title: Assessment of the atmospheric loss processes initiated by OH radicals and sunlight, and the radiative efficiency for a series of hydrofluoroolefins, CF3(CF2)x=1,3,5CHCH2.
abstract: Hydrofluoroolefins (HFOs) of the type CF3(CF2)x≥0CHCH2, are currently being suggested as substitutes of some hydrofluorocarbons (HFCs). In this work, an assessment of the atmospheric removal of CF3(CF2)x=1,3,5CHCH2, initiated by reaction with hydroxyl (OH) radicals and UV solar radiation is addressed. For that purpose, the rate coefficients for the OH + CF3(CF2)x=1,3,5CHCH2 reaction, kOH(T = 263-358 K), were determined by the pulsed laser photolysis-laser induced fluorescence technique. A slightly negative temperature dependence of kOH was observed, obtaining Ea/R (in K) values of -124 ± 15, -128 ± 6 and -160 ± 10, for CF3CF2CHCH2, CF3(CF2)3CHCH2 and CF3(CF2)5CHCH2, respectively. The estimated atmospheric lifetimes are around 8 days, considering that HFOs are well-mixed in the troposphere. Furthermore, an evaluation of the long-wave and short-wave absorption process of these HFOs have been carried out by determining the UV (191-367 nm) and IR (4000-500 cm(-1)) absorption cross sections at 298 K. Based on the obtained UV absorption cross sections, no photolysis of CF3(CF2)x=1,3,5CHCH2 is expected in the troposphere (λ > 290 nm). These species strongly absorb IR radiation in the atmospheric IR window. Despite the strong absorption in the IR region, the lifetime corrected radiative efficiencies are low (0.033 W m(-2) ppb(-1) for CF3(CF2)3CHCH2 and 0.039 Wm(-2) ppb(-1) for CF3(CF2)5CHCH2). Calculation of GWPs for these species has been performed as a function of the horizon time, providing values higher than unity for a short-period term, decreasing dramatically for longer periods. Therefore, it is concluded that emissions of these species do not affect the radiative forcing of climate, making them suitable replacements of large-GWP HFCs.
authors.affiliation: Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, Avda. Camilo José Cela, s/n. 13071, Ciudad Real, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: González
authors.affiliation: Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, Avda. Camilo José Cela, s/n. 13071, Ciudad Real, Spain; Instituto de Investigación en Combustión y Contaminación Atmosférica. Universidad de Castilla-La Mancha. Camino de Moledores, s/n. 13071, Ciudad Real, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Jiménez
authors.affiliation: Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, Avda. Camilo José Cela, s/n. 13071, Ciudad Real, Spain; Instituto de Investigación en Combustión y Contaminación Atmosférica. Universidad de Castilla-La Mancha. Camino de Moledores, s/n. 13071, Ciudad Real, Spain. Electronic address: Jose.Albaladejo@uclm.es.
authors.forename: José
authors.initials: J
authors.lastname: Albaladejo
mesh_terms: D000475:Alkenes / Q000737:chemistry* / Q000528:radiation effects*; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry* / Q000528:radiation effects*; D017665:Hydroxyl Radical / Q000737:chemistry*; D010782:Photolysis; D013472:Sunlight; D013696:Temperature
chemical_list: D000475:Alkenes; D006845:Hydrocarbons, Fluorinated; D017665:Hydroxyl Radical
keywords: Absorption cross sections; Global warming potential; HFC replacement; Kinetics; Lifetime; Rate coefficients