Overestimation of black carbon light absorption due to mixing state heterogeneity

Abstract

AbstractBlack carbon (BC) aerosols, which arise from incomplete combustion processes, possess the capacity to absorb solar radiation, thereby contributing significantly to the issue of climate warming. However, accurately estimating their radiative effect is challenging, influenced by emissions, sizing, morphology, and mixing state. BC particles undergo aging processes that can alter their physical characteristics and mixing state, consequently affecting their optical properties. In this study, we assessed the mixing state of BC across diverse atmospheric environments. Results demonstrate that mixing state heterogeneity is a ubiquitous phenomenon. In background atmospheres, BC exhibited less homogeneous states compared to those in urban and suburban areas, where heterogeneity was driven by primary emissions. Our study provides direct observational evidence that the heterogeneity of particle-particle mixing can reduce the light absorption enhancement of BC in all atmospheres, with a deviation of up to approximately 24% under background conditions.