectively, with a widely distributed “moderate” pollution risk over the majority of the study area, and a “relatively low” and “low” pollution risk located mainly in the central of the Limin Groundwater Resources area, which showed that the potential pollution sources, especially due to human activity, have significantly changed the distribution of pollution risk in groundwater resource areas. [ABSTRACT FROM AUTHOR]

An assessment of the presence and health risks of endocrine-disrupting chemicals in the drinking water treatment plant (DWTP) of Wu Chang was performed. A recombinant yeast assay was used to assess the endocrine disrupting activity of the effluents of the DWTP. Agonistic activities of the estrogen receptor and androgen receptor were not detected in any of the effluent samples. However, anti-estrogenic and anti-androgenic activities were observed. In addition, the removal rates of the DWTP for the anti-androgenic activities were limited. A health risk assessment was performed on the basis of the results of the recombinant yeast assay, and the total daily production of hormones was used to evaluate the health risks of these types of endocrine-disrupting chemicals. The predicted effects of the anti-estrogenic and anti-androgenic disrupting activities were below 1.5%. This study suggested that the combined toxicity bioassays with health risk assessment could provide an available method to assess endocrine-disrupting chemicals and to evaluate the potential adverse effects on human health for aquatic environmental samples. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) have become a major type of persistent organic pollutant (POPs) in the world. To well understand the occurrence, spatial distribution and source apportionment of 16 PAHs in different media in Beijing, a comprehensive study was conducted based on 337 obtained and subsequently selected samples in four specific media, including soil, road dust, surface water and atmosphere covering sampling time spanning from 2005 to 2014. Mean concentrations of Σ16 PAHs in soils (878.5 μg/kg) decreased from inner city to exterior areas with different land uses decreased in the order of industrial estate (2510 μg/kg)>educational area (1331 μg/kg)>Park (783 μg/kg)>cultivated (650 μg/kg)>roadside (583 μg/kg)>residential (568 μg/kg)>green area (478 μg/kg)>forest area (125 μg/kg). Meanwhile, PAHs concentrations in branch roads were slightly higher than trunk roads and mainly concentrated in urban areas (1136 μg/kg). Affected by industrial and residential areas, PAHs concentrations in downstream surface rivers were much higher than upstream surface rivers (475 ng/L). Due to strong mobility, PAHs concentrations in atmosphere were not equally distributed around the study area (157.59 ng/m3). The result of source apportionment determined by diagnostic ratios method indicated PAHs in multiple media in Beijing are mainly from coal and biomass combustion. [ABSTRACT FROM PUBLISHER]

The sorption of U(VI) on shale has been experimentally investigated as a function of pH, initial uranium concentration, rock particle size and water-rock ratio. The results showed the sorption equilibrium time was about 10 days, and the adsorption capacity presented a negative relationship with rock particle size and positive correlation with the liquid-solid ratio, also influenced by pH. The sorption process was fitted well with Freundlich isotherm. Experimental column was fully penetrated by tritium at about 230 min with a velocity of 0.13 cm/min while uranium was not penetrated the rock column in 180 days. [ABSTRACT FROM AUTHOR]

Nitrogenous pollutants from intense human activities have become serious environmental and health problems worldwide, particularly in groundwater source areas used for public water supply. To investigate the genesis and pollution risks associated with elevated concentrations of ammonium nitrogen in a groundwater source area, investigations were undertaken in the Jinji groundwater source area, located in an arid loess plain in northwestern China where 16 groundwater samples were collected from an aquifer used for water supply. The investigation indicated that high concentrations of ammonium nitrogen originated mainly from: infiltration of water from the Yellow River; livestock; and the discharge of industrial wastes. Measured parameters including pH, the permanganate index and the oxidation reduction potential could be used as important indicators of the genesis of ammonium nitrogen. A modified DRTCLN model was applied to the observed distribution of ammonium nitrogen to assess pollution risk of regional groundwater. The model was optimized by rebuilding the index system, and the analytic hierarchy process was used to calculate the rating scale of each index. A Monte Carlo simulation was performed to analyze the uncertainty of results of the risk assessment. The result showed that the risk value is relatively low in most areas of the groundwater source area. Only an industrial area in the southwestern part of the groundwater source area was classified as high risk; it should be the key factor of pollution control. [ABSTRACT FROM AUTHOR]

