The Impact of Black Carbon Aging on Its Optical Properties and Climate Effects

Black carbon, a significant component of atmospheric aerosols, undergoes aging during its atmospheric transport. This process not only exacerbates environmental pollution but also significantly impacts global climate effects and human health risks. Currently, research on black carbon and its aging has become a hot topic in the fields of atmospheric environment and climate science. This paper reviews the development of methods and instruments used in black carbon aging research, deeply analyzes the morphological evolution of black carbon particles from fractal to core-shell structures and examines the transformation process of mixing states from external to internal mixing during aging. Furthermore, it discusses the influence mechanism of aged black carbon on optical parameters, such as the light absorption enhancement factor and single scattering albedo. Although the warming effect of black carbon aging is widely recognized in the academic community, there remain significant discrepancies in the quantitative assessment of the light absorption enhancement amplitude and radiative forcing of black carbon across different studies. This variance is primarily attributed to the complexity of microphysical properties during the aging process and the oversimplification of mixing assumptions in climate models. Therefore, it is essential to further develop high-resolution online measurement and offline characterization techniques in the future, integrate multi-method strategies such as field observations, laboratory simulations, and model simulations, and conduct long-term, comprehensive and integrated black carbon observational research to thoroughly elucidate the interaction and change mechanism of morphology, mixing state and optical properties of black carbon post-aging, thereby reducing the uncertainty in simulating the environmental behavior and climate effects of black carbon in the atmosphere.