Adsorption Characteristics and Mechanisms of Organochlorine Pesticide DDT on Farmland Soils

摘要

The adsorption behavior and the adsorption mechanism of the persistent organic pollutant DDT existing extensively in soils around the world are the key to solve the DDT-contaminated soils. Hence, in this paper, selective extraction and batch experimental method were used to examine the adsorption of DDT on farmland soils H and S in Northeast China. Simultaneously, the parameters indicating soil properties and composition such as soil particle, organic matter, and minerals, ect. were analyzed. Results show that the shape and the best fitted model of adsorption isotherm of DDT in both soils were L-type and Freundlich model, respectively. Smaller soil particle had greater adsorption capacity to DDT. The effects of organic matter and minerals on the adsorption of DDT were related to the composition and the origin of organic matter and minerals. Both SiO_2 and illite-montmorillorite mixed-layer could hardly adsorb DDT, and the iron oxides could adsorb DDT, while the function of manganese oxides was inhibitory of DDT adsorption. Organic matter had greater adsorption capacity to DDT than iron oxides. The adsorption capacity of the plant residues is the greatest, followed by the aromatic substances from the plant and the products from microbial degradation.