化学 化工 毕业 英文 外文 文献翻译 砷在环境中的生化特性

化学 化工 毕业 英文 外文 文献翻译 砷在环境中的生化特性 外文文献及译文 文献、资料题目:Arsenic in the environment: Biology and Chemistry 文献、资料发表(出版)日期: 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 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 1 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; 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 2 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 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 3 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, 1989; Jacks and Bhattacharya, 1998; Juillot et al., 1999; Matschullat, 2000; Pacyna and Pacyna, 2001). Elevated concentrations of As in soils occur only locally, but in areas of former industrial areas it may cause environmental concern (Nriagu, 1994; Smith et al., 1998; Kabata-Pendias and Pendias, 2001). Although many minerals contain As compounds, the anthropogenic contribution to the environment in the past accounted for 82,000 metric tons/year worldwide (Nriagu and Pacyna, 1988). Inorganic As compounds such as calcium arsenate, lead arsenate, sodium arsenate and many others were used by farmers as insecticides pesticides for debarking trees, in cattle and sheep dips to control ticks, fleas, lice and also in aquatic weed control. Water soluble preparatives, such as chromated copper arsenate (CCA) and other As-based chemicals used as wood preservatives during the past have lead to widespread metal contamination in soils around the wood preservation facilities (Bhattacharya et al., 2002c). However, the use of inorganic As compounds in agriculture has gradually disappeared since the 4 1960s due to greater understanding of As toxicity and awareness regarding food safety and environmental contamination (Vaughan, 1993; Sanok et al., 1995; Smith et al., 1998). In addition, during manufacturing of As-containing pesticides and herbicides, release of waste and As-laden liquids near the manufacturing areas may contaminate soil and water bodies (Mahimairaja et al., 2005). There are several “hot spots” around the world where soils have very high concentrations of As caused by natural geochemical enrichment and long-lasting ore mining and processing. For example, in Poland, mine spoils, slag dumps and tailings, that remained in the areas of As manufacturing and industrial processes, also contain extremely high concentrations of As (Karczewskam et al., 2004, 2005). There is a widespread concern regarding bioavailability of As in the terrestrial environment in industrialized regions of the world. The majority of incidences of soil As pollution could be traced back to a period prior to extensive statutory controls over As emissions (Meharg et al., 1994). For example, England was one of the cradles of the industrial revolution in the 19th century that has left behind an extensive legacy of As-contaminated sites. As part of the Land Ocean Interaction Study (LOIS) the As concentrations in the rivers of 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 0.6 and 0.9 mg/L, while for the rivers influenced by industrial discharges the average between 3.2 and 5.6 mg/L, while suspended particulate As is much lower (average 0.1 to 0.2 mg/L for the rural and 0.2 to 0.8 mg/L for the industrial rivers). However, for the industrialized rivers dissolved As concentrations can be as high as 25.6 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. 1.6. Microbial transformations of arsenic Mobilization 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 5 chromosomally borne, and have been best studied in Escherichia coli. Plasmid R773 comprises 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 (e.g. 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 sub-surface (Ahmann et al., 1997; Jones et al., 2000; Islam et al., 2004). 