CDM Smith, 110 Fieldcrest Avenue, #8, 6(th) Floor, Edison, NJ 08837, USA.
CDM Smith, 14432 SE Eastgate Way, # 100, Bellevue, WA 98007, USA.
J Contam Hydrol. 2024 May;264:104359. doi: 10.1016/j.jconhyd.2024.104359. Epub 2024 Apr 28.
Poly- and perfluoroalkyl substance (PFAS) leaching from unsaturated soils impacted with aqueous film-forming foams (AFFFs) is an environmental challenge that remains difficult to measure and predict. Complicating measurements and predictions of this process is a lack of understanding between the PFAS concentrations measured in a collected environmental unsaturated soil sample, and the PFAS concentrations measured in the corresponding porewater using field-deployed lysimeters. The applicability of bench-scale batch testing to assess this relationship also remains uncertain. In this study, field-deployed porous cup suction lysimeters were used to measure PFAS porewater concentrations in unsaturated soils at 5 AFFF-impacted sites. Field-measured PFAS porewater concentrations were compared to those measured in porewater extracted in the laboratory from collected unsaturated soil cores, and from PFAS concentrations measured in the laboratory using batch soil slurries. Results showed that, despite several years since the last AFFF release at most of the test sites, precursors were abundant in 3 out of the 5 sites. Comparison of field lysimeter results to laboratory testing suggested that the local equilibrium assumption was valid for at least 3 of the sites and conditions of this study. Surprisingly, PFAS accumulation at the air-water interface was orders of magnitude less than expected at two of the test sites, suggesting potential gaps in the understanding of PFAS accumulation at the air-water interface at AFFF-impacted sites. Finally, results herein suggest that bench-scale testing on unsaturated soils can in some cases be used to inform on PFAS in situ porewater concentrations.
多氟和全氟烷基物质（PFAS）从受水成膜泡沫（AFFFs）影响的不饱和土壤中浸出是一个环境挑战，仍然难以测量和预测。使该过程的测量和预测变得复杂的是，在收集的环境不饱和土壤样品中测量的 PFAS 浓度与使用现场部署的渗流计测量的相应孔隙水中的 PFAS 浓度之间缺乏理解。用于评估这种关系的台式批量测试的适用性也仍然不确定。在这项研究中，使用现场部署的多孔杯抽吸渗流计测量了 5 个 AFFF 污染地点不饱和土壤中的 PFAS 孔隙水浓度。将现场测量的 PFAS 孔隙水浓度与从收集的不饱和土壤芯中实验室提取的孔隙水以及使用批量土壤泥浆在实验室中测量的 PFAS 浓度进行了比较。结果表明，尽管大多数测试地点在过去几年中都没有发生最后一次 AFFF 释放，但在 5 个地点中的 3 个地点中仍存在大量前体。现场渗流计结果与实验室测试的比较表明，本研究条件下，至少有 3 个地点的局部平衡假设是有效的。令人惊讶的是，在两个测试地点，空气-水界面处的 PFAS 积累量比预期的要少几个数量级，这表明在 AFFF 污染地点空气-水界面处的 PFAS 积累的理解可能存在差距。最后，本文的结果表明，在某些情况下，在不饱和土壤上进行的台式测试可以用于告知原位孔隙水中的 PFAS 浓度。
