Contribution of New Particle Formation to Cloud Condensation Nuclei in the Beijing Megacity

摘要

New particle formation (NPF) events have been recognized as an important process contributing to the cloud condensation nuclei (CCN) formation. In this study, measurement of NPF and predicted number concentrations of CCN using 冔-Kohler theory were analyzed to assess the contribution of NPF to CCN. The enhancement ratios (the ratio of CCN concentrations after to before NPF) were higher under high supersaturation (S). For example, it is about 30-50% higher under S=0.86% than under S=0.07%. The enhancement ratios were higher during the sulfur-poor NPF events with larger growth rates and exhibited similar seasonal variation as the growth rates with a larger value in summer than other seasons. Our results suggest that NPF events increase the CCN number concentrations by 0.4-6 times in the Megacity area of Beijing, growth rate is the key factor in the conversion of NPF to possible CCN, and organic species are implicated as the dominant contributor in facilitating the conversion of newly formed particles to possible CCN.