Climate Change

Biography

Biography: Elena Jimenez Martinez

Abstract

The phase-out of the consumption and production of (stratospheric) ozone-depleting chlorofluorocarbons (CFCs) was completed in 2010, while the scheduled phase-out of most hydrochlorofluorocarbons (HCFCs) is expected by 2030.During the gradual disappearance of HCFCsover the coming decades, hydrofluorocarbons (HFCs) were proposed as long-term replacements in several industrial applications. Despite HFCs are non-depleting ozone substances,most of themare potent greenhouse gases (GHGs) that affect the radiative forcing of climate change. Their strong IR absorption in the atmospheric window and their long atmospheric lifetime result in high global warming potentials (GWPs). To decrease climate forcing,the emissions of high-GWP HFCs have to be reduced and replaced by substances that have low impact on climate. Among these, hydrofluoroolefins (HFOs) and perfluorinated compounds (PFCs) are expected to be good alternatives to HFCs. For instance, CF₃(CF₂)₂CH=CH₂ (HFO‑1447fz) is currently being considered as a substitute of HCFC-141b as expansion agent in polyurethane foams. Or CF₃CH=CH₂ (HFO-1243zf) could replace CF₃CH₂F (HFC-134a) in air-conditioning units.To assess the environmental impact of the potential widespread use of these potential substitutes, an evaluation of the atmospheric chemistry is needed. Degradation of pollutants in the troposphere is usually initiated by OH radicals(the main diurnal oxidant) and, under certain circumstances,by Cl atoms. In our group, the rate coefficients for the OH and Cl reactions with some HFOs and PFCs have been determined under tropospheric conditions of temperature and pressure. Identification of secondary gaseous products and organic aerosols was alsocarried out simulating a clean and polluted atmosphere.The IR spectra of these species were recorded in order to calculate their radiative efficiency. All these resultsallow the estimation of the atmospheric lifetime, GWP and the photochemical ozone creation potential of the HFC substitute. Therefore,we can predict the impact of future emissions on air quality and global warming.