Cadmium Sorption and Desorption in Vegetable Garden Soils

The isothermal sorption and desorption of cadmium in three vegetable garden soils in suburb of Hangzhou city were measured.The isothermal sorption of cadmium fitted well with both Langmuir equation and Freundlich equation.Hence,the parameters in the equations,i.e.,maximum sorption ( x m),constant( k ) and their product ( x m× k )-maximum buffering capacity (MBC) from Langmuir equation and another constant ( α ) from Freundlich equation could be used as comprehensive indexes to characterize the potential Cd sorption of the soils.The maximum sorption and maximum buffering capacity of Cd were both follow the order of Huang Song Tu(Fluavio-marine yellow loamy soil)Fen Ni Tu (Aquic silt -loamy soil) Jiang Tu Sha (Fluvio-marine sandy polder soil).The sorption intensity (α)of Cd on Huang Song Tu(Fluvio-marine yellow loamy soil)was the lowest,and that on Fen Ni Tu (Aquic silt -loamy soil) and Jiang Tu Sha (Fluvio-marine sandy polder soil) were similar.The isothermal desorption of Cd was significantly correlated with isothermally absorbed Cd.It is noticeable that part of added Cd was fixed,which represented the Cd fixation capacity of vegetable garden soils.