【正文】 This has led researchers to conclude that these microorganisms play an important role in As cycling in the subsurface (Ahmann et al., 1997。 Smith et al., 1998). In addition, during manufacturing of Ascontaining pesticides and herbicides, release of waste and Asladen liquids near the manufacturing areas may contaminate soil and water bodies (Mahimairaja et al., 2020). There are several “hot spots” around the world where soils have very high concentrations of As caused by natural geochemical enrichment and longlasting 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., 2020, 2020). 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 Ascontaminated 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, 2020。 Pacyna and Pacyna, 2020). Elevated concentrations of As in soils occur only locally, but in areas of former industrial areas it may cause environmental concern (Nriagu, 1994。 Naidu et al., 2020). Crop quality and the effect of As on crop quality and yield is being a major worldwide concern, particularly for rice which forms the staple for many SouthAsian countries where groundwater is widely used for irrigation (Meharg and Rahman, 2020). 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., 2020). Based on available information on the distribution of As concentration in groundwater (BGS and DPHE, 2020) and the area under shallow tubewell irrigation (BADC, 2020), Saha (2020)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. (2020) revealed reduced yield of a local variety of rice (BR11) irrigated with water having As concentrations in the range of 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., 2020). . 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。 Mandal et al., 2020). In general, MMAIII is more toxic than As(III) and As(V) ( et al., 2020, 2020). 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 buildup in the soil is an active area of research. The fate of As in agricultural soils is often less well studied pared to groundwater, and in general has been studied in the context of As uptake by different plants (Huq et al., 2020, 2020。 Mandal et al., 2020). Studies of As speciation in the urine of exposed humans indicate that the metabolites prise 10–15% inorganic As (iAs) and monomethylarsonic acid (MMAV) and a major proportion (60–80%) of dimethylarsenic acid (DMAV) (Tam et al., 1979。 Kapaj et al., 2020). Arsenic is perhaps the only human carcinogen for which there is adequate evidence ofcarcinogenic risk by both inhalation and ingestion (Centeno et al., 2020。 Khandaker, 2020。 BarragnerBigot, 2020。 Vuki et al., 2020this 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, 2020。 Tandukar et al., 2020), Pakistan (Nickson et al., 2020), the Red River Delta and Mekong Basin of Vietnam and Cambodia (Berg et al., 2020, 2020), 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, 2020。 Bundschuh et al., 2020。 DPHE, 2020。 Mukherjee et al., 2020). 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 amp。 Welch and 2 Stollenwerk, 2020。 Mukherjee et al., 2020). 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., 2020。 Smith et al., 2020, 2020), where the concentrations levels are well above the drinking water standard of 7 μg/L remended by the National Health and Medical Research Council and the Natural Resource Management Ministerial Council of Australia (NHMRC/NRMMC, 2020). In addition, As from anthropogenic sources is also reporte