With the rapid industrialization and urbanization, the number of mercury contaminated sites (MCS) is increasing. These sites are primarily concentrated in multiple industries including primary mercury mining, non-ferrous metal smelting, polyvinyl chloride production using the chlor-alkali process, and mercury catalyst. It is crucial to establish a risk-based mercury contamination prevention and management system. This article analyzes the fundamental characteristics and causes of the MCS, and summarizes the sound experiences in developed countries in terms of policies, regulation, standard, and institutional development. An integrated technical system is proposed for the environmental risk quantification and multi-dimensional risk control, which considers contamination remediation, risk management, institutional control, public participation, etc. Firstly, key factors, including the distribution and bioavailability of mercury forms specific exposure pathways and sensitive receptors, as well as migration and fate within MCS, are carefully considered to precisely quantify the environmental risk. Subsequently, tailored risk management and control measures are selected for the target MCS with different risk levels, encompassing criteria thresholds, remediation technologies, and management systems. Guided by risk management, supported by quantitative assessment, systematic remediation, and overall management, this technology system establishes a comprehensive, three-dimensional, and precise model for the risk management of MCS. It complies with the general requirements of the State Council’s Soil Pollution Prevention and Control Action Plan, also known as “Soil Ten Measures”. This system provides technical support for the remediation of mercury contamination at site scale in China and also enhances the country’s compliance with the Minamata Convention on Mercury.

With the increasing awareness of environmental issues, odor pollution has been recognized as a typical environmental hazard. Odor pollution in China comes from a variety of sources and the cost of odor measurements is high. Currently a hot topic in odor pollution control is to develop odor prediction models based on easily measurable parameters to decrease the difficulty of odor measurement and control. This paper introduces the basic concept of odor pollution and summarizes and compares different odor classification standards and measurement methods. Research progress on odor prediction models is reviewed, including multiple linear regression commonly used to establish quantitative relationship between odor concentration/intensity and pollutant concentrations. There are obvious differences in the results obtained from different studies and models, and accurate odor threshold values are key to optimizing the models. Furthermore, as an environmental issue, atmospheric dispersion and emission rate of odor pollutants are discussed. Different atmospheric diffusion models have been used to predict odor diffusion in the atmosphere, however, different models require different basic data and knowledges, therefore it is important to choose an appropriate model based on the actual application scenario. Emission rate, as an important input parameter in atmospheric dispersion models, can also be measured using different methods and devices, but differences between the results are to be expected, and cross-validation is needed. This review provides scientific guidance for the identification and control of odor pollution.

Arsenic (As) and associated thallium (Tl) can be released from As-bearing tailings and enter the surface water and soil environment. It is of great importance to understand the mineralogy and release characteristics of the toxic elements in tailings. In this study, the ore phases and their release mechanisms of As and Tl in As-bearing tailings from a realgar mining area are studied using batch leaching tests combined chemical analysis and mineral phases analysis. The results showed that the release of As and Tl was affected by the phases and speciation of the elements. The main As phases in the tailings were sperrylite and angelellite and they were prone to As release due to weathering. Thallium, as accompanying element, was associated with phases composed of Ca, Mn, Mg minerals, and the release of Tl was controlled by the precipitation and dissolution of these minerals. In the tailings, As mainly bounded to Fe-Mn oxides and organic materials, whilst Tl mainly bounded to Fe-Mn oxides and residual materials. The exchangeable fraction of As increased from 0.29% (before leaching) to 1.67% (after acid leaching); while for Tl it increased from 5.46% to 8.67%. The release of As was enhanced while Tl was inhibited under acidic conditions, which suggested the release of As and Tl in tailings was competitive. The leaching behavior of As conformed to the two-constant equation, indicating the leaching of As was a physiochemical process controlled by many factors. The leaching of Tl, which conformed to a parabolic diffusion equation, was mainly controlled by diffusion mechanisms such as structural incorporation and surface adsorption. In this study, the release characteristics, speciation and mineralogy of As and Tl in As-bearing tailings were clarified, which provided an essential reference of the pollution risk control for As and Tl in As-bearing tailings.

Understanding the sources of heavy metals in soils and the associated health risks is essential for effective risk management. In this study, taking a typical mining community as an example, the characteristics of soil contamination by heavy metals As, Cd, Cr, Cu, Ni, Pb, Zn, and Hg are evaluated using geo-accumulation index (I_geo). The potential sources of heavy metals are analyzed through correlation analysis in combination with positive matrix factorization (PMF) analysis. The results are applied to identify the driving factors for heavy metal accumulation in soils by redundancy analysis (RDA) and to quantify the associated health risk using the health risk assessment model. The I_geo results indicated a moderate level of Cd accumulation and low levels of Cu, Pb and Zn accumulation. Four potential sources of heavy metals in the study area were identified based on the PMF model. Combined with correlation analysis and regional pollution characteristics the four sources were clarified—they were Pb-Zn ore extraction and smelting (Cd, Pb), mixed sources (natural sources+copper ore mining and smelting) (Cr, Ni, Cu, Pb), non-ferrous metal smelting emission (Hg), and gold ore mining and smelting (As), with mixed sources being the dominant sources (70.10%). Based on RDA results, the key driving factors for heavy metal accumulation were cation exchange, soil moisture and distance to mines. According to the health risk assessment, heavy metal contamination in soils of the study area posed unacceptable carcinogenic hazards to children (probability of 15.21%), and carcinogenic health risks to adults and non-carcinogenic health risks to children and adults were at an acceptable risk level. Notably As was the main carcinogenic risk factor in the study area, and the 95th percentile risk (1.75E-4) exceeded the acceptable risk threshold (1E-4). The above findings can provide data support for priority control and prevention of heavy metal pollution in soils of the study area.

Soil moisture is a critical parameter in the field of hydrology, agriculture and meteorology, and microwave remote sensing is one of the most effective methods for soil moisture detection. This study uses active and passive microwave data and other multi-source remote sensing data and applies Random forest algorithm to perform soil moisture retrieval on both active and passive microwave data scales. First, on passive microwave data scale, the parameters for land cover and normalized difference vegetation index (NDVI) are spatially optimized. Second, ReliefF method is used for evaluating the importance of input parameters and parameter selection. Last, results by using active and passive microwave data jointly or separately are compared to assess the retrial accuracy and effectiveness of the former method. It was found that on the scale of active microwave data, the joint retrieval method yielded results with higher accuracy (r=0.691, RMSE=0.0796) compared to using only active microwave data (r=0.744, RMSE=0.0848); however, on the scale of passive microwave data, the opposite was true (r=0.939, RMSE=0.0451 using joint data; r=0.944, RMSE=0.0435 using only passive microwave data). The joint retrieval method proved to be applicable on the scale of active microwave data.

