| Major components of particulate matters are reported as ionic compositions, carbon species and metallic elements, which have an important effect on air quality, visibility degradation, climate change and human health. In recent years, economy of Nanjing rapid increased and the comprehensive controls to air pollution from Nanjing’s government already made some effrcts, however, number of vehicles jumped very quickly at the same time, air quality has not obviously improvement, visibility degradation and haze days increasing. To reveal the formation mechanism of pollution in Nanjing, and it is necessary to deep analysis chemical composition in PM10 in Nanjing, whole investigation of the pollution.In this study, we use Andersen 9 crash sampler and Thermo Fisher Scientific EMS (EMS). At the same time, DRI Model 2001 A, ion chromatography and Agilent 7500a ICP-MS (Inductively Coupled Plasma Mass Spectrometry) respectly measured organic carbon (OC), elemental carbon (EC), water-soluble ions and metallic elements, and we combine the meteorology elements with chemical composition to analysis. The seasonal variation characteration of EC and OC concentration, size distribution and SOC are discussed, in addition, the positive matrix factorization version 3 (EPA-PMF 3.0) was applied to identify the source contribution,of PM2.1 concentrations. Pollution weather frequently has a siginificant influence on air quality and visibility degradation in Nanjing northern suburb, so four important pollution weathers (Firework displays, dust storms, biomass burning and haze) were discussed, and the characteration water-soluble ions were analyzed.The results showed that the seasonal variation of OC was slightly different for EC:OC was summer< spring< autumn< winter, and EC was spring< summer< autumn< winter. OC and EC show trimodal distribution, and size variations have the same trends in four seasons. In each size, OC/EC has a great different. The seasonal variation of SOC in Nanjing northern suburb was winter< autumn< summer< spring. OC and EC in PM2.1 during spring has a better relation than in PM2.1-10, while summer and autumn and winter in PM2.1 have a lower relation than in PM2.1-10.The features of collected aerosols in PM2.1 in Nanjing northern suburb during summer were described as follows:SO42-, NH4+ and NO3- were the main water-soluble ions; Ca, Na, Fe, K were the main metallic elements. The concentration of OC and EC were respectly 13.04nμg·m-3 and 2.61μg·m-3. There was an enrichment of Mn, Na, Ca, Cr, Cd, Zn, V, Pb, and Mo because the areas were affected by human activity. PMF, which was applied to determine the sources and their contributions in PM2.1, was an effective method of identifying possible aerosol sources. Seven factors were identified by PMF:vehicle exhaust, secondary aerosol and residual oil, the main sources, and road dust, biomass burning, iron and steel industry and metallurgical aerosol, the secondary sources.The concentrations of total water-soluble ions in PM10 (TWSI10) for four pollution episodes and normal days showed a decreasing order as follows:haze>biomass burning>fireworks displays>normal days>dust storms. During the normal days, the concentration of water-soluble ions was lowest in the finer-sized particle. During the haze days, the concentration of water-soluble ions was highest in the finer-sized particle. During the fireworks display periods, the concentration of K+ ion elevated at<1.1μm. During the dust storms periods, the coarse ions were the major part, and Ca2+, Mg2+ and Cl- have an obviously increasing. Biomass burning showed high K+, Cl- and Na+, while hazy days was enriched with secondary ions. Normal days suggested that each ion’spectra showed the same trends and trimodal distribution. Fireworks display, dust storms and biomass burning showed the same trends of spectra, but for haze days were obviously different. The part of SO42- came from the heterogeneous conversion of SO2 to SO42- during fireworks display, dust storms, biomass burning and normal days. Visibility negatively correlated with total of water-soluble ions, NO3-, SO42- and water content. |
PDF Full Text Request