黄泥土不同粒径微团聚体对Cd2+的吸附与解吸研究

对采自太湖地区黄泥土进行了低能量超声波分离,采用平衡吸附法研究了不同粒径微团聚体颗粒对重金属Cd²⁺的吸附和解吸特点.结果表明,不同粒径微团聚体对Cd²⁺的吸附特性均符合Freundlich方程,模拟方程得到的K值介于152～503之间,以粘粒级和粗砂级为最大.微团聚体对Cd²⁺的吸附容量与其中游离氧化铁含量、CEC呈显著正相关.不同微团聚体Cd的解吸特点不同,粘粒级的解吸率仅为8.4%,远远低于其它粒径的微团聚体,这些结果有助于了解田间条件下土壤重金属化学行为和微观尺度的化学过程.

Sorption and Desorption of Cd2+ by Size Fractions of Micro-Aggregates from a Paddy Soil

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 K_d 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.