An effective method for increasing the utilization efficiency of active components in heterogeneous Fenton-like catalysts was provided. 1.5 at.% Fe-Cu bimetal on 1D sepiolite (Sep) (D-FeCu@Sep) with high dispersion and reduced chemical valence was prepared via complexation-carbonization process of glutathione. 93% of ofloxacin (OFX, a typical antibiotic of emerging concern) was degraded over D-FeCu@Sep without any extra energy input at the optimum conditions (100 mL 10 mg/L OFX, pH 5.0, 3.0 g/L catalyst and 0.03 M H2O2), which was enhanced by 2.3, 3.0 and 1.7 times compared with aggregated Fe-Cu on Sep (A-FeCu@Sep), monometallic Fe on Sep (D-Fe@Sep) and Fe-Cu on blocky Celite (D-FeCu@Celite), respectively. Moreover, it exhibited an excellent performance at a wide working pH range from acidic to neutral conditions (pH 3.2-7.2) with a satisfied stability. Based on the characterizations of X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS), transmission electron microscopy (TEM), hydrogen temperature-programmed reduction (H-2-TPR) and electrochemical impedance spectroscopy (EIS), the proposed complexation-carbonization process of glutathione played an important role in the good Fenton performance of D-FeCu@Sep. The complexation of Fe and Cu ion by glutathione favors the high dispersion of Fe-Cu active component, afterward the reduced chemical valence results from carbonization process of glutathione. Moreover, the 1D nanofibrous structure of D-FeCu@Sep could greatly increase the surface electron transfer efficiency compared with D-FeCu@Celite. This study provides a method alternative to the heterogeneous Fenton chemistry by increasing the utilization efficiency of active components. (C) 2020 Elsevier Ltd. All rights reserved.

海水中的稀土元素是海洋和环境研究中很有潜力的地球化学指标,但其极低的浓度（ng/L或更低）和海水样品高盐基体的特征（平均3.5%）使其准确测定极具挑战性。本文提出了一种自动分离超痕量稀土装置（ElSPE-2 Precon）,有效地去除样品中盐分及降低本底,建立了海水、地热地下水中ppt级在线分离ICP-MS全自动检测技术。本装置（图1a）主要包含4个模块:自动进样器、注射泵六通进样阀和分离柱、试剂纯化系统和在线数据处理软件。所有部件均为耐酸腐蚀的惰性材料,整个装置长0.5米,宽0.4米,高0.5米。工作流程:1)螯合分离柱被超纯水清洗并用醋酸铵平衡后,水样经自动进样器抽入定量环中,在注射泵的推动下与线纯化醋酸铵缓冲溶液（p H～6）混合,并进入到螯合柱中进行分离富集;2)待醋酸铵溶液清洗去除基体元素后,用超纯水清洗醋酸铵缓冲溶液后,并用5%硝酸反向淋洗分离柱,洗脱液在线进入ICPMS进行测定,在线软件处理数据。分析性能:1)基体耐受性:10%NaCl;2)基体去除效率:Na, Ba, Ca, Mg, Sr, Mg和各种阴离子等＞99.9%;2)低过程空白:0.002～0.34 ng/L,方法检出限:0.002 （Dy）～0.328 ng/L （Nd）;3)直接测定加拿大海水标样NASS-6（0.22～11.94 ng/L）,测试值与文献报道值（0.19～12.82 ng/L）一致;4)分析速度:15件/小时,样品消耗量0.9 mL/件;5)长期稳定性（8小时）:实际海水RSD＜5%。该技术已成功应用于高基体水样痕量稀土分析,如远洋（航次）海水、珠江入海口的不同盐度河水和海水、地热地下水等。

＜正＞随着工业的发展,土壤中重金属污染成为国内外研究的难点与热点。汞污染尤其是甲基汞由于其具有剧毒性,引起了人民的广泛关注。甲基汞主要在还原环境中形成,然后通过生物地球化学过程降解。其中光降解和微生物降解是甲基汞去甲基化的两个主要过程,目前已有大量研究及相关报道。然而,人们很少关注在黑暗/厌氧土壤/沉积物中甲基汞的降解行为。前期调查发现,在我国南部广州市重汞污染区土壤中汞含量与铁、铜含量成显著的负相关性。

