| With development of urbanization and agriculture, heany metal contamination in the soil becomes increasingly serious.Excesstive amouts of heany metals in the soil can not only produce toxic to soil organisms, but also can harm the health of human through the food chain. Studies have shown that the biotoxicity of heavy metals in the soil related to physical and chemical properties of soil closely, such as organic matter, pH; but the organic matter is the more important factor. Therefore, the study of the relationship between study of soil organic matter and heavy metal toxicity is very important to the protection and governance of heavy metal polluted soil. The paper choose copper and cadmium which is common in the soil polltion, cinnamon soil and dark brown forest soil as the research object. The effects of organic matter on phytotoxity and the fractions of copper and cadmium in soil were studied in cinnamon soil and dark brown forest soil culture experiments. The result shows that:(1) The Cu and Cd toxicity of the barlely is increasing with the concenturation of Cu and Cd in the two soil.In cinnamon soil, when the concentration of copper increased from0mg/kg to3600mg/kg, the relative root length ofbarley was reduced from100%to8%; and when the the concentration of cadmium increased from0mg/kg to120mg/kg, the relative root length of barley was reduced from100%to42.3%. In dark brown forest soil, when the concentration of copper increased from0mg/kg to1200mg/kg, the decreasing amplitude of the the relative root length of barley is67.1%; and when the the concentration of cadmium increased from0mg/kg to200mg/kg, the decreasing amplitude of the the relative root length of barley is78.3%.(2) Under the conditions of the same heavy metal concentration and different organic matter contents, the impact of organic matter was little on Cu and Cd phytotoxity in cinnamon soil. But The Cu and Cd toxicity of the barlely was decreasting with increasing contents of organic matter in dark brown forest soil.(3) In connamon soil, the percentage of exchangeable and weak acid soluble fraction Cu and Cd were increasing with increasing added Cu and Cd, the growth was50%and59.6%; while residual fractions Cu and Cd were decreasing with inceasing added Cu and Cd. The persentage of reducible fraction Cu was first increasing and then decreasing with inceasing added Cu.When the concentration of added Cu was between0mg/kg and600mg/kg, the persentage of reducible fraction Cu increased from20.9%to59.8%, and reduced from59.8%to42.9%when the concentration of added Cu increased from600mg/kg to3600mg/kg. But the persentage of reducible fraction Cd was first incresing and then stable. The persentage of oxidable fraction Cu was decreasing form25.6%to5.6%, while the persentage of oxidable fraction Cd first increasing and then decreasing with inceasing added Cd.(4) In dark brown forest soil, the change trend of exchangeable and weak acid soluble and residual fractions Cu and Cd was as same as that in connamon soil.The change trend of reducible fraction and oxidable fraction CuCd was different between cinnamon soil and dark brown forest soil..(5)Under the conditions of the same added Cu and Cd and different organic matter contents, the persentage of exchangeable and weak acid soluble Cu was decreasing with the increasing organic matter, the persentage of oxidable fraction Cu was increasing with with the increasing organic matter; but the effect of organic matter on the fractions of Cd was not obvious in connamon soil. The change trends of the change trend of exchangeable and weak acid soluble and oxidable fractions Cu and Cd (except exchangeable and weak acid soluble fraction) was as same as that in connamon soil. Cu and Cd phytotoxity had an positvely significant correlation with the amount of copper and cadmium, exchangeable and weak acid soluble fraction Cu and Cd, reducible fraction Cu and Cd in this two soil. |
