Role of the dew water on the ground surface in HONO distribution: a case measurement in Melpitz
<p>To characterize the role of dew water for the ground surface HONO distribution, nitrous acid (HONO) measurements with a Monitor for AeRosols and Gases in ambient Air (MARGA) and a LOng Path Absorption Photometer (LOPAP) instrument were performed at the Leibniz Institute for Tropospheric Res...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/20/13069/2020/acp-20-13069-2020.pdf |
| Summary: | <p>To characterize the role of dew water for the ground surface HONO distribution, nitrous acid (HONO) measurements with a Monitor for AeRosols and Gases in ambient Air (MARGA) and a LOng Path Absorption Photometer (LOPAP)
instrument were performed at the Leibniz Institute
for Tropospheric Research (TROPOS) research site in Melpitz, Germany, from 19 to 29 April 2018. The dew water was also collected and analyzed
from 8 to 14 May 2019 using a glass sampler. The high time
resolution of HONO measurements showed characteristic diurnal variations
that revealed that (i) vehicle emissions are a minor source of HONO at Melpitz
station; (ii) the heterogeneous conversion of <span class="inline-formula">NO<sub>2</sub></span> to HONO on the ground surface
dominates HONO production at night; (iii) there is significant nighttime
loss of HONO with a sink strength of <span class="inline-formula">0.16±0.12</span> <span class="inline-formula">ppbv h<sup>−1</sup></span>; and (iv) dew water with mean <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="dd9770d6620662f8636cc16fd90758f2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-13069-2020-ie00001.svg" width="25pt" height="16pt" src="acp-20-13069-2020-ie00001.png"/></svg:svg></span></span> of <span class="inline-formula">7.91±2.14</span> <span class="inline-formula">µg m<sup>−2</sup></span>
could serve as a temporary HONO source in the morning when the dew droplets
evaporate. The nocturnal observations of HONO and <span class="inline-formula">NO<sub>2</sub></span> allowed the direct
evaluation of the ground uptake coefficients for these species at night:
<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi mathvariant="italic">γ</mi><mrow><msub><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn></msub><mo>→</mo><mi mathvariant="normal">HONO</mi></mrow></msub><mo>=</mo><mn mathvariant="normal">2.4</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">7</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="118pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="47a91ea5cbb50a339d94b04e5c3d465a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-13069-2020-ie00002.svg" width="118pt" height="17pt" src="acp-20-13069-2020-ie00002.png"/></svg:svg></span></span> to <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">3.5</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">6</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="51pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="a3a00797b8ecb59d245117eadf55aecd"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-13069-2020-ie00003.svg" width="51pt" height="14pt" src="acp-20-13069-2020-ie00003.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi mathvariant="italic">γ</mi><mrow><mi mathvariant="normal">HONO</mi><mo>,</mo><mi mathvariant="normal">ground</mi></mrow></msub><mo>=</mo><mn mathvariant="normal">1.7</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">5</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="121pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="99d61e7d8363b1faee98734d0089853b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-13069-2020-ie00004.svg" width="121pt" height="17pt" src="acp-20-13069-2020-ie00004.png"/></svg:svg></span></span> to
<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">2.8</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">4</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="51pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="83f8222f6f3fbda10760d7d459b434c5"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-13069-2020-ie00005.svg" width="51pt" height="14pt" src="acp-20-13069-2020-ie00005.png"/></svg:svg></span></span>. A chemical model demonstrated that HONO deposition
to the ground surface at night was 90 %–100 % of the calculated unknown HONO
source in the morning. These results suggest that dew water on the ground
surface was controlling the temporal HONO distribution rather than
straightforward <span class="inline-formula">NO<sub>2</sub></span>–HONO conversion. This can strongly enhance the OH
reactivity throughout the morning time or in other planted areas that provide a large
amount of ground surface based on the OH production rate calculation.</p> |
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| ISSN: | 1680-7316 1680-7324 |