| To fully understand the characteristics of regional and global changes of atmospheric aerosol, multi-source information, including the aerosol optical parameters, meteorological observation data and atmospheric environmental monitoring data, was applied in comprehensive analysis in this study. Based on the technical approach of atmospheric aerosol optics, synoptic analysis and numerical simulation, the variation of aerosol optical properties during typical periods of changing human activities over Beijing were analyzed. The impact of meteorologic conditions and human activities to urban air quality and the contribution of potential sources areas of atmospheric pollutants were evaluated in this study. Then the simulated climatology of global dust deposition was discussed. The main contents and conclusions are as follows:1) The impact of anthropogenic emission reduction measures to the changes of regional atmospheric aerosols: observational and modeling study of atmospheric aerosols optical properties during the World Athletics Championships and Victory Day Military Parade over BeijingTo ensure a better air quality during these events, unified implementation of interim measures to reduce the factory emission and vehicle numbers took place in seven provinces in North China. A ground base observation at an urban site of Beijing was conducted during this special period and the aerosol optical properties were analyzed. The main results are as follows. During the restrictive stage, the average value of the aerosol optical depth (AOD) and PM2.5 were 0.34±0.20 and 23±12 ?g/m3 and about 69% and 67% less than before, respectively. The average Angstrom exponent(a) was 1.26±0.27 and about 10% larger than before. The atmospheric aerosols showed strong scattering ability with the mean value of single scattering albedo (SSA) was 0.944±0.045. The average absorption aerosol optical depth (AAOD) was 0.008±0.007 and about 58% and 50% smaller than the periods before and after the restrictive stage,respectively. The average peak values of coarse- and fine-mode particles were 0.020±0.016 ?m3/?m2 and 0.032±0.026 ?m3/?m2, and about 60% and 49% lower than before, respectively.2) The effect of urban anthropogenic activities and surrounding emission sources to the change of atmospheric aerosols: an analysis on the relationship of meteorological factors and emission conditions with aerosol optical properties during the Chinese National Day and Spring Festival holiday in BeijingBased on the high-precision ground base observation, the aerosol optical properties during the Chinese National Day and Spring Festival holiday in Beijing were analyzed combined with meteorological conditions using data. The average PM2.5 concentrations over the National Day in 2015, Spring Festival in 2015 and 2016 were 132.29±109.39 ?g/ m3, 114.43±62.93 ?g/ m3 and 96.29±64.24 ?g/ m3, and about 112%,38% and 65% larger than background level (two-month average), respectively; The mean aerosol optical depth (AOD) were 1.14±0.16,0.70±0.07and 0.60±0.07,about 78%, 19% and 36% higher than background level, respectively. Angstrom exponents (a)showed increasing trend with AOD,and the mean value were 1.04±0.07, 0.88±0.09 and 1.21±0.08, respectively. The absorption aerosol optical depth (AAOD) were 0.056±0.040,0.061±0.048 and 0.060±0.044,about 75%,9% and 7% higher than background level, respectively. The averaged Angstrom absorption exponents (AAE)were 1.17±0.53,1.69±0.38 and 1.43±0.35,about 24%,21% and 36% higher than background level, respectively. While the PM2.5 concentration of National Day in 2014 was 68.14±36.06 ?g/ m3, about 26% smaller than background level. Based on potential source contribution function (PSCF), the south area of Hebei province, the west area of Shandong province and the north areas of Henan province were identified as the main source regions of PM2.5. The concentration-weighted trajectory results showed that the contribution value of these regions during the National Day and Spring Festival were about 175-200 ?g/m3 and 100-175 ?g/m3, respectively. The larger contribution of Northwest China region during Spring Festival period than National Day was found with the value of 100-125 ?g/m3.3) The climatic change characteristics of the global and regional atmospheric aerosols: a 20-year simulated analysis of global dust aerosol depositionThe long-range transport of dust aerosols emitted from continental deserts resulted in dry and wet deposition on global and large-scale land and sea areas,affecting loess accumulation, bringing nutrient salt and iron fertilizer to the marine organism, changing the surface albedo. Based on a 20-year (1991-2010) simulation of dust aerosol deposition with the global climate model CAM5.1(Community Atmosphere Model, version 5.1), the spatial and temporal variations of dust aerosol deposition were analyzed using climate statistical methods. The results indicated that the annual amount of global dust aerosol deposition was approximately 1161±31 Mt.with a decreasing trend, and its interannual variation range of 2.70% over 1991-2010.The 20-year average ratio of global dust dry to wet depositions was 1.12,with interannual variation of 2.24%, showing the quantity of dry deposition of dust aerosol was greater than dust wet deposition. High dry deposition was centered over continental deserts and surrounding regions, while wet deposition was a dominant deposition process over the North Atlantic, North Pacific and northern Indian Ocean.Furthermore, both dry and wet deposition presented a zonal distribution.The deposition amounts of each mian land and sea areas showed interannual fluctuations with the largest variation range at around 26.96% in the northern Indian Ocean area, followed by the North Pacific (16.47%), Australia (9.76%), North Atlantic (9.43%) and Eurasia (6.03%). The northern Indian Ocean also had the greatest amplitude of interannual variation in dry to wet deposition ratio, at 22.41%,followed by the North Atlantic (9.69%), Australia (6.82%), North Pacific (6.31%) and Eurasia (4.36%). Dust aerosol presented a seasonal cycle, with typically strong deposition in spring and summer and weak deposition in autumn and winter. The seasonal variation of wet deposition contributed greatly to the seasonal cycle of total dust deposition. The dust deposition over the northern Indian Ocean exhibited the greatest seasonal change range at about 118.00%, while the North Atlantic showed the lowest seasonal change at around 30.23%. The northern Indian Ocean had the greatest seasonal variation range of dry-to-wet deposition ratio, at around 74.57%, while Eurasia had the lowest, at around 12.14%. |
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