6-2 Fluorotelomer alcohol aerobic biodegradation in soil and mixed bacterial culture

Abstract

The first studies to explore 6-2 fluorotelomer alcohol [6-2 FTOH, F(CF 2) 6CH 2CH 2OH] aerobic biodegradation are described. Biodegradation yields and metabolite concentrations were determined in mixed bacterial culture (90 d) and aerobic soil (180 d). 6-2 FTOH primary degradation half-life was less than 2 d in both. The overall mass balance in mixed bacterial culture (day 90) was ∼60%. At day 90, the molar yield was 6% for 6-2 FTA [F(CF 2) 6CH 2COOH], 23% for 6-2 FTUA [F(CF 2) 5CF CHCOOH], 16% for 5-2 sFTOH [F(CF 2) 5CHOHCH 3], 6% for 5-3 acid [F(CF 2) 5CH 2CH 2COOH], and 5% for PFHxA [F(CF 2) 5COOH]. The overall mass balance in aerobic soil was ∼67% (day 180). At day 180, the major terminal metabolites were PFPeA, [F(CF 2) 4COOH, 30%], PFHxA (8%), PFBA [F(CF 2) 3COOH, 2%], and 5-3 acid (15%). A new metabolite 4-3 acid [F(CF 2) 4CH 2CH 2COOH] accounted for 1%, 6-2 FTOH for 3%, and 5-2 sFTOH for 7%. Based on 8-2 FTOH aerobic biodegradation pathways, PFHxA was expected in greatest yield from 6-2 FTOH degradation. However, PFPeA was observed in greatest yield in soil, suggesting a preference for alternate degradation pathways. Selected metabolites were also studied in aerobic soil. 5-3 Acid degraded to only 4-3 acid with a molar yield of 2.3%. 5-2 sFTOH degraded to PFPeA and PFHxA, and 5-2 FT Ketone [F(CF 2) 5COCH 3] degraded to 5-2 sFTOH, suggesting that 5-2 sFTOH is the direct precursor to PFPeA and PFHxA. Another new metabolite, 5-3 ketone aldehyde [F(CF 2) 5COCH 2CHO] was also identified in mixed bacterial culture. The formation of PFBA, PFPeA, and 4-3 acid indicates that multiple –CF 2– groups in 6-2 FTOH were removed during microbial biodegradation.