Environmental fate of fluorotelomer alcohols and esters in soils

Jinxia Liu, Purdue University

Abstract

The fluorotelomer-based compounds are highly fluorinated organics that are uniquely both hydrophobic and oleophobic, thus widely utilized in industrial and consumer products to change surface properties (e.g. , rendering textile fabrics stain-resistant). These products are suspected to contain or degrade into fluorotelomer alcohols (FTOHs) and subsequently into perfluorocarboxylates (PFCAs) including perfluorooctanoate, which has been globally detected in wildlife, humans and the environment. The high fluorination imparts unique physico-chemical properties that are not well-characterized, and subsequently, their behavior in the environment is not well understood. To shed light on potential sources of perfluorochemical contamination observed globally, this dissertation focused on evaluating the solubility, sorption and biotransformation of four dominant FTOH homologues (4:2 to 10:2 FTOH) and biotransformation of two FTOH-derived surfactants with mono-ester and tri-ester linkages. The solubility and sorption of 4:2 and 6:2 FTOHs were measured adequately in aqueous systems, while the higher homologues required the validation and use of a log-linear cosolvency model. The aqueous solubility of FTOHs and the non-fluorine homologues (n-alkanols) followed a single log-linear correlation with modified McGowan molar volumes. However, 8:2 and 10:2 FTOHs (solids at 25°C) exhibited smaller entropy of melt values than expected for long chain molecules. Sorption increased with increasing soil organic carbon (OC) and perfluorocarbon chain length. The aerobic microbial degradation of 8:2 FTOH was assessed by monitoring metabolites over time using liquid chromatography tandem mass spectrometry and included assessing the effect of carrier solvents (ethanol, octanol and 1,4-dioxane). With octanol (the structural analogue of 8:2 FTOH), transformation was temporarily inhibited until depletion of octanol. Similar results were observed with soil bacteria enriched from soil using sole octanol carbon source. In all cases biodegradation pathways appeared the same. Cleavage of the fluorotelomer stearate mono-ester linkage with release of FTOHs occurred in soils with the subsequent generation of the fluorinated acids typical of 8:2 FTOH biotransformation, whereas the fluorotelomer citrate tri-esters appeared more stable. Novel solvent and soil-dependent abiotic hydrolysis was also observed. This study has contributed to a deeper understanding of organo-fluorine chemistry and confirmed that estimations of global PFCA emissions should include breakdown of at least low molecular weight FTOH-derived compounds.

Degree

Ph.D.

Advisors

Lee, Purdue University.

Subject Area

Environmental science

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