Effect of dissolved organic matter on the sorption and desorption hehavior of pyrene in soil
溶解性有机质对芘在土壤中吸附解吸的影响

In this study, dissolved organic matter (DOM) was extracted from rice straw at different decay stages. DAX-8 resins were used to fractionate bulk DOM into hydrophilic and hydrophobic subfractions. The sorption and desorption behaviors of pyrene in soil in the presence of bulk DOM samples was then investigated. The results showed that as straw decay proceeded, the content of the hydrophilic subfractions decreased, whereas the content of the hydrophobic subfractions increased. Under the conditions of this study, the sorption and desorption isotherms can be modeled with a linear equation. In the presence of DOM, the sorption was impeded while the desorption was enhanced significantly (p<0.01). Moreover, the sorption was impeded to a greater degree in the presence of DOM samples extracted from rice straw at later decay stages. The desorption hysteresis was observed during the desorption course and the hysteresis index (HI) values decreased in the presence of DOM. The HI decreased with straw decay time, which was due to the increased hydrophobic subfractions. As straw decay proceeded, more hydrophobic subfractions were produced, thus increasing the binding affinity of pyrene to DOM, so that the solubility of pyrene was enhanced and the sorption was impeded.