地下水砷污染形成机制研究进展

地下水砷污染是全球饮用水的主要威胁之一,目前全世界有超过一亿人受砷污染地下水问题的困扰.因此,深入研究地下水砷污染的形成机制,对预测地下水中砷的分布及解决地下水砷污染问题具有重要意义.本文在归纳总结前人相关研究的基础上,综述了关于地下水砷污染形成机制的不同解释及最新研究进展,重点阐述了铁氧化物还原溶解释放砷机制,并详细...     

微生物砷代谢机制的研究进展（Progress in Study of Mechanisms of Microbial Arsenic Transformation in Environment）

环境砷污染是一个全球性问题.研究砷的生物地球化学循环可以明确环境中砷的来源及其转化特征,为探索砷污染治理的方法提供参考.越来越多的研究表明,自然界中的微生物在砷的迁移转化过程中发挥了重要作用.根据微生物对砷的代谢机制不同将其分为:砷氧化微生物、砷还原微生物和砷甲基化微生物.砷氧化微生物可以将环境中的As(Ⅲ)氧化为毒性较弱并且容易被铁铝矿物吸附固定的As(Ⅴ),因此对降低环境中的砷毒性具有重要作用;微生物对砷的甲基化作用的产物通常为毒性较低的有机砷,因此也被认为是理想的修复环境砷污染的生物手段之一;然而在还原环境中,砷还原微生物却可以将游离态和结合态的As(Ⅴ)还原为毒性更强的As(Ⅲ),从而加重环境中的砷污染状况.由此可见,明确微生物的砷代谢机制及其对砷污染环境中砷迁移转化的影响,是实现生物修复砷污染环境的必要前提.论文总结了近年来国内外微生物砷代谢机制的研究进展,以期为深入研究微生物代谢砷的机理及其在砷污染治理中的应用提供参考.     

铜、砷在水稻－土壤体系中的迁移及其对水稻影响的研究

通过盆栽试验和现场布点试验，研究了铜、砷在水稻－土壤体系中迁移的规律。结果表明，该体系对铜、砷污染具有相当大的缓解作用；土壤中水溶性可交换态铜、砷含量很低；铜、砷主要累积在水稻根部；土壤中铜、砷相互有拮抗作用，确定土壤铜、砷临界值应考虑多因素综合作用。     

铜,砷在水稻—土壤体系中的迁移及其对水稻影响的研究

通过盆栽试验和现场布点试验，研究了铜、砷在水稻－土壤体系中迁移的规律。结果表明，该体系对铜、砷污染具有相当大的缓解作用；土壤中水溶性可产我换态铜、砷含量很低；铜、砷主要累积在水稻根部；土壤中铜、砷相互有拮抗作用，确定土壤铜、砷临临界值应考虑多因炭综合作用。     

序言

<正>随着我国工业化和城市化进程的不断加快,重金属污染频发,砷污染亦呈愈演愈烈之势。1956—1984年以来,我国共发生砷污染事件30余起。近年来,又陆续出现多起砷污染和砷中毒事件。仅2008年以来,已爆发包括云南阳宗海事件在内的7起砷污染事件。2011年批准的《重金属污染防治"十二五"规划》,将砷列为一类重点防控对象之一。由于砷赋存形态复杂,污染来源广泛,对生态系统的危害具有累积性和长期性的特征。目前,关于砷对生态系统的环境效应尚不十分清楚。砷污染控制和毒理效应越来越受到我国政府和公众的重视,有关     

水稻不同生育期土壤砷形态分布特征及其生物有效性研究

采用田间原位试验和Tessier连续提取方法,在水稻（Oryza sativa L.）不同生育期研究了重金属复合污染高、中、低3个水平下的土壤砷的形态分布特征及其生物有效性。结果表明：在水稻不同生育期中,土壤各种形态的砷质量分数均表现为高污染水平土壤〉中等污染水平土壤〉低污染水平土壤;土壤中砷在水稻整个生育期均以残留态为主,占90%以上,交换态砷所占比例最低,不到0.5%;不同形态砷之间大都显著正相关,但是两种有效性较高的砷形态（交换态和碳酸盐结合态）与有机态砷之间的相关性较差;土壤砷的生物有效性表现为高污染水平土壤〉中等污染水平土壤〉低污染水平土壤,且随着水稻生育期的延长,土壤砷的生物有效性逐渐升高。     