＜正＞砷、硒均是剧毒且致癌的重金属污染物。其中,砷主要来源于含砷源的岩石和沉积物的浸出,如盆地湖泊的冲积沉淀、火山堆积、地热资源的输出、矿山废料和垃圾填埋（Robertson,1989;Korte and Fernando,1991）,以及矿石冶炼、含砷农药和木材防毒剂的使用（Lorenzen et al.,1995和Bhattacharya et al.,1995）等。硒是亲硫元素,水体环境中硒主要来源于含硒硫化物矿的冶炼、炼油、制造特种玻璃等行

Datong Basin is a typical groundwater irrigation area in northern China contaminated by As. In order to reveal the distribution of As and the adsorption behavior of As (V) onto topsoil in the Datong Basin, a total of 40 topsoil core samples were collected from a 2 m core. Samples were used for chemical composition analysis and an isothermal adsorption experiment. Results show that the collected samples are not contaminated. The adsorption capacity (S tot value) of topsoil for As (V) at the study site ranged from 257 to 1027 nmol/g with an average of 505.2 ± 200.2 nmol/g. Vertically, both S tot value and topsoil components exhibit a vertical zoning with a positive correlation between the S tot value and KO, CaO, MgO, AlO, FeO contents while NaO and SiO are inversely correlated. FeO content shows a strong positive correlation with As content while AlO does not. Moreover, the correlation between S tot value and AlO is much better than FeO. These results indicate that Fe minerals are the main reservoirs of As in the natural topsoil at the study site. Furthermore, both Fe minerals and clay minerals can adsorb As (V) , but clay minerals have a greater storage potential. This result indicate that a combined effect of Fe minerals and clay minerals for As (V) accumulation onto topsoil should be considered during geochemical modeling and further agricultural management.
© The Authors, published by EDP Sciences, 2019.

To understand the implications of depositional environment on the enrichment of iodine in sediments, the N-alkane analysis has been conducted on the sediment from the North China Plain (NCP). The iodine contents of sediments ranged from 0.03 to 2.54 μg/g with the highest content occurring in the depth of 170-185 m. The results of sediment N-alkane (TAR, ςT/ςM and ACL) indicate that the marine source input is the predominant factor controlling the enrichment of iodine in the groundwater system. The Pr/Ph ratios (from 0.13 to 1.68) and the plot of Pr/n-C 17 vs. Ph/n-C 18 suggest that sediments deposited under suboxic to anoxic conditions. Under the oxdizing conditions, the iodine tends to be rich in the sediment, while the iodine may prefers to be released into groundwater under the reducing conditions.
© The Authors, published by EDP Sciences, 2019.

To understand the implications of depositional environment on the enrichment of iodine in sediments, the N-alkane analysis has been conducted on the sediment from the North China Plain (NCP). The iodine contents of sediments ranged from 0.03 to 2.54 μg/g with the highest content occurring in the depth of 170-185 m. The results of sediment N-alkane (TAR, ςT/ςM and ACL) indicate that the marine source input is the predominant factor controlling the enrichment of iodine in the groundwater system. The Pr/Ph ratios (from 0.13 to 1.68) and the plot of Pr/n-C 17 vs. Ph/n-C 18 suggest that sediments deposited under suboxic to anoxic conditions. Under the oxdizing conditions, the iodine tends to be rich in the sediment, while the iodine may prefers to be released into groundwater under the reducing conditions.
© The Authors, published by EDP Sciences, 2019.