1.7. Remediation Several 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, low-cost remediation methods, such as auto-attenuation and the use of geological material as natural sorbents for As (e.g. laterite, bauxsols, natural red earth or Fe-rich 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 cost-effective way. The concept of phytoremediation of As-contaminated sites was proposed over twenty years ago (Chaney, 1983). Phytoremediation has an advantage over conventional remediation of As-contaminated soils that include burial and chemical stabilization, which may pose long-term health threats due to leakage or chemical instability (Allen, 2001; Fostner and Haase, 1998). Thus phytoremediation has the potential to become an environmentally friendly and low-cost alternative remediation technique. It is well documented that some tropical and sub-tropical plant species can tolerate and uptake various inorganic and organic forms of As (Meharg and Hartley-Whitaker, 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). X-ray absorption spectroscopic (XAS) studies 6 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. 1.8. Current research Research on As is currently very active and includes assessment of interactions at scales ranging from molecular bonding to sub-continental, 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 two-day symposium was organized to facilitate a thorough discussion on a broad range of inter-disciplinary 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 Symposium The Special Symposium (SYP-4) “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; 2) processes that control mobility and speciation of As in soil, water and biota; 3) prediction of the fate of As in natural environments in response to geochemical, hydrologic, and biologic changes; 4) analytical techniques and speciation studies; 5) remediation and management of As-contaminated soils and groundwater; and 6) impact of As on agriculture and water supply management. The articles included in this special issue address many of these issues and pave the way through recent findings on the environmental behaviour of As in terms of its occurrence, sources, health impacts, and remediation. Besides understanding the fundamental processes of As 7 mobilization, the articles discuss a wide variety of chemical and spectroscopic approaches, and increased understanding of the importance of microbes and other biota in As cycling. Although much has been learned about As in the environment the ability to predict the impact of intentional and unintentional changes to hydrologic and geochemical regimes often remains elusive. Key research contributions from several international teams of scientists working on As in the environment, groundwater in the Bengal Delta Plain and elsewhere in the world were presented and discussed during the symposium and are amalgamated in this Special Issue of The Science of the Total Environment. 3. Layout and summary of the articles This special issue comprises 14 articles and 1 short communication, grouped into four sections. 1) Arsenic in the groundwater environment; 2) arsenic in agricultural soils and mining environment; 3) biogeochemistry of As and toxicity, and 4) remediation of Ascontaminated soils and sediments. 3.1. Arsenic in the groundwater environment This section has five articles. The first two contributions deal with the specific issues related to the occurrence of geogenic As in the alluvial aquifers of Bangladesh. The first paper (von Brömssen et al., 2007-this volume) targets low-arsenic 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; Jakariya et al., 2007). The paper discusses the relation between the colour of the sediments and groundwater redox conditions. This study revealed that the sediment colour is a reliable indicator of high and low As concentrations that can be used by local drillers to target low-As groundwater. The presence of As contamination of shallow