溶解性有机质对芘在土壤中吸附解吸的影响

Effect of dissolved organic matter on the sorption and desorption hehavior of pyrene in soil

从腐解不同阶段的水稻秸秆提取溶解性有机质(DOM),用DAX-8树脂分组的方法分析了其亲疏水性,并研究了提取到的DOM对芘在土壤中吸附-解吸行为的影响.结果表明,随秸秆腐解时间的延长,产生DOM中亲水性组分减少,疏水性组分增多.在本试验所研究的吸附解吸实验条件下,芘在土壤中的吸附解吸均可用线性方程进行描述.加入DOM后,芘的吸附受到显著抑制(p<0.01),并且随腐解时间延长,抑制作用增强;芘在土壤中存在解吸迟滞现象,加入DOM后迟滞现象减弱,促进了芘在土壤中的解吸.随腐解作用的进行,DOM促进芘解吸的作用增强,解吸迟滞系数减小.这是由于随秸秆腐解作用的进行,产生DOM中疏水性组分含量增多,其对芘的增溶作用增强所致.

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.