Chemical composition, structures, and light absorption of N-containing aromatic compounds emitted from burning wood and charcoal in household cookstoves
<p>N-containing aromatic compounds (NACs) are an important group of light-absorbing molecules in the atmosphere. They are often observed in combustion emissions, but their chemical formulas and structural characteristics remain uncertain. In this study, red oakwood and charcoal fuels were burn...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/20/14077/2020/acp-20-14077-2020.pdf |
| Summary: | <p>N-containing aromatic compounds (NACs) are an important group of
light-absorbing molecules in the atmosphere. They are often observed in
combustion emissions, but their chemical formulas and structural
characteristics remain uncertain. In this study, red oakwood and charcoal
fuels were burned in cookstoves using the standard water-boiling test (WBT)
procedure. Submicron aerosol particles in the cookstove emissions were
collected using quartz (<span class="inline-formula"><i>Q</i><sub>f</sub></span>) and polytetrafluoroethylene (PTFE) filter
membranes positioned in parallel. A backup quartz filter (<span class="inline-formula"><i>Q</i><sub>b</sub></span>) was also
installed downstream of the PTFE filter to evaluate the effect of sampling
artifacts on NAC measurements. Liquid chromatography–mass spectroscopy
(LC–MS) techniques identified 17 NAC chemical formulas in the
cookstove emissions. The average concentrations of total NACs in <span class="inline-formula"><i>Q</i><sub>b</sub></span>
samples (<span class="inline-formula">0.37±0.31</span>–<span class="inline-formula">1.79±0.77</span> <span class="inline-formula">µg m<sup>−3</sup></span>) were
greater than 50 % of those observed in the <span class="inline-formula"><i>Q</i><sub>f</sub></span> samples (<span class="inline-formula">0.51±0.43</span>–<span class="inline-formula">3.91±2.06</span> <span class="inline-formula">µg m<sup>−3</sup></span>), and the <span class="inline-formula"><i>Q</i><sub>b</sub></span>-to-<span class="inline-formula"><i>Q</i><sub>f</sub></span>
mass ratios of individual NACs had a range of 0.02–2.71, indicating that
the identified NACs might have substantial fractions remaining in the
gas phase. In comparison to other sources, cookstove emissions from red oak
or charcoal fuels did not exhibit unique NAC structural features but had
distinct NAC composition. However, before identifying NAC sources by
combining their structural and compositional information, the gas-particle
partitioning behaviors of NACs should be further investigated. The average
contributions of total NACs to the light absorption of organic matter at
<span class="inline-formula"><i>λ</i>=365</span> nm (1.10 %–2.57 %) in <span class="inline-formula"><i>Q</i><sub>f</sub></span> and <span class="inline-formula"><i>Q</i><sub>b</sub></span> samples
(10.7 %–21.0 %) are up to 10 times larger than their mass contributions
(<span class="inline-formula"><i>Q</i><sub>f</sub></span>: 0.31 %–1.01 %; <span class="inline-formula"><i>Q</i><sub>b</sub></span>: 1.08 %–3.31 %), so the identified NACs
are mostly strong light absorbers. To explain more sample extract
absorption, future research is needed to understand the chemical and optical
properties of high-molecular-weight (e.g., molecular weight, <span class="inline-formula">MW>500</span> Da) entities
in particulate matter.</p> |
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| ISSN: | 1680-7316 1680-7324 |