Abstract：
Per- and poly-fluoroalkyl substances (PFASs) are contaminants of emerging concern, yet the understanding of factors that control their leaching and release from contaminated soils remains limited. This study aimed to investigate the impact of dissolved organic carbon (DOC) on the release of PFASs-specifically, perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), and perfluorooctanoic acid (PFOA)from soils contaminated by aqueous film forming foam (AFFF). Batch aqueous leaching experiments were conducted on AFFF-contaminated soils under alkaline solution conditions (pH 9.5, 10.5, and 12) as it enhances leaching of both PFAS and DOC. Leaching of PFOS was significantly increased under alkaline conditions. Although the leaching of PFAS generally increased with pH, PFOS appeared to be more retained under the very alkaline pH conditions used in this study. At the same solution pH, leaching of PFOS and DOC was less in Ca(OH)2 than in NaOH. The retention of PFOS under these conditions may be attributable to the shielding of the negative charge of the soil components and colloids (e.g., DOC and clay minerals) in the leachates and/or the screening of negative charges on head groups of PFOS due to the high concentration of divalent cations. Solution chemistry affected desorption of PFOS more than PFHxS and PFOA. The study highlights that the influence of DOC on PFAS leaching and transport can be very complex, and depends on leachate chemistry (e.g., pH and cation type), PFAS chemistry, the magnitude of PFAS contamination and factors that influence the solid:liquid partitioning of organic carbon in soil.
摘要：
全氟烷基和多氟烷基物质(PFASs)是新兴问题的污染物，然而，对控制它们从污染土壤中浸出和释放的因素的理解仍然有限。本研究旨在探讨溶解有机碳(DOC)对PFASs释放的影响,全氟己烷磺酸盐(PFHxS)，全氟辛烷磺酸(PFOS)，和全氟辛酸（PFOA）-来自被水性成膜泡沫（AFFF）污染的土壤-。在碱性溶液条件（pH9.5、10.5和12）下，对AFFF污染的土壤进行了分批水浸试验，因为它增强了PFAS和DOC的浸出。碱性条件下全氟辛烷磺酸的浸出显著增加。尽管PFAS的浸出通常随pH增加而增加，在本研究中使用的非常碱性的pH条件下，全氟辛烷磺酸似乎更容易保留。在相同的溶液pH下，Ca（OH）2中PFOS和DOC的浸出量小于NaOH中的浸出量。在这些条件下全氟辛烷磺酸的保留可能归因于土壤成分和胶体的负电荷的屏蔽(例如，DOC和粘土矿物）在渗滤液中和/或由于高浓度的二价阳离子而筛选全氟辛烷磺酸头基的负电荷。与PFHxS和PFOA相比，溶液化学对PFOS解吸的影响更大。研究表明，DOC对PFAS浸出和运输的影响可能非常复杂，并取决于渗滤液的化学性质(例如，pH和阳离子类型），PFAS化学,PFAS污染的程度和影响土壤有机碳固液分配的因素。
