The Sulfate And Nitrate Distribution Characteristics And Formation Mechanism Of Pm_2.5 In Nanchang

PM2.5 mainly come from coal combustion emissions, automobile exhaust emissions,building construction, bare land dust emissions, biomass burning emissions, kitchen lampblack and so on. It is divided into a primary sources and secondary sources, The primary sources is the direct emission particles,The secondary source of sulfate and nitrate is the major secondary products in PM2.5,They are formed by SO2, NOx through a series of chemical reactions.Not only Sulfate and nitrate has a profound influence on the atmospheric environment quality and climate change.but also affects on human body health.It has important theoretical and realistic significance to formulate scientific and effective measures to control the air pollution and reduce the ash haze that research the formation mechanism and source analysis of secondary particles in Nanchang.This paper is mainly studies the formation mechanism of inorganic secondary particles.This study research the formation mechanism of PM2.5 in the atmospheric though analysis the time and space distribution and seasonal variation characteristics of SO2 and NO2,SO42- and NO3– components in PM2.5 and SOR\NOR in the air among the outdoor pollution sources(motor vehicle emission source, power plant,the urban area) and the atmospheric pollution of chemical process, Thus the gray haze formation were discussed.This study selectes qianhu campus of Nanchang university,road and power plant sampling site as the monitoring area,and it is analyzed by spectrophotometric method and ion chromatography, We can draw the following conclusions through discussing the space-time distribution characteristics and formation mechanism:( 1) The NO2 concentration is max in spring, The variation of NO2 concentration is not obvious during each season. The SO2 concentration in the daytime is higher than at night, morning is higher than afternoon, the peak of that is during 9-11 and 19-21;The diurnal variation of the NO2 concentration is the trend of M type during all the seasons, the peak of the NO2 concentration is during 7-9 and 18-21,and the peak at night is higher than that in the daytime, The valley of the NO2 concentration appeares at zero and 14-16, the peak appears in the morning and evening rush hour.(2)In A1 sampling site, the SO2 concentration is max in winter, minimum in summer.The average SO2 and NO2 concentration in the A2 and A3 sampling sites are higher than the A1 sampling site, the influence of coal combustion for the SO2 concentration is more than others, the influence of automobile exhaust for the NO2 concentration is more than others.The SO2 and NO2 concentration in Nanchang during each season is lower than that in other cities, it shows that the environment quality in Nanchang is better than that in other cities. The humidity has an effect on NO2 concentration in the air in Nanchang.The SO2 and NO2 concentration showed correlation with O3 concentration.(3)The seasonal variation of salfate concentration in A1:winter > summer > autumn > spring, The seasonal variation of SOR:Summer > autumn > spring > winter, the photochemical of SO2 is active. The seasonal variation of nitrate concentration: Winter > autumn > spring > summer. The seasonal variation of NOR: Winter > autumn > spring > summer. The NOR is smaller than SOR during all the year round,In summer,the NO2 in the air nearly no secondary changes in Nanchang.(4)The diurnal change of salfate concentration is obvious in Nanchang, the peak of the salfate concentration is during 10-13,the peak in summer is earlier,it appeares at 9,the valley of the salfate concentration appeares at zero, it is basiclly smooth after midnight,the salfate concentration in the daytime is higher than at night all the seasons, the change trend of the salfate concentration is later than that of SO2,but it is overall consistent.The SOR in the daytime is higher than at night, the peak of the nitrate concentration is during 9-11, the valley of that appeares at 14,but it is not obviously in autumn and winter, The diurnal variation of the NO2 concentration is the trend of M type in spring and summer, the peak of the nitrate concentration 2 hours later than that of NO2,the trend of NOR is the same as what of nitrate. The nitrate concentration in the daytime is higher than at night in spring,autumn and winter, NOR at night is greater than that in the daytime in summer.(5)Aerosol pollution is greatly influenced by outside sources in Nanchang. The main way of the Sulfate secondary reaction is the gas phase homogeneous reaction in summer and autumn in Nanchang. It may have happened the liquid phase reaction in spring.In the winter it is to the disadvantage of the formation of local secondary particles,it is likely to happen the adsorption on the surface of the particles. In the autumn and winter it is mainly affected by the nonlocal source, the high temperature in the summer of Nanchang is disadvantage to photochemical reaction of NO2。(6)The pollution indexes in autumn fog weather are higher than normal days, The fog event may be caused by motor vehicle pollution emissions, and it is influenced by southern pollution sources. The sulfate happened secondary reaction during the fall normal weather, There are some sulfate that may be from the gas phase homogeneous xidation process, the other may have happened the reaction on the surface of the particles.