CONTROL OF ARSENIC TOXICITY IN RICE PLANTS GROWN ON AN ARSENIC-POLLUTED PADDY SOIL

Paddy soils of over 500 hectares had been polluted by arsenic (As) fro m tailings at an abandoned lead-zinc mine at Shaoxing, Zhejiang, China . Several field experiments were conducted to establish measures for r educing As toxicity to rice plants. The results obtained were as follo ws. Fresh Chinese milkvetch (Astragalus sinicus L.) was not supposed t o be used as green manure in arsenic polluted paddy soils. Although li ming (1,500 kg CaO hectare(-1)) could reduce water-soluble As (H2O-As) in the soil, the rice plant grew badly. The treatments of FeCl3 (25 m g Fe kg(-1) soil) and MnO2 (25 mg Mn kg(-1) soil) could markedly lower the H2O-As and arsenite [As(III)] percentage in the soil and make the plant grow better than the control experiment (CK). Without adding an y materials to the soil, wetting and drying (furrowing and draining) i n the paddy soil could increase soil redox potential greatly and lower the H2O-As and As(III) percentage obviously leading to better rice gr owth. In addition, the As contents of roots, flag leaf, grain, and hus ked rice of 11 new cultivars of early rice were determined and correla tion analysis was conducted. Uptake and accumulation of As in differen t parts of cultivars Zhefu-802 and Erjiufeng at the 4 As levels of the paddy soil demonstrated that the As contents in husked rice of both c ultivars exceeded the hygienic standard (0.7 mg As kg(-1)) when they g rew in the paddy soil having total As content of about 70 mg kg(-1) fo r Zhefu-802 and 100 mg kg(-1) for Erjiufeng, respectively.