外文文献及译文
化学工程与工艺砷污染 中英文资料外文翻译文献
外文文献：
Arsenic in the environment: Biology and Chemistry
Abstract：
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 regional.There 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 agriculture.Remediation of As-affected 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 long-standing 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 impacts.Crown Copyright . 2007 Published by Elsevier B.V. All rights reserved.
1. Introduction
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外文文献及译文
1.1. Location and scale of problem
Arsenic (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 (e.g. 50 μg/L in India and Bangladesh, Ahmedet al., 2004; Mukherjee et al., 2006). Arsenic in groundwater is often associated with geologic sources, but in some locations anthropogenic inputs can be extremely important. Ingestion of geogenic As from groundwater sources is manifested as chronic health disorders in most of the affected regions of the world (BGS & DPHE, 2001; Bhattacharya et al.,2002a,b; Smedley and Kinniburgh, 2002; Welch and Stollenwerk, 2003; Bundschuh et al., 2005; 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; 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 As-related 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; Mukherjee et al., 2006). During the past few years, As has also been detected in groundwaters of the sedimentary aquifers of the Terai Belt in Southern Nepal (Bhattacharya et al., 2003; Tandukar et al., 2006), Pakistan (Nickson et al., 2005), the Red River Delta and Mekong Basin of Vietnam and Cambodia (Berg et al., 2001, 2007), raising severe constraints on its use as a drinking water resource. However, few reports are available on the epidemiology and prevalence of Asrelated diseases in these areas. Arsenic is also reported in groundwaters of Australia (Smith, 2005; O'Shea, 2006; Smith et al., 2003, 2006), where the concentrations levels are well above the drinking water standard of 7 μg/L recommended by the National Health and Medical Research Council and the Natural Resource Management Ministerial Council of Australia (NHMRC/NRMMC, 2004). In addition, As from anthropogenic sources is also reported in groundwaters of Guam (ATSDR, 2002; Vuki et al., 2007-this volume), a small island in Western Pacific Ocean. Arsenic is also found in widely scattered geographical areas in the United States and Canada as well as in many other countries of Latin America such as Mexico, Argentina, Bolivia, Brazil andNicaragua,where the sources of As are geogenic as well as anthropogenic sources (Matschullat, 2000; Nordstrom, 2002; Smedley et al., 2002; 2005; Barragner-Bigot, 2004; Bundschuh et al., 2005; Bhattacharya et al., 2006b;
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Nriagu et al., 2007).
1.2. Field screening for arsenic
Following the discovery of As in the Bengal Basin, there is now an urgent need to address the public health implications due to exposure from drinking water sources. In order to do this and initiate appropriate mitigation measures, there is an urgent need to identify the As-contaminated tubewells (TW) that supply most of this drinking water (Chowdhury and Jakariya, 1999). This involves screening of water in millions of TW, and raising community awareness about the health problems related to chronic As exposure from drinking water. An overall risk assessment including a component of mitigation for As contamination should be based on accurate determination of As levels in TW water using economically viable methods for As screening. Field test kits offer a more practical tool than laboratory measurements within the time frame and financial resources available for screening and assessment of the As-contaminated wells as well as their monitoring. Simple, low-cost methods for As determination, such as the field test kits have proved to be most suitable for performing the TW screening quickly. Several commercial field test kits are available for determination of As in TW water (Rahman et al., 2002; Khandaker, 2004; Deshpande and Pande, 2005; van Geen et al., 2005; Steinmaus et al., 2006). Field kits provide semiquantitative results and the reliability of several field kits are questioned because of poor accuracy (Rahman et al., 2002). Thus, there is a need for further evaluation of the screening results by the field kit, prior to its recommendation for wide scale use in Bangladesh and elsewhere in the world.
1.3. Epidemiology
Ingestion of groundwater with elevated As concentrations and the associated human health effects are prevalent in several regions across the world. Arsenic toxicity and chronic arsenicosis is of an alarming magnitude particularly in South Asia and is a major environmental health disaster (Chakraborti et al., 2004;
Kapaj et al., 2006). Arsenic is perhaps the only human carcinogen for which there is adequate evidence ofcarcinogenic risk by both inhalation and ingestion (Centeno et al., 2002; Chen and Ahsan, 2004). Most ofthe ingested As is rapidly excreted via the kidney within a few days (Tam et al., 1979; Buchet et al., 1981; Vahter, 1994). However, high levels of As are retained for longer periods of time in the bone, skin, hair, and nails of exposed humans (Karagas et al., 2000; Mandal et al., 2003). Studies of As speciation in the urine of exposed humans
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indicate that the metabolites comprise 10–15% inorganic As (iAs) and monomethylarsonic acid (MMAV) and a major proportion (60–80%) of dimethylarsenic acid (DMAV) (Tam et al., 1979; Vahter et al., 1995; Hopenhayn-Rich et al., 1996). Recent studies have found monomethylarsonous acid (MMAIII) and dimethylarsinous acid (DMAIII) in trace quantities in human urine (Aposhian et al., 2000; Del Razo et al., 2001; Mandal et al., 2001). In general, MMAIII is more toxic than As(III) and As(V) (viz.Petrick et al., 2000, 2001).
1.4. Agriculture
The adverse effects of As in groundwater used for irrigation water on crops and aquatic ecosystems is also of major concern. In addition to potential human health impacts caused by ingestion of food containing As, thep otential for reduced crop yield due to its build-up in the soil is an active area of research. The fate of As in agricultural soils is often less well studied compared to groundwater, and in general has been studied in the context of As uptake by different plants (Huq et al., 2001, 2006; Das et al., 2004; Al Rmalli et al., 2005; Correll et al., 2006; Naidu et al., 2006). Crop quality and the effect of As on crop quality and yield is becoming a major worldwide concern, particularly for rice which forms the staple for many South-Asian countries where groundwater is widely used for irrigation (Meharg and Rahman, 2003). In a recent study it was reported that irrigation has increased in Bangladesh since 1970, while since 1980, the area under groundwater irrigation for the cultivation of Boro rice has increased by almost an order of magnitude (Harvey et al., 2005). Based on available information on the distribution of As concentration in groundwater (BGS and DPHE, 2001) and the area under shallow tubewell irrigation (BADC, 2005), Saha (2006)n estimated that approximately 1000 metric tons of As is cycled with irrigation water during the dry season of each year. Rice yield has been reported to decrease by 10% at a concentration of 25 mg/kg As in soil (Xiong et al., 1987). A greenhouse study by Abedin et al. (2002) revealed reduced yield of a local variety of rice (BR-11) irrigated with water having As concentrations in the range of 0.2 to 8 mg/L. The accumulation of As in rice field soils and its introduction into the food chain through uptake by the rice plant is of major concern (Duxbury et al., 2003).
1.5. Anthropogenic arsenic
Large quantities of As are released into the environment through industrial activities, which can be dispersed widely and as such play an important role in the contamination of soils, waters, and air (Nriagu,
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