溶解性有机碳在红壤水稻土中的吸附及其影响因素

吸附作用是影响土壤中溶解性有机碳(DOC)迁移转化及生物有效性的重要反应过程,研究DOC在土壤中的吸附行为,对正确阐明土壤有机碳的循环和转化特征以及进行污染风险评估有重要意义.采用平衡法研究了红壤水稻土对DOC的吸附特征,并分析土壤有机质、粘粒含量及pH值与DOC吸附量之间的关系.结果表明,供试土壤对DOC的吸附等温线符合Freundlich和Linear方程.不同土壤对DOC的吸附能力有明显差异.在相同浓度下,DOC吸附量以第四纪红色粘土发育的低肥力水稻土最大,第三纪红砂岩风化物发育的低肥力水稻土次之,两种高肥力水稻土最小.土壤对DOC的吸附过程分为快、慢两个阶段,0-0.25 h内DOC的吸附速率最大,随着时间的推移,吸附速率渐小,2-4 h后基本达到吸附平衡.描述供试土壤对DOC吸附动力学过程的最优模型为一级扩散方程,其次为Elovich方程和抛物扩散方程.粘粒含量和有机质是影响土壤DOC吸附量的重要因素,随着粘粒含量的增加,有机质含量的降低,DOC的吸附量增大.

Adsorption of dissolved organic carbon on paddy soils of subtropical China

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.