8-2 Fluorotelomer alcohol aerobic soil biodegradation: Pathways, metabolites, and metabolite yields

Abstract

The biodegradation pathways and metabolite yields of [3- 14C] 8-2 fluorotelomer alcohol [8-2 FTOH, F(CF 2) 7 14CF 2CH 2CH 2OH) in aerobic soils were investigated. Studies were conducted under closed (static) and continuous headspace air flow to assess differences in degradation rate and metabolite concentrations in soil and headspace. Aerobic degradation pathways in soils were in general similar to those in aerobic sludge and bacterial culture. 14C mass balance was achieved in soils incubated for up to 7 months. Up to 35% 14C dosed was irreversibly bound to soils and was only recoverable by soil combustion. The average PFOA yield was approximately 25%. Perfluorohexanoic acid (PFHxA) yield reached approximately 4%. 14CO 2 yield was 6.8% under continuous air flow for 33 days. Three metabolites not previously identified in environmental samples were detected: 3- OH-7-3 acid [F(CF 2) 7CHOHCH 2COOH], 7-2 FT ketone [F(CF 2) 7COCH 3] and 2 H-PFOA [F(CF 2) 6CFHCOOH]. No perfluorononanoic acid (PFNA) was observed. The formation of 2 H-PFOA, PFHxA, and 14CO 2 shows that multiple –CF 2– groups were removed from 8-2 FTOH. 7-3 Acid [F(CF 2) 7CH 2CH 2COOH] reached a yield of 11% at day 7 and did not change thereafter. 7-3 Acid was incubated in aerobic soil and did not degrade to PFOA. 7-2 sFTOH [F(CF 2) 7CH(OH)CH 3], a transient metabolite, was incubated and degraded principally to PFOA. 7-3 Acid may be a unique metabolite from 8-2 FTOH biodegradation. The terminal ratio of PFOA to 7-3 acid ranged between 1.8–2.5 in soils and 0.6–3.2 in activated sludge, sediment, and mixed bacterial culture. This ratio may be useful in evaluating environmental samples to distinguish the potential contribution of 8-2 FTOH biodegradation to PFOA observed versus PFOA originating from other sources.