Abstract View
Light Absorbing Properties of Biomass Burning-influenced Organic Aerosols in Southeast Asia
NETHMI KASTHURIARACHCHI, Laura-Helena Rivellini, Alex Lee, National University of Singapore
Abstract Number: 277
Working Group: Carbonaceous Aerosol
Abstract
Biomass burning (BB) used for agriculture and forest management in Southeast Asia have been responsible for severe haze that have generated light absorbing aerosols that heat up the upper troposphere by up to 20 Wm-2 (Ge et al., 2014). The widespread peatlands in this region usually undergo smoldering conditions below surface levels at low temperatures for prolonged periods with occasional surface flaring, which is different to the burning conditions of surface vegetation.
In this work, we use a soot particle aerosol mass spectrometer (SP-AMS) to identify the sources of organic aerosols (OA) during two BB-influenced periods in Singapore, a highly urbanized country in Southeast Asia where influence from transboundary smoke together with local urban emissions and atmospheric processing of BB-influenced aerosols during transport results in a complex mixture of OA. Together with absorption measurements from a seven-wavelength aethalometer, we quantify the absorption properties of both primary and secondary OA (POA and SOA) influenced by BB. We find that for the first period, which was influenced by relatively fresh BB, a small fraction of strongly absorbing BBOA were responsible for a majority of the light absorption by OA while another BBOA factor had very weak light absorbing properties. Haze, influenced by transboundary smoke, governed the second BB-influenced period where the BBOA factors were more oxygenated and less light absorbing than the fresh BB observed in the previous campaign, likely due to photobleaching that may have occurred during transport. A SOA factor, influenced by both local chemistry and atmospheric processing of BB emissions, had significant light absorbing properties highlighting the importance of the impact of BB on the absorptivity of SOA. This is the first field study to quantify absorption properties of different types of POA and SOA influenced by BB in Southeast Asia.
References
[1] Ge, C., Wang, J., & Reid, J. S. (2014). Mesoscale modeling of smoke transport over the Southeast Asian maritime continent: Coupling of smoke direct radiative effect below and above the low-level clouds. Atmospheric Chemistry and Physics, 14(1), 159–174. https://doi.org/10.5194/acp-14-159-2014.