紫色土可溶性有机碳的吸附-解吸特征

选择代表性的酸性、中性和石灰性紫色土为实验材料,采用平衡吸附和动力学吸附法研究了紫色土对可溶性有机碳(DOC)的吸附-解吸特征,分析了土壤理化性质与DOC吸附量之间的关系.结果表明,紫色土对DOC的吸附容量呈以下顺序:酸性紫色土＞中性紫色土＞石灰性紫色土.石灰性紫色土对DOC的解吸率明显高于酸性、中性紫色土,其迁移淋失问题值得重视.紫色土对DOC的吸附过程包括快速吸附和慢速吸附2个阶段,0～0.5 h内吸附速率最大,随后吸附速率逐渐减小,4～6 h内基本达到吸附平衡.土壤pH值、有机质、粘粒和活性铁铝氧化物含量是影响土壤DOC吸附量与解吸率的重要因素.通径分析表明,土壤理化性质对DOC吸附量的直接作用系数大小顺序为活性铝含量＞土壤pH值＞有机质,对DOC解吸率的直接作用系数大小顺序为活性铁含量＞粘粒＞有机质.多元线性回归模型能较好地预测土壤对DOC的吸附及解吸的变化.

Adsorption and Desorption Characteristics of Dissolved Organic Carbon(DOC) on the Purple Soils

The representative acidic,neutral and calcareous purple soils were collected in the hilly area of the central Sichuan Basin.Adsorption-desorption characteristics of dissolved organic carbon(DOC) by the purple soils were studied with the batch equilibrium technique.There were markedly differences of DOC adsorption between the 3 kinds of purple soils,with the adsorption capacities in the following sequence:acidic purple soils> neutral purple soils>calcareous purple soils.The desorption rate of DOC of calcareous purple soils was higher than that of other purple soils.The DOC adsorption kinetics of the purple soils could be divided into the two stages:fast(first 0.5 h) and slow reactions(after 4~6 h).The pH,clay,active iron and aluminum oxides and soil organic matter contents influenced DOC adsorption-desorption characteristics significantly.The results of path analysis indicated that the direct affecting coefficients of soil physical and chemical factors on DOC adsorption capacities were in the following order:active aluminum oxides>pH>soil organic matter;the direct acting coefficients on DOC desorption rate were in the following order:active iron oxides>clay content>soil organic matter.The multiple linear regression models could be used for simulation for DOC adsorption and desorption rate.