The Research On Transference Rule Of Cadmium In Cd-contaminated Soil In The Seasons

Heavy metals are one of the fatalest contaminants in soil, and Cadmium(Cd) is a chief contaminant of heavy metals, Cd in soil can restrain activity of soil enzymes and growth of plants ,also decline the quality of crops and so on. Cd toxicity research always is a hot point of environmental protection from Japan's Ostealgia Disease.Nowadays some areas contaminated by Cd change to dwelling district.High value of Cd concentration in that areas may be a potential threat to dwellers.Soil contaminated by Cd was sampled from university town of Shenyang western suburb in different seasons. Researched the rule of temporal and spatial variabilities of soil Cd. Results showed that soil Cd mainly concentrated in surface layer(1-20cm),Cd concentrations sharply decreased with depth of soil,but soil Cd was continuously transferring to deep layer(21-50cm) from surface layer. Cd concentrations of surface layer decreased gradually in spring, summer and autumn, but increased a little in winter than that of autumn. Contrarily Cd concentrations of 21-30cm layer increased gradually in spring, summer and autumn, but decreased a little in winter than that of autumn. Cd concentrations of 31-50cm layer ,however, gradually increased in four seasons. The relation between soil Cd and soil water is significant positive correlation.Cd concentration descended and ascended with change of water content.The reasons of transferring of soil Cd may be rainfall washing, effect of soil capillary and plants absorption and so on. Soil Cd was gradually transferring into deep layer from surface layer, Range of Cd contaminated region was gradually expanding in researched area.Potted experiment researched growth of corn under different content of water in soil contaminated by Cd and Cd transfer in soil, during period of corn growing, period of corn tasseling, and period of corn maturating. The result showed that Cd concentrations of different profiles in every samples were seed < soil < stem < root; During period of corn growing, period of corn tasseling, and period of corn maturating, Cd concentrations of soil, root, and stem firstly ascended remarkably, then descended, and gradually stabilized when corn maturating. Increasing water content of soil can increased content of bioavailable Cd, and accelerated plant absorbs Cd.Cd concentration of root is 4-5 times more than that of soil during corn growing period, though the number reduced to only 1.6 times when corn maturating.