Measurement report: Emission factors of NH<sub>3</sub> and NH<sub><i>x</i></sub> for wildfires and agricultural fires in the United States
<p>During the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) study, the NASA DC-8 carried out in situ chemical measurements in smoke plumes emitted from wildfires and agricultural fires in the contiguous United States. The DC-8 payload included a modified pro...
| Main Authors: | , , , , , , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-02-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/2331/2023/acp-23-2331-2023.pdf |
| Summary: | <p>During the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) study, the NASA DC-8 carried out in situ chemical measurements in smoke plumes emitted from wildfires and agricultural fires in the contiguous United States. The DC-8 payload included a modified proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) for the fast measurement of gaseous ammonia (<span class="inline-formula">NH<sub>3</sub></span>) and a high-resolution time-of-flight aerosol mass spectrometer (AMS) for the fast measurement of submicron particulate ammonium (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="6ca56caa63735c5009fe6b299c1a126b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-2331-2023-ie00001.svg" width="24pt" height="15pt" src="acp-23-2331-2023-ie00001.png"/></svg:svg></span></span>). We herein report data collected in smoke plumes emitted from 6 wildfires in the Western United States, 2 prescribed grassland fires in the Central United States, 1 prescribed forest fire in the Southern United States, and 66 small agricultural fires in the Southeastern United States. Smoke plumes contained double to triple digit ppb levels of <span class="inline-formula">NH<sub>3</sub></span>. In the wildfire plumes, a significant fraction of <span class="inline-formula">NH<sub>3</sub></span> had already been converted to <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="9641cdd414b305565815b5b604dabf23"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-2331-2023-ie00002.svg" width="24pt" height="15pt" src="acp-23-2331-2023-ie00002.png"/></svg:svg></span></span> at the time of sampling (<span class="inline-formula">≥2</span> h after emission). Substantial amounts of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="8cff18dc7544e09830abea500d71300b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-2331-2023-ie00003.svg" width="24pt" height="15pt" src="acp-23-2331-2023-ie00003.png"/></svg:svg></span></span> were also detected in freshly emitted smoke from corn and rice field fires. We herein present a comprehensive set of emission factors of <span class="inline-formula">NH<sub>3</sub></span> and <span class="inline-formula">NH<sub><i>x</i></sub></span>, with <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><mrow class="chem"><msub><mi mathvariant="normal">NH</mi><mi>x</mi></msub></mrow><mo>=</mo><mrow class="chem"><msub><mi mathvariant="normal">NH</mi><mn mathvariant="normal">3</mn></msub></mrow><mo>+</mo><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="89pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="af1400529af5292f7904d75790a54816"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-2331-2023-ie00004.svg" width="89pt" height="15pt" src="acp-23-2331-2023-ie00004.png"/></svg:svg></span></span>. Average <span class="inline-formula">NH<sub>3</sub></span> and <span class="inline-formula">NH<sub><i>x</i></sub></span> emission factors for wildfires in the Western United States were <span class="inline-formula">1.86±0.75</span> g kg<span class="inline-formula"><sup>−1</sup></span> and <span class="inline-formula">2.47±0.80</span> g kg<span class="inline-formula"><sup>−1</sup></span> of fuel burned, respectively. Average <span class="inline-formula">NH<sub>3</sub></span> and <span class="inline-formula">NH<sub><i>x</i></sub></span> emission factors for agricultural fires in the Southeastern United States were <span class="inline-formula">0.89±0.58</span> and <span class="inline-formula">1.74±0.92</span> g kg<span class="inline-formula"><sup>−1</sup></span>, respectively. Our data show no clear inverse correlation between modified combustion efficiency (MCE) and <span class="inline-formula">NH<sub>3</sub></span> emissions. The observed <span class="inline-formula">NH<sub>3</sub></span> emissions were significantly higher than measured in previous laboratory experiments in the FIREX FireLab 2016 study.</p> |
|---|---|
| ISSN: | 1680-7316 1680-7324 |