Uptake and Bioaccumulation of Heavy Metals in Rice Plants as Affect by Water Saving Irrigation

To reveal the impact of Non-Flooding controlled Irrigation (NFI) on the bioavailability and bioaccumulation of metals (Cu, Pb, Cd and Cr) in rice fields, metals concentration in different organs of rice plant growing under both Flooding Irrigation (FI) and NFI were measured. It indicated that metals concentrations in root are always the highest one among all the plant organs and in the spike is the lowest. Compared with FI rice, NFI resulted in higher metal concentrations, bioaccumulation factors and metals uptakes of Cd, Cu and Pb. That might ascribed to the higher solubility and bioavailability of metals and the higher rice root absorbent ability under dryingwetting condition. But for Cr, NFI resulted in lower Cr concentration and uptakes in rice root than FI. It indicated that the Cr bound to the Fe and Mn oxides which were more stable under NFI condition may play a more important role in determining the bioavailability of Cr in paddy soil, but metals bound to organic matter which were more likely released may play a more important role for metals of Cu, Cd and Pb. When the soil is free from metals polluted, NFI can help to improve the availability of Cu as a micronutrient and reduce soil metals accumulation by drawing more metals out of the soil by plant uptakes. If the soil is metal polluted, NFI might result in the higher risk of food metals pollution in short-term. But long-term use of NFI will result in less metals accumulation in soil and finally resulted in reduced crop metals uptakes.