Biomass burning in Indonesia is an important contributor to global and regional budgets of atmospheric aerosols, including climate-warming and potentially human hazardous air pollutant PM2.5. During the boreal fall of 2015, Indonesia experienced an exceptionally high fire season partially due to El Niño induced drought. We analyzed PM2.5 aerosol measurements taken from Singapore from September 2014 – October 2015 for total carbon (TC) and black carbon (BC) concentrations and radiocarbon content [Wiggins et al. in preparation]. The BC was separated from the TC and measured using a modified thermo-optical OC/EC analyzer (Sunset Laboratory Inc., Tigard, OR, USA) coupled to an in-house designed vacuum line to cryogenically trap the CO2 from the BC [Mouteva et al., 2015a]. The CO2 was then converted to graphite using the hydrogen reduction method for ultra-small samples of [Santos et al., 2007]. The CO2 from the TC was derived from combusting the aerosol filters in a sealed quartz tube. The TC CO2 was later graphitized using hydrogen reduction method [Santos et al., 2004]. The radiocarbon content of the TC and ultra-small BC of &gt; 0.9 μg C was measured using a modified accelerator mass spectrometry unit from National Electrostatics Corporation (NEC 0.5MV 1.5SDH-21 spectrometer) at UC Irvine [Beverly et al. 2010]. We discovered enhanced TC and BC concentrations during September – October 2015 relative to low fire background periods. The results were positively correlated with regional active fire counts and aerosol optical depth estimates derived from remote sensing along with Pollutant Standards Index (PSI) values reported by the National Environment Agency in Singapore. The TC and BC radiocarbon content during this time was enriched in radiocarbon compared to the heavily fossil-fuel influenced background. We used these results to estimate the depth of burn into the peat lands in Borneo and Sumatra following previous work by Mouteva et al. [2015b]. Our study suggests the hazardous air quality conditions experienced in Singapore during September – October 2015 was heavily influenced by PM2.5 emissions from biomass burning and accumulated peat.

Streamlining analyses of atmospheric carbonaceous aerosols: Determining the sources of fires in Indonesia

253rd National Meeting (2017)

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