fluvio-deltaic aquifers in the Bengal Basin has also resulted in increasing exploitation of groundwater from deeper aquifers that generally contain low concentrations of dissolved As (Stollenwerk, 2003). However, infiltration of high-As groundwater induced by increased pumping of these aquifers clearly indicate the possible risks for an increase in As concentrations. The following paper (Stollenwerk et al., 2007-this volume) presents a study on the investigation of the adsorption capacity for As of sediment from a low-As aquifer near Dhaka, Bangladesh. At this site a shallow, chemically reduced aquifer with 900 μg/LAs overlies a more oxidized aquifer with b5 μg/L As. Since no 8 thick layer of clay was present at the site to inhibit vertical transport of groundwater, there was an apparent risk for an increase in the concentration of dissolved As in the deeper aquifers. Laboratory experiments and geochemical modeling were used to show that oxidized sediments have a substantial but limited capacity for removal of As from groundwater. The problem of geogenic As is not only restricted to the Bengal Basin and its surrounding region. DissolvedAs in groundwaters from coastal aquifers used extensively for human consumption has led to widespread concern in eastern Australia. In the next paper O'Shea et al. (2007-this 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 As-rich 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., 2007-this 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 compared. The study indicated that the field kit correctly determined the status of 87% of the As levels compared 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 10–24.9 μg/L and 50–99.9 μg/L. Proper training of the field personnel, verification of the field test kit results with laboratory analyses, and further development of the field test kits, will improve the accuracy of As measurements at low concentrations. The concluding short contribution in this section (Vuki et al., 2007-this volume) deals with a study on the speciation of As in spring waters located along Tumon Bay in the small island of Guam in Western Pacific Ocean. Earlier investigation conducted by the Guam Environmental Protection Agency (GEPA, 2002) on total concentrations of As in groundwater springs and seepages at Guam indicated concerns over As contamination resulting predominantly from anthropogenic sources. Although more detailed studies are required for a detailed evaluation of 9 the extent of As contamination in Guam. The results of this study show that total As concentrations in the spring water samples ranged from b0.3–1.2 μg/L with inorganic arsenate As(V) the dominant species. The low concentrations of dissolved As are also consistent with the values recorded for the groundwater wells in the northern part of Guam (GWA, 2003). These concentrations are much lower than the previously reported values, probably due to a much more rigorous methodological approach; this suggests the need for and requires further investigations on the status of As contamination in groundwater on the island. 3.2. Arsenic in agricultural soils and miningenvironment The first article in this section (Saha and Ali, 2007- this volume) deals with the dynamics of arsenic in agricultural soils irrigated with As-contaminated groundwater in Bangladesh. Arsenic concentrations in the soil layers of 12 rice fields located in four Asaffected areas and two unaffected areas in Bangladesh were monitored systematically. This study clearly shows enrichment of As in the top soil of rice fields irrigated with As-contaminated groundwater (79–436 μg/L), compared to areas where irrigation water contained very lowAs (b1 μg/L).The study also revealed significant spatial and temporal variations of As concentrations in the contaminated rice field. Arsenic concentration of rice field soils increased