Wang Meichen, Rivenbark Kelly J, Nikkhah Hasan, Beykal Burcu, Phillips Timothy D
Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA.
Interdisciplinary Faculty of Toxicology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA.
Appl Soil Ecol. 2024 Apr;196. doi: 10.1016/j.apsoil.2024.105285. Epub 2024 Feb 1.
Remediation methods for soil contaminated with poly- and perfluoroalkyl substances (PFAS) are needed to prevent their leaching into drinking water sources and to protect living organisms in the surrounding environment. In this study, the efficacy of processed and amended clays and carbons as soil amendments to sequester PFAS and prevent leaching was assessed using PFAS-contaminated soil and validated using sensitive ecotoxicological bioassays. Four different soil matrices including quartz sand, clay loam soil, garden soil, and compost were spiked with 4 PFAS congeners (PFOA, PFOS, GenX, and PFBS) at 0.01-0.2 μg/mL and subjected to a 3-step extraction method to quantify the leachability of PFAS from each matrix. The multistep extraction method showed that PFAS leaching from soil was aligned with the total carbon content in soil, and the recovery was dependent on concentration of the PFAS. To prevent the leaching of PFAS, several sorbents including activated carbon (AC), calcium montmorillonite (CM), acid processed montmorillonite (APM), and organoclays modified with carnitine, choline, and chlorophyll were added to the four soil matrices at 0.5-4 % /w, and PFAS was extracted using the LEAF method. Total PFAS bioavailability was reduced by 58-97 % by all sorbents in a dose-dependent manner, with AC being the most efficient sorbent with a reduction of 73-97 %. The water leachates and soil were tested for toxicity using an aquatic plant () and a soil nematode (), respectively, to validate the reduction in PFAS bioavailability. Growth parameters in both ecotoxicological models showed a dose-dependent reduction in toxicity with value-added growth promotion from the organoclays due to added nutrients. The kinetic studies at varying time intervals and varying pHs simulating acidic rain, fresh water, and brackish water suggested a stable sorption of PFAS on all sorbents that fit the pseudo-second-order for up to 21 days. Contaminated soil with higher than 0.1 μg/mL PFAS may require reapplication of soil amendments every 21 days. Overall, AC showed the highest sorption percentage of total PFAS from studies, while organoclays delivered higher protection in ecotoxicological models (). This study suggests that immobilization with soil amendments can reduce PFAS leachates and their bioavailability to surrounding organisms. A combination of sorbents may facilitate the most effective remediation of complex soil matrices containing mixtures of PFAS and prevent leaching and uptake into plants.
需要采用修复方法来处理受多氟和全氟烷基物质（PFAS）污染的土壤，以防止其渗入饮用水源，并保护周围环境中的生物。在本研究中，使用受PFAS污染的土壤评估了经过处理和改良的粘土及碳作为土壤改良剂螯合PFAS并防止其淋溶的效果，并通过灵敏的生态毒理学生物测定法进行了验证。将四种不同的土壤基质（石英砂、粘壤土、花园土和堆肥）分别添加浓度为0.01 - 0.2μg/mL的4种PFAS同系物（全氟辛酸（PFOA）、全氟辛烷磺酸（PFOS）、GenX和全氟丁烷磺酸（PFBS）），并采用三步萃取法来量化每种基质中PFAS的淋溶性。多步萃取法表明，土壤中PFAS的淋溶与土壤中的总碳含量相关，回收率取决于PFAS的浓度。为防止PFAS淋溶，向四种土壤基质中添加了几种吸附剂，包括活性炭（AC）、钙蒙脱石（CM）、酸处理蒙脱石（APM）以及用肉碱、胆碱和叶绿素改性的有机粘土，添加量为0.5 - 4%（重量）,并采用LEAF法萃取PFAS。所有吸附剂均以剂量依赖的方式使总PFAS生物有效性降低了58 - 97%，其中AC是最有效的吸附剂，降低幅度为73 - 97%。分别使用一种水生植物和一种土壤线虫对水浸出液和土壤进行毒性测试，以验证PFAS生物有效性的降低情况。在这两种生态毒理学模型中，生长参数均显示毒性呈剂量依赖性降低，并且由于添加了养分，有机粘土还具有促进生长的增值作用。在不同时间间隔以及模拟酸雨、淡水和微咸水的不同pH值条件下进行的动力学研究表明，PFAS在所有吸附剂上的吸附作用在长达21天的时间内符合准二级动力学，具有稳定性。PFAS含量高于0.1μg/mL的受污染土壤可能需要每21天重新施用土壤改良剂。总体而言，在各项研究中，AC对总PFAS的吸附百分比最高，而有机粘土在生态毒理学模型中提供了更高的保护作用。本研究表明，通过土壤改良剂固定PFAS可以减少其向周围生物的淋溶及其生物有效性。吸附剂的组合可能有助于最有效地修复含有PFAS混合物的复杂土壤基质，并防止其淋溶和被植物吸收。
