Adsorption of dissolved organic carbon on paddy soils of subtropical China
溶解性有机碳在红壤水稻土中的吸附及其影响因素

Soil adsorption significantly influences translocation,transformation and bioavailability of dissolved organic carbon(DOC).Studies on DOC adsorption are crucial to elucidate the cycling and transformation of soil organic carbon and assess the risk of contamination in polluted soils.In this study DOC adsorption on paddy soils of subtropical China and its relation to organic matter,clay content and pH were investigated by equilibrium methods.The results showed that DOC adsorption in the tested soils followed Freundlich and Linear adsorption models.Variation of DOC adsorption was observed among different soils,with the following order: Paddy soil with low productivity derived from Quaternary red clay > Paddy soil with low productivity from Tertiary red sandstone> Paddy soil with high productivity from Quaternary red clay > Paddy soil with high productivity from Tertiary red sandstone.The kinetics of DOC adsorption in the soils can be divided into the two stages: fast(first 0.25 h) and slow reactions(after 2-4 h).The First-order equation gave the best fittings of the adsorption of DOC,followed by Elovich equations and Parabolic diffusion equation.Clay and soil organic matter contents significantly influenced DOC adsorption,which increased with the increasing soil clay content,but declined with the increasing organic matter content.