Search Results (28)

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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 (P_i), the geological accumulation index (I_geo), the Nemerow index (P_n), 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 P_i 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 P_n 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. Full article

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. Full article

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. Full article

Peat-derived organic matter, as powerful chelators, is of great significance for the transport of Fe to the ocean and the enhancement of dissolved Fe. However, the iron binding capacity of molecular weight (MW)-fractionated dissolved organic matter is variable, due to its structure and composition heterogeneity. In this work, we used the standard Pahokee Peat fulvic acid (PPFA) as an example, and investigated the spectroscopy properties and Fe(III) binding ability of PPFA and different molecular weight fractions by UV–Vis absorbance and fluorescence spectroscopy and the Donnan Membrane Technique (DMT). The results showed binding sites for Fe(III) at the 263 nm and >320 nm regions in differential absorbance spectra. Upon increasing the iron concentration to 18.00 μmol·L⁻¹, the critical binding capacity was exceeded, which resulted in a decrease in absorbance. Fe(III) was found to prefer to bind to humic-like components, and ultraviolet humic-like fluorophores displayed stronger binding strength. High molecular weight PPFA fractions (>10 kDa) possessed more aromatic and hydrophobic components, displayed a higher degree of humification, and exhibited higher metal binding potential. Furthermore, the speciation analysis and stability constant (^cK) were calculated using Donnan membrane equilibrium. The correlation between ^cK values and PPFA spectral properties demonstrated that aromaticity, hydrophobicity, molecular weight and humification degree were crucial indices of PPFA–Fe(III) affinity. Significantly, the humification degree, represented by HIX, showed the strongest correlation (r = 0.929, p = 0.003), which could be used to estimate the binding strength. This study provides further understanding of the complexation mechanism of iron and DOM in the peat environment and identifies the considerable effect of molecular weight. Full article

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. Full article

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. Full article

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. Full article

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. Full article

Heavy metals pollution in groundwater and the resulting health risks have always been an environmental research hotspot. However, the available information regarding this topic and associated methods is still limited. This study collected 98 groundwater samples from a typical agricultural area of Songnen Plain in different seasons. The pollution status and sources of ten heavy metals (As, Ba, Cd, Co, Cr (VI), Cu, Fe, Mn, Ni, Pb, and Zn) were then analyzed and compared. In addition, the human health risks assessment (HHRA) model was used to calculate human health risks caused by heavy metals in groundwater. The results revealed that heavy metals were mainly distributed in the northwest of the study area and along the upper reaches of the Lalin river and that the concentrations of heavy metals were higher during the wet season than the dry season. Industrial and agricultural activities and natural leaching are the main sources, and each kind of heavy metal may have different sources. Fe and Mn are the primary pollutants, mainly caused by the native environment and agricultural activities. The exceeding standard rates are 71.74% and 61.54%, respectively based on the Class III of Quality Standard for Groundwater of China (GB/T 14848-2017). The maximum exceeding multiple are 91.45 and 32.05, respectively. The health risks of heavy metals borne by different groups of people were as follows: child > elder > young > adult. Carcinogenic heavy metals contribute to the main risks, and the largest risks sources are Cr and As. Therefore, the government should appropriately restrict the use of pesticides and fertilizers, strictly manage the discharge of enterprises, and control man-made heavy metals from the source. In addition, centralized water supply and treatment facilities shall be established to prevent the harm of native heavy metals. Full article

The DPSIR model is a conceptual model established by the European Environment Agency to solve environmental problems. It provides an overall framework for analysis of environmental problems from five aspects: driving force (D), pressure (P), state (S), impact (I), and response (R). Through use of the DPSIR model framework, this paper presents the SEEC model approach for evaluating watershed ecological security. The SEEC model considers four aspects: socioeconomic impact (S), ecological health (E), ecosystem services function (E), and control management (C). Through screening, 38 evaluation indicators of the SEEC model were determined. The evaluation results showed that the ecological security index of the study area was >80, indicating a generally safe level. The lowest score was mainly attributable to the low rate of treatment of rural domestic sewage. The water quality status was used to evaluate the applicability of the SEEC model, and the calculation results indicated that the higher the score of the ecological security evaluation results, the better the water quality status. The findings show that the SEEC model demonstrates satisfactory applicability to evaluation of watershed ecological security. Full article