As the major producer and consumer of hydrofluorocarbons (HFCs), China is obligated to phase-down HFCs to mitigate global warming if China ratifies the Kigali Amendment (KA) to the Montreal Protocol. Based on historical HFCs consumption in each sector, here we estimated historical HFCs emissions with a bottom-up method, and projected the consumption baseline and schedule for HFCs phase-down in China under the KA and the corresponding potential for emission reduction. Results showed that China's HFCs consumption and emissions in 2017 were 164,000 t (311 Mt CO2-eq) and 108 Mt CO2-eq, respectively. HFCs consumption baseline was projected to be (724 ± 18) Mt CO2-eq in 2024, and China should take measures to phase-down HFCs by 2029, at the latest, to meet the requirements of the KA. HFCs consumption in 2050 under KA would reach the level of 2012–2013. Cumulative reduced consumption was estimated at 10.8 (10.1–11.6) Gt CO2-eq, and cumulative reduced emissions were estimated at 5.38 (4.90–5.64) Gt CO2-eq by 2050.

The airborne occurrence, isomer profiles, and phase distribution of perfluoroalkyl acids (PFAAs), including perfluoroalkyl carboxylates (PFCAs) and sulfonates (PFSAs), have received little scientific attention to date. Here we collected gaseous and particulate phase (PM2.5) samples in China, between June and November 2013, using alkalized annular denuders and downstream filters toavoid sampling artefacts associated with traditional air sampling. We analysed the concentrations of 18 linear PFAAs and the branched isomers of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS). Concentra- tions of total PFAAs were dominated by PFCAs, with a range of 6.6e610 pg/m3 in the gaseous phase and 2.3e290 pg/m3 in the particulate phase. Concentrations of total PFCAs were higher in summer than winter in both phases. Branched PFOA isomers accounted for 10e22% of total PFOA in the gaseous phase and 13e24% in the particulate phase, which is close to, but slightly lower than, their abundance in the commercial PFOA mixtures manufactured using the electrochemical fluorination (ECF) process. In con- tract, branched PFOS isomers accounted for 26-63% of total PFOS in the gaseous phase and 39-77% in the particulate phase, which is much higher than their abundance in commercial PFOS mixtures manufac- tured by ECF. Most PFCAs had mean particle-associated fractions (F) higher than 0.5. PFHxS had a much higher mean F (0.65) than linear PFOS (0.31). We hypothesise that PFAAs observed in Beijing air may originate from the local water bodies through processes such as aerosol generation, although trans- formation of precursors also contribute.