Short chain chlorinated paraffins (SCCPs) are persistent organic pollutants (POPs) which are widely used in the industrial production of cables, artificial leather, etc. SCCPs are biotoxins and can enter the soil environment through various pathways, threatening the ecological and environmental safety of soil. As a newly identified pollutant under UNECE, a SCCOs safety benchmark under the freshwater environment has been made, however, relevant research and benchmark under the soil environment are still lacking. To address this gap, this study analyzes published data on SCCP toxicity in soil and aquatic organisms to derive the predicted no effect concentration in soil (PNEC_soil) using the species sensitivity distribution (SSD) or partition coefficient (PE) methods. Briefly, soil toxicity data using SSD method yielded a PNEC_soil value of 71.46 mg/kg, and aquatic toxicity data using PE method yielded a PNEC_soil value of 10.1 mg/kg. By comparing with related studies, the PNEC_soil value obtained by PE method was selected as the ecological safety benchmark value for SCCPs in soil. The benchmark value obtained from this study is somewhat different from those of other countries due to the differences in research conditions such as species selection and research methods. The environmental risk of SCCPs in soil was also evaluated by risk quotient method, which showed that the current HQ values of SCCPs in soil ranged between 7.23×10^-5 to 0.5017 for different soil types in the main regions of China, which is considered low risk. The results of this study provide a reference for the development of environmental quality standards and risk assessment of soil SCCPs.

Soil evaluation guidelines are essential for soil evaluation and soil environmental protection. The United States (USA) was one of the developed countries first paid attention to contaminated sites protection and soil pollution control, and it has since developed fairly comprehensive guidelines such as the Soil Screening Guidance (SSG) for soil evaluation, whilst China is still in its infancy in this regard. In this paper we review research results on soil screening levels (SSLs) in the USA, focusing on the laws and regulations and technical specifications for soil protection and remediation, and discuss the methodology of SSL formulation based on five health hazard types: direct ingestion, dermal absorption, ingestion of contaminated groundwater, inhalation of outdoor volatiles/particulates and vapor intrusion. On this basis, we propose that researches on soil evaluation in China should be conducted based on soil environmental conditions in China, with emphasis on establishing regional and national soil parameter databases, standardizing national soil evaluation guidelines and carrying out combined research on soil and groundwater evaluation criteria, so as to provide a reference for formulating soil evaluation criteria in China.

In order to understand the characteristics of heavy metal pollution in agricultural land around non-ferrous metal taillings ponds in the mountainous areas of northern Hebei and the ecological and human health risks, a representative Au-Pb-Zn tailings pond and its surrounding agricultural land is selected as the research area. The soil pH and the contents of heavy metals Cd, Cr, Pb, Hg, As, Cu, Zn, Ni in the agricultural soils are determined by physiochemical analysis using ISE, XRF, AFS, ICP-MS methods. Heavy metal accumulation, potential ecological risks, and human health risks are analyzed to evaluate the ecological and human health risks caused by heavy metal pollution in the study area. The results showed that surface soil in the study area was heavily contaminated with Zn, Cu, Cd, Pb, and As to varying degrees with high levels of accumulation, except for As. The potential ecological hazard level was very high, specially for Cd, Pd and Hg. In terms of human exposure and health risks, heavy metal exposure by hand-to-mouth contacts was the main cause of both non-carcinogenic and carcinogenic health risks, and Zn and Pb were of special concerns in terms single element daily exposure levels. In both children and adults regarding hand-to-mouth contacts, the non-carcinogenic hazard level was unacceptable—in children, the risk indices for Pb and As were 11.23 and 1.75, respectively; in adults, Pb was of special concern. In terms of carcinogenic health risks caused by hand-to-mouth contacts, the risk level of Cd exposure was unacceptable in both children and adults, with relevant risk indices of 3.38×10^-4 and 1.63×10^-4, respectively. In short, risk monitoring and early warning systems should be strengthened in the mining areas, and pollution control measures for at-risk agricultural land should be implemented accordingly to eliminate potential health risks.

In this study, we perform a meta-analysis to investigate the distribution characteristics of heavy metals in soils in mining areas, in different regions and of different mining types in China, using 2002-2022 relevant soil data from CNKI, Wanfang, and Web of Science databases. In addition, geo-accumulation index and potential ecological risk index were used to assess the ecological risk of heavy metals in soils around mining areas. The Meta-analysis findings revealed that the concentrations of Cd, Hg, Cu, Pb, Zn, As, Ni, and Cr in soils around mining areas in China increased by 820.7%, 309.6%, 158.6%, 158.6%, 146.0%, 103.4%, 24.6%, and 15%, respectively, compared to the corresponding background values, among which Cd and Hg showed the greatest increases. Region wise, the central south and southwest of China were greatly impacted by mining and showed increases of 285.7% and 180.1%, respectively. Nationwide, Cd, Hg, Zn, Pb, and Cu increased the most in the southwest, central south, and east; Cd and As in the north and northeast; and Cd and Hg in the northwest. In terms of mined mineral/material types, heavy metal contamination increased greatly around metal mines such as lead-zinc, polymetallic nudule, copper, gold, mercury, molybdenum, manganese, and tin mines, and non-metal mines such as graphite mines, with increases of 166.4% to 617.1%. Lead-zinc mining led to significant accumulation of Cd, Hg, Pb, and Zn, and gold mining resulted in significant accumulation of As, Hg, and Pb. Copper mining and others such as graphite and pyrite mining all showed significant accumulation of Cd and Cu, except Ni and Cr which showed relatively small accumulation regardless mined mineral/material types. Evaluation results using geo-accumulative index and potential ecological risk index showed that the overall levels of Cd and Hg contamination in soils around mining areas were moderate and slight geo-accumulation, respectively, and a high potential ecological risk level was observed in most soil sites. Therefore, it is necessary to pay more attention to Cd and Hg pollution control and prevention in mining areas.

China is the world’s largest producer and consumer of rice. In some areas heavy metal contamination of paddy soils is a serious problem and poses risks to food security and human health. At present, the major challenge for soil pollution control in China is remediation of paddy soils contaminated with multiple heavy metals. Iron, as the fourth most abundant element in the Earth’s crust and a highly reactive element in soils, is involved in the geochemical processes of many heavy metals. In this review, the mechanism by which iron oxides influence heavy metals, the biochemical process of iron in soils, the effects of iron on heavy metal transformation in soil-rice system, and the application of iron derived materials in the remediation of heavy metal contaminated soils are summarized as the follows: (1) Iron oxides in soils can achieve heavy metal fixation through adsorption/complexation /precipitation, and can reduce heavy metal bioavailability through redox reaction. (2) With change of soil environmental conditions iron oxides are prone to reduction-dissolution/oxidation-precipitation or microbial mediated Fe(III) reduction and Fe(II) oxidation. (3) Change of soil pH and Eh in paddy soils can lead to transformation of iron oxides, formation of iron plaque, and iron uptake by rice, which in turn can affect heavy metal transport in soil-rice system. (4) Iron derived materials show high remediation efficiency for soils contaminated with a single heavy metal, but such materials have not been widely used for remediation of soils contaminated with multiple heavy metals. To provide a reference for addressing this issue this paper discusses the application-related problems and proposes future research directions.

