| Aerosol optical properties,as one of the important physical and chemical properties of aerosol,can estimate the influence of aerosol radiation forcing of climate.It is necessary to understand the optical properties and influence mechanism of aerosol in the regional compound pollution,which is significance for assessment of regional climate change and establishing regional aerosol pollution control countermeasures.This paper studied the time series and diurnal variation of aerosol properties and its influence mechanism by three filed observation during Asian Youth Games,Youth Olympic Games and Wintertime in Nanjing,respectively.The main conclusions are summarized as follows:Aerosol βabs and βsca were(27.72± 15.99)Mm-1 and(131.57±62.03)Mm-1,(23.75± 13.75)Mm-1 and(198.95± 101.90)Mm-1 during Asian Youth Games,and Youth Olympic Games in Nanjing,respectively.The diurnal variation of absorption and scattering coefficients showed a bimodal distributuin.The SSA were(0.82±0.07),and(0.89±0.04)during two field observation,respectively.SSA peak value appeared at noon.The AAE were(1.04±0.16)and(1.06±0.09),SAE were(1.95±0.25)and(1.57±0.25)during Asian Youth Games and the Youth Olympic Games in Nanjign,respectively,indicating the predominance of aerosol light absorbing material was black carbon or black carbon mixed with absorbing,non-absorbing material,aerosol particle sizes were mainly concenteated in the fine mode in Nanjing.The aerosol extinction coefficient showed positive correlation with PM2.5 mass concentration,the mass extinction coefficients were 3.93 m2·g-1,and 4.21 m2·g-1 during Asian Youth Games,and Youth Olympic Games in Nanjing,respectively.(NH4)2SO4 and OM were predomiance aerosol extinction material,accounting for over 70%of the total extinction coefficient.A clear negative sigificant linear correlation between aerosol extinction coefficient and atmospheric visibility in Nanjing,when aerosol extinction coefficient was under 500 Mm-1,extinction coefficient increased 100 Mm-1,atmospheric visibility reduced 3.5 km,and 2.6 km during Asian Youth Games,and Youth Olympic Games in Nanjing,respectively.During Nanjing Youth Olympic Games filed observation,Ammonium nitrate,volatile organic compounds and part of the ammonium salt had contributed 30.45%of BC absorption enhancement,its scattering contribution was 48.0%.While ammonium sulfate had contributed 9.5%of BC absorption enhancement,its scattering contribution was 36.3%.In terms of the average BC mixing state level was internally mixed BC,the enhancement of BC absorption due to internally mixed BC ranged from 1.11 to 2.06.Aerosol scattering hygroscopic growth factor[fsca(RH)]increased with the increase of relative humidity(RH),the maximum increase factor of 9.78.The average aerosol βabs,and βsca were(78.50±21.66)Mm-1 and(689.41±233.61)Mm-1 during winter haze days in northern suburb of Nanjing,which were 2.43 and 3.22 times higher than those on clean days,respectively.The diurnal variation of aerosol optical properties were not obvious.PM2.5 mass extinction coefficient was 4.47 m2·g-1.The relationship between visibility and aerosol extinction coefficient was affected by relative humidity,when RH<80%,a clear inverse sigificant linear correlation between aerosol extinction coefficient and atmospheric visibility in Nanjing winter.The pollutions of haze days were mainly affected by local pollution from the east and northeast of observation site,and affected by long-range transportation of pollution from the west and north of observation site.A clear negative significant correlation between surface wind speed and aerosol absorption coefficient,while it was not obvious correlation betwween surface wind speed and other optical properties.However,when surface wind speed exceed 4.00 m·s-1,the surface wind speed was favour to the spread of pollutants. |
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