Aerosol optical properties and chemical composition apportionment in Sichuan Basin, China.
PM2.5and its major chemical components, and light scattering (σscat) and absorption (σabs) coefficients were measured in Chengdu (CD) and Chongqing (CQ) in Sichuan Basin, from October 2014 to July 2015. Annual mean PM2.5, σscatand σabswere 67.0±43.4μgm-3, 421.4±290.1Mm-1and 36.7±26.4Mm-1, respectively, in CD, and annual mean PM2.5and σabswere 70.9±41.4μgm-3and 45.4±24.5Mm-1, respectively, in CQ. PM2.5, σscatand σabswere all evidently higher in winter than in other seasons mainly due to the unfavorable meteorological conditions for dispersion of local pollutants. Diurnal patterns of σscatand σabsexhibited a peak value around 7:00-8:00 LT and a valley value around 17:00-18:00 LT. High levels of PM2.5accompanied with low wind speed and high relative humidity conditions were the major causes of visibility impairment in Sichuan Basin. Both σscatand σabswere remarkably higher under calm wind condition, indicating that local emissions were largely responsible for the aerosol pollutions in this region. High relative humidity enhanced extinction coefficient (bext) by up to around 1.6 and 1.4 times in CD and CQ, respectively, due to the hygroscopic growth of water soluble components. On annual basis, (NH4)2SO4contributed the most to bext, accounting for 34.4% and 31.5% in CD and CQ, respectively, followed by NH4NO3and organic matter, 28.1% and 17.5%, respectively, in CD, and 20.1% and 26.8%, respectively, in CQ. EC contributed about 10% and the rest contributed to <12% at both urban sites. Therefore, reducing emissions of the precursor gases such as SO2, NOx, NH3and VOCs systemically may be efficient to improve the air quality and visibility simultaneously in Sichuan Basin.
Research Center for Atmospheric Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China; Chongqing University, Chongqing 400044, China.
Huanbo
H
Wang
Research Center for Atmospheric Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
Guangming
G
Shi
Research Center for Atmospheric Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China. Electronic address: tianmi@cigit.ac.cn.
Mi
M
Tian
Air Quality Research Division, Science and Technology Branch, Environment and Climate Change Canada, Toronto M3H 5T4, Canada.
Leiming
L
Zhang
Research Center for Atmospheric Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
Yang
Y
Chen
Research Center for Atmospheric Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China; Chongqing University, Chongqing 400044, China; Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; Yangtze Normal University, Chongqing 408100, China. Electronic address: fmyang@cigit.ac.cn.
Fumo
F
Yang
Research Center for Atmospheric Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
Xuyao
X
Cao
Light extinction; PM(2.5); Scattering and absorption coefficient; Sichuan Basin