The degree of cadmium (Cd) uptake and transport in plants and its ecological risk are largely determined by the chemical form it takes in soils. In risk assessment of Cd contaminated farmland soils two urgent issues need to be addressed: risk assessment based on the effective form of Cd in soil, and formulation of safety threshold values for heavy metal remediation. Currently, although many effective chemical extraction methods are available for heavy metal remediation, there lacks a versatile extraction method for bioavailable Cd in soils with different soil properties. In this study, farmland soil samples of nine soil types in China are collected for soil culture and pot experiments using rice, Chinese cabbage, and corn as test crops. Chromium contaminated soil samples are prepared by exogenous addition methods. Overall, five commonly used chemical extraction methods—neutral inorganic salt (CaCl₂), weak acid (HCl), chelating agent (DTPA, ETPA), and combined (Mehlich-3, or M3) extraction methods—are tested to quantitatively evaluate the effectiveness of these methods for Cd extraction under different soil types and the relationship between Cd extracted from soils and Cd accumulation in crops, with the goal of finding an extraction method that is widely applicable in different soil types. Chromium bioavailability determined by different methods differed significantly (p<0.05), and the extraction rates (%) followed the order of DTPA≈EDTA≈HCl>M3≈CaCl₂. Through comprehensive correlation analysis, the comprehensive correlation coefficients (I_p) between Cd extracted from soil and Cd uptake in the shoots of crops were calculated for each method, yielding I_M3=0.765, I_EDTA=0.641, I_DTPA=0.627, I_HCl=0.606, $I_{CaCl_{2}}=0.711$. Thus, M3 was considered a versatile extraction method which showed the highest I_p values for rice, Chinese cabbage, and corn in soils with different soil properties. The above results provide a theoretical basis for the evaluation of Cd bioavailability in farmland soils and remediation of Cd contaminated farmland.

The lack of toxicology data is the main factor hindering the ecological risk assessment of Cr contamination in soils and the revision of soil environmental quality standards in China. In this study, we conduct toxicology tests on seven soil types (with different soil properties) in China, using earthworm biomass, cabbage biomass, and microbial matrix induced respiration (SIR) as measurement endpoints. We determined the effective concentration (EC_x) values under different soil types based on the Log-logistic dose-effect relationship and low-dose stimulus effect function model. On this basis we developed predictive models for estimating toxicity thresholds of Cr under different soil properties. Chromium toxicity in earthworms, Chinese cabbage, and soil microorganisms under different soil types showed significant inhibitory effect with increased soil Cr concentrations, and the dose-response (D-R) relationship was clearly sigmoid in shape. Under different soil types, the EC₁₀ values for soil microorganisms (SIR), earthworms, and Chinese cabbage ranged between 22.1-53.7, 65.0-137.2, and 82.1-220.2 mg/kg, respectively, and the EC₅₀ values between 50.3-103.7, 103.9-369.0, and 159.9-441.9 mg/kg, respectively. The Cr toxicity thresholds for the tested species, from high to low, followed the order of Chinese cabbage>earthworms>soil microorganisms, with soil microorganisms being the most sensitive to Cr toxicity. Under low Cr concentrations (<112 mg/kg), the tested species showed significant hormesis effects, among which earthworms had a maximum hormesis between 102%-108% under different soil types, and Chinese cabbage between 105%-112%, while soil microorganisms showed relatively small effect at 104%. Chromium toxicity thresholds under different soil types can be well predicted based on soil pH and clay/CEC contents. The research results provide a scientific basis for the ecological risk assessment of Cr in soils and for the formulation and revision of environmental quality standards for Cr in soils.

The ecological safety issue due to cadmium (Cd) contamination in soils cannot be ignored. Presently, China has no environmental criteria established for Cd in soil based on ecological safety considerations. In this study, we collect and screen relevant Cd toxicity data related to China from results of domestic and international studies on Cd ecotoxicity in soil. We use species sensitivity distribution, combined with prediction models for Cd ecotoxicity in soil to derive ecological safety criteria for the total Cd and EDTA-extractable Cd in soils under different land use types. We obtained a total of 126 Cd toxicity data on 13 species and ecological processes, involving 60 terrestrial plants (6 species), 39 invertebrates (3 species), and 27 ecological processes (4 indicators). The prediction models we developed suggested that soil pH was the most important factor affecting Cd ecotoxicity in soil. The ecological safety criteria for the total Cd/EDTA-extractable Cd in soils with different pH values were 1.91-5.25/1.13-3.12 mg·kg^-1 for protected natural areas and agricultural land; 3.94-11.1/2.34-6.62 mg·kg^-1 for park land; 7.59-22.0/4.51-13.1 mg·kg^-1 for residential land; and 10.5-30.8/6.24-18.4 mg·kg^-1 for commercial services and industrial land. The results provide a basis for the establishment and revision of soil pollution control standards in China.

With increasing cobalt (Co) uses cobalt contamination in soil has attracted increasing attention. However, the potential ecological risks of Co contamination in soil and related risk thresholds have not been well researched. This study aims to derive ecological risk thresholds of Co in soil in China, using Co ecotoxicity data collected and screened through literature research, combined with ecotoxicological experiments and species sensitivity distribution (SSD) method. According to results, the EC₁₀ values of Co in soils with different properties ranged between 7 to 4696 mg/kg. The relationships between EC₁₀ and soil properties (pH, CEC, OC, Clay) and sensitivity k value of species were established by stepped-linear regression for eight species. The k value of the eight species ranged between -0.21 to 1.458. The k value (-1.207 and 2.201) of the non-normalized ryegrass and maize residue mineralization(MR) were obtained by extrapolation of the interspecies correlation estimation (ICE) model.Finally, regression models, with soil properties and k value as independent variables, were obtained for 10 species, and the predicted EC₁₀ values were normalized to four soil conditions. Using SSD method and adjusting for aging leaching factor,the ecological risk threshold (HC₅) values for Co in soil were derived for acidic (7.3 mg/kg), neutral (44 mg/kg), alkaline (72.08 mg/kg) and calcareous (38.88 mg/kg) soil conditions. The results provide a scientific basis for the formulation of soil standards for Co and for risk management.

