Abstract
Abstract. There is a lack of knowledge of how biomass burning aerosols in the tropics age, including those in the fire-prone Northern Territory in Australia. This paper reports chemical characterization of fresh and aged aerosols monitored during the 1-month-long SAFIRED (Savannah Fires in the Early Dry Season) field study, with an emphasis on the chemical signature and aging of organic aerosols. The campaign took place in June 2014 during the early dry season when the surface measurement site, the Australian Tropical Atmospheric Research Station (ATARS), located in the Northern Territory, was heavily influenced by thousands of wild and prescribed bushfires. ATARS was equipped with a wide suite of instrumentation for gaseous and aerosol characterization. A compact time-of-flight aerosol mass spectrometer was deployed to monitor aerosol chemical composition. Approximately 90 % of submicron non-refractory mass was composed of organic material. Ozone enhancement in biomass burning plumes indicated increased air mass photochemistry. The diversity in biomass burning emissions was illustrated through variability in chemical signature (e.g. wide range in f44, from 0.06 to 0.18) for five intense fire events. The background particulate loading was characterized using positive matrix factorization (PMF). A PMF-resolved BBOA (biomass burning organic aerosol) factor comprised 24 % of the submicron non-refractory organic aerosol mass, confirming the significance of fire sources. A dominant PMF factor, OOA (oxygenated organic aerosol), made up 47 % of the sampled aerosol, illustrating the importance of aerosol aging in the Northern Territory. Biogenic isoprene-derived organic aerosol factor was the third significant fraction of the background aerosol (28 %).
Highlights
Tropical regions are some of the most fire-prone areas in the world (Crutzen and Andreae, 1990)
The Beta Plus particle measurement system (BAM) organic mass (OM) and Organic aerosol (OA) mass concentration sampled by the AMS are in good agreement (R value of 0.94), with slightly higher concentrations measured by the BAM (Fig. S2c in the Supplement), probably due to the lower collection efficiency of the AMS above 700 nm
A 1-month-long campaign called SAFIRED was conducted in northern Australia during a period of significant burning
Summary
Tropical regions are some of the most fire-prone areas in the world (Crutzen and Andreae, 1990). An extensive area of the Northern Territory of Australia is burned each year during the dry season (May–October) and the region is strongly affected by BB emissions Considering that this area is a globally significant source of BB aerosol emissions (Mitchell et al, 2013), and that there have been a limited number of studies on aerosol characterization and aging, there is a need for more research. This will contribute to a better understanding of fire emissions in tropical regions. This publication presents insights into fresh and aged aerosols emitted during SAFIRED, while a detailed description of the campaign can be found in Mallet et al (2017)
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