By means of factor analysis (FA) and positive matrix factorization (PMF) methods, groundwater pollution sources were identified in the Jinji groundwater source area, which is beside the Yellow River and is the only urban water supply source for the city of Wuzhong in Northwestern China. The sources of groundwater were quantified based on 16 samples of shallow groundwater from the source area. The source apportionment with the PMF model identified three dominant groundwater pollution sources. These were anthropogenic activities of agricultural and industrial pollution with a pollution contribution of 53.0%, water–rock interaction of 24.6%, and evaporation and concentration of 22.4%. The source apportionment with the FA model identified four sources which were evaporation and concentration, with the largest contribution (42.6%), followed by anthropogenic activities (29.2%), mineral dissolution and industrial pollution (22.4%), and natural effects (5.8%). Specific attention should be paid to these natural (fluoride, TH,etc.) and anthropogenic sources (NH4+, NO2−, turbidity, total bacterial count,etc.), and pertinent measures should be taken to control local groundwater pollution. The most significant trait of the PMF is its scientific interpretation and physical explanation of the results, depending on non-negative restriction of the pollution source profiles and contributions. [ABSTRACT FROM PUBLISHER]

A novel ethylene diamine tetraacetic acid derivative of 4-nitroimidazole (EDTA-4-EtNHNM) was successfully synthesized as a carrier molecule and it was radiolabeled with Tc in high yield to obtain Tc-EDTA-4-EtNHNM, which was hydrophilic and had good in vitro stability. The tumor cell experiment and the biodistribution study in mice bearing S180 tumor showed that this complex exhibited a hypoxic selectivity and had high accumulation in tumor tissue with major clearance through urinary tract. High tumor uptake and tumor/muscle ratio of the complex suggests promise towards further evaluation. [ABSTRACT FROM AUTHOR]

Nitrate pollution has pervaded many parts of the world, especially in developing countries such as China. Based on the available groundwater nitrate data sets in China (2000-2015), the groundwater pollution levels at the provincial scale are evaluated which contains 33 provinces (units) except for Macau because of lacking data. Then, the potential risks posed to human health in national scale are quantified. In order to make the results more precise and systematical, both drinking and dermal contact exposure pathways are considered, and the influenced crowd are more finely divided into four groups to study the impacts of age and gender on the outcome, which include infants (0-6 months), children (7 months-17 years old), adult males (18 years old-), and adult females (18 years old-). Results indicate that there are seven units whose groundwater nitrate concentrations exceed the standard value with Shaanxi being a seriously poor condition. Facing the same level of nitrate, the health risk level changes in the order of infants > children > adult males > adult females. That is to say, minors and males are more vulnerable compared with adults and females, respectively. There is no adverse effect on adult females of the whole country, while gender really impacts on the health risk assessment result. Adult males, children, and infants face various degrees of health risk respectively in Shaanxi and Shandong, which are needed to pay more attention to. [ABSTRACT FROM AUTHOR]

Groundwater pollution risk assessment is a useful tool to prevent and control groundwater pollution, but its quantitative research is still relatively immature. In this study, a geographic information system based LVF model for a semiquantitative assessment of groundwater pollution risk is established, based on the groundwater pollution source load (L), groundwater vulnerability (V), and groundwater function value (F). Further, the pollution source load is characterized by seven specific pollution sources, the vulnerability is calculated by the modified DRASTIC method, and the groundwater function value is evaluated with the water quality and quantity. The model was used to assess the risk of shallow groundwater pollution in Shenyang city, Northeast China, with an area of 8,263 km2. The results show that highest risk areas account for 16.3% of the study area and are mainly distributed in the east of the study area. High risk areas are significantly affected by a shallow buried depth of groundwater and many types of harmful pollutants from industrial, agricultural, and domestic pollution sources. The evaluation results reflect the risk of groundwater pollution in the Shenyang area, which is relevant to the management and sustainable use of groundwater resources in the area. [ABSTRACT FROM PUBLISHER]

