AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Impacts of Transboundary Peatland Burning Smoke on In Situ Acidity of Urban Aerosols
Shiguo Jia, Wei Hong Fan, Choon Nam Ong, Jeffrey Reid, LIYA YU, National University of Singapore
Abstract Number: 180 Working Group: Biomass Burning Aerosol: From Emissions to Impacts
Abstract The smoke episode in June 2013 marks the highest aerosol burden in Singapore in the past decade, raising strong concerns about potential impacts on urban atmosphere and public health. Our study campaign conducted in 2012 and 2013 show that transboundary peatland burning smoke surged the local PM2.5 concentration, in average, by a factor of 4, with organic matter (>50% of PM2.5 concentration) dominating over sulfate as the most abundant compound class. This characterizes the peatland burning in Southeast Asia, degrading one of the major carbon sinks in the world.
Bulk PM2.5 in Singapore are strongly acidic (in situ pH=0.4) with the most acidic aerosols of 10–18 nm (in situ pH=-0.3). Interestingly, the transboundary smoke neutralized the urban PM2.5 by introducing more ammonium and increasing the average in situ pH to 1.4. As a worst case scenario for an adult with a tidal volume of 625 ml per breath, and a breathing rate of 12 times/min, 1-hour exposure to local emitted aerosols yielded a deposition of 4.0 micro-gram in the head, tracheobronchial, and alveolar regions together, with an average in situ pH of 0.6. Aerosols depositing in the tracheobronchial region are most acidic with an average in situ pH of 0.3. When the transboundary smoke was present, the total aerosol deposition after 1-hour exposure increased by 2.5 times; aerosols settling in the alveolar region exhibited the largest increment, changing from 1.2 to 4.2 micro-gram. The in situ acidity of depositing aerosols differs, depending on the amount of alkaline matter introduced by the transboundary smoke. During the smoky period in 2012, aerosols parking in the tracheobronchial region are most acidic (average in situ pH=-0.2) whereas during the smoke episode in 2013, the acidity of aerosols settling in all three regions is similar (average in situ pH=~1.0).