多环芳烃(PAHs)在砂质土壤中的吸附行为

Adsorption of Polycyclic Aromatic Hydrocarbons(PAHs)in Sand Soils

采用室内试验方法,研究了多环芳烃(PAHs)在砂质土壤中的吸附行为。结果表明,两阶段吸附模型可较好地模拟PAHs在砂土中的动力吸附过程:快速的线性吸附阶段和慢速吸附阶段。慢速吸附阶段可用乘幂方程拟合,幂指数反映了吸附速率的大小。多环芳烃在砂土中的吸附行为不仅与砂土的性质有关(例如有机碳含量),而且受PAHs物化性质(辛醇/水吸附系数、分子连接指数、分子长度、水溶解度)的影响。与低环PAHs相比,高环PAHs较易吸附到砂土中,且吸附量较大,可用土-水吸附系数表示PAHs的吸附行为。

Adsorption of PAHs in sand soils was studied in this investigation.The results showed that two-phase model can be used to describe the sorption dynamic of PAHs in the soils. The first phase was linear sorption and the sorption velocity was rapid, while the adsorption speed of PAHs in the soils may be described by sorption coefficient. The second phase was simulated by power equation and power exponent indicated the sorption speed. The sorption of PAHs was not only affected by soil properties (e.g. TOC content), but also affected by physical and chemical structures (e.g. octane-water partition coefficient, molecularconnectivity index, molecular length, solubility) of the individual PAHs. logKoc value of PAHs calculated by isotherm sorption experiment was proportion to octane-water partition coefficient and molecular connectivity index, while inverse proportion to solubility of PAHs. The capacities of PAHs sorption increased with the increase of octane-water partition coefficient and molecular connectivity index, while decreased with the increase of solubility of PAHs. However, there was no a marked relativity between logKoc values of PAHs and their molecular length. The soil samples with higher TOC contents had stronger sorption capability, and PAHs with biger ring had higher sorption amount and speed in soil compared to low ring PAHs. It has been also discovered that the sorption characters canbe depicted by soil/water partition coefficient.