外文文献翻译---砷在环境中的生化特性-环境工程(编辑修改稿)

外文文献翻译---砷在环境中的生化特性-环境工程(编辑修改稿)内容摘要：

northeastern England reveal As enrichment within the urban and industrially affected rivers (Neal and Robson, 2000。 Neal and Davies, 2003). The study revealed that the concentration of dissolved As in the rural areas averaged between and mg/L, while for the rivers influenced by industrial discharges the average between and mg/L, while suspended particulate As is much lower (average to mg/L for the rural and to mg/L for the industrial rivers). However, for the industrialized rivers dissolved As concentrations can be as high as mg/L.The possible mobilization of As in the soils, and subsequent leaching into ground or surface water or entry into the human food chain, should always be considered as a serious hazard. Detailed investigations are therefore necessary to estimate the total concentrations of As in soils in such areas, its chemical fractionation, and potential solubility to evaluate the potential risks from As mobilization.. Microbial transformations of arsenicMobilization of As in natural ecosystems is predominantly driven by microbially mediated biogeochemical interactions. Microbial reduction of As(V) to the more toxic and mobile As(III) species occurs via detoxification (Cervantes et al., 1994) 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。 arsA and arsB act as the As(III) efflux pumps。 arsR and arsD regulate the ars operon. Only a handful of microorganisms capable of respiring As(V) have been isolated (Oremland and Stolz, 2003). The As(V) reductase genes (arrA and arrB) involved in As(V) reduction have been identified in a number of bacteria, and they share high sequence identities (Santini and Stolz, 2004). The As(V)respiring microorganisms can use different electron donors (. acetate, hydrogen), and range from mesophiles to extremophiles (Oremland and Stolz, 2003). These laboratory studies indicate that microbial processes involved in As(V) reduction and mobilization is many times faster than inorganic chemical transformations (Ahmann et al., 1997。 Jones et al., 2000). This has led researchers to conclude that these microorganisms play an important role in As cycling in the subsurface (Ahmann et al., 1997。 Jones et al., 2000。 Islam et al., 2004).. RemediationSeveral technologies are currently available for As removal, ranging from simple and effective coagulation– flocculation, to sophisticated technologies such as ion exchange and reverse osmosis (Naidu and Bhattacharya, 2006). In addition, lowcost remediation methods, such as autoattenuation and the use of geological material as natural sorbents for As (. laterite, bauxsols, natural red earth or Ferich oxisols) have emerged as possible alternatives for the removal of As from groundwater in the developing world (Gen?Fuhrman et al., 2004, 2005。 Naidu and Bhattacharya, 2006。 Vithanage et al., 2006), but there is a pressing need to develop these methods further and in a costeffective way. The concept of phytoremediation of Ascontaminated sites was proposed over twenty years ago (Chaney, 1983). Phytoremediation has an advantage over conventional remediation of Ascontaminated soils that include burial and chemical stabilization, which may pose longterm health threats due to leakage or chemical instability (Allen, 2001。 Fostner and Haase, 1998). Thus phytoremediation has the potential to bee an environmentally friendly and lowcost alternative remediation technique. It is well documented that some tropical and subtropical plant species can tolerate and uptake various inorganic and organic forms of As (Meharg and HartleyWhitaker, 2002). Mesquite is am plant that grows well in humid and desert environments that has been shown to absorb Cr(VI) and other metals such as Pb (Aldrich et al., 2004). Xray absorption spectroscopic (XAS) studies revealed that mesquite can bioreduce Cr(VI) to the less toxic Cr(III) (Aldrich et al., 2003). However, a significant gap of information exists on the ability of desert plant species to uptake As or other toxic elements.. Current researchResearch on As is currently very active and includes assessment of interactions at scales ranging from molecular bonding to subcontinental, As speciation in inorganic and organic materials through a wide variety of chemical and spectroscopic approaches, and an emerging understanding of the role of microbes and other biota in As cycling. A recent review on health impacts of As resulted in drinking water standards of 10 μg/L or even lower in some countries (Kapaj et al., 2006). These lowered standards are projected to greatly increase water supply costs in many regions. The increased pressure on society to protect human health and the ecosystem has stimulated research using a wide multitude of approaches and techniques (Naidu et al., 2006。 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 charac。