Determination of equivalent black carbon mass concentration from aerosol light absorption using variable mass absorption cross section

Abstract. Atmospheric black carbon (BC) is the strongest solar radiative absorber in atmosphere, exerting significant influences on earth's radiation budget. The mass absorption cross section (MAC) a crucial parameter for converting light coefficient (σab) to equivalent BC concentration (EBC). Traditional filter-based instruments, such as AE33, use constant MAC of 7.77 m2/g at 880 nm derive EBC, which may lead uncertainty EBC. In this paper, new method σab EBC proposed by incorporating variations attributed aerosol coating state. A Mie simulation showed that varied dramatically with different core sizes and shell thicknesses. We compared our traditional during field measurement site North China Plain. results was smaller (larger) than particles 280 nm, resulting an size distribution derived from higher (lower) nm. size-integrated 16 % method. Sensitivity analysis indicated caused refractive index (RI) within 35 %, imaginary part RI had dominant influence This study emphasizes necessity take into account when deriving can help constrain measurements.