박건도 (경북대학교)

김성환 (경북대학교)

김영환 (한국기초과학지원연구원)

박건도 (경북대학교)

김성환 (경북대학교)

김영환 (한국기초과학지원연구원)

안윤경 (한국기초과학지원연구원)

조정민 (이화여자대학교)

During the Southeast Asian dry season (February–April), slash-and-burn and agricultural residue burning are major sources of regional air pollution. Primary organic aerosols (POA) undergo atmospheric oxidation to form secondary organic aerosols (SOA), yet the molecular composition and formation mechanisms of residue-burning SOA remain unclear. In this study, PM from chamber combustion of rice straw and ambient PM collected in northern Thailand (4 March–10 April 2025) were analyzed to elucidate oxidation pathways of POA-derived compounds. Samples were characterized by FT-ICR MS with negative-mode atmospheric pressure chemical ionization, while PAHs were quantified by GC-MS for source apportionment. A rule-based molecular prediction approach was applied, and predicted products were matched with FT-ICR MS molecular formulas to confirm SOA formation. Rice straw POA was dominated by CHO and CHON compounds with low O/C and H/C ratios, abundant in the PAH-like region of the Van Krevelen diagram. In contrast, ambient PM showed higher O/C ratios and more oxidized distributions, with increased oxidized CHON species indicating that functionalization dominates during atmospheric aging. SOA prediction identified both monomeric and oligomeric products, clarifying formation pathways. These results demonstrate that residue-burning PM2.5 in northern Thailand undergoes oxidative aging to form SOA, advancing understanding of its chemical evolution and health impacts.

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