the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Emission factors and evolution of SO2 measured from biomass burning in wild and agricultural fires
- 1Cooperative Institute for Research in Environmental Science, University of Colorado, Boulder, CO, USA
- 2Chemical Sciences Laboratory, NOAA, Boulder, CO, USA
- 3Department of Chemistry, University of Colorado, Boulder, CO, USA
- 4Atmospheric Chemistry and Dynamics Lab, NASA Goddard Space Flight Center, Greenbelt, MD, USA
- 5Bay Area Environmental Research Institute, NASA Ames Research Center, Moffett Field, CA
- 6Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
- 7Earth System Research Center, University of New Hampshire, Durham, NH, USA
- 8NASA Langley Research Center, Hampton, VA, USA
- 9Faculty of Physics, Aerosol Physics and Environmental Physics, University of Vienna, 1090 Vienna, Austria
- 10Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
- 11Environmental Protection Agency, Research Triangle, NC, USA
- 12Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, MD 21250, USA
- 13Goddard Earth Science Technology and Research (GESTAR) II, University of Maryland Baltimore County, Baltimore, MD, USA
- 14CACC, Aerodyne Research, Inc.
- 15Science Systems and Applications, Inc., Hampton, VA, USA
- 16National Institute of Aerospace, Resident at NASA Langley Research Center, Hampton, VA, USA
- 17Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA
- anow at: Scientific Aviation, Boulder, CO, USA
- 1Cooperative Institute for Research in Environmental Science, University of Colorado, Boulder, CO, USA
- 2Chemical Sciences Laboratory, NOAA, Boulder, CO, USA
- 3Department of Chemistry, University of Colorado, Boulder, CO, USA
- 4Atmospheric Chemistry and Dynamics Lab, NASA Goddard Space Flight Center, Greenbelt, MD, USA
- 5Bay Area Environmental Research Institute, NASA Ames Research Center, Moffett Field, CA
- 6Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
- 7Earth System Research Center, University of New Hampshire, Durham, NH, USA
- 8NASA Langley Research Center, Hampton, VA, USA
- 9Faculty of Physics, Aerosol Physics and Environmental Physics, University of Vienna, 1090 Vienna, Austria
- 10Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
- 11Environmental Protection Agency, Research Triangle, NC, USA
- 12Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, MD 21250, USA
- 13Goddard Earth Science Technology and Research (GESTAR) II, University of Maryland Baltimore County, Baltimore, MD, USA
- 14CACC, Aerodyne Research, Inc.
- 15Science Systems and Applications, Inc., Hampton, VA, USA
- 16National Institute of Aerospace, Resident at NASA Langley Research Center, Hampton, VA, USA
- 17Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA
- anow at: Scientific Aviation, Boulder, CO, USA
Abstract. Fires emit sufficient sulfur to affect local and regional air quality and climate. This study analyzes SO2 emission factors and variability in smoke plumes from US wild and agricultural fires, and their relationship to sulfate and hydroxymethanesulfonate (HMS) formation. Observed SO2 emission factors for various fuel types show good agreement with the latest reviews of biomass burning emission factors, producing an emission factor range of 0.47–1.2 g SO2 kg-1 C in the emissions. These emission factors vary with geographic location in a way that suggests that deposition of coal burning emissions and application of sulfur-containing fertilizers likely play a role in the larger observed values, which are primarily associated with agricultural burning. A 0-D box model generally reproduces the observed trends of SO2 and total sulfate (inorganic + organic) in aging wildfire plumes. In many cases, modeled HMS is consistent with the observed organosulfur concentrations. However, a comparison of observed organosulfur and modeled HMS suggests that multiple organosulfur compounds are likely responsible for the observations, but that the chemistry of these compounds yield similar production and loss rates to that of HMS, resulting in good agreement with the modeled results. We provide suggestions for constraining the organosulfur compounds observed during these flights and we show that the chemistry of HMS can allow for organosulfur to act as a S(IV) reservoir under conditions of increased pH (>6) and liquid water content (>10-7 g m-3). This can facilitate long-range transport of sulfur emissions resulting in increased SO2 and eventually sulfate in transported smoke.
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Pamela Rickly et al.
