土壤对全氟化合物的吸附作用

Sorption of perfluoroalkyl substances on soils

全氟化合物（Perfluoroalkyl substances,PFASs）是一类受到全世界关注的新型污染物,有关其环境行为的研究报道很多,但目前有关PFASs吸附的研究多是针对沉积物或碳质材料,对于其在土壤上的吸附研究较少。因此,本文研究了3种不同性质的土壤对6种PFASs（全氟辛酸、全氟辛烷磺酸、全氟壬酸、全氟癸酸、全氟十一酸和全氟十二酸）的吸附特征。结果表明,PFASs在土壤中吸附1h就达到平衡。6种PFASs均符合Freundlich吸附等温式,土壤-水分配系数随碳氟链增加而增加,且PFASs的分配系数（lgKd）与其辛醇-水分配系数（lgKow）呈显著正相关（p〈0.01）。PFASs在土壤上的吸附量随土壤有机碳含量和阳离子交换量的增加而增加,6种PFASs的土壤有机碳标化分配系数范围为102.26~105.07 L/kg。除疏水作用外,氢键作用和静电作用也是PFASs在土壤上吸附的重要机制。

Perfluoroalkyl substances（PFASs）,one kind of emerging contaminants,have attracted worldwide attentions,and there are many research reports concerning their environmental behaviors.For the sorption of PFASs,most researches were focusing on the sorption of PFASs on sediment or carbonaceous materials;less work was conducted to study their sorption on soils.Therefore,the sorption of six kinds of PFASs on three soil samples was studied,which included perfluorooctanoic acid（PFOA）,perfiuorooctane sulfonate（PFOS）,perfiuorononanoic acid（PFNA）,perfluorodecanoic acid（PFDA）,perfluoroundecanoic acid（PFUdA）,and perfiuorododecanoic acid（PFDoA）.The results indicate that the sorption equilibrium can be reached within 1h,and the sorption of all tested PFASs fits the Freundlich sorption isotherms very well.The distribution coefficients（Kd）of PFASs between soil and water increase with fluorocarbon chain length,and the distribution coefficients（lgKd）are significantly positively correlated with octanol-water partition coefficients（lgKow）（p0.01）.The sorption capacity of PFASs increases with organic carbon content and cation exchange capacity of the soil samples,and the organic carbon normalized distribution coefficients（Koc）of the six PFASs are in the range of 102.26-105.07 L/kg.In addition to hydrophobic interaction,the hydrogen bond and electrostatic interaction are also important mechanisms for the sorption of PFASs on soils.