Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 80401, United States.
Department of Agronomy, Purdue University, West Lafayette, Indiana 47907, United States.
Environ Sci Technol. 2022 May 17;56(10):6647-6657. doi: 10.1021/acs.est.2c00654. Epub 2022 May 6.
Hydrothermal alkaline treatment (HALT) can effectively degrade per- and polyfluoroalkyl substances (PFASs) present in aqueous film-forming foam (AFFF). However, information is lacking regarding the treatment of PFASs in actual groundwater and soil from AFFF-impacted sites, especially for complex soil matrices. Given the lack of studies on direct soil treatment for PFAS destruction, we herein applied HALT to two groundwater samples and three soil samples from AFFF-impacted sites and characterized the destruction of PFASs using high-resolution mass spectrometry. Results showed that the 148 PFASs identified in all collected field samples, including 10 cationic, 98 anionic, and 40 zwitterionic PFASs, were mostly degraded to nondetectable levels within 90 min when treated with 5 M NaOH at 350 °C. The near-complete defluorination, as evidenced by fluoride release measurements, confirmed the complete destruction of PFASs. While many structures, including perfluoroalkyl carboxylic acids and polyfluorinated substances, were readily degraded, perfluoroalkyl sulfonates (PFSAs, CF-SO), most notably with short chain lengths ( = 3-5), were more recalcitrant. Rates of PFSA destruction in groundwater samples were similar to those measured in laboratory water solutions, but reactions in soil were slow, presumably due to base-neutralizing properties of the soil. Further, the degradation of PFASs in groundwaters and soils was found to be a function of reaction temperature, NaOH concentration, and reaction time. These findings have important implications for the remediation of AFFF-impacted sites.
水热碱处理（HALT）可以有效降解存在于水系灭火剂（AFFF）中的全氟和多氟烷基物质（PFASs）。然而，关于受 AFFF 影响的地下水和土壤中 PFASs 的处理信息还很缺乏，特别是对于复杂的土壤基质。鉴于缺乏关于 PFAS 破坏的直接土壤处理研究，我们在此应用 HALT 处理了来自 AFFF 影响现场的两个地下水样本和三个土壤样本，并使用高分辨率质谱对 PFASs 的破坏进行了表征。结果表明，在 350°C 下用 5M NaOH 处理时，在所采集的所有现场样本中鉴定出的 148 种 PFASs（包括 10 种阳离子型、98 种阴离子型和 40 种两性离子型 PFASs），在 90 分钟内大部分降解至无法检出的水平。氟化物释放测量证明了几乎完全的脱氟，证实了 PFASs 的完全破坏。虽然许多结构，包括全氟烷基羧酸和多氟化合物，很容易被降解，但全氟烷基磺酸盐（PFSAs，CF-SO），尤其是短链长度（=3-5）的 PFSAs 更难降解。地下水样本中 PFSA 破坏的速率与实验室水溶液中测量的速率相似，但土壤中的反应较慢，可能是由于土壤的中和性质。此外，发现地下水和土壤中 PFASs 的降解是反应温度、NaOH 浓度和反应时间的函数。这些发现对受 AFFF 影响的场地的修复具有重要意义。
