The Influence of Different Black Carbon and Sulfate Mixing Methods on their Optical and Radiative Properties

摘要

Three different internal mixing methods (Core-Shell, Maxwell-Garnett, and Bruggeman) and one external mixing method were used to study the impact of mixing methods of black carbon (BC) with sulfate aerosol on their optical properties, radiative flux, and heating rate. The optical properties of a mixture of BC and sulfate aerosol particles were considered for three typical bands. The results showed that mixing methods, the volume ratio of BC with sulfate, and relative humidity have a strong influence on the optical properties of mixed aerosols. Compared to internal mixing, external mixing underestimated the particle mass absorption coefficient by 20-70% and the particle mass scattering coefficient by up to 50%, whereas it overestimated the particle single scattering albedo by 20-50% in most cases. However, the asymmetry parameter was strongly sensitive to the equivalent particle radius, but was only weakly sensitive to the different mixing methods. Of the internal methods, there was less than 2% difference in all optical properties between the Maxwell and Bruggeman methods in all bands; however, the differences between the Core-Shell and Maxwell/Bruggeman methods were usually larger than 15% in the ultraviolet and visible bands.