Soil environmental benchmarks serve as the scientific cornerstone for establishing soil environmental quality standards. This cutting-edge field in soil environmental protection research encompasses interdisciplinary and foundational scientific issues such as soil environmental chemistry, environmental toxicology, biology, and risk assessment. Understanding and addressing these complex scientific challenges represent the forefront of soil environmental benchmark research. This article delves into several crucial scientific considerations that influence the toxicity thresholds of heavy metals in soil environmental benchmark research. These factors include non-biological elements, biological components, and the determination of dose-response relationships, encompassing the adjustment for soil aging and leaching factors, the modeling of low-dose stimulation effects, and methods for normalizing toxicity data. Furthermore, using Cd contamination in agricultural soil as a case study, this research establishes the Cd environmental benchmark (HC₅) for soils with varying properties. Equations based on cumulative distribution curves relating HC₅ values to soil properties are developed (e.g., LogHC₅=0.132pH+0.083OC+0.008CEC-1.448). The findings of this study are anticipated to offer valuable insights for the exploration of agricultural soil environmental indicators.

Chlorinated hydrocarbons (CAHs) are widely used as raw materials in industrial and agricultural productions, and their improper disposal and accidental leakage has made it one of the most common toxic and harmful contaminants in soil and groundwater, posing serious risks to human health and the environment. Bioremediation is ideal for the treatment of chlorinated hydrocarbon pollution due to its green, economic, efficiency, and no-secondary-pollution advantages. This paper first summarizes the physical and chemical properties of CAH, CAH transport in the environment, and CAH biodegradation mechanisms, and reviews research progress on bioremediation technologies (biostimulation, bioaugmetation and combined technology) for CAH polluted environment, as well as on mechanisms of bacterial degradation and transformation, with examples of bioremediation testing conducted at different scales, from laboratory to pilot testing. The paper then discusses factors influencing the effectiveness of bioremediation technology for CAH pollution management. Finally, the paper discusses the challenges in bioremediation of CAH contaminated sites and future research to address these challenges, which include mining and analyzing low-abundance CAH-degrading bacteria using single-cell technology (microporous chips, extreme dilution, etc.), developing efficient combined technology such as combining solar heating with in-situ bioremediation, and strengthening research on the factors affecting the remediation outcomes, in order to provide technical support for efficient and green treatment of CAHs pollution.

Hunan Province is one of the main grain-producing areas in China. Due to mining economic and other human activities, large areas of cultivated land soil are contaminated by heavy metals, which caused the concentrations of heavy metals in rice from some places exceed national food hygiene standard values. In this study, the current pollution status and reasons of heavy metal contaminated cultivated land soil and rice in Hunan Province are analyzed. The results showed that the characteristic of heavy metal contaminated farmland soil in Hunan is multiple-heavy metal pollution, and the level of pollution increases year by year, which is mainly distributed around the Xiangjiang River Basin and industrial and mining areas, and the contaminated area gradually spreads to breeding areas. The prominent heavy metal in rice is cadmium (Cd), followed by arsenic (As) and lead (Pb). In view of the various prevention and control measures for heavy metal pollution in rice from Hunan, their working principles, application examples, advantages and disadvantages were introduced. Then the remediation measures on heavy metal contaminated soil and their researches carried out in Hunan Province were summarized and discussed. Finally, in order to remediate heavy metal contaminated soil, reduce heavy metal contents in rice, and ensure safe food production, the economical, green, and efficient comprehensive technical method including in-situ passivator materials which based on soil composition coupled with easy-to-operate agronomic measures would be recommended.

Microplastics (MPs) are tiny plastic particles less than 5 mm in length. As an emerging pollutant, MPs are widely found in the marine and terrestrial environments. It has been found that the terrestrial environment is an important sink for MPs, where the content of MPs is 4-23 times higher than the marine environment. Microplastics not only affect the soil environment, but also can enter plant tissues and the human body through food chain or other pathways, posing health risks and becoming an urgent environmental problem. Detection technology is an indispensable tool for the study of environmental pollutants, but research on terrestrial ecosystems is still in its infancy and detection technology for MPs is still developing. At present, the detection of microplastics is ususally done in two steps: sample pretreatment and sample analysis. Density flotation, sieving and filtering, extraction and disintegration methods are commonly used for sample pretreatment, and visual inspection, spectroscopy and mass spectrometry are used for qualitative/quantitative sample analyses—with field emission Scanning Electron Microscopy (SEM), Confocal Laser Scanning Microscope (CLSM), Raman spectra (Raman), Fourier Transform Infrared Spectrometer (FTIR) and Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) most commonly used. For complex environmental samples combination methods are often required. Thus this paper summarizes research progress on detection methods for MPs in soils and plants, and discusses the application conditions and advantages and disadvantages of different detection techniques, aiming to provide a scientific reference for future studies, qualitative and quantitative, of MPs in terrestrial ecosystems and MPs transfer and accumulation in plants.

Soil constitutes a crucial component of agricultural ecosystem, and heavy metal contamination in arable soil can adversely affect the quality and safety of agricultural products. This study focuses on weakly acidic farmland soils of colluvial and alluvial accumulation zones in the granite region of northern Hebei. Utilizing two remediation techniques—phytostabilization and phytoextraction (with maize and Solanum nigrum as the phytoremediation agents), this study explores the impacts of different parent material types and remediation methods on heavy metal remediation efficacy in cultivated soils. According to results, (1) significant differences existed in organic matter, readily available potassium, available phosphorus, and pH values between soils of colluvial and alluvial zones, with the former exhibiting substantially lower pH levels and both zones having high background levels of lead (Pb). (2) Following phytostabilization, the colluvial zone showed significant reduction in cadmium (Cd) and lead (Pb) concentrations in maize grains, with an increase in yield ranging from 19.10% to 33.00%, indicating superior remediation outcomes compared to its counterpart. (3) The colluvial zone, employing an intercropping system of Solanum nigrum and maize, demonstrated higher annual extraction of Cd, Pb, and copper (Cu) per mu (a traditional unit of area) of farmland, with respective extraction amounts of 167.25, 208.35, and 555.05 g, and removal rates of 2.727%, 0.043%, and 0.234%, showcasing more effective remediation compared to the alluvial zone. (4) The intercropping system of Solanum nigrum and maize outperformed single-crop cultivation by enhancing the bioavailability of heavy metals in the soil and improving the plants’ absorption efficiency. (5) When designing remediation strategies one should consider soil characteristics, parent material types, and the influence of different crops and choose appropriate remediation techniques and cultivation models. This study provides a reference for the safe utilization and remediation of farmland soils in geologically anomalous regions.

