Ground-based investigation of HO<sub><i>x</i></sub> and ozone chemistry in biomass burning plumes in rural Idaho

oleh: A. J. Lindsay, D. C. Anderson, D. C. Anderson, D. C. Anderson, R. A. Wernis, R. A. Wernis, Y. Liang, A. H. Goldstein, A. H. Goldstein, S. C. Herndon, J. R. Roscioli, C. Dyroff, E. C. Fortner, P. L. Croteau, F. Majluf, J. E. Krechmer, T. I. Yacovitch, W. B. Knighton, E. C. Wood

Format: Article
Diterbitkan: Copernicus Publications 2022-04-01

Deskripsi

<p>Ozone (O<span class="inline-formula"><sub>3</sub>)</span>, a potent greenhouse gas that is detrimental to human health, is typically found in elevated concentrations within biomass burning (BB) smoke plumes. The radical species OH, HO<span class="inline-formula"><sub>2</sub></span>, and RO<span class="inline-formula"><sub>2</sub></span> (known collectively as <span class="inline-formula">RO<sub><i>x</i></sub></span>) have central roles in the formation of secondary pollutants including O<span class="inline-formula"><sub>3</sub></span> but are poorly characterized for BB plumes. We present measurements of total peroxy radical concentrations ([XO<span class="inline-formula"><sub>2</sub></span>] <span class="inline-formula">≡</span> [HO<span class="inline-formula"><sub>2</sub></span>] <span class="inline-formula">+</span> [RO<span class="inline-formula"><sub>2</sub></span>]) and additional trace-gas and particulate matter measurements from McCall, Idaho, during August 2018. There were five distinct periods in which BB smoke impacted this site. During BB events, O<span class="inline-formula"><sub>3</sub></span> concentrations were enhanced, evident by ozone enhancement ratios (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Δ</mi><msub><mi mathvariant="normal">O</mi><mn mathvariant="normal">3</mn></msub><mo>/</mo><mi mathvariant="normal">Δ</mi><mi mathvariant="normal">CO</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="54pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="53a08b7626bf7424513aa9dc24e1bb27"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-4909-2022-ie00001.svg" width="54pt" height="14pt" src="acp-22-4909-2022-ie00001.png"/></svg:svg></span></span>) that ranged up to 0.06 ppbv ppbv<span class="inline-formula"><sup>−1</sup></span>. [XO<span class="inline-formula"><sub>2</sub></span>] was similarly elevated during some BB events. Overall, instantaneous ozone production rates (<span class="inline-formula"><i>P</i></span>(O<span class="inline-formula"><sub>3</sub>))</span> were minimally impacted by the presence of smoke as [<span class="inline-formula">NO<sub><i>x</i></sub></span>] enhancements were minimal. Measured XO<span class="inline-formula"><sub>2</sub></span> concentrations were compared to zero-dimensional box modeling results to evaluate the Master Chemical Mechanism (MCM) and GEOS-Chem mechanisms overall and during periods of BB influence. The models consistently overestimated XO<span class="inline-formula"><sub>2</sub></span> with the base MCM and GEOS-Chem XO<span class="inline-formula"><sub>2</sub></span> predictions high by an average of 28 % and 20 %, respectively. One period of BB influence had distinct measured enhancements of 15 pptv XO<span class="inline-formula"><sub>2</sub></span> that were not reflected in the model output, likely due to the presence of unmeasured <span class="inline-formula">HO<sub><i>x</i></sub></span> sources. To the best of our knowledge, this is the first BB study featuring peroxy radical measurements.</p>