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

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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 st andards (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

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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 ar e 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

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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

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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

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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

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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

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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

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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 Br?mssen 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

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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

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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

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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 V?sterbotten 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

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protecting plants against As contamination. However, little is known about the direct and indirect involvement of AMF in detoxification