title: Aerobic biodegradation of toluene-2,4-di(8:2 fluorotelomer urethane) and hexamethylene-1,6-di(8:2 fluorotelomer urethane) monomers in soils.
abstract: Aerobic soil biodegradation of toluene-2,4-di(8:2 fluorotelomer urethane) (FTU) and hexamethylene-1,6-di(8:2 fluorotelomer urethane) (HMU) in a forest soil and FTU in an agricultural silty clay loam soil was monitored for up to 6 months. Fluorotelomer alcohols were measured in headspace and parent monomers and all metabolites in soil extracts. Negligible degradation of FTU biodegradation occurred in the agricultural soil with 94 ± 15% recovered at day 180. However, in the forest soil, both FTU and HMU degradation was evident with significant losses of 24% (117 d) and 27% (180 day), respectively, and concomitant increases in the terminal metabolite, perfluorooctanoic acid (PFOA) concentrations were well above what could result from residual 8:2 FTOH. Kinetic modeling estimated half-lives for FTU (aromatic backbone) and HMU (aliphatic backbone) in the forest soil to be 3-5 months and 15.9-22.2 months, respectively. The addition of a structurally similar non-fluorinated FTU analog, toluene-2,4-dicarbamic acid diethyl ester (TDAEE) enhanced production of terminal end products from 8:2 FTOH degradation. However, there was no clear evidence that TDAEE enhanced cleavage of the urethane bond, thus TDAEE appeared to just serve as an additional carbon source. TDAEE's half-life was ∼ one week. A second addition of TDAEE appeared to retard subsequent degradation of FTU exemplifying the microbial dynamics and diversity impacting degradation of polyfluoroalkyl substances. Enhanced degradation of HMU was observed upon re-aeration indicating oxygen may have been limiting during some periods although degradation of intermediate metabolites to terminal metabolites was still occurring, albeit at slower rates.
authors.affiliation: Department of Agronomy, Purdue University, West Lafayette, IN 47907-2054, USA.
authors.forename: Kavitha
authors.initials: K
authors.lastname: Dasu
authors.affiliation: Department of Agronomy, Purdue University, West Lafayette, IN 47907-2054, USA. Electronic address: lslee@purdue.edu.
authors.forename: Linda S
authors.initials: LS
authors.lastname: Lee
mesh_terms: D000332:Aerobiosis; D001673:Biodegradation, Environmental; D065928:Forests; D006845:Hydrocarbons, Fluorinated / Q000378:metabolism*; D007196:Indiana; D012989:Soil Pollutants / Q000378:metabolism*; D013997:Time Factors; D014050:Toluene / Q000737:chemistry*
chemical_list: D006845:Hydrocarbons, Fluorinated; D012989:Soil Pollutants; D014050:Toluene
keywords: Biotransformation; Fluorotelomer urethane monomers; PFOA; Perfluoroalkyl substances; Urethane cleavage