This study explores linkages between the microbial composition and hydrochemical variables of pristine groundwater to identify active redox conditions and processes. Two confined aquifers underlying the city of Qianjiang in the Jianghan Plain in China were selected for this study, having different recharge sources and strong hydrochemical gradients. Typical methods for establishing redox processes according to threshold concentration criteria for geochemical parameters suggest iron or sulphate reduction processes. High-throughput 16S rRNA sequencing was used to obtain diversity and taxonomic information on microbial communities. Instead of revealing iron- and sulphate-reducing bacteria, salt- and alkali-tolerant bacteria, such as the phylum Firmicutes and the class Gammaproteobacteria, and in particular, the family Bacillaceae, were dominant in the downstream groundwater of the first aquifer that had high ion concentrations caused by the dissolution of calcite and dolomite; meanwhile, the heterotrophic microaerophilic families Comamonadaceae and Rhodocyclaceae prevailed in the upstream groundwater of the first aquifer. Sulphate-reducing bacteria were extremely abundant in the upstream groundwater of the second aquifer, as the SO42- concentration was especially high. Methanogens and methanotrophs were predominant in the downstream groundwater of the second aquifer even though the concentration of SO42- was much higher than 0.5 mg L-1. The microbial communities, together with the geochemical parameters, indicated that the upstream region of the first aquifer was suboxic, that Fe(III) and Mn(IV) reductions were not the main redox processes in the downstream groundwater of the first aquifer with high Fe and Mn concentrations, and that the redox processes in the upstream and downstream regions of the second confined aquifer were SO42- reduction and methanogenesis, respectively. This study expands understanding of the linkages between microbial communities and hydrogeochemistry in pristine groundwaters and provides more evidence for identifying active redox conditions and processes.

Arsenic (As) is a ubiquitous constituent in geothermal waters. Geothermal fluids with As concentrations ranging from 0.01 to tens of mg/L occur in different locations around the world, especially in geothermal systems along the boundaries of active plates. Leaching of reservoir rocks is the most important source of As in geothermal fluids. Arsenic exists in different As-bearing minerals in geothermal reservoirs with different temperatures, and the As concentrations in aqueous phase are affected by reservoir temperature to various degree. Arsenic concentration in geothermal waters depends on their genesis and geochemistry, with deep neutral chloride waters commonly containing much higher As concentrations than shallow acidic sulfate waters. During the upflow of geothermal fluids from the reservoir to the surface, As experiences a series of abiotic and biotic processes: oxidation, reduction, methylation and As-S redox cycling. Arsenic oxidation could happen under both aerobic and anaerobic conditions. Up till now a total of twelve aerobic As(III)-oxidizing bacteria have been isolated and thousands of clones harboring arsenite oxidase gene were detected in hot springs worldwide. As(III)-oxidizing rate of these isolates reached up to 1.27 mu M/min. In situ microbial arsenate reduction in geothermal environment was found in the bottom water of Mono Lake fed by hot spring waters, and several arsenate reducers were reported in some geothermal waters as well. Inorganic As could be methylated in hot springs by biological activity. Arsenic and sulfur often coexist in geothermal environments and undergo similar chemical and microbial redox transformations. In sulfidic hot springs, thioarsenates/thioarsenites can be formed preferentially by replacing several hydroxyl groups in arsenate and arsenite with thiol groups, respectively, and thioarsenites/ thioarsenates could be reciprocally transformed regardless of the presence of sulfur. Microorganisms in hot springs have been found to exert a profound influence on As and sulfur speciation by using them as both electron donors and acceptors, forming various thioarsenate species. Geothermal As from depth can be released into the surface or near-surface environments either via discharge of hot springs or geothermal wastewater, or via natural mixing of geothermal waters with local shallow groundwaters. Some rivers contaminated by geothermal As were estimated to discharge tens to more than one hundred tons of As per year. Understanding the biogeochemical behaviors of As in geothermal systems before and after mixing with shallow groundwaters and surface waters is therefore critical for the protection of water resources and the environment.

Microscale water distribution in the subsurface is key to many geochemical and biogeochemical reactions. This study investigated microscale water distribution and movement in unsaturated soils using micro-continuum hydrodynamic models, and examined the effect of microscale water distribution on organic carbon (C) decomposition using a micro-continuum biogeochemical reaction model. The micro-continuum hydrodynamic model that relates capillary pressure to porosity captured the measured water imbibition curve at the core scale, and exhibited reasonable water distribution and movement at the microscale. The simulations of organic C decomposition illustrate that microscale water distribution strongly affected the distribution of C decomposition rates by regulating the availability of dissolved organic C and oxygen. Particularly, changes in water distribution altered the location and intensity of reactive hotspots and thereby CO2 flux from soils. The microscale interactions between water content and organic C decomposition rate provide underlying mechanisms for explaining macroscale phenomenon observed in laboratory and fields. Overall, this study presents a useful tool for explicating hydro-biogeochemical behaviors in the subsurface by integrating micro-continuum hydrodynamic and biogeochemical reaction modeling. (c) 2018 Published by Elsevier B.V.