土壤中黑碳对农药敌草隆的吸附-解吸迟滞行为研究

采用批处理振荡法和连续稀释法分别测定了敌草隆在人工添加黑碳土壤和自然形成的不同有机质和黑碳含量的土壤中的吸附一解吸行为。吸附结果表明，人工添加黑碳的土壤对敌草隆的吸附强度和吸附容量以及吸附等温线的非线性均随土壤黑碳添加浓度的增加而逐步增大；自然土壤的吸附容量和吸附强度随土壤总有机质含量增加而增加，但吸附等温线的非线性则与土壤中黑碳对有机质的相对含量有关，黑碳比例越高，等温线非线性越大。解吸实验结果表明，无论是人工添加黑碳的土壤还是自然土壤，对敌草隆的解吸迟滞作用均随土壤黑碳含量增高而愈明显。

HYSTERESIS EFFECT OF CHARCOAL ON SORPTION AND DESORPTION OF DIURON BY SOILS

Charcoal derived from incomplete combustion of vegetation is ubiquitous and potentially effective for sequestration of environmental contaminants.To demonstrate effects of this type of charcoal on sorption and desorption of pesticides in soil,synthetic charcoal from burning of red gum chips was mixed into soils at different rates,sorption and desorption behavior of diuron in the charcoal-amended soils were determined by means of batch equilibrium and consecutive dilution techniques,respectively.For comparison,sorption and desorption of diuron in three natural soils with known contents of organic carbon and charcoalwere also measured.The sorption and desorption isotherms were fitted linearly with the Freundlich equation,and the ratio of sorption Freundlich exponent coefficient(N) and that of desorption(Nf) was used to indicate degree of sorption/desorption hystersis.Results of the sorption determination show the sorption capacity of the soil newly amended with charcoal increased with the rate of charcoal amended.The Freundlich sorption coefficient K increased from 4.08 to 500,while the other Freundlich coefficient(N) that shows the non-linearity of sorption isotherm decreased from 0.83 to 0.16,when the content of charcoal in soil increased from 0% to 1.0%.The diuron sorption capacity of natural soils was related to the content of organic carbon,while the isotherm non-linearity was closely related with the relative content of organic carbon and charcoal.The higher the proportion of charcoal in total organic carbon,the higher the isotherm non-linearity.Results of the desorption experiment in soils newly amended with charcoal show that the desorption hystersis index H increased rapidly in value from 1.14 to 14.92 when the content of charcoal increased from 0% to 1.0% in the soil,and H values of natural soils SS7,SS8 and SS6 were 2.49,1.61 and 1.42,respectively,when the content of charcoal was 2.145%,0.819%,and<0.07%,respectively.The results indicated that the hysteresis effect of charcoal on desorption of diuron seemed to be closely correlated with the content of charcoal in the soils.