Comparing the Leaching Behavior of Per- and Polyfluoroalkyl Substances from Contaminated Soils Using Static and Column Leaching Tests

Abstract

Soil contaminated with aqueous film-forming foams (AFFFs) containing per- and polyfluoroalkyl substances (PFASs) at firefighting training sites has become a major concern worldwide. To date, most studies have focused on assessing soil–water partitioning behavior of PFASs and the key factors that can affect their sorption, whereas PFASs leaching from contaminated soils have not yet been widely investigated. This study evaluated the leaching and desorption of a wide range of PFASs from twelve contaminated soils using the Australian Standard Leaching Procedure (ASLP), the U.S. EPA Multiple Extraction Procedure (MEP), and Leaching Environmental Assessment Framework (LEAF). All three leaching tests provided a similar assessment of PFAS leaching behavior. Leaching of PFASs from soils was related to C-chain lengths and their functional head groups. While short-chain (CF2 ≤ 6) PFASs were easily desorbed and leached, long-chain PFASs were more difficult to desorb. PFASs with a carboxylate head group were leached more readily and to a greater extent than those with a sulfonate or sulfonamide head group. Leaching of long-chain PFASs was pH-dependent where leaching increased at high pH, while leaching of short-chain PFASs was less sensitive to pH. Comparing different leaching tests showed that the results using the alkaline ASLP were similar to the cumulative MEP data and the former might be more practical for routine use than the MEP. No single soil property was adequately able to describe PFAS leaching from the soils. Overall, the PFAS chemical structure appeared to have a greater effect on PFAS leaching from soil than soil physicochemical properties.

Leaching Potential of Per- and Polyfluoroalkyl Substances from Source Zones with Historic Contamination of Aqueous Film Forming Foam - a Surfactant Mixture Problem

“…The same trend is observed for other long-chain PFAS with relatively low water solubilities like 8:2 FTS, PFNA (only in sample D) and PFDeA, although a much lower eluate concentration. Similar observations have recently been reported by Maizel et al (2021) and Kabiri et al (2022). One hypothesis put forward is kinetic constrains that might explain that equilibrium is not attained for PFOS and other PFAS with low aqueous solubility.…”

Per- and Poly-Fluoroalkyl Substances in Runoff and Leaching from AFFF-Contaminated Soils: a Rainfall Simulation Study

“…The sums of PFAS concentrations varied by orders of magnitude across the soils from 2.9 × 10 4 μg/kg (soil A) to 2.2 × 10 3 μg/kg (soil A-W) and 1.3 × 10 2 μg/kg (soil B). The soil washing treatment clearly removed a large part of the PFAS load in soil A, while the lower concentration observed in soil B may be due to the site’s different AFFF application history and likely enhanced desorption and leaching under field conditions due to a coarser and sandier soil texture. , …”

“…In contrast to the diffuse nature of many PFAS inputs, the repeated use of AFFF at fire training areas (FTAs) results in the accumulation of highly localized soil contamination, with concentrations ranging from μg/kg to hundreds of mg/kg total PFAS load. ,− The specific makeup of this PFAS load is complex and varied due to the application of proprietary formulations and in situ transformations in the years and decades post application. Affected soils have been shown to become long-term point sources for later PFAS transport to water bodies . The severity of the environmental risk posed by such pools is mediated by the extent of PFASs leaching through soils and whether this ultimately leads to delivery of PFASs to groundwater and thereafter to surface water. , However, an additional mechanism for the contamination of surface waters is the transport of PFASs from soils by water or sediment due to runoff.…”

“…Affected soils have been shown to become long-term point sources for later PFAS transport to water bodies. 7 The severity of the environmental risk posed by such pools is mediated by the extent of PFASs leaching through soils and whether this ultimately leads to delivery of PFASs to groundwater and thereafter to surface water. 9,10 However, an additional mechanism for the contamination of surface waters is the transport of PFASs from soils by water or sediment due to runoff.…”

Evaluation of the Transformation and Leaching Behavior of Two Polyfluoroalkyl Phosphate Diesters in a Field Lysimeter Study

“…Although the concentration of PFOA decreased slowly after reaching the maximum, 141 μg/L PFOA could still be detected in the last water sample of the first year of the experiment. This can be explained by the low water solubility of PFOA and high retardation in the soil compared to shorter chain PFCAs, which results in a reduced ability to be washed out with the leachate. , …”