Comparison of new particle formation events in urban, agricultural, and arctic environments

Abstract

New particle formation (NPF) significantly contributes to the number-based aerosol population in the ambient atmosphere, thereby affecting cloud formation and human health. We compared NPF characteristics, including the occurrence frequency, occurrence criteria, particle formation rate (J), and growth rate (GR) obtained from continuous measurements of the number–size distribution of particles and various gases, among different atmospheric environments (urban, agricultural (livestock and cropland), and Arctic sites). The highest NPF occurrence frequency (55%) was observed at agricultural (livestock) site (vs. urban, 45%; agricultural (cropland), 26%; Arctic, 24%). Despite the increased evaporation rate of nucleating clusters in summer, the NH3-rich environment (79.6 ppb) of pig and chicken farms promoted NPF. The NPF frequency at the Arctic showed a distinct seasonal pattern (high in summer and low in winter) when compared with that at the urban site (high in spring and fall and low in summer and winter). The J varied more significantly than GR among different sites, suggesting that J is more sensitive to the environment than GR. The highest GR (7.94 nm h−1) and J (2.72 cm−3 s−1) were observed at the agricultural (livestock) site, whereas the Arctic site had the lowest GR (3.34 nm h−1) and J (0.04 cm−3 s−1). The contribution of H2SO4 vapor to NPF was the least in the Arctic and the highest in the urban environment. For NPF to occur, the ratio of the loss rate of condensable vapors to preexisting aerosols to their growth rate should be low, and this ratio was substantially lower in the Arctic than in the other environments. Our results underscore the complexity of NPF characteristics in different environments and highlight the interplay of various factors in governing NPF. © 2024 Elsevier Ltd