Road and foliar dust samples from four land-use districts of Panzhihua City, a famous V-Ti magnetite production area of China, were collected to investigate the sources and distribution characteristics of 9 heavy metals (V, Pb, Cd, Cu, Zn, Ni, Cr, Fe, and Mn). The results suggest that foliar samples had smaller particle size and higher heavy metal contents than road dusts. The contamination assessments of heavy metals were as follows: Pb and V (significant enrichment) > Zn, Ni, Cr, Fe, and Mn (moderate enrichment) > Cd and Ni (minimal enrichment). Statistical analyses showed Pb, as the primary pollution element, originated from waste incineration and lead-fuel combustion. The sources of Zn, Ni, Cr, Fe, V, and Mn were fugitive dust and traffic activities. Potential origins of Cu were corrosion of alloys used in vehicle components, vehicle covers, or other metallic surfaces and materials. The sources of Cd were different from any other heavy metals. Traffic and industrial activities were the main anthropogenic origins of heavy metals in dusts of Panzhihua, and more attention should be paid to heavy metal pollution in agricultural area. [ABSTRACT FROM AUTHOR]

Due to their toxicity and bioaccumulation, trace metals in soils can result in a wide range of toxic effects on animals, plants, microbes, and even humans. Recognizing the contamination characteristics of soil metals and especially apportioning their potential sources are the necessary preconditions for pollution prevention and control. Over the past decades, several receptor models have been developed for source apportionment. Among them, positive matrix factorization (PMF) has gained popularity and was recommended by the US Environmental Protection Agency as a general modeling tool. In this study, an extended chemometrics model, multivariate curve resolution-alternating least squares based on maximum likelihood principal component analysis (MCR-ALS/MLPCA), was proposed for source apportionment of soil metals and applied to identify the potential sources of trace metals in soils around Miyun Reservoir. Similar to PMF, the MCR-ALS/MLPCA model can incorporate measurement error information and non-negativity constraints in its calculation procedures. Model validation with synthetic dataset suggested that the MCR-ALS/MLPCA could extract acceptable recovered source profiles even considering relatively larger error levels. When applying to identify the sources of trace metals in soils around Miyun Reservoir, the MCR-ALS/MLPCA model obtained the highly similar profiles with PMF. On the other hand, the assessment results of contamination status showed that the soils around reservoir were polluted by trace metals in slightly moderate degree but potentially posed acceptable risks to the public. Mining activities, fertilizers and agrochemicals, and atmospheric deposition were identified as the potential anthropogenic sources with contributions of 24.8, 14.6, and 13.3 %, respectively. In order to protect the drinking water source of Beijing, special attention should be paid to the metal inputs to soils from mining and agricultural activities. [ABSTRACT FROM AUTHOR]

Underground injection (UI) is an effective and efficient means of disposing of wastewater from shale gas production. However, the influence of UI on groundwater systems should be examined carefully to protect drinking groundwater sources. A regional hydrogeological model based on TOUGH2-MP/EOS7R of part of the Sichuan Basin is established to simulate pressure changes and solute transport in response to wastewater injection into deep aquifers. Wastewater is assumed to be injected through a well at a rate of 5.45 kg s−1 for 5 years and a post-injection period of 45 years. The simulation results indicate that UI will cause significant pressure buildup during the injection period, after which pressure will dissipate during the post-injection period. The mass fraction of solute increased over the entire simulation period. The draft regulation under the Safe Drinking Water Act and the level III groundwater quality standards regulated by the Chinese government is referenced as the criteria for evaluating the influence of UI on groundwater systems. It is found that maximum pressure levels caused by UI may exceed safe levels. Uncertainties with respect to permeability are analyzed from previous studies and injection test results. Lower levels of permeability incur higher degrees of pressure buildup when UI is implemented. Different injection schemes are discussed, and we verify that pressure buildup from time-variant injection schemes is less than that from constant injection schemes for the same total injection volume. Injection schemes should be carefully evaluated before implementing UI in a shale gas reservoir. [ABSTRACT FROM AUTHOR]

