Study On Particle Size Distribution And Extinction Characteristics Of Atmospheric Aerosol Northern Suburb Of Nanjing

The size distribution of particulate was analyzed by the FA-3 and KC-120H sampler in Northern-suburb of Nanjing from January to November in 2014, and chemical components in particles were determined in lab. The results showed that particulate pollution in Northern-suburb Nanjing was serious and the most particles were concentrated in fine particles; particle size distribution was bimodal with peak in 0.43～0.65 and 9-10μm. In winter, the fine particle concentration was higher and in spring the coarse particle size was higher; the nocturnal concentration was mainly higher than diurnal in fine segment. The precipitation had significant cleaning effect for fine particles. In haze days, the particle concentration in 0.43～2.1μm diameter increased obviously, when humidity was greater than 70%, mass concentration of particle increased obviously in 0.43～2.1μm.Water-soluble ions were the main components of the atmospheric aerosol in Northern-suburb of Nanjing, particularly in fine particles, which accounted for 37.3～47.9% of particle mass. The SO42-, NO3-,NH4+ were the most important component of ions, and displayed as unimodal distribution with the peak in 0.43～0.65μm. The three kinds of ions presented different change rules in different periods, in winter, SO42- and NO3-’s peak migrated to 0.65～1.1μm, NH4+ concentration in 0.65～1.1μm was also higher than other reason obviously; NO3-concentration in night was higher than day significant, then SO42- concentration in day was higher than night, NH/has little gap between day and night.OC(Organic Carbon)and EC (Element Carbon) were the important components of aerosol, respectively, accounted for the quality of the concentration of 19.6-24.8% and 4.2～5.2%, concentrated in the fine particle. OC and EC concentration were higher in winter than other seasons, higher in night than daytime. As relative humidity increasing, concentration of OC and EC decreased, may related to the moisture absorption characteristics of both them.The biggest contribution to the aerosol extinction in North-suburb of Nanjing were organic compounds, sulfate, nitrate and ammonium, accounting for 64.4% of total extinction coefficient (340.4Mm-1), winter extinction coefficient was the highest with the higher concentrations of NO3-, OM and EC, and fall lower extinction value was mainly due to the low concentration of OM and EC, the higher extinction value in summer was related to relative humidity and NHj+ and SO42- concentration. In this paper, there were certain differences between the extinction coefficient through IMPROVE formula and the observed value, according to the pollution condition of Nanjing, IMPROVE equation may need further revision.