Elemental carbon (EC) is a carbonaceous aerosol with strong light-absorbing properties, and is recognized as an important short-lived climate forcer that contributes to global warming. When EC particles form an "internally mixed" structure with other components in the atmosphere, their radiative forcing effect is significantly amplified due to the "lensing effect". Actual observations indicate that the heterogeneity of the EC mixing state manifests even during the initial emission stage and is closely related to fuel type. As one of the major sources of EC emissions in China, the physical and chemical properties and mixing structures of emitted particles from residential solid fuel combustion require in-depth research to improve the accuracy of climate effect and health risk assessments.

Aiming at this scientific question, the Aerosol Physicochemical Processes and Environmental Effects team at the Institute of Earth Environment, Chinese Academy of Sciences, utilized a high time-resolution single-particle aerosol mass spectrometer (SPAMS) to systematically analyze the chemical composition, size distribution, and mixing state of EC-containing particles emitted during the combustion of five typical solid fuels (wheat straw, corn straw, rice straw, bituminous coal, and anthracite). They also utilized ART-2a algorithm to cluster EC-containing particles according to representative components on single particles.

The researchers found that almost all types of EC-containing particles showed varying degrees of mixing with sulfate, indicating that the residential solid fuel combustion process can directly contribute to the mixing characteristics of "aged" EC particles observed in the atmosphere. This discovery challenges the traditional view that "sulfate coating originates from atmospheric aging," providing crucial support for the source apportionment of atmospheric secondary components and the optimization of climate models.

This work published in npj Climate and Atmospheric Science, was jointly supported by the “Western Light”–Key Laboratory Cooperative Research Cross-Team Project of Chinese Academy of Sciences, the Natural Science Basic Research Program of Shaanxi, the Innovation Capability Support Plan Project in Shaanxi Province, the National Natural Science Foundation of China, and the Youth Innovation Promotion Association of the Chinese Academy of Sciences.