In order to clarify the source of volcanic ash found in early Mesozoic “mung bean rocks” and the spatiotemporal relation between the volcanic ash and Paleotethyan arc volcanism, geochronology, trace elements and Hf isotope of zircons from samples collected from two mung bean rock layers, Wumengshan area, northeastern Yunnan, are analyzed. For rock sample from the Jialingjiang Formation, it yields zircon U-Pb age of (250.0 ± 2.8) Ma, ε_Hf(t) values from -18.1 to -9.5 and T_DM2 ages of 2141-1674 Ma, and from the Guanling Formation it yields zircon U-Pb age of (247.0 ± 1.2) Ma, ε_Hf(t) values from -16.4 to -7.5 and T_DM2 ages of 2050-1559 Ma. The similarity of results between samples indicates the mung bean rocks are derived from the same source, and are products of Paleo-Mesoproterozoic crustal materials. The trace element characteristics of zircons from mung bean rocks are consistent with data from acidic magmas, indicating protoliths of mung bean rocks are felsic. Combined with previous results, it is determined that volcanic ash found in mung bean rocks comes from the Sanjiang orogenic belt. Evidences have shown that there exists a magmatic arc along the Sanjiang-Songma-Shiwandashan area during the Early-Middle Triassic, arisen from the subduction of the Paleo-Tethys Ocean, and the mung bean rocks are records of volcanic activities caused by the subduction of the ancient Tethys oceans. Combined with geological data, it is considered the ancient Tethys arc volcanism starts before mung bean rock diagenesis in the Jialingjiang Formation (254.9 Ma) and lasts until sedimentation at the bottom of the Guanling Formation (247.1 Ma).

The Early Paleozoic Caledonian orogeny caused extensive magmatic activities in the South China Block (SCB), but its tectonic attribute is still controversial over weather it was subduction collisional or intracontinental. Study on the petrogenesis of I-type granites in the Qin-Hang junction zone is of great geological significance to reveal the Early Paleozoic geodynamic background and tectonic evolution in southeastern Guangxi. In this study, whole-rock geochemical analysis, LA-ICP-MS zircon U-Pb dating and Lu-Hf isotope analysis of granite samples from the Liandong and Gulong plutons in southeastern Guangxi are carried out. The two plutons are granodioites with similar formation ages, at 435-434 and 436-435 Ma, respectively, and with similar geochemical characteristics (10000Ga/Al value of 2.07; (Zr+Nb+Ce+Y) content of 183×10^-6; A/CNK ratio of 0.87-1.1, averaging 0.97; ε_Hf(t) value of -2.2-1.8, mostly between 0-2; T_DM2 age of 1.6-1.2 Ga, with a peak at 1.5-1.3 Ga; Nb/Ta ratio of 11.47-14.66, averaging 12.80; Rb/Sr ratio of 0.22-0.52), indicating both are calc-alkaline I-type granite originated from the partial melting of Mesoproterozoic meta-igneous rocks, probably containing some mantle-derived materials. A pluton formation model is proposed as follows: Large-scale collision between the southern SCB and the northern Gondwana margin created S-N and E-W stresses to the SCB triggering intracontinental orogeny. The thickened lithosphere underwent post-orogenic extension and thinning, and upwelling of mantle materials provided heat for the partial melting of the lower crust, forming the parental magma of the melting-type newborn crust (e.g. the Gulong pluton) or the mixed melting-type newborn crust with ancient crust component (e.g. the Liandong pluton). Under extensional environment after the intracontinental orogenic period, the parental magma upwelling along the channel formed the I-type granite with subduction-collision characteristics.

The Hongqiling mafic-ultramafic rocks include three belts (I, II and III) and are composed of over 30 small intrusions. They are located in the southern margin of the eastern segment of the Central Asian Orogenic Belt (CAOB). Several intrusions in belt I develop Ni and Cu mineralization, with Nos.1 and 7 intrusions forming medium- and large-sized magmatic Ni-Cu sulfide deposits, respectively. The major host rocks for Ni-Cu ore bodies are harzburgite, lherzolite, orthopyroxenite, websterite, norite and gabbro. These mafic-ultramafic rocks are characterized by high Mg (w(MgO)~20.7%-31.1%), moderate Si (w(SiO₂)~40.03%-53.01%) and low Ti (w(TiO₂)~0.33%-0.79%) and alkalis (w(K₂O+Na₂O)~0.60%-2.29%) contents. The patterns of trace elements show weak enrichments of LREE (La, Ce, Pr, Nd) and LILE (Th) and depletions of HREE and HFSE (Nb, Ta, Ti). Whole-rock geochemical data and mineral (olivine, orthopyroxene, clinopyroxene, spinel, plagioclase, amphibole) chemistry indicate the Hongqiling mafic-ultramafic intrusions are different from OIB, Alaskan-type complex and komatiite, but similar to arc-type basalt and mafic-ultramafic rocks from the Huangshanxi and Huangshandong Ni-Cu sulfide deposits in the western CAOB. The parental magma for the Hongqiling mafic-ultramafic intrusions is a high-Mg and low Nb-Ta tholeiitic melt which has undergone crustal contamination and fractional crystallization during evolution. Ore-bearing parental magma for the Hongqiling deposit likely experienced “second” separation of sulfide, forming the PGE-depleted Ni-Cu sulfide deposit.

The Pajiang uranium deposit is located in the southern Taoshan-Zhuguang uranium metallogenic belt of the southwestern Fogang pluton. It is a typical granite-related U deposit, the only one found in the Fogang pluton, and uranium mineralization is strictly controlled by fault structures. In this paper, the mineralogy, microgeochemistry and chronology of pitchblende and pyrite in the Pajiang uranium deposit are studied by means of petrography, scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and in-situ laser ablation inductively coupled technique (LA-ICP-MS). In-situ LA-ICP-MS U-Pb dating of pitchblende yielded a weighted mean age of 49.70 ± 0.1 Ma, which corresponds to the Late Cretaceous, and is within the main metallogenic epoch (75-50 Ma) of South China. This indicates that the formation of the Pajiang uranium deposit is consistent with regional metallogeny and belongs to a regional metallogenic event. The total rare earth element (REE) content in pitchblende was (311.5-368.3)×10^-6 and the U/Th ratio was 17067-26524, suggesting that the uranium deposit is of medium-low-temperature hydrothermal origin. The TE_1,3 value of REE was 0.95-1.01, with quasi tetrad effect characteristics, indicating fluorine enrichment in the ore-forming fluids. In addition, the Co/Ni ratio of pyrite ranged between 5-26 in the Pajiang uranium deposit, suggesting the uranium deposit is of hydrothermal origin. Based on the above analysis, it is considered that the Pajiang uranium deposit is of medium-low-temperature hydrothermal type.