significantly by the end of the irrigation season. About 71% of the As that was applied to the rice field with irrigation water accumulated in the top 0 to 75 mm soil layer. Most of this As was leached from the soil during the following wet season. It is very important that the observed spatial and temporal variability of As in rice field soils is taken into consideration in the future studies on As contamination of rice production. There are several hot spots in Poland where soils have very high concentrations of As, caused both by natural geochemical enrichment and long-lasting ore mining and processing operations (Karczewska et al., 2004, 2005). Detailed investigations are therefore necessary to estimate the total concentrations of As in soils in such hot-spot-areas, its chemical fractionation, and potential solubility to evaluate the risks for mobilization of As. In the second article in this section (Krysiak and Karczewska, 2007-this volume) an attempt has been made to assess the levels and environmental risk associated with possible increases in As mobility under changing pH and redox conditions in soils and waste material in two areas of former As mining and processing activities Zloty Stok (Zlote Mts.) and lezniak (Kaczawskie Mts.) in SW Poland. Arsenic concentrations were measured in twenty six soil samples collected from 12 sites, and 10 represented a broad spectrum of soil properties and parent material origin, including natural soils, mine spoils, slags and tailings. Most soils in the area had extremely high concentrations of As (range 100?3,500 mg/kg), both of natural and anthropogenic origin. Sequential extraction techniques suggested that the main species of As in all soils were those bound to iron (Fe) oxides, whereas the contributions of mobile and specifically sorbed As forms were relatively low. In tailings and tailing-affected alluvial soils, As occurred mainly in residual forms, however these soils also had considerable amounts of mobile As. In all other soils, mobile As forms were very low. The last paper in this section (Eapaea et al., 2007-this volume) discusses the dynamics of As in the mining sites of Pine Creek Geosyncline of Northern Territory of Australia. This study examined the mobility and retention of As in soil and sediments from five mine sites in the region, based on measuring the operationally- defined forms of As in soils and other sediments using a modified sequential extraction procedure. The study revealed that As was present both in soluble and loosely bound forms, such as Al–As, Fe–As, Ca–As associations, Fe(OH)3 occluded As, organic bound As and residual As in sediment phases. Two general management principles were suggested for trapping the mine waste contaminants to minimize dispersion of As and heavy metals into the environment. These included prevention of direct discharge to creeks or water ways and discharges into constructed wetland with aquatic macrophytes to trap sediment that provides organic matter for arsenic and heavy metal retention. 3.3. Biogeochemistry of arsenic This section contains three articles describing the aspects of biogeochemical interactions of As and toxicology. The first article deals with Arsenicicoccus bolidensis, a novel As-reducing actinomycete in contaminated sediments near the Adak mine (Routh et al., 2007). At Adak, a small mining town in the Västerbotten district of Northern Sweden, high-As concentrations are encountered in surface and groundwater, sediments, and soil. In spite of the oxic conditions, As-rich surface and ground water samples indicate a predominance of As(III) species (up to 83%). Several microorganisms potentially involved in As cycling were isolated from the sediment enrichment cultures (Routh et al., 2007-this volume). Results from laboratory investigations show that A. bolidensis (a novel gram-positive, facultatively