Changes in PM 2.5 peat combustion source profiles with atmospheric aging in an oxidation flow reactor

Chow, Judith C.; Cao, Junji; Antony Chen, L.-W.; Wang, Xiaoliang; Wang, Qiyuan; Tian, Jie; Ho, Steven Sai Hang; Watts, Adam C.; Carlson, Tessa B.; Kohl, Steven D.; Watson, John G.

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 (inline-formula∼2 d) and well-aged (inline-formula∼7 d) source profiles. Species abundances in inline-formulaPM2.5 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 inline-formulaPM2.5 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 inline-formulaC). Ratios of organic matter (OM) to OC abundances increased by 12 %–19 % from intermediately aged to well-aged smoke. Ratios of ammonia (NHinline-formula3) to inline-formulaPM2.5 decreased after intermediate aging.

Well-aged inline-formula M9inlinescrollmathml chem normal NH normal 4 + 24pt15ptsvg-formulamathimg9641cdd414b305565815b5b604dabf23 amt-12-5475-2019-ie00001.svg24pt15ptamt-12-5475-2019-ie00001.png and inline-formula M10inlinescrollmathml chem normal NO normal 3 - 25pt16ptsvg-formulamathimgdd23f13eb24280cbe650be4567ce8571 amt-12-5475-2019-ie00002.svg25pt16ptamt-12-5475-2019-ie00002.png abundances increased to 7 %–8 % of inline-formulaPM2.5 mass, associated with decreases in inline-formulaNH3, 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 inline-formulaPM2.5 mass for fresh and aged profiles, respectively. The water-soluble organic carbon (WSOC) fractions of inline-formulaPM2.5 were over 2-fold higher in fresh Russian peat (inline-formula37.0±2.7 %) than in Malaysian (inline-formula14.6±0.9 %) peat. While Russian peat OC emissions were largely water-soluble, Malaysian peat emissions were mostly water-insoluble, with WSOC inline-formula∕ 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 (inline-formula∼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.



Chow, Judith C. / Cao, Junji / Antony Chen, L.-W. / et al: Changes in PM2.5 peat combustion source profiles with atmospheric aging in an oxidation flow reactor. 2019. Copernicus Publications.


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