乌达矿区煤火污染点土壤中砷的定量分析与评价

采集了矿区不同区域的72个土壤样品以及对照背景区的8个土壤样品,采用液相色谱-原子荧光联用技术测定了土壤中砷的含量,对乌达煤火污染点土壤中砷含量进行了定量分析,并对该区土壤砷污染程度进行了初步评价.结果表明,矿区土壤中砷含量范围为0.74—55.41 mg·kg~(-1),平均值12.59 mg·kg~(-1),约是该区土壤背景值(3.83 mg·kg-1)的3.29倍;不同采样点土壤中砷含量及土壤污染程度存在明显差异:烟点土壤污染点土壤非污染点土壤.乌达矿区土壤中存在砷污染,煤层自燃是该区土壤中砷污染的主要来源之一.     

砷和磷在不同污染类型土壤中的竞争吸附动力学

采用吸附实验研究了化工污染土壤(HG)、钢铁冶炼污染土壤(GT)和未受污染的农田土壤(CK)中的砷和磷吸附及竞争吸附特征,以期解释不同污染土壤此种吸附的动力学差异,为应用超富集植物修复场地污染土壤时合理施用磷肥提供理论依据。结果表明,在HG、GT和CK土壤中砷和磷的吸附特征有所差异,砷的最大吸附量分别为95.1、100、95.9 mg·kg-1,磷的最大吸附量分别为148、103、100 mg·kg-1。磷的存在能明显抑制土壤对砷的吸附,HG、GT、CK土壤在添加磷后,对砷的吸附量降低幅度分别为45.6%、57.3%、69.6%。而砷的存在对磷的吸附的影响不大,HG、GT、CK土壤在添加砷后,对磷的吸附量降低幅度分别为7.43%、6.41%、16.0%。3种土壤中铁、铝和磷的含量不同造成了砷、磷吸附和竞争吸附的差异,并且污染土壤上砷的配位体交换作用更容易受到磷的抑制。     

无机砷在植物和微生物体内的代谢机制研究进展

砷污染是全球的热点问题之一.土壤中的无机砷在植物中的积累可通过食物链传递,从而对人体健康构成严重威胁.了解微生物和植物对无机砷的代谢机制,对认识和控制土壤中砷的风险至关重要.近年来,微生物对无机砷的代谢机制研究已经比较深入,但是仍有一些问题亟待解决,如信号传导、抗砷基因筛选等.在植物对无机砷的摄取、还原机制等方面也取得了一定进展,但是植物体内砷的转运机制、排出机制等仍有待进一步研究.论文综述了微生物、植物体内无机砷的代谢过程中,砷摄取、转运、还原和排出机制的最新进展,并对今后的研究方向进行了展望.     

广州市蔬菜地土壤重金属污染状况调查及评价

探讨了广州市蔬菜地土壤重金属污染状况,测定了95份土壤样品中铅、镉、铬、砷、汞的含量水平。土壤中铅、镉、铬、砷、汞的含量分别在6.44～153.10mg/kg、0-0.682mg/kg、5.82～101.60mg/kg、0.04～45.36mg/kg、0.01～O.32mg/kg之间。就污染的普遍性而言,铅污染最为普遍,其次是砷污染;就污染的程度而言,镉污染最严重.其次为砷、汞。对比今昔污染变化.广州市土壤污染治理已取得显著成效,但仍需努力。土壤中镉、砷、汞三种元素的变异系数,特别是镉的变异系数较大,这可能预示着点源性污染的存在。     

Health effects of arsenic in drinking water: Research needs

Research needed to resolve the uncertainties of cancer risk from ingestion of arsenic in drinking water is described. The recommendations fall into two categories reflecting the areas of greatest uncertainty regarding the assessment of arsenic risk: research on the mechanism of cancer, and research on the metabolism and detoxification of arsenic. The recommendations are discussed in light of risk assessment and risk management issues, stressing the need for scientists to interpret research findings for decision managers.This document has been reviewed in accordance with the US Environmental Protection Agency Policy and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendations for use.     

