A multi-site passive approach to studying the emissions and evolution of smoke from prescribed fires
<p>We conducted a 2-year study utilizing a network of fixed sites with sampling throughout an extended prescribed burning period to characterize the emissions and evolution of smoke from silvicultural prescribed burning at a military base in the southeastern USA. The measurement approach and a...
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| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2024-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/24/12749/2024/acp-24-12749-2024.pdf |
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| Summary: | <p>We conducted a 2-year study utilizing a network of fixed sites with sampling throughout an extended prescribed burning period to characterize the emissions and evolution of smoke from silvicultural prescribed burning at a military base in the southeastern USA. The measurement approach and an assessment of the instrument performance are described. Smoke sources, including those within and off the base, are identified, and plume ages are determined to quantify emissions and study the evolution of smoke PM<span class="inline-formula"><sub>2.5</sub></span> (particulate matter with aerodynamic diameters 2.5 <span class="inline-formula">µ</span>m or smaller) mass, black carbon (BC), and brown carbon (BrC). Over the 2021 and 2022 prescribed burning seasons (nominally January to May), we identified 64 smoke events based on high levels of PM<span class="inline-formula"><sub>2.5</sub></span> mass, BC, BrC, and carbon monoxide (CO), of which 61 were linked to a specific burning area. Smoke transport times were estimated in two ways: using the mean wind speed and the distance between the fire and the measurement site, and from Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) back-trajectories. PM<span class="inline-formula"><sub>2.5</sub></span> emission ratios based on <span class="inline-formula">Δ</span>PM<span class="inline-formula"><sub>2.5</sub></span> mass <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="36bd7baae116a5efc17e692d563c2b51"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-12749-2024-ie00001.svg" width="8pt" height="14pt" src="acp-24-12749-2024-ie00001.png"/></svg:svg></span></span> <span class="inline-formula">Δ</span>CO for fresh smoke (age <span class="inline-formula">≤</span> 1 h) ranged between 0.04 and 0.18 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span> ppb<span class="inline-formula"><sup>−1</sup></span> with a mean of 0.117 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span> ppb<span class="inline-formula"><sup>−1</sup></span> (median of 0.121 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span> ppb<span class="inline-formula"><sup>−1</sup></span>). Both the mean emission ratio and the variability were similar to findings from other prescribed fire studies but were lower than those from wildfires. The mean emission ratios of BC and BrC were 0.014 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span> ppb<span class="inline-formula"><sup>−1</sup></span> and 0.442 Mm<span class="inline-formula"><sup>−1</sup></span> ppb<span class="inline-formula"><sup>−1</sup></span>, respectively. Ozone enhancements (<span class="inline-formula">Δ</span>O<span class="inline-formula"><sub>3</sub></span>) were always observed in plumes detected in the afternoon. <span class="inline-formula">Δ</span>PM<span class="inline-formula"><sub>2.5</sub></span> mass <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M28" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="6e9042c80619a800f49fe8d9da77f107"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-12749-2024-ie00002.svg" width="8pt" height="14pt" src="acp-24-12749-2024-ie00002.png"/></svg:svg></span></span> <span class="inline-formula">Δ</span>CO was observed to increase with plume age in all of the ozone-enhanced plumes, suggesting photochemical secondary aerosol formation. In contrast, <span class="inline-formula">Δ</span>BrC/<span class="inline-formula">Δ</span>CO was not found to vary with plume ages less than 8 h during photochemically active periods.</p> |
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| ISSN: | 1680-7316 1680-7324 |