The coexistence of hydrocarbon source rocks and sandstone-hosted uranium (U) deposits in the same basin has been widely reported. Hydrocarbon source rock contributes to uranium precipitation and enrichment by providing oil and gas; whereas, whether it can be a source of uranium supply is of great relevance as to weather uranium prospecting should expand deep into the basin. This study reviews relevant domestic and international studies and offers perspectives on this topic, focusing on three key issues: migration potential of uranium in source rock, possible ways of uranium transport by formation fluids, and mechanisms of uranium precipitation and accumulation. Hydrothermal modeling results show that uranium migration can occur during hydrocarbon generation and expulsion, and the migrated-uranium, probably a mix of U(IV) and U(VI), is likely transported by both hydrocarbon-bearing formation water and oils. The transported-uranium precipitates due to a decrease of uranium solubility and decomposition of the transport fluids caused by a decrease of temperature and pressure and change of pH and Eh; the uranium precipitates can also redissolve in oxygen-rich formation water. The main perspectives are: (1) the amount of migrated-uranium is uncertain, and the mechanism and laws of U migration are still unclear, thus further modeling experiments on source rock-uranium system is recommended to understand the kinetics of uranium migration. (2) Up to now, little is known about the dominant U mobile forms and their thermodynamic properties and distribution between hydrocarbon-bearing formation water and oil, thus, in-situ thermal testing via thermal simulation experiments is recommended to address this issue. (3) During uranium upward transport, changes in temperature, pressure, Eh, and organic/inorganic components of the transport fluids control uranium geochemistry, thereby, in order to understand uranium geochemistry and its controlling factors under different conditions, multi-variable simulation experiments on hydrocarbon-uranium transport is suggested.

A large number of magmatic hydrothermal tungsten deposits were formed in Nanling area in the Mesozoic with complex fluid source and evolution process. The ore deposits differ in the ore-forming granite type, intrusion depth and surrounding rock, and formed under influences of multi-stage fluid activities and meteoric water mixing. In this study the oxygen isotope composition of scheelites from different types of tungsten deposits are analyzed. The results show that scheelite related to S-type granite intrusion had the highest δ¹⁸O values (5.7‰-7.8‰), and those to A- and I-type granites had the lowest (2.9‰-4.5‰) and in-between (5.6‰) δ¹⁸O values, respectively. The ore-forming fluids in the early stage were mainly magmatic water, while the contribution of meteoric water in the late stage varied, where the addition of meteoric water, which had little effect on skarnization and greisenization, had large impact on quartz vein mineralization. The δ¹⁸O values in single quartz vein scheelite grain showed high spatial heterogeneity, with a decreasing trend from core to edge, reflecting multi-stage fluid activity. The study concludes based on the δ¹⁸O data that although scheelite of the early stage had undergone magmatic differentiation, fluid exsolution and hydrothermal precipitation, it still retains some characteristics of magmatic melt; while scheelite of early-late stage can reveal the fluid source and evolution in detail. The mineralization of skarn and greisen scheelite is mainly related to intense fluid-rock interactions, while scheelite precipitation in quartz vein is mainly related to the addition of large amounts of meteoric water.

The Guixi outcrop is located at the southernmost margin of the Sichuan Basin, northeastern Yunnan. The Longwangmiao Formation in the outcrop experienced strong dolomitization activity and developed widespread micritic limestone, arenaceous limestone, micritic dolomite, dolomitic limestone and calcareous dolomite. The three limestone-transition-dolomite cycles in the outcrop were characterized by presence of large quartz grains, and appeared mostly dark red under cathodoluminescence, with observable gypsum. Geochemical tests showed that the isotopic compositions of limestone-dolomite in cycle 1 were: carbon, -0.78‰--0.49‰, oxygen, -9.28‰--8.96‰, strontium, 0.70979554-0.71218318, calcium, 0.54‰-1.12‰; in cycle 2: carbon, 0.37‰-0.41‰, oxygen, -9.76‰-9.64‰, strontium, 0.71008711-0.71374167, calcium, 0.63‰-0.81‰; and in cycle 3: carbon, -0.03‰-0.23‰, oxygen, -9.90‰--9.24‰, strontium, 0.70990934-0.71237617, calcium, 0.56‰-0.94‰. The strontium and calcium isotope values were obvious low in limestone and high in dolomite. Calcium isotope simulation revealed the Mg²⁺ concentration in dolomitized fluid in cycle 1 was twice the seawater equivalent (105.64 mmol/kg, Mg²⁺/Ca²⁺ = 1.99), in cycle 2 seven times (369.74 mmol/kg, Mg²⁺/Ca²⁺ = 6.79), and in cycle 3 2.3 times (121.48 mmol/kg, Mg²⁺/Ca²⁺ = 2.29). Temperature simulation revealed the temperature of dolomitization fluid was around 30 ℃. The above results indicate dolomitization in the Longwangmiao Formation in northeastern Yunnan was mainly by seepage reflux.

The Hala’alate Mountain (Hashan) area located in the northwestern margin of the Junggar Basin is associated with an ancient continental margin island arc, where the Carboniferous-Permian (C-P) volcanic rock reservoirs are the main target for oil and gas exploration. To further assess the exploration prospect of the volcanic rock reservoirs we carry out a systematic investigation into the mechanism of reservoir development in Hashan. Core log, thin section, scanning electron microscope, micro CT, fluid inclusion and other techniques are used for the characterization of reservoir rocks, in combination with major and trace element analysis. We find (1) the main pore types in the volcanic rock reservoirs are dissolution pores, intergranular pores and dissolution fractures with large pore-diameter and good connectivity but strong heterogeneity. (2) Volcanic rock facies, fractures, weathering leaching and deep hydrothermal fluid are key factors affecting reservoir quality, where overflow facies and explosive facies are favorable facies belts for reservoir development. Tectonic uplift and thrust napping improve reservoir quality at the front wing of nappes and fault intersections (“Triangle” area), and weathering/leaching contribute to further improvement. (3) Based on the combined analysis of reservoir rock property and lithofacies, the volcanic rock reservoirs are classified into three quality grades. High-quality reservoirs are mainly located in the “Triangle” area of the thrust nappe belt. We conclude that the C-P volcanic rocks in Hashan area has good prospect of forming large-scale, high-quality reservoirs with huge exploration and development potentials.

