Observation And Numerical Simulation Of Aerosol Dry Deposition In Nanjing Area

Atmospheric dry deposition is the main mechanism for the removal of atmospheric aerosols and their precursors and intermediates, which plays a very important role in maintaining the relative stability of atmospheric constituents. At the same time, dry deposition can bring some aerosols in the atmosphere into soil or water, causing soil acidification and other reactions, which in turn affect human activities and ecosystems. In recent years, with the development of economy, the Yangtze River Delta region, represented by Nanjing, has become one of the most serious air pollution areas in China. Therefore, it is necessary to study the aerosol dry deposition in this area.In this paper, 84 effective dry deposition samples were collected from the summer and autumn of Nanjing in the summer of July and October, and the chemicalcomposition and source of the water soluble ions in the dry and dry settling of summer and autumn in Nanjing were analyzed and discussed. And the spatial and temporal distribution characteristics of PM10 and its dry deposition in the case of heavy pollution in Nanjing and its surrounding areas in January 2014 were studied by using the air quality model WRF-chem.The results show dry deposition samples in Nanjing Summer and Autumn indicated that the average of pH was 6.2,dry deposition samples usually appeared neutral.Ca2+ and Nn4+ were the major cations and their average daily concentrations were 1115.μeq·L-1 and 31.2μeq·L-1, accounting for 68.2% and 18.5% of total cations.SO42-,Cl- and NO3- were the main anions, and their average daily concentration were 30.4、20.7 and 18.7μeq·L-1, a total of 89.4% of the total anions,respectively. High temperature and humidity of meteorological factors and contaminated air mass affected dry deposition. Local air mass had greater impact on dry deposition pollution, which indicated that dry deposition pollution have local property. The Nanjing summer and autumn season from stationary sources contribute to atmospheric dry deposition of water-soluble ions is greater than mobile sources,while the environmental control measures for the Nanjing Youth Olympic Games have greater effect on stationary sources than mobile sources. Studies of the origins of major ions indicated that SO42- and NO3- were mostly attributed by the anthropogenic activities, and Cl- mainly from ocean sources, while K+ and Mg2+mostly from the terrestrial input.In the model simulation, the simulation results have a good correspondence with the observed values. At the same time, it was found that the dry sedimentation flux was mainly affected by the aerosol concentration under the constant static condition of the underlying surface. The results show that the dry sedimentation flux in Nanjing is larger than that in the Yangtze River Delta, east of Nanjing, and the contribution of Anhui and northern Jiangsu is smaller than that of the Yangtze River Delta. Compared with the emission reduction, The gale of this wind is the main reason for the increase in dry deposition flux.