Aerosol New Particle Formation At Western Yangtze River Delta

Based on the long-term observation at SORPES(The Station for Observing Regional Processes of the Earth System)site of Nanjing University,this paper comprehensively analyzes the particle size distribution and new particle generation characteristics of the western Yangtze River Delta,especially the sub-3 nm particles.The average total concentration of 1-3 nm aerosols was17600 ± 14500(mean ± standard deviation)cm-3,and the total concentration of 6-800 nm aerosols was30300 ± 13000 cm-3.The averaged number concentration of nucleation mode(6nm-30 nm),the Aitken mode(30nm-100 nm)and accumulated mode(100nm-800 nm)aerosols were 7000 ± 6500 cm-3,12800 ± 8300 cm-3,and 10500 ± 7200 cm-3,respectively.The particle number concentration below 3 nm had a positive correlation with the number concentration of the nucleation mode aerosol.The frequency of new particle formation events at the SORPES site was 29.1%.The frequency of new particle formation events from high to low in the three observation seasons was 37.3%in spring,28.8%in autumn,and 19.1%in summer.The nucleation rates in the three seasons were 198.8 cm-3s-1,206.3 cm-3s-1 and 241.2 cm-3s-1,respectively.The 6-nm particle generation rate was 3.8 cm-3s-1,1.73 cm-3s-1 and 3.1 cm-3s-1.The growth rate has no correlation with temperature,wind speed,and air pressure,but has a weak negative correlation with relative humidity.The average growth rate of 1-30nm particles was the highest in autumn,and there was a negative correlation between the growth rate below 3nm and temperature,and a weak positive correlation between the growth rate of 6-20nm and temperature.No obvious correlation between the growth rate with the relative humidity,wind speed and air pressure can be observed.The growth rate of 1.1-20 nm particles was found to be related to the particle size,indicating that the growth of the particles is not caused by the same gaseous precursor material that nucleating.The contribution of sulfuric acid to the growth of particulate matter decreased with increasing particle size supported the above statement.The role of sulfuric acid in the nucleation process is low,and there may be other substances participating in the nucleation process.Nighttime new particle formation events can be observed at the SORPES site.The average annual frequency of events is 5%.At the nighttime events,the overall ozone concentration was high at 16.6 ± 19.8 ppbv.There are high concentration peaks of gaseous sulfuric acid sometimes of the event days.Sulfuric acid may also contribute to the nighttime nucleation process.