Arsenic toxicity in humans: Research problems and prospects

The disposition and toxicity of the metalloid, arsenic, is affected by its oxidation state and on the extent to which it is converted to methylated species. Given that these chemical modifications influence the fate and action of arsenic, new research efforts should be directed both towards elucidating the molecular processes involved in the metabolism of arsenic and in characterising interindividual variation in capacity for processes such as the methylation of arsenic. This information will contribute to a better understanding of the mechanisms of arsenic toxicity and carcinogenicity and to a better assessment of the hazards associated with chronic exposure to this agent.     

黄河(内蒙古段)水体及悬浮物中砷的形态分布

以系统形态分析结合上浮水和悬浮物中砷的总量及形态分布特征,评价了黄河(内蒙古段)水体中砷的潜在危害程度.结果表明,水和悬浮物中砷的总含量出现了比较一致的沿河变化趋势,说明水中的砷主要是泥沙携带的砷,水中含砷量的高低取决于水中悬浮物即泥沙的含量.悬浮物中的砷以Ca-As为主,O-As次之,其它三种形态砷的含量均很低,与黄土中各形态砷的含量比较接近,进一步说明了黄河水体中的砷主要来源于自然界.     

中国关于砷的研究进展

综述了近年来有关中国的砷污染状况、相关的分析监测技术及砷化合物毒性的研究进展.在中国部分地区,长期砷暴露导致了严重的区域性的砷中毒,主要的暴露途径是饮用水、食物和煤炭的燃烧.样品前处理、砷的富集和形态分析技术的丰富和发展,为环境科学、毒理学和流行病学的研究提供了可靠的技术支持.生物检测是一种直接有效的污染物健康风险评估...     

Arsenic in groundwaters of the Lower Mekong

Increasing incidence and awareness of arsenic in many alluvial aquifers of South-east Asia has raised concern over possible arsenic in the Lower Mekong Basin. Here, we have undertaken new research and reviewed many previous small-scale studies to provide a comprehensive overview of the status of arsenic in aquifers of Cambodia and the Cuu Long Delta of Vietnam. In general natural arsenic originates from the Upper Mekong basin, rather than from the local geology, and is widespread in soils at typical concentrations of between 8 and 16 ppm; (dry weight). Industrial and agricultural arsenic is localised and relatively unimportant compared to the natural alluvial arsenic. Aquifers most typically contain groundwaters of no more than 10 μg L⁻¹, although scattered anomalous areas of 10 to 30 μg L⁻¹ are also quite common. The most serious, but possibly ephemeral arsenic anomalies, of up to 600 μg L⁻¹, are associated with iron and organic-rich flood-plain sediments subject to very large flood-related fluctuations in water level, resulting in transient arsenopyrite dissolution under oxidizing conditions. In general, however, high-arsenic groundwaters result from the competing interaction between sorption and dissolution processes, in which arsenic is only released under reducing and slightly alkaline conditions. High arsenic groundwaters are found both in shallow water-tables, and in deeper aquifers of between 100 and 120 m depth. There is no evidence of widespread arsenicosis, but there are serious localised health-hazards, and some risk of low-level arsenic ingestion through indirect pathways, such as through contaminated rice and aquaculture. An almost ubiquitous presence of arsenic in soils, together with the likelihood of greatly increased groundwater extraction in the future, will require continuing caution in water resources development throughout the region.     

