Military bases and airports are often contaminated by per- and polyfluoroalkyl substances (PFAS) due to the repeated use of aqueous film forming foams (AFFFs) from decades of training exercises, equipment testing, and extinguishing of fuel- and solvent-based fires. Pump-and-treat systems combined with sorption processes are common ex situ remediation strategies; however, they can be expensive and may require decades of operation, particularly at sites where long-term diffusion and desorption of contaminants are the primary release processes. Alternatively, in situ chemical oxidation is an effective remediation strategy in which oxidants (e.g., persulfate, hydrogen peroxide) are injected into an aquifer to react with contaminants on site, and is competitive with alternative remediation techniques, such as pump-and-treat and ex situ treatment options. Specifically, heat-activated persulfate oxidation (HAPO) creates highly reactive sulfate radicals that under sufficiently acid conditions can mineralize perfluoroalkyl carboxylic acids (PFCAs) and many of the polyfluoroalkyl substances in AFFF. Sulfate radicals, however, can be scavenged by solutes present in groundwater, reducing the efficiency of PFCA transformation. To assess the application of HAPO, we conducted experiments under conditions typical of source zones where remediation is likely to be employed. We found that repeated treatment of aquifer solids with modest amounts of persulfate (50-300 mM) at low temperature activation (40 °C) could reduce the concentrations of precursors and PFCAs with chain lengths greater than three carbons by over 95%. Following treatment, addition of strong base (i.e., NaOH) was needed to neutralize acidity and convert dissolved metals back into less mobile forms.

中文翻译：

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使用过硫酸盐氧化优化全氟羧酸和多氟烷基物质原位矿化的实际考虑


军事基地和机场经常受到全氟烷基和多氟烷基物质 （PFAS） 的污染，这是由于数十年的训练演习、设备测试以及燃料和溶剂型火灾扑灭过程中重复使用的水性成膜泡沫 （AFFF）。泵送处理系统与吸附工艺相结合是常见的异位修复策略;然而，它们可能很昂贵，并且可能需要数十年的运行，尤其是在污染物的长期扩散和解吸是主要释放过程的场所。或者，原位化学氧化是一种有效的修复策略，其中氧化剂（例如过硫酸盐、过氧化氢）被注入含水层中，与现场的污染物发生反应，并且与其他修复技术（如泵送处理和非原位处理方案）具有竞争力。具体来说，热活化过硫酸盐氧化 （HAPO） 会产生高反应性硫酸根，在足够的酸条件下，这些自由基可以矿化全氟烷基羧酸 （PFCA） 和 AFFF 中的许多多氟烷基物质。然而，硫酸根可以被地下水中的溶质清除，从而降低 PFCA 转化的效率。为了评估 HAPO 的应用，我们在可能采用修复的源区的典型条件下进行了实验。我们发现，在低温活化 （40 °C） 下用适量的过硫酸盐 （50-300 mM） 重复处理含水层固体可以将链长大于三个碳的前体和 PFCA 的浓度降低 95% 以上。处理后，需要添加强碱（即 NaOH）来中和酸性并将溶解的金属转化回流动性较差的形式。