anaerobic, coccus-shaped actinomycete) actively reduced As(V) to As(III) in aqueous media. The second article (Chen et al., 2007-this volume) reveals that arbuscular mycorrhizal fungi (AMF) may play an important role in 11 protecting plants against As contamination. However, little is known about the direct and indirect involvement of AMF in detoxification mechanisms. A compartmented pot cultivation system („cross-pots?) investigated the roles of AMF Glomus mosseae in plant phosphorus (P) and As acquisition bym Medicago sativa, and P–As interactions. The results indicate that fungal colonization dramatically increased plant dry weight by a factor of around 6, and also substantially increased both plant P and As contents (i.e. total uptake). Irrespective of P and As addition levels, AMF plants had shoot and root P concentrations 2 fold higher, but As concentrations significantly lower, than corresponding uninoculated controls. The decreased shoot As concentrations were largely due to “dilution effects” that resulted from stimulated growth of AMF plants and reduced As partitioning to shoots. The study provides further evidence for the protective effects of AMF on host plants against As contamination, and have uncovered key aspects of underlying mechanisms. The third article in this section (Krishnamohan et al., 2007-this volume) deals with the systematic study of the urinary As methylation and porphyrin profile of C57Bl/6J mice chronically exposed to sodium arsenate. The results indicate that As interferes with the function of enzymes responsible for haem biosynthesis leading to alteration in the porphyrin profile. The levels of total As were significantly related to dose. No significant differences in the urinary As methylation pattern between control and test groups were observed. Coproporphyrin I (Copro I) showed a significant dose response relationship after 12, 14 and 20 months of exposure. Significant differences in the levels of coproporphyrin III (Copro III) were observed in the 8th month in 250 and 500 mg/L treatment groups and the dose response pattern was maintained after 10 and 12 months. These results suggest that urinary As can be used as a useful biomarker for internal dose, and that urinary coproporphyrin can be used as an early warning biomarker of effects before the onset of cancer. 3.4. Remediation of arsenic contaminated water, soils and sediments This section contains three articles and one short communication that discuss aspects of remediation of As-contaminated water, spoils and sediments. The first article (Vithanage et al., 2007-this volume) examines Natural Red Earth (NRE) as a novel adsorbent for retention of As(III) and As(V) from aqueous solution. Results of laboratory experiments show that As(V) has a strong affinity for NRE surface sites compared to As (III). With an increase in the initial loading, As(V) adsorption deviated from the formation of simple monolayer sorption sites to multi-layer 12 sorption due to the complexation mechanism of two different reactive surface sitesNFeOH and NAlOH. Thus, NRE can be a cost-effective As-retention methodology, especially for the economically poorer sections of the developing world. The second article in this section (Aldrich et al., 2007-this volume) deals with the uptake of As(III) and As(V) by the desert plant species Mesquite (Prosopis spp.) and its potential application for phytoremediation of As-contaminated soils. Seedlings were grown in agarbased medium containing 5 mg/L of either As(III) or As (V). Results showed that the As concentrations from As (V) were significantly higher than the As concentrations from As(III) in all portions of the plant. X-ray absorption spectroscopy (XAS) revealed that As(V) was reduced to As(III) inside the mesquite plant. Mesquite could thus be a good candidate for the uptake of As in contaminated soils in arid