Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer?
<p>Nitrous acid, <span class="inline-formula">HONO</span>, is a key net photolytic precursor to <span class="inline-formula">OH</span> radicals in the atmospheric boundary layer. As <span class="inline-formula">OH</span> is the...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2021-12-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/21/18213/2021/acp-21-18213-2021.pdf |
| _version_ | 1819004476237807616 |
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| author | L. R. Crilley L. R. Crilley L. J. Kramer L. J. Kramer F. D. Pope C. Reed C. Reed J. D. Lee L. J. Carpenter L. D. J. Hollis S. M. Ball W. J. Bloss |
| author_facet | L. R. Crilley L. R. Crilley L. J. Kramer L. J. Kramer F. D. Pope C. Reed C. Reed J. D. Lee L. J. Carpenter L. D. J. Hollis S. M. Ball W. J. Bloss |
| author_sort | L. R. Crilley |
| collection | DOAJ |
| description | <p>Nitrous acid, <span class="inline-formula">HONO</span>, is a key net photolytic precursor to <span class="inline-formula">OH</span>
radicals in the atmospheric boundary layer. As <span class="inline-formula">OH</span> is the dominant
atmospheric oxidant, driving the removal of many primary pollutants and the
formation of secondary species, a quantitative understanding of <span class="inline-formula">HONO</span> sources is important to predict atmospheric oxidising capacity. While a number of
<span class="inline-formula">HONO</span> formation mechanisms have been identified, recent work has ascribed
significant importance to the dark, ocean-surface-mediated conversion of
<span class="inline-formula">NO<sub>2</sub></span> to <span class="inline-formula">HONO</span> in the coastal marine boundary layer. In order to evaluate
the role of this mechanism, here we analyse measurements of <span class="inline-formula">HONO</span> and related
species obtained at two contrasting coastal locations – Cabo Verde
(Atlantic Ocean, denoted Cape Verde herein), representative of the clean remote tropical marine
boundary layer, and Weybourne (United Kingdom), representative of
semi-polluted northern European coastal waters. As expected, higher average
concentrations of <span class="inline-formula">HONO</span> (70 ppt) were observed in marine air for the more
anthropogenically influenced Weybourne location compared to Cape Verde (<span class="inline-formula">HONO</span> <span class="inline-formula"><i><</i></span> 5 ppt). At both sites, the approximately constant <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">HONO</mi><mspace linebreak="nobreak" width="0.125em"/><mo>/</mo><mspace width="0.125em" linebreak="nobreak"/><msub><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="65pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="2b45f25831a74b6b87a56a771d67638f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-18213-2021-ie00001.svg" width="65pt" height="14pt" src="acp-21-18213-2021-ie00001.png"/></svg:svg></span></span>
ratio at night pointed to a low importance for the dark, ocean-surface-mediated conversion of <span class="inline-formula">NO<sub>2</sub></span> into <span class="inline-formula">HONO</span>, whereas the midday maximum in the
<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">HONO</mi><mspace width="0.125em" linebreak="nobreak"/><mo>/</mo><mspace width="0.125em" linebreak="nobreak"/><msub><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="65pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="180349e123cb250f82d08dca8e4cb15f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-18213-2021-ie00002.svg" width="65pt" height="14pt" src="acp-21-18213-2021-ie00002.png"/></svg:svg></span></span> ratios indicated significant contributions from photo-enhanced
<span class="inline-formula">HONO</span> formation mechanisms (or other sources). We obtained an upper limit to
the rate coefficient of dark, ocean-surface <span class="inline-formula">HONO</span>-to-<span class="inline-formula">NO<sub>2</sub></span> conversion of
<span class="inline-formula"><i>C</i><sub>HONO</sub></span> <span class="inline-formula">=</span> 0.0011 ppb h<span class="inline-formula"><sup>−1</sup></span> from the Cape Verde observations; this
is a factor of 5 lower than the slowest rate reported previously. These
results point to significant geographical variation in the predominant <span class="inline-formula">HONO</span>
formation mechanisms in marine environments and indicate that caution is
required when extrapolating the importance of such mechanisms from
individual study locations to assess regional and/or global impacts on
oxidising capacity. As a significant fraction of atmospheric processing
occurs in the marine boundary layer, particularly in the tropics, better
constraint of the possible ocean surface source of <span class="inline-formula">HONO</span> is important for a
quantitative understanding of chemical processing of primary trace gases in
the global atmospheric boundary layer and associated impacts upon air
pollution and climate.</p> |
| first_indexed | 2024-12-20T23:37:30Z |
| format | Article |
| id | doaj.art-391e163535f340799c5e34e05a359d3a |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-20T23:37:30Z |