It is believed that Lower Paleozoic marine source rock in the Tarim Basin is mainly mudrock of the Lower Cambrian Yuertusi Formation and minor mudrock of the Middle-Lower Ordovician, while the Lower Cambrian Upper Xiaoerbulake Formation is mainly dolostone reservoir rock. Wells drilled in Tazhong and Tabei areas discovered argillaceous limestone in the Upper Xiaoerbulake Formation. Argillaceous limestone samples from recently drilled wells Jingnengketan-1 and Luntan-3 possess high TOC (most exceed 0.3%, some over 2%). Other five wells in different locations in the Tarim Basin reveal effective source rock in argillaceous limestone (and/or dolostone) of the Upper Xiaoerbulake Formation. Evidences from wells agree with dark argillaceous limestone observed in the Upper Xiaoerbulake Formation at the Sugaitebulake outcrop. TOC of the samples selected from the outcrop is 0.41% on average, and R_o 1.14%. The above observations demonstrate the existence of effective argillaceous limestone source rock in the Upper Xiaoerbulake Formation. Based on data from outcrop, seismic, and well, the paper proposes a sedimentary mode of multi-period overlaid reef-shoal-source system in the inner platform in the Upper Xiaoerbulake Formation by means of seismic sedimentology, seismic attributes and forward modeling. According to the findings, source rock is located in the area where dip angle decreases from fore-reef to slope. The argillaceous limestone source rock is wide and thick, which makes it a large-scale effective hydrocarbon source for the nearby reservoir rock. The source rock in Gucheng 3D seismic survey can provide billions of tons of hydrocarbon. The knowledge derived from this paper extends type, stratum and area of Lower Paleozoic marine source rock in the Tarim Basin, elevates hydrocarbon resource potential in the presalt Cambrian plays, strengthens the strategy of transferring exploration focus from platform margin to inner platform, and inspires hydrocarbon exploration in Gucheng area as well as in the Tarim Basin.

The Wenchang Formation is the main source rock development interval in the southern Lufeng area. In order to restore the sedimentary paleoenvironment of the Wenchang period and explore the main controlling factors of organic enrichment in high-quality source rocks, the major and trace element data of 166 mudstone samples from the Wenchang Formation are analyzed. The elemental geochemical method is used to analyze the paleosalinity, paleoclimate, paleowater depth and the vertical and horizontal evolution of the paleo-oxygen phases in different subsags and different intervals of the Wenchang period for the first time in the study area. The causes of salinity anomalies in some wells and the indicative significance of triaromatic steranes and chlorella to the paleoenvironment are discussed; combined with TOC, paleoproductivity and terrestrial input changes, the main controlling factors of high-quality hydrocarbon source rocks in the study area are clarified. The results show that the water body of the Eocene Wenchang Formation is mainly freshwater during the deposition period, with slight increase in salinity in the local layer. Vertically, the salinity of the water body gradually decreases from the 4^th to the 1^st+2^nd members of the Wenchang Formation; horizontally, water salinity is highest in the Lufeng 15 subsag during deposition of the 4^th member, and relatively high in the Lufeng 13 eastern subsag during deposition of the 3^rd to the 1^st +2^nd members. It considers the change in water salinity in the Wenchang Formation is due to transgression effect, where water transgression is mainly concentrated in the Lufeng 15 subsag during deposition of the 4^th member, and expands to the eastern Lufeng 15 subsag and Lufeng 13 eastern subsag during deposition of the 3^rd member. Granodiscus and triaromatic dinoflagellate sterane cannot be used as indicators of water salinization or transgression in the study area. The change in Granodiscus content is closely related to paleoclimate, paleoproductivity and paleowater depth, but not much affected by paleosalinity changes. During deposition of the 4^th member, the paleoclimate was warm and humid, paleowater depth the largest, and paleowater reducibility the strongest; whilst in the 3^rd and 1^st+2^nd members, all three indicators decrease in values. During the deposition of the 4^th member, the water depth in the Lufeng 13 eastern subsag is the largest, followed by Lufeng 15 subsag; in the Lufeng 13 eastern subsag paleowater reducibility is the strongest, followed by Lufeng 13 western subsag. Organic enrichment in the source rocks of the Wenchang Formation is mainly controlled by paleoproductivity and paleocontinental input, followed by paleoclimate and paleowater depth. The change in paleooxygen phase has weak impact on organic enrichment. High paleoproductivity is the dominating factor controlling the formation and distribution of high-quality source rocks in the Wenchang Formation, mainly by influencing the modes of organic enrichment.

The magnitude and orientation information of in situ stresses in the basement of the Songliao Basin are important data in geodynamics research, seismology, and deep resources exploitation and utilization. The anelastic strain recovery (ASR) method is a three-dimensional in situ stress measurement method based on drill cores. In this report, three-dimensional in situ stresses at 6-7 km depth in basement of SK-2 borehole in the Songliao Basin, Northeast China, is determined using ASR method. The stress state of basement (6646-6846 m) is consistent with thrust and strike-slip faulting regime (σ_H>σ_V>σ_h) and the orientation of maximum horizontal principal stress is near E-W. The stress state determined by stress measurement is in agreement with results from focal mechanisms of shallow earthquakes (7-15 km) within the Songliao Basin and adjacent regions. The research findings should provide an important reference for the understanding of regional tectonic stress field and the formation and evolution of the Songliao Basin.

Sediment accommodation space has many controlling factors and is difficult to analyze quantitively. To address this issue, we designate a “total accommodation space”, which is the sum of all accommodation spaces during the deposition process, and summarize various controlling factors into three main factors: initial topography, global (absolute) sea level change, and total settlement. Based on the principle that the volume of the total accommodation space equals its fill volume, a quantitative relationship between the initial topography, global sea level change, total settlement/sedimentary thickness, and water depth is established. The influence of the main controlling factors on the stratum structure is analyzed, and a method for quantitative analysis of total accommodation space is proposed. This method can be applied to not only calculate the total settlement—thus reducing the difficulty in recovery and characterization of 3D sedimentary parameters, and ensuring the total accommodation space provided by sedimentary forward and inversion modeling is in line with expectations—but also establish the quantitative relationship between the main controlling factors and quickly recover the reasonable stratigraphic sedimentary parameters, which is conducive to establishing a sedimentary model. This study not only provides a more intuitive understanding of the quantitative relationship between the main controlling factors of accommodation space, but also lays a foundation for the quantitative study of effective accommodation spaces.

Petrogenic-derived organic carbon is an important carbon storage on Earth. Oxidation of petrogenic organic carbon releases carbon dioxide into the atmosphere—a key process in the geological carbon cycle. This process is of great significance for maintaining long-scale carbon balance on Earth and long-term habitability of the Earth’s surface environment. In recent years, research advancement has been made on petrogenic organic carbon weathering. This paper systematically reviews the current research status at home and abroad, focusing on carbon structural properties, quantitative methods for weathering rate, weathering controlling factors, and weathering flux statistics, in order to improve systematic understanding of petrogenic organic carbon and promote in-depth research on related key scientific issues.

