Importance of gas-particle partitioning of ammonia in haze formation in the rural agricultural environment
<p>Ammonia in the atmosphere is essential for the formation of fine particles that impact air quality and climate. Despite extensive prior research to disentangle the relationship between ammonia and haze pollution, the role of ammonia in haze formation in high ammonia-emitting regions is stil...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/20/7259/2020/acp-20-7259-2020.pdf |
| Summary: | <p>Ammonia in the atmosphere is essential for the formation
of fine particles that impact air quality and climate. Despite extensive
prior research to disentangle the relationship between ammonia and haze
pollution, the role of ammonia in haze formation in high ammonia-emitting regions is still not well understood. Aiming to better understand secondary
inorganic aerosol (sulfate, nitrate, ammonium – SNA) formation mechanisms under high-ammonia conditions,
1-year hourly measurement of water-soluble inorganic species (gas and
particle) was conducted at a rural supersite in Shanghai. Exceedingly high
levels of agricultural ammonia, constantly around 30 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>, were
observed. We find that gas-particle partitioning of ammonia (<span class="inline-formula"><i>ε</i></span><span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="91d49abe6d72fd4b0e5a1f1b4385a2d5"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-7259-2020-ie00001.svg" width="31pt" height="15pt" src="acp-20-7259-2020-ie00001.png"/></svg:svg></span></span>), as opposed to ammonia concentrations, plays a critical
role in SNA formation during the haze period. From an assessment of the effects of
various parameters, including temperature (<span class="inline-formula"><i>T</i></span>), aerosol water content (AWC),
aerosol pH, and activity coefficient, it seems that AWC plays predominant
regulating roles for <span class="inline-formula"><i>ε</i></span><span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="459544f7453cdb23fbb6134fb577afe9"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-7259-2020-ie00002.svg" width="31pt" height="15pt" src="acp-20-7259-2020-ie00002.png"/></svg:svg></span></span>. We propose a
self-amplifying feedback mechanism associated with <span class="inline-formula"><i>ε</i></span><span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="b3dc5eafd33a1d448ae2e5721d3e9b65"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-7259-2020-ie00003.svg" width="31pt" height="15pt" src="acp-20-7259-2020-ie00003.png"/></svg:svg></span></span> for the formation of SNA, which is consistent with diurnal
variations in <span class="inline-formula"><i>ε</i></span><span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="9035a82d717fef1a3b8f58fb0723e83a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-7259-2020-ie00004.svg" width="31pt" height="15pt" src="acp-20-7259-2020-ie00004.png"/></svg:svg></span></span>, AWC, and SNA. Our results
imply that a reduction in ammonia emissions alone may not reduce SNA
effectively, at least at rural agricultural sites in China.</p> |
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| ISSN: | 1680-7316 1680-7324 |