Abstract View
Mixing State of Urban Aerosol under the Influences of Biomass Burning and Transboundary Smoke Haze in Southeast Asia
LAURA-HELENA RIVELLINI, Nethmi Kasthuriarachchi, Mutian Ma, Alex Lee, National University of Singapore
Abstract Number: 547
Working Group: Wildfire Aerosols
Abstract
Biomass burning (BB) emissions from forest and tropical peat lands strongly impact air quality in Southeast Asia. BB emissions can mix with urban pollutants and undergo atmospheric aging, leading to a complex mixture of transboundary haze. Advanced understanding on aerosol mixing state can provide insight into resolving aging processes that can significantly impact the aerosol properties of BB emissions. In this study, a soot-particle aerosol mass spectrometer (SP-AMS) was deployed in Singapore during the northeast (NEM) and southwest (SWM) monsoons in 2019. The SP-AMS was operated with dual vaporizers to measure chemical composition and size distribution of non-refractory (inorganic and organic) and refractory (black carbon and metals) particulate matter in bulk and single-particle scales. Positive matrix factorization (PMF) of bulk organic aerosol (OA) data evidences the occasional influences of relatively fresh biomass burning OA (BBOA) during the NEM. Single particle characterization shows that potassium-rich (i.e. an indicator of flaming fire emissions) and a few types of OA-rich particles (e.g. Heavy molecular weight, hydrocarbon-like and cooking OA) had moderate correlations with BBOA factor identified by PMF. In particular, the diel cycles of these OA-rich particles depict higher concentrations with BBOA between 2am and 6am, suggesting a potential mixing of BB emissions on urban primary OA. The intense transboundary smoke haze caused by Indonesian wildfires during the SWM period resulted in high concentrations of highly oxygenated haze-related OA factor, and two major types of sulfate and OA internally mixed particles were observed. The first composed of a higher OA content (~50wt%, SO4~30wt%) and had moderate correlations with the haze-related OAs, highlighting the importance of sulfate chemistry on aging of regional peat fires emissions. In contrast, the second had a higher sulfate content (~50wt%, OA~25wt%) with a smaller peak diameter, which is probably formed locally by oxidation of mixed biogenic and industrial emissions.