Status: open (until 24 Jun 2022)
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RC1: 'Comment on acp-2022-309 Please check rate constant', Anonymous Referee #1, 19 May 2022
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This paper reports the surprising result that HMS can act as a sulfur reservoir by conversion of HMS back to bisulfite and/or sulfite on relatively short time scales. The reaction describing this conversion is given in Table S1 and the work of Song et al. (2021) (and references therein) is referenced. In this paper's Table S1 the pre-exponential factor for the rate of HMS loss by this reaction is 6.2 x 10 +8 , however, in Song et al the factor is k = 6.2 x 10 -8, a difference of 16 orders of magnitude. Maybe this is a typo, or maybe it explains the unexpected short lifetime of HMS? It would be optimal for the authors to address this issue prior to a full review of the paper since it impacts a large portion of the manuscript.
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AC1: 'Reply on RC1', Pamela Rickly, 19 May 2022
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Thank you for pointing this out. This is a typo in Table S1, but the reaction is correctly represented in the model as k = 6.2 x 10 -8. The SI will be corrected accordingly.
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AC1: 'Reply on RC1', Pamela Rickly, 19 May 2022
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RC2: 'Comment on acp-2022-309', Anonymous Referee #2, 19 May 2022
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The manuscript investigates the sulfur dioxide (SO2) emissions, and sulfate and hydroxymethanesulfonate (HMS) formation from US wild and agricultural fires. The study includes a combination of field data, collected during the course of two flights (one in Boise, ID and the other in Salina, KS) and modeling, using a 0-D box model. The authors provide SO2 fuel emission factors in agreement with previously literature reported values and provide evidence that HMS acts as S(IV) reservoir under higher pH and liquid water content conditions. This new role of HMS provides valuable insight on the role of sulfur-containing species under biomass burning conditions. I believe that the authors have conducted an analytical work that is of interest to the readers of ACP, however there are some points that need to be addressed. Please find below some comments that I believe need to be addressed in order to clarify specific results and the model mechanism used in this work.
- The authors provide an HMS loss rate constant of: 6.2 × 10^8 × exp(−11400 × (1/T − 1/298)) +4.8 × 103 × (Kw/ H + ) × exp(−4700 × (1/T − 1/298), while Song et al. (2021, ACP), which is used as the reference of the rate, provide a rate constant of: 6.2 × 10^−8 × exp(−11400 × (1/T − 1/298)) +4.8 × 103 × (Kw/ H + ) × exp(−4700 × (1/T − 1/298). I assume that this is a typo, but please clarify.
Assuming that the HMS loss rate has a typo, additional comments are:
- The role of HMS as S(IV) reservoir is very interesting, especially since this result is mainly under conditions of pH>6 and high LWC, in which HMS has been shown to be unstable and prone to additional reactions. In the model, the formation and decomposition of HMS is included (Table S1), however its reactions with OH and H2O2, which has been shown to occur at pH>6 (Kok et al., 1986. J. Geoph. Res.; Martin et al., 1989, Atmos. Environ.; Chapman et al., 1990, Atmos. Environ.) are not included. How are the results affected upon inclusion of these reactions?
- The model represents efficiently the field data of August 3rd, however it does not capture the trend of all the field data for the case of August 7th. Since both days are within the same campaign in Boise, ID, what was the main differences between these days? It would be interesting to provide a brief explanation on why the two days differ, as provided for the two passes of the 7th of August.
- Field data are provided for mainly August 3rd and 7th, which correspond to the Boise flights. It would be beneficial to provide field data and the model performance for the Saline flights. Are the main results the same for both flights? This is not very clear.
- It is stated in the manuscript that HMS can be over-predicted and that additional organosulfur species can be “the result of further reactions of HMS suggesting that the model is correctly reproducing the HMS formation chemistry, but indicating that the model aqueous phase chemistry is incomplete” (lines 639-641). The inclusion of HMS oxidation via OH and H2O2 might improve the HMS prediction for the cases that pH>6, however for more acidic conditions there is another pathway that can lead to sulfate formation but also add to the HCHO loading and potentially affect the HMS chemistry. HCHO can react directly with H2O2 forming hydroxymethyl hydroperoxide, which can then decompose to reform HCHO and H2O2 (Dovrou et al., 2022, PNAS). Since H2O2 and HCHO are observed via the flight measurements, could this pathway be useful for the model representation of these species as well as the organosulfur chemistry (as it provides further information regarding HCHO (source of HMS))?
Pamela Rickly et al.
Pamela Rickly et al.
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