Observational study on particle nucleation process in the Yangtze River Delta, China: The growth property in different air masses

The particle nucleation process was studied in summer of 2005, in a downwind site of the Yangtze River Delta. In the 29 observation days, particle formation and growth was mainly found to occur in the air masses with regional characteristic and well-developed photochemical process. Using the measured spectral evolution of aerosol particles as a function of time the formation and growth properties of nucleation mode aerosols were evaluated. The averaged growth rate of newly formed particles is 6.0nm/h. The needed concentration of condensable vapor is 8.2 × 107/cm3, and its source rate is 3.1 × 106/(cm3 · s), which were higher than previous researches in similar latitude. The further calculation on the source rate of sulphuric acid vapor indicated the average participation of sulphuric acid to the particle growth rates has large variation among the events in different air masses. That is, the contribution of H2SO4 to particle growth is 59% in air masses originated in the YRD region, 53.8% in the air masses northward and 30% in southerly air masses.