Adsorption-Desorption Behaviors and Environmental Risk Assessment of Lead,Cadmium in Typical Tobacco Growing Soils

Taking red,paddy,yellow and cinnamon soils,which are typical in major tobacco growing areas in China,as experimental material,the Pb and Cd adsorption-desorption behaviors of these soil samples were investigated with linear equilibrium method and the environmental risk of the presence of Pb and Cd in these soils was assessed with retention factors.The results showed that Pb and Cd adsorption differed significantly between the soil samples with highest adsorption capacity of cinnamon soil,followed by yellow soil,tailed by paddy soil and red soil.The Pb and Cd adsorption in tobacco growing soil could be well described by Langmuir and Freundlich equation with the exception of Cd in cinnamon soil.The mean distribution coefficient of Cd and Pb decreased by 14%-34% and 8%-25%,respectively,under a competitive condition,which means that the presence of Pb obviously inhibits Cd adsorption,while the presence of Cd imparts less effects on Pb adsorption;and Pb and Cd adsorption in paddy soil and red soil dropped more sharply.The environmental risk assessment indicated that the environmental risk was multiplied geometrically with the increase of Pb and Cd contents in soils,their presence in paddy soil and red soil was potentially more risky.