Aging And Mixing State Of Particulate Matter During Aerosol Pollution Episode In Autumn Shanghai Using An Single Particle Aerosol Mass Spectrometer (SPAMS)

A Single Particle Aerosol Mass-Spectrometer (SPAMS) was applied to characterize the size distribution (200nm-2.0μm) and chemical compositions of ambient particles during a polluted event from11th to18th, November2011. OCEC, METAL, EC, SECONDARY and K-Na types of particulates were dominant groups observed in Hazy Day period, which were27.4%,3.4%,7.3%,45.6%and5.4%of the overall measured particles, respectively. The observed five types of particles contains secondary composition such as18NH4+, SO3-,96SO4-,97HSO4-,NO2-, NO3-and H(NO3)-,showing that they probably went through different aging processes, and the increasing of the SECONDARY particles during the event clearly indicated a secondary aerosol pollution. Heterogeneous reactions of SO2and particles could be the reason of strong97HSO4-signals in the mass spectrums of OCEC type particles while the existence of the organic compounds might have an important influence on the aerosol formation with the gas-phase sulfuric acid. Fresh EC particles in the environment tended to aging with above-mentioned secondary ions by the analysis of the particle size distribution and eventually lead to a particle type conversion from EC to SECONDARY. Organic amine in marine environment was brought to the land by warm, moist marine air mass that dramatically removed atmospheric SECONDARY and OCEC particles from the air with a heavy rain and leading to the observation of amine particles in the Clean Day period.The comparisons of size distributions for the five types particles shows that:sources, degree of aging and physical and chemical properties of aerosol particles influence size distributions. The number of particles in haze days was much more than clean days, resulting in the size distributions of five types of particles were smoother curves. The size distributions of OC/EC,EC and SECONDRY types particles in haze days were in the larger particle size range than that in clean days. However, The size distribution of METAL type particles is similar to that in clean days, the size distribution of K-Na type particles in haze days was in the smaller particle size range than that in clean days. And the type of EC type particles in clean days was a obvious bio-modal distribution, the same to the SECONDRY particles, but not obviously.The comparison of size distributions of the results for SMPS-3080and Single Particle Aerosol Mass Spectrometer offered the scaling factors in200to1252nm, and then obtaining the actual change of the number concentration of EC type particles, contrasting with mass concentrations, results showed generally better. A calibration of OC and EC ion intensities observed the time change of OC and EC concentrations.