Abstract
Black carbon (BC) and brown carbon (BrC) aerosols that are released from the combustion of fossil fuels and biomass are of great concern because of their light-absorbing ability and great abundance associated with various anthropogenic sources, particularly in East Asia. However, the optical properties of ambient aerosols are dependent on the mixing state and the chemical composition of absorbing and non-absorbing aerosols. Here we examined how, in East Asian outflows, the parameters of the aerosol optical properties can be altered seasonally in conjunction with the mixing state and the chemical composition of aerosols, using 3-year aerosol measurements. Our findings highlight the important role played by sulfate in East Asia during the warm season in both enhancing single scattering albedo (SSA) and altering the absorption properties of aerosols—enhancing mass absorption cross section of BC (MACBC) and reducing MAC of BrC (MACBrC,370). Therefore we suggest that in global radiative forcing models, particular attention should be paid to the consideration of the accurate treatment of the SO2 emission changes in the coming years in this region that will result from China’s air quality policy.
Highlights
Black carbon (BC) and brown carbon (BrC) aerosols that are released from the combustion of fossil fuels and biomass are of great concern because of their light-absorbing ability and great abundance associated with various anthropogenic sources, in East Asia
The climate effect of carbonaceous aerosols is of great concern because of their great abundance associated with various anthropogenic sources[1,2]
East Asia is the region with the greatest emissions of SO22,3 and anthropogenic organic carbon (OC), including brown carbon (BrC), which together with BC account for almost 60% of aerosol optical depth (AOD)[4]
Summary
Black carbon (BC) and brown carbon (BrC) aerosols that are released from the combustion of fossil fuels and biomass are of great concern because of their light-absorbing ability and great abundance associated with various anthropogenic sources, in East Asia. The optical properties of ambient aerosols are dependent on the mixing state and the chemical composition of absorbing and non-absorbing aerosols. In East Asian outflows, the parameters of the aerosol optical properties can be altered seasonally in conjunction with the mixing state and the chemical composition of aerosols, using 3-year aerosol measurements. It is crucial to understand the intimate link between optical properties and the chemical composition of aerosols in the ambient air to assess their climate forcing more accurately. Considering the noticeable seasonal changes[8], measurement results are discussed in seasonal groups: cold (Oct.– Mar.) and warm (Apr.–Sep.; April and May [spring] and June to September [summer])
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