Bosen Jin

Date of Award

January 2019

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

First Advisor

Feng Xiao

Abstract

Per- and polyfluoroalkyl substances (PFASs) are man-made chemicals, widely used in both industries and daily lives, such as in non-stick cookware, waterproof clothing, and painting materials. Researchers have investigated PFASs for about two decades, but most of the studies focus on perfluoroalkyl substances with very limited information available on polyfluoroalkyl substances. In this research, we investigated the sorption/desorption mechanisms perfluorooctanoic acid (PFOA) and its two cationic and zwitterionic precursor compounds, perfluorooctanesulfonamido ammonium salt (PFOSAmS) and perfluorooctaneamido betaine (PFOAB) in a group of soil. We also studied the bioaccumulation and bioconcentration of these chemicals along with perfluorooctane sulfonate (PFOS) and its cationic and zwitterionic precursor compounds, perfluorooctanesulfonamido ammonium salt (PFOSAmS) and perfluorooctanesulfonamido betaine (PFOSB), in earthworm (Lumbricus terrestris).

Chapter 2 of this thesis presents the sorption and desorption results of PFOA, PFOAB, and PFOAAmS in five soils. The Freundlich model was fitted to the sorption and desorption data. The value of the distribution coefficient (Kd) was computed and used to compare the adsorption and desorption of different PFAS compounds. The result showed that Kd values of PFOAB and PFOAAmS were much higher than PFOA, with the ranked order of PFOAAmS > PFOAB > PFOA. Soil properties, especially including the soil organic matter, the cation exchange capacity, and the BET surface area, were found to affect the adsorption of these chemicals. The sorption-desorption hysteresis of the zwitterionic PFAS (PFOAB) was found in soils with a relatively low soil organic matter. The desorption hysteresis index was calculated and employed to assess the degree of hysteresis. The sorption study could help to understand and predict the fate and transport of cationic and zwitterionic poly-PFASs in the soil environment.

Chapter 3 presents the bioaccumulation and biotransformation results of all the six PFAS compounds in earthworm. Earthworms were exposed to a PFAS in a loamy soil for up to 28 days and in water for up to 21 days. The bioaccumulation factors were calculated, and the bioaccumulation factor (BAF) of PFOS was observed the highest one in all the experiments. The order of BAF values was PFOAB > PFOSB > PFOSAmS > PFOAAmS in the first bioaccumulation experiment. The results also demonstrate the generation of PFOA and PFOS from their cationic and zwitterionic precursor compounds in earthworm.

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