Projections of emission, fate and impact of HFO-1234yf in China

Hydrofluoroolefins (HFOs) are being used as substitutes for potent greenhouse gases hydrofluorocarbons (HFCs). However, the use and environmental impacts of HFOs are of great concern due to the rapid degradation of HFOs to produce persistent and phytotoxic trifluoroacetic acid (TFA), one of the per- and polyfluoroalkyl substances (PFAS). HFO-1234yf is the most widely used HFO and has the greatest formation potential of TFA. Here, we provided a comprehensive projection of HFO-1234yf emission in China during 2025-2060. GEOS-Chem was applied to simulate the atmospheric processes of HFO-1234yf and to characterize the distribution of the degradation product TFA. A water quality model was further adopted to assess the impact of HFO-1234yf emissions on surface terminal water body TFA concentrations in China. Under the Kigali Amendment to the Montreal Protocol, HFO-1234yf emission in China was estimated to increase from 1.5 to 79.0 kt in 2025-2060 with cumulative emission of 1.7 Mt. The annual deposition flux (dry plus wet) of TFA due to HFO-1234yf emission was expected to grow from 0.02 kg/km²/year in 2025 to 0.9 kg/km²/year in 2060, dominated by wet deposition. After continuous emission of HFO-1234yf from 2025 to 2060, the average concentration of TFA in terminal waters in China was projected to increase by 7.4 μg/L. The results of this study can provide scientific support for evaluating the environmental risks of HFOs uses and help in developing HFCs phase-out pathways for addressing climate change.