LAUSR

Abstract This study aimed to characterize the PM2.5 (particulate matter ≤ 2.5 μm in aerodynamic diameter) chemical components obtained at Doi Ang Khang (DAK; high mountain and near-source of biomass-burning (BB) emissions) and Chiang Mai University (CMU; foothill site and an urban location) in northern peninsular Southeast Asia (PSEA) during dry BB season of 2015 through the analysis of water-soluble inorganic ions, organic carbon (OC), and elemental carbon (EC) contents. The 24-h average PM2.5 levels (μg m−3) at DAK (118 ± 36) and CMU (113 ± 45) were about 4 folds greater than the WHO health-based guideline (25 μg m−3). Major diagnostics ratios between selected ions and carbonaceous fractions showed the significant BB influence on ambient aerosols. Enriched tracers in collected aerosols, such as NO3−, OC3 (evolved at 280–480 °C), and EC1-OP (EC evolved at 580 °C minus the pyrolized OC) confirmed that the samples were influenced by significant BB emissions. OC was the most abundant component in PM2.5 and the contribution of BB to OC was estimated to be ~90%. For the first time, the conversion factor of OC to organic matter was estimated on the basis of mass closure approach to be 1.7 ± 0.3 and 1.6 ± 0.3 at DAK and CMU, respectively. Effective carbon ratio, which indicates an association between carbonaceous particles and climatic impact, at DAK revealed the significant atmospheric warming due to the presence of more absorbing aerosols attributed to near-source BB emissions at the high mountain site. The estimated inhalation dose of PM2.5 and EC indicated severe health risk for local inhabitants during their outdoor activities. This study enhances the knowledge of aerosol chemical characterization and also addresses exposure to fine aerosols for local inhabitants during intense BB emissions in northern PSEA.