Distribution and Accumulation of Arsenic in Rice Plants Grown in Arsenic-Rich Agricultural Soil

The level of arsenic (As) in rice plants can be affected by the groundwater used for irrigation, type and concentration of As in the soil, and soil properties of paddy fields. In this study, the interrelationships among As levels in various parts of rice plants (Oryza sativa L.) and soils, as well as the As concentrations in soil pore water and groundwater in paddy fields that were irrigated with As-contained groundwater have been investigated at selected locations in an area where there was an endemic Blackfoot disease (BFD) before 1990, in the Chianan Plain of southwestern Taiwan. Results show that the total As concentrations in the groundwater used for irrigation of the sampled paddy fields at Hsuechia, Yichu, and Budai in the Chianan Plain are in the range of 32.9 to 175.7 mu g L-1. Arsenite is present in paddy soils under flooded conditions, as a result of As accumulation from irrigated groundwater, and this As has been taken up into the roots and translocated to the shoots and leaves of the rice plants. The translocation of As from roots to shoots is minor for all the sampled rice plants, keeping the As in the root system and allowing rice plants to survive in high As soil. The lower translocaton factor (<0.05) for the translocation from roots to shoots indicates a lower proportion of As transfer from roots to the parts of the plant aboveground, suggesting that root tissues have a strong capability to hold As.