1. Introduction
Inorganic arsenic (As) is identified as a non-threshold, class 1 human carcinogen, and the intake of As through rice consumption may lead to serious health effects such as bladder and skin cancers [1] and [2]. The sources of As in rice paddy fields include natural (biogeochemical process) and anthropogenic (As-containing irrigation water, metal mining activity, arsenical pesticides and fertilizer applications) pathways [3] and [4]. Rice is the dietary staple for about half of the world’s population and unfortunately, rice consumption has been the main arsenic exposure route in recent years [1] and [5]. This is due to the high bioavailability and mobility of As in flooding conditions, enhancing the uptake and accumulation of As by rice plants [6]. The concentration of As accumulated in rice grains is approximately 10-fold higher than other cereal crops [5] and [7]. Meharg and Rahman [8] found that the concentrations of As in rice grains grown in As-contaminated soils in certain parts of Bangladesh to be up to 1.8 mg kg−1, resulting in serious As related risks to the local residents. Moreover, paddy rice grown in As-contaminated soils result in As phytotoxicity (inhibition of ATP formation and oxidative stress) which causes lower grain yields [9] and [10].
In pore water found in paddy soil, the concentration and speciation