Purpose: Taking into account great spatial heterogeneity in soil environments is essential to carrying out an accurate soil contamination assessment at the regional scale. Although there are numerous methods for distinguishing between natural and anthropogenic element contents, few studies focus on on-site determination methods, with few site-specific and sensitive references available. In this study, site background concentration is estimated as an on-site reference for soil contamination assessment. Materials and methods: Here, a support vector machine (SVM) is used to predict the site background concentration based on nine influential factors of soil formation. Three machine-learning algorithms, which are considered efficient in solving optimization problems, are used to select the optimal parameters of the SVM. These three algorithms are as follows: (1) a grid search algorithm, (2) a genetic algorithm, and (3) a particle swarm optimization algorithm. Results and discussion: Model performances were evaluated using squared correlation coefficients and root-mean-square error. Their subsequent application to soil contamination assessment demonstrated that indiscriminate use of a consistent reference across all soil types in an environmental site assessment may result in under- and over-estimation. These problems are likely to be resolved by using site background concentration predictions to establish contaminated versus un-contaminated regions. Conclusions: We conclude that a SVM based on factors of influence for soil formation is an effective method for site background concentration prediction and substantially improved the suitability of background references at our study site. Slight modifications would make this approach applicable to other regions and soil types. [ABSTRACT FROM AUTHOR]

Regional environmental risk assessment has been a significant means of environmental management and decision-making. To assess the regional integrated environmental risk at a nationwide scale, a new index system named the Hazard, Intensity, Vulnerability, and Effectiveness (HIVE) model was designed and evolved from previous researches. The HIVE model consisted of a relatively complete framework with accessible indexes related to environment and social economy, and it considered different risk sources, pathways, and receptors as well as the influence of the risk control. As an important segment of the assessment process, a simple gridding information diffusion method was also proposed to assess the diffusion effect of risk factors in nationwide rivers. Taking China as a case study, this study calculated the environmental risk value of every sub-unit. Through the clustering function of Statistical Package for Social Sciences and the visual representation of a geographic information system, the study area was divided into nine zones that were visualized on maps according to their different risk levels and risk characteristics. This study also identified the dominant factors of each zone, which could provide the foundation for regional environmental management. Moreover, the results implied some significant correlations between risk system components and the regional social economy in China. [ABSTRACT FROM AUTHOR]

Heavy metals are known to have adverse effects on soil ecosystems, while soil enzyme activities are sensitive to soil pollution. This study investigated the combined effects of Cu, Zn and Pb on the activities of invertase (IN), urease (U) and alkaline phosphatase (ALP) in soil obtained from the vicinity of a wellhead protection area via an orthogonal array (OA) design method. The experimental results showed the following: (1) Cu showed higher inhibition on the activities of all three enzymes than Zn and Pb when three metals were all present in the soil sample. IN activity, U activity and ALP activity decreased as the levels of Cu increased, and ranged from 15.9% to 55.7%, 3.57% to 78.6%, and 3.23% to 75.3%, respectively. Their lowest values were found in samples at 35 days with 400 mg/kg Cu. (2) Zn and Pb had different influences on the activities of the three enzymes. The lowest IN activity (the highest reduction 58.0%) and U activity (76.8%) were observed when Zn was at the concentration of 100 mg/kg after 35 days, whereas the highest inhibitory function of Zn on ALP activity (75.3%) was at 300 mg/kg after 7 days. When the concentration of Pb increased from 35 to 350 mg/kg, the activities of IN (62.5%) and U (69.6%) were most inhibited at 35 days and 14 days, respectively. However, when Pb was at the concentration of 500 mg/kg after 14 days, ALP activity (72.0%) showed the lowest value. (3) With respect to the three hydrolases in this study, ALP was the most sensitive to the two-variable interactive effects of Cu, Zn and Pb, especially Cu × Pb. It is concluded that the soil ALP activity may be a sensitive tool for assessing additive toxic effect on soil biochemical parameters. To provide more information about the potential ecological risk of chemicals on soil ecosystems, much more should be done to clearly determine the mechanisms of the combined effects of heavy metals in soil. [ABSTRACT FROM AUTHOR]

