Optical, radiative and chemical characteristics of aerosol in Changsha city of Central China

Industrial pollution has a significant effect on aerosol properties in Changsha City, a typical city of Central China. Therefore, year-round measurements of aerosol optical, radiative and chemical properties from 2012 to 2014 at an urban site in Changsha were analyzed. During the observation period, the energy structure was continuously optimized, which was characterized by the reduction of coal combustion. The aerosol properties have obvious seasonal variations. The seasonal average aerosol optical depth (AOD) at 500 nm ranged from 0.49 to 1.00, single scattering albedo (SSA) ranged from 0.93 to 0.97 and aerosol radiative forcing at the top of the atmosphere (TOA) ranged from -24.0 to 3.8 W m-2. The chemical components also showed seasonal variations. Meanwhile, the scattering aerosol such as organic carbon (OC), SO42-, NO3-, and NH4%2B showed a decrease and elemental carbon (EC) increased. Compared with the observation in winter 2012, AOD and TOA decreased by 0.14 and -1.49 W m-2 in winter 2014. The scattering components SO42-, NO3- and NH4%2B decreased by 12.8 μg m-3 (56.8%), 9.2 μg m-3 (48.8%) and 6.4 μg m-3 (45.2%) respectively. The atmospheric visibility and pollution diffusion conditions improved. The extinction and radiative forcing of aerosol significantly controlled by the scattering aerosol. The results indicate that Changsha is an industrial city with strong scattering aerosol. The energy structure optimization had a marked effect on controlling pollution, especially in winter (strong scattering aerosol).