Impact of Biomass Burning on Organic Carbon and PM_2.5 Concentrations in South Korea: Comparison between Urban and Rural Areas

Biomass burning (BB) in Northeast Asia significantly affects air quality. However, its contribution to atmospheric particulate matter (PM_2.5) and organic carbon (OC) has rarely been studied. Atmospheric PM_2.5 samples were collected using preheated quartz filters from December 15, 2020, to January 14, 2021, during the winter period, from Seoul and Seosan, Republic of Korea. BB tracers, including levoglucosan and mannosan, were quantified from filter sample extracts using gas chromatography-mass spectrometry (GC-MS) analysis, and potassium ions (K⁺) were measured using an online aerosol inorganic monitor (AIM). Concurrently, PM_2.5 mass, OC, and ions were measured. The type of BB, such as hardwood, softwood, crops, grass, duff, and leaves, was identified using the levoglucosan/mannosan and levoglucosan/K⁺-BB ratios. The concentration of OC attributed to BB (OC-BB) was calculated by multiplying the measured levoglucosan concentration by the optimized OC/levoglucosan ratio derived from the source samples. The optimum OC/levoglucosan ratio was calculated using regression analysis between OC from non-BB sources (OC-non-BB) and levoglucosan measured at the site. Softwood was identified as the primary BB source at both sites. The optimal OC/levoglucosan ratios were 21.4 and 13.1 in Seoul and Seosan, respectively. The contribution of OC-BB to the total OC was significantly higher in Seosan (58 ± 18% and 60 ± 24%) than in Seoul (47 ± 10% and 27 ± 17%) during the winter and spring periods, respectively. The data obtained in this study are valuable for the global scientific community in estimating OC-BB contributions, which can be applied to other locations, different particle sizes, and BB types, providing a framework for assessing and mitigating biomass burning activities.