Groundwater vulnerability assessment has become a useful tool to delineate areas for the prevention and control of groundwater pollution. The paper proposed the APLIE method by combining the DRASTIC, PI, COP, European approach with the characteristics of karst-phreatic aquifer in North China in the help of ARCGIS, which was used to assess the groundwater vulnerability of Dawu water source, Shandong Province, China. Water abundance (A), protective cover (P), types of land use (L), infiltration amount of precipitation (I) and groundwater exploitation (E) were picked up to compose the index system for characterizing the hydrogeology and environmental geology setting and evaluating the aquifer vulnerability. Weights of new index system were reassigned using the analytic hierarchy process method based on the relative importance of indexes. The assessment results indicated that groundwater vulnerability mapping with APLIE method is in better agreement with the current hydrogeological and environment geological understanding of Dawu water source area compared with the results obtained from PI and COP methods. And the exceeding standard subareas of ammonia nitrogen (NH-N) and electric conductivity in the study area proved the reliability of groundwater vulnerability results. Subareas of vulnerability were portioned by natural breaks based on the spatial platform of ARCGIS. The integrated vulnerability map showed that the very high and high vulnerability subareas were formed for reasons of highest or higher infiltration amount of precipitation (I), worst or worse protective cover (P), most complex type of land use (L), poor water abundance (A) and over groundwater exploitation (E). Sensitivity analyses showed that infiltration amount of precipitation (I) is the most sensitive factor affecting groundwater vulnerability in the case study. In short, APLIE method was applicable to assess the karst-phreatic vulnerability in the study area with readily available hydrogeological and environment geological data. Hence, the groundwater vulnerability mapping is a promising tool for sensible groundwater resource management and land use planning, which contributes to the development of human survival and sustainable development of groundwater. [ABSTRACT FROM AUTHOR]

The soil pollution by heavy metals was characterized in the mine tailings and surrounding soils of an old Pb-Zn mine in Huize County. Three hundred and ninety-six samples of agricultural and non-agricultural soil were analyzed for the total metal concentration by acid digestion and sixty-eight selected soil samples were used to determine the chemical fractionation of heavy metals with the modified BCR sequential extraction method. The pollution index of the heavy metals indices for As, Cd, Cr, Cu, Hg, Pb and Zn of non-agricultural soil and agricultural soils in the study area indicated the spreading of heavy metal pollution. Sequential extraction showed that most of Cd existed in an exchangeable form (31.2 %). The available content of Pb, Cu and Zn was mainly distributed in acid extractable fractions and Fe/Mn oxide fractions (27.9, 30 and 27.2 %), and Hg, As and Cr were mainly associated with residual fractions (90.4, 72.9 and 76.8 %). The risks of heavy metals were also evaluated by the risk assessment code (RAC) and potential ecological risk index, respectively. The results of RAC showed a medium and high risk of Cd (45.6 and 54.4 %), medium risk of Zn (100 %), low and medium risk of Cu (41.2 and 58.8 %), largely no risk of Hg (97.1 %), and mainly low risk of As and Pb (92.6 and 91.8 %). The range of the potential ecological risk of soil was 58.2-1839.3, revealing a considerably high ecological risk in the study area, most likely related to acid mine drainage and the mining complexes located in the area. The results can be used during the ecological risk screening stage, in conjunction with the total concentrations and metal fractionation values, to better estimate ecological risk. [ABSTRACT FROM AUTHOR]