Metabolism and disposition of inorganic arsenic in laboratory animals and humans

The carcinogenicity of inorganic arsenic in humans, particularly in the lung and skin, has been reasonably well established through epidemiological investigations. However, there is no substantial experimental evidence for carcinogenicity in animals to support the human studies. Studies of metabolism and disposition of inorganic arsenic in various animal species are particularly relevant to determining the factors that might account for the lack of an animal model. Numerous studies of this type have been reported, but there do not appear to be clear qualitative or quantitative differences in the overall fate and disposition of inorganic arsenic in most animalsversus humans, although little is known at the cellular and subcellular level.Sulphur chemistry, especially thiol status, is emerging as an important regulating factor in the overall fate and distribution of inorganic arsenic in the body, playing a role in the initial reduction of arsenate to arsenite and subsequent methylation, and possibly in determining tissue affinity and distribution properties. The metabolism of inorganic arsenic can be viewed as a redox cycle in which thiol compounds such as glutathione (GSH) possibly function as reducing agents and methyl donors as oxidising agents. One explanation for the possible sensitivity of certain malnourished human populations to the carcinogenic effects of inorganic arsenic may be related to the reduced availability of nonprotein sulphhydryl compounds such as GSH needed to drive the redox cycle and facilitate arsenic detoxification. Future carcinogenicity studies of inorganic arsenic in animals could be designed to address directly this aspect of the problem.Disclaimer: Although the research described in this article has been supported by the United States Environmental Protection Agency, it has not been subjected to Agency review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred. Mention of trade names or commercial products does not constitute endorsement or recommendalion for use.     

Risk assessment for ingested inorganic arsenic: A review and status report

Arsenic presents several unique problems in risk assessment. First, there is no good animal model for arsenic as a carcinogen, although in humans arsenic exposure through inhalation is judged to cause lung cancer and ingested inorganic arsenic is judged to cause skin cancer. Second, detoxification of arsenic through methylation is believed to be important, but the mechanisms and the quantitative relationships are not yet understood.EPA provided a risk assessment for ingested inorganic arsenic in its 1984 Health Assessment Document and a revised version in 1988. In both cases EPA calculated a cancer potency or slope factor using epidemiological data from Taiwan. EPA's standard or default risk assessment procedure is to use the linear coefficient from the multistage model in order to calculate cancer risk. This procedure was challenged by the EPA Science Advisory Board (SAB) in a report to the Administrator in September of 1989. The SAB recommended that EPA (1) develop a revised risk assessment based on estimates of the delivered dose of non-detoxified arsenic to target tissues, and (2) consider the potential reduction in cancer risk due to detoxification in establishing an MCL for arsenic.This paper will draw upon the author's experience with the SAB to summarise major issues in arsenic risk assessment and to examine how these issues might be resolved through further research.     

Characteristics of Environmental Geochemistry in the Arseniasis Area of the Inner Mongolia of China

In China, endemic arseniasis attributable to the geological-geochemistry environment is mainly found in the plain of the Great Bend of the Yellow River and the Hu-Bao plain in the Inner Mongolia Autonomous Region, in the Datong basin of Shanxi Province, the floodplain of the northern side of the Tian Mountain of Xinjiang Uygur Autonomous Region, and in the southwest coastal plain of Taiwan. These areas share many similar characteristics including widespread occurrences, a large population being affected, and the magnitude of risk involved. The population living in these areas is estimated to be around 5.5 × 10⁵, of which of 2.5 × 10⁵ are resident in Inner Mongolia. Based on our systematic research and comparison of various areas, we found the different types of arseniasis are often associated with different regions. The neural arseniasis is distributed in Xinjiang Uygur Autonomous Region and Shanxi Province, caused by inorganic arsenic in drinking water while the cycling-obstacle arseniasis is mainly found in Inner Mongolia and Taiwan, associated with organic arsenic in water. The distribution of arsenic affected villages in Inner Mongolia exhibits orientation and focus on low-lying land in the subsiding centre of the Great Bend basin, which was enriched with humus in the lake and limnetic deposits. Much CH₄ gas can be detected in the water of shallow and deep wells in these villages. Some of the wells with higher concentrations of CH₄ can even be ignited. This is a typical reductive geochemical environment. We tested the total amount of arsenic (As), As³⁺, and methyl arsenate in all types of water sources. It is found that the number of arseniasis cases is not clearly related to the total amount of arsenic (As) in the water. However, it is related to the ratio of As³⁺ plus methyl arsenic to the total amount of arsenic (As). The higher the ratio, the higher the number of people affected and the more serious the illness. The statistical results also indicate that good drinking water accounts for 60% of the drinking water source while the arsenic contaminated water makes up about 25% of the drinking water in the study area. This research reveals that the local geochemical environment is responsible for the spreading of the endemic arseniasis in the area and thus suggests a new direction of how to prevent such disease.