Changes in PM<sub>2.5</sub> peat combustion source profiles with atmospheric aging in an oxidation flow reactor

Abstract

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.

Gaseous, PM<sub>2.5</sub> mass, and speciated emission factors from laboratory chamber peat combustion

“…Hydrogen contents of 2 % H-7 % H in Table 1 are consistent with abundances found elsewhere, including (1) ∼ 6 % H for northern Minnesota, USA, peat (Yokelson et al, 1997); (2) ∼ 2 % H-3 % H for the eastern North Carolina peat (Black et al, 2016); and (3) ∼ 5 % H-7 % H for Indonesian peats (Iinuma et al, 2007;Christian et al, 2003;Hatch et al, 2015). Sulfur (S) contents are below detection limits (< 0.01 %), and nitrogen contents are 1 % N-4 % N. Ratios of N/C are 0.02-0.08, consistent with the reported N/C ratios of (1) 0.036 for Neustädter Moor, northern Germany (Iinuma et al, 2007); (2) 0.017-0.04 for Ireland and the United Kingdom (Wilson et al, 2015); (3) 0.02-0.03 for Alberta and Ontario, Canada (Stockwell et al, 2014); (4) 0.062 for Minnesota, USA (Yokelson et al, 1997); (5) 0.022-0.03 for the eastern coast of North Carolina, USA (Black et al, 2016); and (6) 0.036-0.039 for Kalimantan and Sumatra, Indonesia (Christian et al, 2003;Hatch et al, 2015).…”

“…Table 1 shows that peat contains 44 % C-57 % C and 31 % O-39 % O with the exception of the two Guizhou, China, peats (20 % C-30 % C and 21 % O-24 % O). The carbon content (50.6 ± 2.5 % C) in the Borneo, Malaysia, peat is within the range of carbon fractions reported for the Kalimantan and Sumatra, Indonesia, peat (44 % C-60 % C) (Christian et al, 2003;Hatch et al, 2015;Iinuma et al, 2007;May et al, 2014;Setyawati et al, 2017). The low carbon content (20 % C-30 % C) of Guizhou peats is similar to the 28 % C-30 % C reported for two eastern North Carolina, USA, peats (Black et al, 2016).…”

“…, and average boreal/temperate peats (Hu et al, 2018), respectively. Malaysian peat EF CO 2 measured in this study is 20 % lower than the 1681 ± 96 g kg −1 , averaged from seven studies of Kalimantan and Sumatra, Indonesia, peats (Christian et al, 2003;Stockwell et al, 2014;Huijnen et al, 2016;Nara et al, 2017).…”

Development and application of a mass closure PM&lt;sub&gt;2.5&lt;/sub&gt; composition online monitoring system

“…Factor 8 displayed large EV values of Zn, and Fe and Ca also had high enrichment factors. The Zn might have been due to industrial sources, such as plastic incineration, coating and metallurgy (Zabalza et al, 2006;Cruz Minguillón et al, 2007). The Ca might come from the soot produced by the inferior coal and diesel combustion in the industry (Lewis and Macias, 1980).…”

Development and application of a mass closure PM&lt;sub&gt;2.5&lt;/sub&gt; composition online monitoring system

“…OM can be calculated by multiplying the OC concentrations by a multiplier that is an estimation of the average molecular weight per carbon weight for the organic aerosol. This multiplier has been investigated in previous studies (Turpin and Lim, 2001;Boris et al, 2019;Chow et al, 2019) and is widely used to estimate OM concentrations (Chow et al, 2015). This estimation method has large uncertainty because the multiplier varies with time and location and ranges from 1.2 to 2.6 (Chow et al, 2015).…”