regions. There are few published accounts of As uptake by natural vegetation growing on As-polluted soils (Environment Agency, 2002). In the third article in this section, Madejón and Lepp (2007-this volume) investigated the distribution of arsenic in soils and plants of woodland regenerated on As-contaminated soils that exceeded the UK guidelines for „safe? soil As concentrations (50 mg/ kg; MAFF, 1993). Each site had a different source of soil As, but all had either been spontaneously colonized by native vegetation, or were in the process of such activity. This investigation revealed that there is a very little transfer of As from soils to plants at three As-polluted sites where total soil As contents exceed a statutory threshold for action. The lack of soil-plant As transfer is independent of the source of soil As. The last contribution to this section is a short communication (Anderson andWalsh, 2007-this volume) that examines As uptake by the common marsh fern Thelypteris palustris and its potential use for phytoremediation. The wide range of habitat and ease of cultivation of the marsh fern would make it an ideal plant for remediation in many environments. Hydroponic and soil cultivations of T. palustris, revealed As accumulations in both roots and fronds of the plant. The levels of As were up to 100 times the concentration of treatment solutions of 250 mg/L and 500 mg/L As, but values varied widely and there was no significant difference in As concentrations in fronds between the control (without As) and treatments. However, plants exposed to 500 mg/L exhibited necrosis in their fronds, suggesting that T. palustris is not a good candidate for phytoremediation of contaminated sites with extremely high concentrations of bioavailable As. 13 4. Conclusions Arsenic contamination of water supplies is a problem on a global scale. Past anthropogenic practices have released large amounts of As into the environment and caused contamination of groundwater resources, usually at relatively small scales. In many areas of the world, biogeochemical processes have resulted in a release of naturally occurring As into groundwater; in some cases, large regions are affected. The adverse impact of As on human health has been documented, and there are now indications that As can also have a negative effect on agricultural production systems. Remediation of Ascontaminated water is therefore critical. Phytoremediation is one potentially cost-effective means for removing As from water. Natural geologic materials have also been shown to be effective in removing As from water. To solve the problem of As contamination will require avariety of approaches from different fields of research. We sincerely hope that these articles are of considerable interest to the readers. They reflect the latest state of the art on our understanding of various inter-disciplinary facets of the problem of arsenic in environmental realm, mechanisms of mobilization in groundwater, fate of arsenic in the agricultural systems, biogeochemical interactions and the measure for remediation. We believe that discussions during the symposium significantly improved our understanding of the global problem of As impact on land and water resource management vital for millions of people across the world. Acknowledgements This special issue would remain incomplete without expressing our sincere and deep sense of gratitude to the International Society of Trace Element Biogeochemistry (ISTEB) and the organizers of the 8th International Conference on the Biogeochemistry of Trace Elements (ICOBTE) who have considered the Special Symposium (SYM-4) on “Arsenic in the Environment: Biology and Chemistry” for initial phases of planning, organization and sponsor for this important platform for the scientific discussions on an important issue of environmental health concern. We would