DOM及pH对典型PAHs在土壤中迁移影响模拟实验研究

Influences of DOM and pH on PAHs Migrations in Soil Columns

影响多环芳烃(PAHs)在土壤中垂向迁移的因素很多,通过柱实验模拟研究了溶解性有机质(DOM)浓度及pH对多环芳烃在土壤中迁移及转化的影响,以氯离子做示踪剂进行校正,探讨了不同浓度DOM及pH对多环芳烃迁移的影响。结果表明,校正后的多环芳烃迁移速率随着DOM浓度增加呈逐渐增大趋势,与空白柱对照可得低浓度的DOM由于累积吸附与共吸附作用对多环芳烃的迁移起抑制作用,随着DOM浓度增加,抑制作用逐渐减弱,当浓度达到一定程度时,DOM形成表面活性剂胶体束,多环芳烃进入胶体束内部,从而迁移速率加快。当pH为6、8、10时多环芳烃的迁移速率与空白柱相比均较大,且pH为8、10时多环芳烃迁移速率大于pH为6时的迁移速率,由此可见pH会影响多环芳烃迁移速率,其原因为pH的改变会影响DOM所带电荷的电性,当pH升高到中性或碱性时由于空间排斥理论,DOM的迁移会加快,从而影响多环芳烃的迁移速率。

Vertical migrations of polycyclic aromatic hydrocarbons（PAHs） in soils are influenced by many factors. In a simulated experiment, vertical migrations of PAHs in soil columns were investigated at different levels of DOM and pH. Chloride ion （Cl-） was used to correct the migration rates of PAHs. The migration rates of PAHs were influenced by DOM concentrations. At low concentrations, DOM restrained the vertical migrations of PAHs, due to its cumulative adsorption and co-adsorption. At high concentrations, however, DOM formed surfactant colloids, and the PAHs could enter the colloids, leading to increased migrations. The migrations of PAHs in the columns increased with increasing pH values, due to promoted electrostatic exclusion from more charges of DOM from the dissociation at higher pH.