Sorption and Desorption of Cd2+ by Size Fractions of Micro-Aggregates from a Paddy Soil
黄泥土不同粒径微团聚体对Cd2+的吸附与解吸研究

Size fractions of micro-aggregates were separated from undisturbed soil samples from a paddy soil in Taihu Lake region,(China.) The sorption and desorption of Cd2+ by the particle separates were studied by using equilibrium adsorption method.Adsorption of Cd2+ by different size fractions of the micro-aggregates fitted well the Freundlich isotherm,as being well reported for the bulk soil samples.However,much lower K values(between 152 to 503) were obtained than those reported for the bulk sample.The size fractions of micro-aggregates differed in K and Kd values, being high for the coarser fraction and the clay fraction.When desorped under 0.01mol·L-1 CaCl2,only 8.4% of adsorbed Cd was removed from the clay size fraction,indicating the clay fraction has the most strong capacity for Cd adsorption.The adsorption capacity of the size fractions was dependent of the contents of oxyhydrates,SOM,and correlated well to CEC of the fractions.The findings here may be helpful for understanding the micro-scale soil process of heavy metal mobility in field conditions.