like to thank the Swedish Development Cooperation Agency (Sida-SAREC), Swedish Research Council (VR), Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas), Knut Alice andWallenberg's Foundation of the Royal Institute of Technology (KTH) and the MISTRA for support to the participants in this conference as well as for the editorial time for this special issue. We appreciate the support from our colleagues, L.Q. Ma, D. Chakraborti, D. Caussy, J. Ng, K.R. Gunaratna, M. Vithanage, O. 14 Selenius,.K.G. Scheckel, J. Morrisson, K. Savage, S. Hirano, G. Jacks, N. Lepp, P. Ravenscroft, M. von Brömssen, J. Saunders, D.B. Kent, M. Elrashidi, S. Mahimairaja and B. Dousova who have devoted their valuable time to review the manuscripts submitted for this special issue. We wish to express our sincere thanks to them which helped to contribute to the high quality of the papers in this volume. PB is especially grateful to Roger Thunvik, Head, Department of Land and Water Resources Engineering, and Ramon Wyss, Vice President (International Cooperation) at KTH for their constant encouragements and organizational support. We would like to express our sincere thanks to Colin Neal, Executive Editor of the Special Issues of The Science of the Total Environment for his encouraging notes and his valuable time for final editorial comments and corrections of the manuscripts for this volume. 15 山东建筑大学毕业论文外文文献及译文 中文译文: 砷在环境中的生化特性 摘要 砷在环境中的分布和毒性是一个严重的问题，世界上有上百万的人在遭受砷毒性的危害。砷污染的来源有自然方面和人类活动，还有污染的规模使一个小区域的污染影响整个区域，有许多地方的研究发现了砷污染的这一问题。这些因素使得对于砷污染去除的方法有了新的方法，研究出了砷对人类的传染病学，还有研究出了在农业中植物对砷吸收后的产生的危害影响。对于受到砷污染过的给水处理是重要的，而且这一研究意味着评估自然恢复和植物修复的潜力，在砷环境中另一有效的研究领域就是对于微生物的新陈代谢和生物地球化学之间的作用。 在2005年，召开一个会议，参加者来自不同地区的对于砷研究科学家。在这篇文献中，呈现了这次会议中对于长期从事砷问题研究的综述还有新的发现。这一会议的贡献提供了对于砷问题研究的一次交流机会，还有对于砷对于人类健康影响和砷污染的当前过去的评价。 关键词:砷;污染;地下水;管井式井泵筛选;现场检测组件;健康;安全水体;农业;土壤;矿场环境;植物修复;吸附;修复 1 引言 1(1 砷污染的地理位置和污染规模 砷已经被世界上许多国家的地下水中检测到，砷的浓度超过了WHO对于饮用水(10µg/l)和自然水源砷浓度(50µg/l)的 标准 excel标准偏差excel标准偏差函数exl标准差函数国标检验抽样标准表免费下载红头文件格式标准下载 。地下水中的砷通常联系到地质原因，但是在一些地区人为排放的砷对于地下水的危害也是极大的，从地下水中摄入的砷已经被证明对身体造成慢性的健康紊乱。研究者检测到许多地方的地下水中含有砷，这些地方亚洲尤甚。澳大利亚的地下水中叶发现到砷，而且砷浓度超过了其本国对于饮用水中含砷的浓度标准7µg/l)，除此之外，地下水中砷的来源是人为原因的也被报道过。 1(2砷的检测 目前，在孟加拉国，对于由饮用砷污染水而造成的公共健康影响需要迫切的研究，为了解决这个问题和采取适当的缓和措施，孟加拉的采取的措施，是一种对于大多数饮用水输送设备叫做管井的识别确定，这牵扯到上百万这样的管井中水的检测，并且也对居民对于饮用砷污染水带来健康问题的认识有一定的提高，这样的措施因此需要经济可行性的方 - - 16 山东建筑大学毕业论文外文文献及译文 法。对于砷污染的水井的检测、评估和监控，考虑到时间框架和经济来源可利用行，现场测试装置比实验室措施更实用，它对于水井的水的检测快速，而且简单、成本低。但是现场测试装置它的正确率低下，它所提供的半定量的结果和可依赖型受到质疑。因而，在这一检测装置在孟加拉国和世界上其他地方被推荐大规模使用之前，需要对这一装置的检测结果做进一步的评估。 1(3砷毒性所产生的流行病学 世界上多个区域的居民饮用高砷污染水使他们的健康受到影响这一现象是普遍的，砷的毒性 长期暴露在砷条件下是令人担忧的，尤其是在南亚。砷可能是唯一的被足够证据证明出来的致癌物质。摄取的砷大部分通过肾脏排出体外，但是，高浓度的砷会在骨骼、皮肤、头发和指甲存留很长时间。在对暴露人体的尿液中砷的形态研究表明代谢物组成10-15%是无机砷和一甲基砷酸，还有大部分60-80%的二甲基砷酸。最近的研究已经发现了一甲基砷酸和二甲基砷酸在人体尿液的踪迹。此外，一甲基砷酸比三价砷和五价砷更具毒性。 1(4砷在农业方面产生的影响 用含砷的地下水对于农作物和水生生态系统的灌溉所产生的副作用也是一个令人关心的重要问题，除此之外还有由于摄取含有砷的食物而造成的对人类健康的影响，由于砷在土壤的逐渐积累使得农作物产量减产的可能性，这些方面都是研究的热点。相比于地下水中的砷和不同植物吸收砷方面，在农业土壤方面，砷的影响没有很好的研究。农作物质量和砷对于农作物质量和产量方面产生的影响已经变的越来越令人关心的问题了，尤其那些使用地下水灌溉水稻的南亚国家，大米是这些国家的主要产品。研究表明，土壤中砷的浓度在25mg/kg时大米将减产10%。一项在温室内做的研究表明，用砷浓度为0.2-8mg/L时，使用的是一种叫做BR-?型的大米。砷在大米中的积累和通过摄入大米进入食物链这两个方面是一个令人关心的问题。 1(5人为原因产生的砷 工业活动产生的大量的砷广泛的释放到环境中，这对于土壤、水体和空气的污染起着重要的作用。矿场含有砷的矿物质，但是全球的人类活动在过去每年产生砷总共有82000吨。无机砷物质像砷酸钙、砷酸铅、砷酸钠和许多其他物质，这些物质被用来作为杀虫剂、除草剂大量使用。在过去，水溶性的保护剂，像砷酸铜还有以砷为化合物质的化学品已经在土壤中导致大范围的金属污染，但是由于对砷的毒性、食物安全和环境污染的理解，无机砷物质在农业的使用的大量减少是在20世纪60年代。此外，制作含有砷的杀虫剂和除草剂的工场，会向附近释放污染物和负载砷的物质，这可能回污染土壤和水体。 - - 17 山东建筑大学毕业论文外文文献及译文 全球有许多地方由于地理地质因素富含高浓度的砷，例如波兰，此外还有制作含砷工业产生的矿渣、垃圾和尾料也含有大量的砷。对于全球工业区域的陆地环境中的砷的生物可利用性是一个广泛关注的问题，大部分砷污染的土壤能够恢复到先前砷排放时候法定标准。研究表明，农村区域溶解性的砷浓度平均在0.6-0.9mg/L，而被工业水释放影响的河流砷浓度平均在3.2-5.6mg/L，但是悬浮性的砷相对于溶解性的砷是十分低的，农村区域和工业河流的悬浮性砷浓度分别为0.1-0.2mg/L、0.2-0.8mg/L。但是，对于工业河流，溶解性的砷浓度能够达到25.6mg/L。 土壤中砷的迁移，可能随后进入陆地或者水体表面或者进入人类食物链，这些被看作是一个危害严重的问题，因此有必要对这些区域土壤中的砷浓度做一个细节调查，还有它的化学特性、溶解性，以此来评估砷迁移所带来的潜在危害。 1(6微生物对砷的转移作用 自然生态系统的砷的迁移主要通过微生物新陈代谢在生物地球化学方面作用使砷发生迁移，微生物五价砷还原到更具毒性和迁移性的三价砷是通过解毒作用或者呼吸作用发生的，只有一小部分微生物具有通过呼吸作用把五价砷还原为三价砷。