Abstract
Abstract. We have investigated trifluoroacetic acid (TFA) formation from emissions of HFO-1234yf (CF3CFH2), its dry and wet deposition, and rainwater concentration over India, China, and the Middle East with GEOS-Chem and WRF-Chem models. We estimated the TFA deposition and rainwater concentrations between 2020 and 2040 for four previously published HFO-1234yf emission scenarios to bound the possible levels of TFA. We evaluated the capability of GEOS-Chem to capture the wet deposition process by comparing calculated sulfate in rainwater with observations. Our calculated TFA amounts over the USA, Europe, and China were comparable to those previously reported when normalized to the same emission. A significant proportion of TFA was found to be deposited outside the emission regions. The mean and the extremes of TFA rainwater concentrations calculated for the four emission scenarios from GEOS-Chem and WRF-Chem were orders of magnitude below the no observable effect concentration. The ecological and human health impacts now, and the continued use of HFO-1234yf in India, China, and the Middle East, are estimated to be insignificant based on the current understanding, as summarized by Neale et al. (2021).
Highlights
The use of olefinic hydrofluorocarbons (HFCs) as substitutes for HFC-134a (1,1,1,2-tetrafluoroethane; CF3CFH2) are increasing in both the developed and developing countries (Velders et al, 2009)
Wet deposition is one of the primary removal processes for trifluoroacetic acid (TFA). This deposition depends on precipitation amounts and how well our model captures the wet deposition process, making it crucial to evaluate the models used here to capture these two factors
WRFChem underestimated the precipitation amounts compared to TRMM in the three regions
Summary
The use of olefinic hydrofluorocarbons (HFCs) as substitutes for HFC-134a (1,1,1,2-tetrafluoroethane; CF3CFH2) are increasing in both the developed and developing countries (Velders et al, 2009). The chemical lifetime of HFC-134a (∼ 14 years) is such that it is reasonably well mixed globally upon emission into the atmosphere. Other research (Wallington et al, 1996) shows that hot (vibrationally excited) CF3CFHO formed in the degradation scheme would significantly reduce the TFA yield from HFC-134a. This reduction is not explicitly considered here, but we acknowledge that the noted TFA yields from HFC134a can be viewed as upper limits. The fraction of HFC-134a degraded per year from 1 year’s emission would be small, leading to small TFA in rainwater concentrations at a given location. TFA deposition per year of emission will be higher, depending on the year, and more localized spatially
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