Source Apportionment of Optical Properties of Carbonaceous Aerosols between Urban and Rural areas in Republic of Korea, spring 2022

Light-absorbing carbonaceous aerosols (LACs) are key contributors to climate change due to their ability to absorb solar radiation and reduce surface albedo. These aerosols primarily comprise black carbon (BC) and brown carbon (BrC). The optical properties of LACs are influenced by a complex interplay of factors, including emission sources, atmospheric conditions, and secondary formation processes. However, clearly distinguishing the light-absorption characteristics of various sources remains a significant challenge. Instruments such as the Aethalometer, for example, can differentiate between BC from fossil fuel combustion and biomass burning based on the frequency dependency of absorption strength. Yet, the reliance on empirical values for the Absorption Ångström Exponent (AAE) introduces uncertainties in these estimates. Source apportionment models, such as Positive Matrix Factorization (PMF) and the Multilinear Engine (ME-2), help address these uncertainties by directly attributing sources through the integration of optical and chemical composition data (Wang et al., ACP, 2020). In this study, we applied the PMF model to quantify and compare the source-specific optical properties of carbonaceous aerosols in Chuncheon, a rural area surrounded by forests, and Seoul, a representative urban area in Republic of Korea, during the spring of 2022. The input data included ionic, carbonaceous, and elemental components, as well as light absorption coefficients measured using an Aethalometer (model AE33, Magee Scientific, United States) from March 14 to April 13, 2022. The PMF analysis identified four major sources; mineral dust, biomass burning, industrial emissions, and traffic emissions. Biomass burning was the largest contributor to light absorption in Chuncheon, whereas traffic emissions were the dominant contributor in Seoul. This trend was consistently reflected in the AAE and Mass Absorption Cross-section (MAC) values calculated for each source. This study provides new insights into the quantification of source-specific optical properties of aerosols using PMF, offering a robust approach to understanding their impacts on atmospheric radiative forcing.