研究表明，微生物参与的把五价砷还原为三价砷的过程比通过使用无机的化学转化作用快许多倍，因此，微生物对于地下土壤中砷的循环起着一个重要的作用。 1(7修复作用 目前有多种可利用性除砷技术，简单有效的如混凝沉淀技术，精细技术如离子交换技术和反渗透技术。除此之外，低成本的修复技术，如稀释，还有在发展中国家对于来自地下水中砷的去除方法，通过使用地质材料作为自然吸附剂除砷已经被认作相对可能的技术，但是，现在迫切的需要研究出一种低成本有效率的除砷技术。 利用植物修复技术来除砷这一观点已经提出了20多年，植物修复技术与以往的砷污染土壤的修复术如掩埋和化学稳定有许多优点，具有成本低、环境污染小的优点。研究表明，一些热带和温带植物种类能够对于无机砷和有机砷很好的忍受和积累。豆科灌木是一种能够在潮湿或者干旱环境中很好生存的植物，研究发现它能够吸附铬和其他金属像铅，它能够把六价铬还原为毒性较小的三价铬，但是目前，还没有发现沙漠的植物能够吸收砷或者其他毒性元素。 1(8目前除砷技术 目前对于砷的研究是十分积极的，包括在反应规模上、砷的形态包括无机砷和有机砷通过各种化学和光谱实验转化评估，还有一种新兴的评估就是砷在微生物和生物之间的循 - - 18 山东建筑大学毕业论文外文文献及译文 环的评估。当前的研究认为饮用水的砷浓度不能高于10ug/L，这也使得供水成本增加，还让人们意识到人类的健康和生态系统联系，刺激了对于除砷技术进一步研究。 考虑到砷的危害性，一个两天的关于砷污染问题的会议召开，下面就是介绍了会议的主题和会后刊发的文件。 2 会议主题 这次特殊的会议是在澳大利亚2005年4月举行的，主题是“砷在环境中的生化特性”，此次的会议的举办作为第八届关于微量元素的生物地球化学特性国际会议的一部分。这次会议的主要主题为: (1)地下水环境中砷的来源和特性 (2)砷在土壤、水体和生物体的迁移和形态过程 (3)在自然环境中砷在地球化学、水文学和生态学的转变方面的对含量的预测 (4)砷的分析技术和形态研究 (5)对于受到砷污染的土壤和地下水的恢复和管理 (6)砷对于农业和供水管理的影响。 除此之外，基于对砷迁移过程基础的理解，这次会议还讨论了各种化学方面和光谱学方面的实验，并且更加重视微生物和植物对于砷循环的重要性，这次会议重要的研究都在这次会议的期刊刊发出来。 3研究文献的综述 研究文献综述由14篇论文和1个短的会议组成，由4部分组成: (1)砷在地下水环境中 (2)砷在农业土壤和冶矿环境中 (3)砷的生物地球化学特性和毒性 (4)受砷污染过的土壤和沉积物的恢复 3(1砷在地下水环境中 这一部分由五篇文章组成，前两篇文章是关于孟加拉国冲击水层中砷地球成因学的发生。第一篇文章是关于对低砷水层区域的研究，这一区域的地下水却含有高浓度的地质成因的砷。这篇文章讨论了沉积物的颜色与地下水氧化反应条件的相关性，文章认为沉积物的颜色可以作为判断砷的高低浓度的相关性。第二篇文章是研究了对于来自孟加拉国的低砷水层沉积物的吸附容量，研究表明，实验室实验和地球化学过程对沉积层处理来自地下水中砷的去除有实质性的但是只是有限的吸附容量。第三篇文章讨论澳大利亚东部沿海岩 - - 19 山东建筑大学毕业论文外文文献及译文 石水层中砷的来源，研究表明砷是由于港口腹地的富含砷的SbS侵蚀作用。河流冲刷作用23 把侵蚀的材料经过一段时间的沉积形成富含砷的沉积层，研究表明，从矿石岩层冲刷形成的任何沉积层都有可能造成砷污染的危险。第四篇文章研究了在孟加拉的12532口输水管井进行的分析现场检测组件和实验室方法的结果通过AAS(黄金标准)做出的比较。结果表明，通过现场检测装置依照孟加拉饮用水50ug/l的标准能够确定输水管井中87%砷形态，依照WHO饮用水10ug/L的标准能够确定管井中91%的砷形态。 这一部分的最后一篇文章研究了一个地方泉水中砷的形态和地下泉水中砷的总浓度，研究表明，泉水样本的总砷中主要是五价的无机砷含量在0.3-1.2ug/L，研究还认为对于地下水中砷浓度的检测需要进步的调查。 3(2砷在农业土壤和冶矿环境中 这一部分的第一篇文章研究了孟加拉国使用砷污染的地下水进行农业灌溉后的土壤中砷的动力学，研究表明与使用低砷地下水(<1ug/L)灌溉的的小麦土壤相比，使用高砷地下水(79-436ug/L)灌溉的土壤中含有大量的砷。还认为，在砷污染过的小麦土壤中，砷浓度是空间性和当时性是十分重要的。研究者发现，土壤中的砷浓度在灌溉期结束之后会剧增，大约有71%的灌溉水中的砷沉积在0-75mm土壤层中。对于研究砷污染的大米农作物产量时，考虑空间性和时间线是十分重要的。 在波兰有许多地方的土壤含有高浓度的砷，原因是由于自然地质化学富含砷，矿石冶炼工业还有加工厂排放物，因此有必要进行细节调查来估计这些地方砷的总浓度，还有化学分馏和潜在的溶解性来评估砷迁移的危害。这一部分的第二篇文章讲述了在土壤和废物材料中，通过改变pH和氧化还原条件下结合砷迁移性的增加评估了砷的含量与环境危害性。本文对兰两个地方的土样进行了研究，这两个地方分别是砷矿场和加工厂，对12个点中取得的26个土样进行了检测，土壤来源包括自然界中的土壤、矿场残渣、尾料和废矿场的土样。结果表明，大多数的土样含有高浓度的砷，浓度范围在100-43500mg/kg。连续的分离技术结果表明在所有土壤中砷的主要种类是在铁的氧化物，但是这一氧化物对于砷的迁移和专性吸附没有多大的作用，除了尾料和经尾料影响过的冲击层土壤外，其他土壤中的迁移性的砷含量很低。 这一部分的最后一篇文章讨论了澳大利亚一个矿场中砷的动力学特性。文章研究了这一区域五个矿场中土壤和沉积物中砷的迁移率和滞留率，研究表明，砷的形态分为可溶性的和固态的，像Al–As, Fe–As, Ca–As的化合物，Fe(OH)与砷的聚合物，有机砷还有3 沉积物中的砷。目前，澳大利亚大体上有两个管理法规来约束矿场废物丢弃到环境中，目 - - 20 山东建筑大学毕业论文外文文献及译文 的减轻砷和重金属对环境的污染。 3(3生物地球化学特性 这一部分包含三篇文章描述了生物地球化学过程对砷和砷毒性的作用。第一篇文章研究了一种新奇的生长于瑞典一矿场的砷还原放线菌，这一矿场的地上水、地下水和沉积物都面临着高浓度砷着污染，尽管存在氧化条件，但是三价砷含有超过总砷的83%，研究发现，一种革兰氏阳性的、兼性厌氧的放线菌能够在水体中把五价砷还原为三价砷。 第二篇文章研究发现一种灌木真菌能够保护植物免于砷污染方面起着重要作用，但是对这种真均的解毒机理研究很少。一种盆栽系统调查了这一真菌的对于植物获取砷和磷的作用，还研究了磷和砷的相互作用。研究表明，这一真菌能够促进植物吸收磷和砷。 第三篇文章研究了长期暴露在砷酸钠的老鼠尿液中砷的甲基化作用和卟啉形态。研究表明，尿液可以对于生物体在患癌症之前有一个预警作用。 3(4受砷污染过的土壤和沉积物的恢复 这一部分包含三篇文章和一个短的会议，这一部分讨论了受砷污染过的土壤、水体和沉积物的恢复过程。第一篇研究了一种自然红土能够作为滞留在水体中三价砷和五价砷的吸附剂，研究表明，这一吸附剂对五价砷的吸附性能强于三价砷。因而，它可以作为低成本高效的吸附剂，尤其对于那些贫穷的发展中国家。 第二篇文章研究了一种沙漠的豆科灌木对于三价砷和五价砷的吸收能力，还有利用它做为砷污染的土壤植物修复的可能性，研究表明，这一植物对于五价砷的吸收能力大于三价砷的吸收能力，因而，豆科灌木可以作为干旱地区污染过的土壤中砷去除的一个很好的选择。 目前关于植物生长在砷污染土壤中对于砷的吸收的研究很少。第三篇文章调查了砷在土壤中的分布，还有林地对于砷的浓度超过50mg/kg的土壤的再生作用，研究表明，爱尔兰这一林地中的植物对于砷吸收很少，效果不好。 这一部分的最后一个内容是一个简短的会议，会议讨论了一种生长在沼泽地区的蕨类植物(沼泽山雀)对于砷的吸收效果，还有把它用作植物修复手段的可能性。研究表明，生长在水体和土壤环境中的沼泽山雀的叶子和根部都能够对砷积累，它体内的砷含量能够达到处理溶液中砷含量浓度(250 mg/L和 500 mg/L)的一百倍，但是它的体内砷的浓度原本就是这么高。研就发现，当砷浓度含量在500 mg/L时，沼泽山雀的植物修复作用效果不好，不是除砷技术的好的选择，因为它自身就是一个砷污染体。 4总结 - - 21 山东建筑大学毕业论文外文文献及译文 水体砷污染给全球范围内带来一个安全问题，以前的人类活动已经释放到环境中大量的砷，并且导致的地下水的污染，通常这些污染的范围很小。世界上许多地方，生物地球化学过程已经使得砷释放到地下水中，某些地方，污染范围很大。砷对于人类的健康危害已经研究过，现在的研究表明，砷对于农业产量也有一个消极的影响，因此砷污染水体的修复问题变得越来越重要，植物修复技术是一种可能的低成本高校的技术，自然地质材料也被研究表明对于水体除砷很有效，要解决这一问题，需要对多个地方做多种研究。 本篇综述热情希望读者能够反应砷问题的各个方面，包括环境领域方面、砷在地下水迁移方面、砷在农业系统中的含量方面、生物地球化学作用方面和水体修复技术方面，通过这些努力，能够改善环境，使全世界人民生活在相对安全的环境中。 - - 22