The Effects And Regulations Of Heavy Metals Runoff From Soil

This paper emphasized on the rules of runoff loss of heavy metals in different nature and simulation rainfall, planting density, vegetation coverage, fertilizer rate and irrigation amount, based on an outdoor pot experiment with rice and cabbage. Collected the runoff loss water and sediment samples after rainfall, analyzed the conditions of heavy metals (Pb, Zn, Cd, As) loss. The main results were as follow:(1) As rainfall increased, the volume of loss water in rice and cabbage increased. Density and vegetation cover sheltered soil from wash out in rain; The volume of loss water increased with the decrease of coverage.(2) Due to the long time inundation, the texture of rice soil glue serious, there was little sand migrated with water. Cabbage soil pore was bigger than rice soil, water content less, and the ability of sediment migration greater, a lot of sediment in loss water will be washed under the heavy rain. Vegetation cover had some cushioning effect on the rain erosion, the less coverage, the more sediment loss; but at the earlier stage of cabbage planting, the larger planting density of soil produced more loss sediment.(3) The volume of loss water gradually increased and the more loss sediment washed away with the increase of irrigation water depth.(4) Nitrogen could alter the physical and chemical properties of soil environment, and effect the transformation of heavy metals in soil.(5) Rice and cabbage soil, the size of four water-soluble heavy metals are expressed as:Zn> Cd> As> Pb. Because of the complex soil environment, the interaction between elements, the absorption of heavy metals in plants, rainfall and other reasons, the concentration of loss heavy metals in water changes after every rainfall; the amount of heavy metals in loss water were determined by the volume and concentration of loss water.(6) The concentration of heavy metals in loss sediment was much higher than it in loss water. In particular, the concentration of Pb and As in loss water were very low; The water-solubility of Zn and Cd was strong, when the volume of loss water was large, the contribution rate of total amount of heavy metals in loss water was high and over 90%.