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Abstract. Smoke from laboratory chamber burning of peat fuels from Russia, Siberia, the USA (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 intermediately aged (∼2 d) and well-aged (∼7 d) source profiles. Species abundances in PM2.5 between aged and fresh profiles varied by several orders of magnitude with two distinguishable clusters, centered around 0.1 % for reactive and ionic species and centered around 10 % for carbon. Organic carbon (OC) accounted for 58 %–85 % of PM2.5 mass in fresh profiles with low elemental carbon (EC) abundances (0.67 %–4.4 %). OC abundances decreased by 20 %–33 % for well-aged profiles, with reductions of 3 %–14 % for the volatile OC fractions (e.g., OC1 and OC2, thermally evolved at 140 and 280 ∘C). Ratios of organic matter (OM) to OC abundances increased by 12 %–19 % from intermediately aged to well-aged smoke. Ratios of ammonia (NH3) to PM2.5 decreased after intermediate aging. Well-aged NH4+ and NO3- abundances increased to 7 %–8 % of PM2.5 mass, associated with decreases in NH3, low-temperature OC, and levoglucosan abundances for Siberia, Alaska, and Everglades (Florida) 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. The water-soluble organic carbon (WSOC) fractions of PM2.5 were over 2-fold higher in fresh Russian peat (37.0±2.7 %) than in Malaysian (14.6±0.9 %) peat. While Russian peat OC emissions were largely water-soluble, Malaysian peat emissions were mostly water-insoluble, with WSOC ∕ OC ratios of 0.59–0.71 and 0.18–0.40, respectively. 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 (∼7 d) 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.

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24Smoke from laboratory chamber burning of peat fuels from Russia, Siberia, U.S.A. (Alaska 25 and Florida), and Malaysia representing boreal, temperate, subtropical, and tropical regions was 26 sampled before and after passing through a potential aerosol mass-oxidation flow reactor (PAM-27 OFR) to simulate ~2-and 7-day atmospheric aging. Species abundances in PM2.5 between aged 28 and fresh profiles varied by >5 orders of magnitude with two distinguishable clusters: around 29 0.1% for reactive and ionic species and mostly >10 % for carbon. 30Organic carbon (OC) accounted for 58-85 % of PM2.5 mass in fresh profiles with low EC 31 abundance (0.67-4.4 %). After a 7-day aging time, degradation was 20-33 % for OC, with 32 apparent reductions (4-12 %) in low temperature OC1 and OC2 (thermally evolved at 140 and 33 280 °C), implying evaporation of higher vapor pressure semi-volatile organic compounds 34 (SVOCs). Additional losses of OC from 2-to 7-days aging is somewhat offset by the formation 35 of oxygenated organic compounds, as evidenced by the 12-19 % increase in organic mass (OM) 36 to OC ratios. However, the reduction of OM abundances in PM2.5 by 3-18 % after 7 days, 37 reconfirms that volatilization is the main loss mechanism of SVOCs. Although the ammonia 38 (NH3) to PM2.5 ratio rapidly diminished with a 2-day aging time, it represents an intermediate 39 profile -not sufficient for completed OC evaporation, levoglucosan degradation, organic acid 40 oxidation, or secondary inorganic aerosol formation. 41Week-long aging resulted in an increase to ~7-8 % of NH4 + and NO3abundances, but with 42 enhanced degradation of NH3, low temperature OC, and levoglucosan for Siberia, Alaska, and 43 Everglasdes (FL) peats. Elevated levoglucosan was found for Russian peats, accounting for 35-44 39 % and 20-25 % of PM2.5 mass for fresh and aged profiles, respectively. Abundances of water-45 soluble organic carbon (WSOC) in PM2.5 was >2-fold higher in fresh Russian (37.0 ± 2.7 %) than 46 Malaysian (14.6 ± 0.9 %) peats. While Russian peat OC emissions are largely water-soluble, 47to-particle partitioning of semi-volatilized species, gas-phase oxidation, and particle volatilization 54 to achieve representative source profiles for regional-scale source apportionment. 55 56 Keywords: fresh and aged source profiles, atmospheric aging, organic mass, organic carbon, 57 levoglucosan, oxidation flow reactor (OFR) 58

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