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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 29 May 2019

Research article | 29 May 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).

Changes in PM2.5 Peat Combustion Source Profiles with Atmospheric Aging in an Oxidation Flow Reactor

Judith C. Chow1,2, Junji Cao2,3, L.-W Antony Chen4, Xiaoliang Wang1, Qiyuan Wang2,3, Jie Tian2,3, Steven Sai Hang Ho1,5, Tessa B. Carlson1, Steven D. Kohl1, and John G. Watson1,2 Judith C. Chow et al.
  • 1Division of Atmospheric Sciences, Desert Research Institute, Reno, Nevada, USA
  • 2Key Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710061, China
  • 3CAS Center for Excellence in Quaternary Science and Global Change, Xi’an, 710061, China
  • 4Department of Environmental and Occupational Health, University of Nevada, Las Vegas, Nevada, USA
  • 5Hong Kong Premium Services and Research Laboratory, Hong Kong, China

Abstract. Smoke from laboratory chamber burning of peat fuels from Russia, Siberia, U.S.A. (Alaska and Florida), and Malaysia representing boreal, temperate, subtropical, and tropical regions was sampled before and after passing through a potential aerosol mass-oxidation flow reactor (PAM-OFR) to simulate ∼2- and 7-day atmospheric aging. Species abundances in PM2.5 between aged and fresh profiles varied by >5 orders of magnitude with two distinguishable clusters: around 0.1 % for reactive and ionic species and mostly >10 % for carbon.

Organic carbon (OC) accounted for 58–85 % of PM2.5 mass in fresh profiles with low EC abundance (0.67–4.4 %). After a 7-day aging time, degradation was 20–33 % for OC, with apparent reductions (4–12 %) in low temperature OC1 and OC2 (thermally evolved at 140 and 280 °C), implying evaporation of higher vapor pressure semi-volatile organic compounds (SVOCs). Additional losses of OC from 2- to 7-days aging is somewhat offset by the formation of oxygenated organic compounds, as evidenced by the 12–19 % increase in organic mass (OM) to OC ratios. However, the reduction of OM abundances in PM2.5 by 3–18 % after 7 days, reconfirms that volatilization is the main loss mechanism of SVOCs. Although the ammonia (NH3) to PM2.5 ratio rapidly diminished with a 2-day aging time, it represents an intermediate profile – not sufficient for completed OC evaporation, levoglucosan degradation, organic acid oxidation, or secondary inorganic aerosol formation.

Week-long aging resulted in an increase to ∼7–8 % of NH4+ and NO3 abundances, but with enhanced degradation of NH3, low temperature OC, and levoglucosan for Siberia, Alaska, and Everglasdes (FL) peats. Elevated levoglucosan was found for Russian peats, accounting for 35–39 % and 20–25 % of PM2.5 mass for fresh and aged profiles, respectively. Abundances of water-soluble organic carbon (WSOC) in PM2.5 was >2-fold higher in fresh Russian (37.0 ± 2.7 %) than Malaysian (14.6 ± 0.9 %) peats. While Russian peat OC emissions are largely water-soluble, Malaysian peat emissions are mostly water-insoluble, with WSOC/OC ratios of 0.59–0.71 and 0.18–0.40, respectively.

Source profiles can change with aging during transport from source to receptor. This study shows significant differences between fresh and aged peat combustion profiles among the four biomes that can be used to establish speciated emission inventories for atmospheric modeling and receptor model source apportionment. A sufficient aging time (∼one week) is needed to allow gas-to-particle partitioning of semi-volatilized species, gas-phase oxidation, and particle volatilization to achieve representative source profiles for regional-scale source apportionment.

Judith C. Chow et al.
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Publications Copernicus
Short summary
Source profiles that allow peat fire contributions to be distinguished from other source contributions using receptor models, are lacking for a wide variety of peat fuels and burning conditions. These profiles change with photo-chemical aging during transport. Fresh and aged profiles for a variety of peat fuels are measured with an oxidation flow reactor to improve source attributions at distant receptors.
Source profiles that allow peat fire contributions to be distinguished from other source...