【正文】 ) or respiration processes (Ahmann et al., 1994). The genes that encode the proteins involved in As resistance are either plasmid or chromosomally borne, and have been best studied in Escherichia coli. Plasmid R773 prises of five genes arsRDABC organized in an operon (Chen et al., 1986). The arsC gene encodes the As(V)reductase。 Jacks and Bhattacharya, 1998。 Vahter et al., 1995。 Deshpande and Pande, 2005。 Nordstrom, 2002。 Naidu et al., 2006). In Asia, the impact of As toxicity is particularly alarming. For example, in the Bengal Basin of Bangladesh and West Bengal, India (Bhattacharya et al., 1997, 2002a,b, 2004, 2006a。中國石油大學(xué)勝利學(xué)院畢業(yè)論文外文文獻(xiàn)及譯文本科畢業(yè)論文外文文獻(xiàn)及譯文文獻(xiàn)、資料題目：Arsenic in the environment: Biology and Chemistry 文獻(xiàn)、資料來源： 網(wǎng)絡(luò)文獻(xiàn)、資料發(fā)表（出版）日期：院 （部）：化學(xué)化工系專 業(yè)：化學(xué)工程與工藝班 級：四 班姓 名：韓 其 成學(xué) 號： 200809011407指導(dǎo)教師：張慧敏翻譯日期：.14外文文獻(xiàn)：　Arsenic in the environment: Biology and ChemistryAbstract：Arsenic (As) distribution and toxicology in the environment is a serious issue, with millions of individuals worldwide being affected by As toxicosis. Sources of As contamination are both natural and anthropogenic and the scale of contamination ranges from local to are many areas of research that are being actively pursued to address the As contamination problem. These include new methods of screening for As in the field, determining the epidemiology of As in humans, and identifying the risk of As uptake in of Asaffected water supplies is important and research includes assessing natural remediation potential as well as phytoremediation. Another area of active research is on the microbially mediated biogeochemical interactions of As in the environment.In 2005, a conference was convened to bring together scientists involved in many of the different areas of As research. In this paper, we present a synthesis of the As issues in the light of longstanding research and with regards to the new findings presented at this conference. This contribution provides a backdrop to the issues raised at the conference together with an overview of contemporary and historical issues of As contamination and health Copyright . 2007 Published by Elsevier . All rights reserved.1. Introduction. Location and scale of problemArsenic (As) has been detected in groundwater in several countries of the world, with concentration levels exceeding the WHO drinking water guideline value of 10 μg/L (WHO, 2001) as well as the national regulatory standards (. 50 μg/L in India and Bangladesh, Ahmedet al., 2004。 Mukherjee and Bhattacharya, 2001), As in groundwater has emerged as the largest environmental health disaster putting at least 100 million people at risk of cancer and other Asrelated diseases. Recent studies indicate the occurrence of geogenic As in the Central Gangetic Plains of Uttar Pradesh, Bihar, Jharkhand and the Brahmaputra valley in Assam, and several regions of Madhya Pradesh and Chattisgarh, India (Chakraborti et al., 2004。 Smedley et al., 2002。 van Geen et al., 2005。 HopenhaynRich et al., 1996). Recent studies have found monomethylarsonous acid (MMAIII) and dimethylarsinous acid (DMAIII) in trace quantities in human urine (Aposhian et al., 2000。 Juillot et al., 1999。 arsA and arsB act as the As(III) efflux pumps。 Bhattacharya et al., 2007). Considering the seriousness of this global As problem, a twoday symposium was organized to facilitate a thorough discussion on a broad range of interdisciplinary issues that are related to the research on As in the environment. These include understanding the natural and anthropogenic processes which accelerate or control human exposure to As and different aspects of remediation. The outline of the symposium and the subsequent publications are described below.2. Theme of the Special SymposiumThe Special Symposium (SYP4) “Arsenic in the Environment: Biology and Chemistry” was organized as part of the 8th International Conference on Biogeochemistry of Trace Elements (ICOBTE) in Adelaide, Australia during April 2005. This Special Symposium attracted a wide range of contributions from a large number of multidisciplinary As researchers, that covered major themes, such as: 1) sources and characterization of As in groundwater environment。mssen et al., 2007this volume) targets lowarsenic aquifers in areas with high concentrations of geogenic As in groundwater with a case study from Matlab Upazila in Southeastern Bangladesh. The local drillers are constructing deeper tubewells than in the recent past (60 m instead of 30 m), primarily because of low concentrations of dissolved Fe and As (von Bromssen et al., 2005。Shea et al. (2007this volume), discuss about the source of naturally occurring As in a coastal sand aquifer of eastern Australia. The study suggests that As is regionally derived from erosion of Asrich stibnite(Sb2S3) mineralisation present in the hinterland. Fluvial processes have transported the eroded material over time to deposit an aquifer lithology elevated in As. The findings of this study indicate that any aquifer containing sediments derived from mineralised provenances may be at risk of natural As contamination. Groundwater resource surveys should thus incorporate a review of the aquifer source provenance when assessing the likely risk of natural As occurrence in an aquifer. In the next paper (Jakariya et al., 2007this volume) analytical results of field test kits and laboratory measurements by AAS as a “gold standard” for As in water for 12,532 TWs in Matlab Upazila in Bangladesh were pared. The study indicated that the field kit correctly determined the status of 87% of the As levels pared to the Bangladesh Drinking Water Standard (BDWS) of 50 μg/L, and 91% of the WHO guideline value of 10 μg/L. However, due to analytical and human errors during the determination of As by the field test kits, there were considerable discrepancies in the correct screening of As concentrations between 10– μg/L and 50– μg/L. Proper