| publishDate | 2021-12-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-391e163535f340799c5e34e05a359d3a2022-12-21T19:23:10ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242021-12-0121182131822510.5194/acp-21-18213-2021Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer?L. R. Crilley0L. R. Crilley1L. J. Kramer2L. J. Kramer3F. D. Pope4C. Reed5C. Reed6J. D. Lee7L. J. Carpenter8L. D. J. Hollis9S. M. Ball10W. J. Bloss11School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, United Kingdomnow at: Department of Chemistry, York University, Toronto, ON, CanadaSchool of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, United Kingdomnow at: Ricardo Energy & Environment, Harwell, Oxfordshire, United Kingdom.School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, United KingdomWolfson Atmospheric Chemistry Laboratory (WACL), Department of Chemistry, University of York, Heslington, York, United Kingdomnow at: FAAM Airborne Laboratory, Building 146, Cranfield University, Cranfield, United KingdomWolfson Atmospheric Chemistry Laboratory (WACL), Department of Chemistry, University of York, Heslington, York, United KingdomWolfson Atmospheric Chemistry Laboratory (WACL), Department of Chemistry, University of York, Heslington, York, United KingdomSchool of Chemistry, University of Leicester, Leicester, United KingdomSchool of Chemistry, University of Leicester, Leicester, United KingdomSchool of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom<p>Nitrous acid, <span class="inline-formula">HONO</span>, is a key net photolytic precursor to <span class="inline-formula">OH</span> radicals in the atmospheric boundary layer. As <span class="inline-formula">OH</span> is the dominant atmospheric oxidant, driving the removal of many primary pollutants and the formation of secondary species, a quantitative understanding of <span class="inline-formula">HONO</span> sources is important to predict atmospheric oxidising capacity. While a number of <span class="inline-formula">HONO</span> formation mechanisms have been identified, recent work has ascribed significant importance to the dark, ocean-surface-mediated conversion of <span class="inline-formula">NO<sub>2</sub></span> to <span class="inline-formula">HONO</span> in the coastal marine boundary layer. In order to evaluate the role of this mechanism, here we analyse measurements of <span class="inline-formula">HONO</span> and related species obtained at two contrasting coastal locations – Cabo Verde (Atlantic Ocean, denoted Cape Verde herein), representative of the clean remote tropical marine boundary layer, and Weybourne (United Kingdom), representative of semi-polluted northern European coastal waters. As expected, higher average concentrations of <span class="inline-formula">HONO</span> (70 ppt) were observed in marine air for the more anthropogenically influenced Weybourne location compared to Cape Verde (<span class="inline-formula">HONO</span> <span class="inline-formula"><i><</i></span> 5 ppt). At both sites, the approximately constant <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">HONO</mi><mspace linebreak="nobreak" width="0.125em"/><mo>/</mo><mspace width="0.125em" linebreak="nobreak"/><msub><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="65pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="2b45f25831a74b6b87a56a771d67638f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-18213-2021-ie00001.svg" width="65pt" height="14pt" src="acp-21-18213-2021-ie00001.png"/></svg:svg></span></span> ratio at night pointed to a low importance for the dark, ocean-surface-mediated conversion of <span class="inline-formula">NO<sub>2</sub></span> into <span class="inline-formula">HONO</span>, whereas the midday maximum in the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">HONO</mi><mspace width="0.125em" linebreak="nobreak"/><mo>/</mo><mspace width="0.125em" linebreak="nobreak"/><msub><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="65pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="180349e123cb250f82d08dca8e4cb15f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-18213-2021-ie00002.svg" width="65pt" height="14pt" src="acp-21-18213-2021-ie00002.png"/></svg:svg></span></span> ratios indicated significant contributions from photo-enhanced <span class="inline-formula">HONO</span> formation mechanisms (or other sources). We obtained an upper limit to the rate coefficient of dark, ocean-surface <span class="inline-formula">HONO</span>-to-<span class="inline-formula">NO<sub>2</sub></span> conversion of <span class="inline-formula"><i>C</i><sub>HONO</sub></span> <span class="inline-formula">=</span> 0.0011 ppb h<span class="inline-formula"><sup>−1</sup></span> from the Cape Verde observations; this is a factor of 5 lower than the slowest rate reported previously. These results point to significant geographical variation in the predominant <span class="inline-formula">HONO</span> formation mechanisms in marine environments and indicate that caution is required when extrapolating the importance of such mechanisms from individual study locations to assess regional and/or global impacts on oxidising capacity. As a significant fraction of atmospheric processing occurs in the marine boundary layer, particularly in the tropics, better constraint of the possible ocean surface source of <span class="inline-formula">HONO</span> is important for a quantitative understanding of chemical processing of primary trace gases in the global atmospheric boundary layer and associated impacts upon air pollution and climate.</p>https://acp.copernicus.org/articles/21/18213/2021/acp-21-18213-2021.pdf |
| spellingShingle | L. R. Crilley L. R. Crilley L. J. Kramer L. J. Kramer F. D. Pope C. Reed C. Reed J. D. Lee L. J. Carpenter L. D. J. Hollis S. M. Ball W. J. Bloss Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer? Atmospheric Chemistry and Physics |
| title | Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer? |
| title_full | Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer? |
| title_fullStr | Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer? |
| title_full_unstemmed | Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer? |
| title_short | Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer? |
| title_sort | is the ocean surface a source of nitrous acid hono in the marine boundary layer |
| url | https://acp.copernicus.org/articles/21/18213/2021/acp-21-18213-2021.pdf |
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