Understanding the nonaqueous partitioning of per- and poly-fluoroalkyl substances (PFAS)

Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants that have been extensively used as firefighting agents and released to the environment, accumulating in waters, soils, and the atmosphere. PFAS are known to bioaccumulate, leading to adverse health outcomes. Therefore, understanding the PFAS fate, including their environmental distribution, bioaccumulation in biota, and treatment process, is of particular interest. Soil acts as a reservoir of PFAS in the environment, serving as a secondary contaminant source for the vadose zone, surface water, groundwater, and biota. PFAS leaching into groundwater and/or uptake by plants cause potential contamination of drinking water and food chain, posing environment and human health risks. Given this, the first part of the thesis investigated the extent and distribution of PFAS soil concentrations at a global scale and assessed PFAS levels against regulatory standards. To gain insight into the origins of unknown PFAS in soil, a multi-class machine learning was used, suggesting associations with aqueous film-forming foam (AFFF), landfills, and wastewater treatment plants (WWTP). The limited PFAS treatment technologies in WWTPs contribute to high levels of PFAS in water effluent and biosolids, leading to the re-spreading of contamination. PFAS retention in biosolids has been found to be strongly correlated to protein content. Additionally, further investigations have found that PFAS bioaccumulation is primarily attributed to binding to specific proteins. Salts strongly impact PFAS and protein behaviours in the environment and biota, but salt impact on PFAS/protein interaction has not been assessed. The impact of salt on anionic PFAS and bovine serum albumin (BSA) interactions were investigated in the laboratory. PFAS/BSA binding affinity is a function of PFAS chain length and headgroup but also salt composition and ionic strength. A model was developed to predict binding affinity between PFAS and protein at a range of salt valency and concentration conditions. This model can be used to predict the environmental fate of PFAS as well as in PFAS toxicity predictions. To mitigate PFAS risks, a potential PFAS removal technique using ion exchange resin received attention. However, the natural or recycled water environments are complex and the water matrix components, such as inorganic ions and organic matter, influence the removal efficiency of ion exchange resin. Given this, the last part of the thesis assessed the removal affinity of PFAS using magnetic ion exchange resin (MIEX) under varying water matrix conditions. A predictive model was developed to simulate removal efficiency as environmental compositions vary, allowing exploration of adsorption across a range of background compositions (e.g., salts) and predicting the removal of other unmeasured PFAS in conjunction with a group contribution model. This thesis provides an improved understanding of PFAS fate, investigating their distribution in the environment (soil), bioaccumulation in the biota (protein association), and treatment (removal using MIEX). The knowledge gained from this work offer valuable contribution to understanding PFAS behaviour and informing regulatory and remediation efforts.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2025

Author dc:creator

• Gao, Yi

• PFAS

Statement dc:rights

• embargoed access
• CC BY 4.0

Licence

• http://purl.org/coar/access_right/c_f1cf
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

en

Identifier

https://doi.org/10.26190/unsworks/31112

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/104840