Impact of biomass burning on PM2.5 and organic aerosol: Quantitative estimates and spatial distributions in four Northeast Asian sites

An extensive study was conducted to comprehensively assess simultaneous quantitative estimates of biomass burning organic carbon (OC-BB) within fine particulate matter (PM2.5) across four distinct sites encompassing metropolitan and rural regions of Northeast Asia during the spring season. PM2.5 samples were simultaneously collected in sites in Seoul and Seosan (SE: urban and SS: rural, Korea, respectively), Beijing (BJ: urban, China) and Ulaanbaatar (UB: urban, Mongolia), spanning from March to April 2022. The analysis of these samples aimed to quantify BB markers, including levoglucosan, mannosan, and K+, alongside OC. This analysis aimed to provide valuable insights into the impact and contribution of BB to PM2.5 and OC. BB types were identified using levoglucosan/K+-BB and levoglucosan/mannosan ratios. In addition, our study focused on deriving an optimized OC/levoglucosan ratio, which is crucial for the accurate estimation of OC-BB concentrations. Moreover, an approach utilized in this study can be applied in other regions to estimate region-specific OC ∕ levoglucosan ratios for OC-BB. The contribution of OC-BB to total OC varied significantly across sites: SE (27 ± 17%), SS (60 ± 24%), BJ (5 ± 3%), and UB (51 ± 14%). Concentrations of levoglucosan and OC-BB were highest at UB and SS, indicating a greater impact of BB aerosols compared to SE and BJ. Cluster and potential source contribution function analyses showed that in SE, aerosols were influenced by BB originating from both the northwest and southwest directions. Conversely, in SS, the presence of aged, regional, and long-range transported aerosols from the northwest and south directions was observed. This study has the potential to assist in devising precise strategies aimed at mitigating BB, thus fostering improved air quality and environmental protection.