Influence of Application CaCO_3 on Content of Pb,Cd,Zn Exchangeable in Soil and the Cumulative Distribution of Soybean Plants

The purposes of these experiments were to study the effects of calcium carbonate addition on exchangeable Pb,Cd,Zn contents in the tested soils,to analyze and compare the effects of calcium carbonate addition on biomass of soybean plants and accumulation and distribution of heavy metals in each organs of soybean plants.The primary results of the experiments were as follows:(1) Application of calcium carbonate to contaminated soils reduced contents of exchangeable Pb,Cd,and Zn in the soils,and exchangeable Pb,Cd,and Zn contents in soils decreased obviously with increase in amount of calcium carbonate.The growth conditions of soybean plants were improved greatly,and the absorption of Pb,Cd,Zn from soils onto soybean plants were inhibited effectively due to addition of calcium carbonate,so as to reduce toxicity of soil heavy metals to soybean plants and biomass soybean increase greatly.(2) The optimal amount of calcium carbonate was 2.0 g/kg,which made yields of soybean seeds increased 47.5%,Pb and Cd contents in soybean seeds decreased 73.0% and 53.8%,respectively.Although application of calcium carbonate to the contaminated soils could reduce effectively heavy metal contents in soybean seeds,Pb and Cd contents in soybean seeds were still higher than the national standards in foods of 0.2 mg/kg.