| Summary: | Long-chain perfluorinated carboxylic acids (PFCAs, CnF2n+1COOH: n > 6) are persistent and bioaccumulative chemicals with proven adverse effects on human health and the environment. Detection of elevated concentrations of PFCAs in remote locations such as, the Arctic and Great Lakes, prompted a suggestion of the existence of an atmospheric formation gateway for PFCAs from potent precursors. The most discussed precursors for the atmospheric formation of PFCAs are the linear fluorotelomer alcohols (FTOHs, CnF2n+1CH2CH2OH). The latter are widely deployed in various industrial applications, including paints, polymers and electronic materials. The general perception is that FTOHs degrade in the atmosphere to give PCFAs that endure wet deposition by precipitation. It is assumed that the relatively long atmospheric lifetimes of FTOHs (10-20 days) enable long-range transport and widespread dispersion of these compounds. Great deal of research, in last few years, provided insightful information into the atmospheric precursor hypothesis. Based on experimental observations, several mechanisms have been proposed to account for the observed burden fraction of PFCA formed from the atmospheric degradation of FTOHs. Initially, FTOHs are consumed via OH abstraction of H gem to the -CH2OH group. Oxygen addition to the apparent radical site followed by unimolecular elimination of HO2 affords CnF2n+1CH2CHO. Further atmospheric oxidation of CnF2n+1CH2CHO produces CnF2n+1CH2C(O)O2. The reaction of the latter with HO2 produces PFCA. Roles of various species such as NOx, H2O and CH3O2 were also highlighted in alternate mechanisms. To this end, we report in this contribution, an atomic-based insight that encompasses the initial atmospheric decomposition of CF3CF2CH2CH2OH (i.e., n = 2). As the size of the (CF2)n group induces minor influences the atmospheric decomposition behaviour of FTOHs, CF3CF2CH2CH2OH serves as a representative model compound for longer chains of FTOHs.
|
|---|