Abstract

Per- and polyfluoroalkyl substances (PFAS) are a class of anthropogenic compounds that are ubiquitous environmental contaminants. PFAS have been detected worldwide and pose concerns due to their toxicity and resistance to natural degradation. When PFAS enter the soil system, their movement can be slowed or even stopped due to interactions with soil components including clay and organic matter. This study tests the mobility of PFAS with variable functionalization and chain length across soils of varying compositions. A sample of the Mechanicsburg silt loam (29% sand, 64% silt, 7% clay by weight, 2% organic matter) was amended with powdered kaolin and dry powdered peat moss to create two additional soils with 23% clay and 5% organic matter respectively. Powdered activated carbon (PAC) was also tested as a soil amendment, with a soil mixture created containing 5% by weight PAC. Soils were exposed to PFAS-contaminated artificial groundwater until breakthrough of one or multiple compounds was determined by high-performance liquid chromatography triple quadrupole tandem mass spectrometry (HPLC-QQQ-MS/MS). PFAS mobility in fully contaminated soils was measured through comparison of total PFAS concentrations adsorbed to the soil versus mobile PFAS that were measured in situ using passive sampling devices. Findings revealed that PFAS functionalization was the primary factor influencing their adsorption capacity and mobility in soils. Perfluoroalkyl sulfonic acids (PFSAs) were found to have lower adsorption capacities and were overall less mobile than their perfluoroalkyl carboxylic acid (PFCA) counterparts. PFOS demonstrated a much higher adsorption capacity when compared to PFOA (>226 versus 84 µg/kg respectively). Soils amended with kaolinite and dry powdered peat moss were not found to increase the PFAS adsorption capacities or aid in the immobilization of PFAS, and in some cases were found to be counterproductive amendments, reducing adsorption capacity by up to 50%. PAC greatly increased both the adsorption capacity and PFAS immobilization potential of soils when used as an amendment, highlighting its potential for use as a remediation tool for contaminated sites. Heightened mobility of short-chained PFCAs highlighted their importance for environmental contaminant monitoring in groundwaters where they may be more present, even in sites not associated with large-scale contamination. Concerns for PFAS presence in sites thought uncontaminated were corroborated by the analysis of PFAS in the Funk Bottoms wetland (Wayne County, Ohio) where high concentrations of PFAS were detected, emphasizing the need for a better understanding of PFAS in the soil-groundwater system.

Advisor

Edmiston, Paul

Second Advisor

Pollock, Meagen

Department

Chemistry; Geology

Disciplines

Analytical Chemistry | Environmental Chemistry | Environmental Monitoring | Geochemistry | Soil Science

Keywords

PFAS, soil, groundwater, contaminant transport

Publication Date

2024

Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis

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Available for download on Tuesday, January 01, 2075

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