Reduction of anthropogenic emissions enhanced atmospheric new particle formation: Observational evidence during the Beijing 2022 Winter Olympics

Strictly restrictions on anthropogenic emissions during the Beijing 2022 Winter Olympics Game (WOG) provided a distinctive chance to investigate the behavior of new particle formation events in highly polluted atmosphere under reduced primary emission conditions. In this study, comprehensive observations focus of nucleation events and their gaseous precursor were conducted before and after WOG. Our results showed that nucleation events were enhanced during the WOG and the Winter Paralympics Game (WPG) period, with much higher frequencies of NPF event (52.4%; 38.5%) compared with those before WOG (Pre-WOG: 25.0%), and after WOG (Post-WOG: 27.8%) which mainly caused by lower CS. In addition, the average formation rate (J3) during WOG (6.4 ± 4.1 cm−3·s−1) and WPG (6.1 ± 2.9 cm−3·s−1) was also higher than those in Pre-WOG (5.6 ± 2.9 cm−3·s−1) and Post-WOG (5.7 ± 3.1 cm−3·s−1), while the growth rate (GR) (2.3 ± 1.8 nm·h−1, 2.7 ± 1.4 nm·h−1) was slightly higher compared with Pre-WOG (2.1 ± 1.5 nm·h−1) and Post-WOG (2.2 ± 1.6 nm·h−1). We find that the higher J3 during WOG and WPG would be contributed by the higher amines, considering lower concentrations in sulfuric acid (SA) and ammonia was observed. Further evidence comes from the observed correlations between log J3 and SA was highly consistent with CLOUD experimental results which suggested sulfuric acid nucleation enhanced by amines. Sulfuric acid was found to be contributed over 20% to GR3–7nm, while the contribution from organic compounds increased rapidly when particles grow above 10 nm, especially during the WOG and WPG when atmospheric oxidative capacity was largely enhanced. In addition, ammonium nitrate was also found to play an important role in NPF-initiated haze episodes, characterized by higher nitrate production in late growth stage of NPF event during Post-WOG than that of WPG, suggested control measures on the emissions of NH3 and NO2 would benefit for reducing the PM2.5 pollution caused by the new particle formation and growth events.