Assessing the Impact of Atmospheric Photochemical Aging on Organic Aerosol Tracers Derived from Burning African Biomass Commonly Found in Botswana

Due to climate change, wildfires are becoming increasingly frequent and intense, leading to substantial production of biomass burning (BB)-derived organic aerosol (BBOA). Although African fires account for over 50% of worldwide BB organic emissions, few studies have systematically analyzed molecular tracers of BBOA in fresh versus photochemically-aged BB emissions representative of African fires. Therefore, using gas chromatography and electron ionization quadrupole mass spectrometry, we analyzed aerosol filter samples collected from both fresh and photochemically-aged BB emissions of six biomass fuel types found in Botswana. The emissions were generated from a furnace mimicking smoldering. For each biomass fuel, 16 known BBOA tracer compounds were quantified and compared between fresh and photochemically-aged BB emissions. Total-suspended atmospheric particulate matter (PM) samples collected from Botswana during fire season were also analyzed. We identified laboratory-generated BBOA constituents (e.g., D-pinitol) that were also found in Botswana PM that could plausibly serve as unique tracers for African BBOA.