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 soilscalcareous 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 oxidespHsoil organic matter;the direct acting coefficients on DOC desorption rate were in the following order:active iron oxidesclay contentsoil organic matter.The multiple linear regression models could be used for simulation for DOC adsorption and desorption rate.