Computational fluid dynamics (CFD) has been used extensively in palaeontology in recent years. This method is important for the study of the relationships among individual morphology of fossils, function of organs, and their living environments. Currently, CFD methods in paleontology are mostly applied to simulate centimeter-sized organisms, while there are relatively few simulations on millimeter-sized microscopic organisms. In contrast to centimeter-sized macrofauna, microbenthos lived closer to the surface of the seabed and are more significantly influenced by the low velocity zone of the near-bottom viscous boundary layer, and therefore the reduction of the boundary layer basin environment needs to be taken into account in the simulation of these fossils. In this paper, a new model of an uneven coastal seabed surface is constructed using a random surface generation method, and the flow state of the bottom boundary layer is simulated as influenced by the topography of the seabed surface. Based on the velocity data obtained from this simulation, we carried out another simulation to analyze the drag forces of sedentary Cambrian cnidaria fossil Quadrapyrgite at four varied locations on the undulating seabed surface environment. The results illustrate that the flow near the seabed surface can form a distinct low-flow region, and the thickness of the low-flow region becomes thinner with the increase of the flow velocity. The bottom boundary layer is thinner in the upslope region of the waterward side where the flow velocity varies rapidly, and thicker, by contrast, in the downslope and gully regions of the backwater side where the flow velocity is slower and more prone to vortex formation. The influence of the difference in flow velocity is also shown in the amounts of drag forces of Quadrapyrgite at different locations, which can vary by a factor of 1-10 to several tens. This variation in drag forces can influence the distribution and feeding behavior of different microbenthos at the micrometer-centimeter scale. The work in this paper provides more in-depth ideas and methods for simulating the survival environment of benthic microfossils.

Lake Tongting area has a dynamic water environment with developed surface water networks, complex hydrogeological conditions and intensive human activities, which makes it difficult to gain in-depth understanding of groundwater storage and movement in the lake area. This study applies dynamic analysis of water levels and radon (²²²Rn) tracer method to carry out qualitative and quantitative analyses of surface water-groundwater interaction and exchange fluxes in Lake Tongting area in the dry season. The spatial distribution patterns of water levels and ²²²Rn concentrations in the lake area in the dry season (between 2018-2020) indicated that groundwater (GD) discharge to the lake occurred in the dry season, especially in eastern Lake Dongting. According to calculation using radon box model, the GD-borne ²²²Rn flux in the dry season was 455.09 Bq/(m²·d), or 60.07% of total ²²²Rn flux to the lake; the total groundwater discharge was 0.29×10⁸ m³/d, and the average discharge rate was 56.27 mm/d. Groundwater discharge contributed to 7.04% of surface water in the dry season. Sensitivity analysis showed that sensitive variables in the model were wind speed, ²²²Rn concentration in groundwater/lake water and surface area. Improvements of sampling scheme and measurement accuracy of sensitive variables can improve reliability of calculation results. With clear physical significance and simple application protocol, radon (²²²Rn) tracer has certain application advantageous that it can be effectively used to quantify groundwater recharge, runoff and discharge in complex water environments. The research results provide better understanding of water balance in Lake Dongting and can serve as reference for water resource evaluation and management in the lake area.

Glacial meltwater is an important constituent of water resource in arid region of northwestern China. Quantitative assessment of meltwater changes is of significance to environmental protection and sustainable development of industry and agriculture in the middle and lower reaches. In this study, the glacier mass balance and meltwater runoff in the Akesu River Basin, southern Tianshan during a 60-yr period from 1957 to 2017 are simulated by the degree-day method, using daily precipitation and air temperature data, Digital Elevation Model (DEM) and glacier distribution data. Runoff components and runoff response to climate change are analyzed. During the 60-yr period, the mean annual mass balance was -94.6 mm w.e./a and the accumulative mass balance was -5.8 m w.e. The Equilibrium-Line Altitude (ELA) showed a trend of runoff increase at a rate of 1.6 m/a. During the same period, meltwater runoff and runoff components showed significant increasing trend, where the mean-annual-total-runoff was 53.1×10⁸ m³/a and the rate of runoff increase was 0.24×10⁸ m³/a. Under warm and humid climate, glacier ice accumulation increased with increasing precipitation in the basin. Whilst, due to significant rise in temperature, glacial melting intensified and the effect of temperature on meltwater runoff increased. Therefore, the hydrological effect caused by the loss of glacier mass balance is enhanced. Results from this study help to further understanding of the effects of changes in regional glacier water resource.

In recent years, uranium (U) isotopes as geochemical indicators play an increasingly important role in environmental studies. To accelerate the development and application of U isotopes in China, this paper performs a systematic review on U geochemistry, U isotope analysis and testing techniques, U cycling and isotopic composition of surface U, mechanism of U isotope fractionation, and research progress on and technical barriers to the application of U isotopes in environmental geosciences in the past two decades. Uranium as a redox-sensitive element, significant U isotope fractionation has been observed in natural and anthropogenic environments. Uranium isotopes have been successfully applied to trace U distribution, transport, and diffusion behavior in modern terrestrial epigenetic systems and to reconstruct the history of synergistic coevolution between the environment and living organisms over geological and historical periods. However, in general, U isotope research both at home and abroad is still in its infancy, mostly limited to qualitative analysis, and some application issues need to be solved. For example, U isotopes with certain valency are still not measurable, hindering a further understanding of the mechanism of U isotope fractionation during redox processes; other lackings include the means to deal with U contamination in groundwater; systematic, regional U isotope test data on epigenetic sediments; and analytical models for quantitative atmospheric source calculations. Among other issues, the mechanism of U isotope fractionation during carbonate rock formation is still unclear and the fractionation correction factor is difficult to determine. In paleoreconstruction, the use of U isotopes of black shale is problematic as accurate isotope data are difficult to obtain due to local signal interference, and the lack of isotope data on non-major geological events makes it impossible to recover the complete redox history of the Earth. Research on the geochemical mechanism of U isotope fractionation at high temperature and related application is scarce. Future directions on U isotope research and application include: improve testing techniques; increase precision in instrumental detection/analysis; conduct more systematic testing; establish comprehensive databases; deepen mechanistic understanding of isotopic fractionation; improve application quality; expand application to more fields; use multi-element tracers to improve tracer accuracy. This paper provides an essential reference for the application of U isotopes in environmental Earth sciences in China.

1,2,4-Trichlorobenzene (TCB) is a typical organic contaminant in soil and groundwater at industrial plant in China. 1,2,4-TCB is recalcitrant, bio-accumulative and highly toxic, posing serious threats to the environment and human health. 1,2,4-TCB is denser than water and easily penetrates into an anaerobic environment. Therefore, understanding the anaerobic biotransformation of 1,2,4-TCB is of great practical significance to on-site remediation. In this study, an anaerobic enrichment culture, which can sustainably dechlorinate 1,2,4-TCB to MCB via 1,4-DCB, is obtained. 16S rRNA gene amplicon sequencing and qPCR demonstrated Dehalobacter is responsible for the observed reductive dechlorination with a growth yield of (1.68±0.8)×10⁶ copies per μmol released Cl^-. A complete 16S rRNA gene sequence was obtained through PCR and a corresponding phylogenetic tree was constructed. This study provides a reference for the enrichment culture technique as well as theoretical guidance for the in-situ anaerobic bioremediation of contaminated sites.