Contribution Of New Particle Formation To Cloud Condensation Nuclei Activity And Its Controlling Factors In A Mountain Region Of Inland China

A 1-month field campaign (May 29-June 29, 2018) was conducted at a mountain site (862 m above sea level) on the Wudang Mountains in China. The particle number size distribution (3-400 nm), size-resolved cloud condensation nuclei (CCN, at 0.2% and 0.8% SS), and nonrefractory PM1 chemical composition were measured, respectively. The occurrence of the three chosen new particle formation (NPF) events (June 4, 7, and 11) was facilitated by southwest or west winds with a speed of about 3-4 m s(-1). The hygroscopicity parameter (kappa) value of newly grown particles varied in a wide range (0.25-0.8) during the events, leading to large uncertainties (-98% to 38%) on the N-CCN prediction compared to the campaign. During growth of the newly formed particles for the three events, condensation of sulfuric acid vapor accounts for 14%-42%, 2%-8%, and 3%-9%, respectively, indicating that organic vapors may play an important role in particle growth. For plume-type events with rapid growth, the observed high CCN activity (i.e., June 7 event) may be explained by the contribution of amines and depression of surface tension in the presence of organic surfactants during particle growth. Our study demonstrates that the contribution of NPF to CCN concentration is modulated by many key factors including growth rate, hygroscopicity, concentrations of new particles and preexisting particles, and variation of those factors from one event to another leads to large uncertainties on the CCN prediction.Plain Language Summary A 1-month field experiment (May 29-June 29, 2018) was conducted at a mountain site (862 m above sea level) on the top of the Wudang Mountains in China. Several particle characteristics including particle sizes, chemical composition, and cloud condensation nuclei (CCN) were measured using advanced analytical instruments. During the campaign, events corresponding to a well-known atmospheric phenomenon called new particle formation were observed and facilitated by southwest or west winds. New particles, once they are formed, can grow to CCN sizes to enhance cloud formation. Prediction of CCN concentration is subject to large uncertainties during particle formation events because of large variation of particle hygroscopicity. In the atmosphere, sulfuric acid, an important condensable gas, plays an important role in particle growth. However, in our study, sulfuric acid vapor contributes minor to particle growth compared to organic compounds. Our study concludes that contribution of new particles to CCN concentration was controlled by many factors and might vary substantially from one event to another.Key PointsSubstantial variation of hygroscopicity leads to significant uncertainties in cloud condensation nuclei predictionContribution of new particle formation to cloud condensation nuclei concentration varies in a large range from one event to anotherThe growth rate, hygroscopicity, new particle concentration, and preexisting particles are the key factors of the cloud condensation nuclei contribution