The impact of aerosols on photolysis frequencies and ozone production in Beijing during the 4-year period 2012–2015
<p>During the period 2012–2015, photolysis frequencies were measured at the Peking University site (PKUERS), a site representative of Beijing. We present a study of the effects of aerosols on two key photolysis frequencies, <span class="inline-formula"><i>j</i></...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2019-07-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/9413/2019/acp-19-9413-2019.pdf |
| _version_ | 1818909991207174144 |
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| author | W. Wang X. Li M. Shao M. Shao M. Hu L. Zeng Y. Wu T. Tan |
| author_facet | W. Wang X. Li M. Shao M. Shao M. Hu L. Zeng Y. Wu T. Tan |
| author_sort | W. Wang |
| collection | DOAJ |
| description | <p>During the period 2012–2015, photolysis frequencies were measured at the
Peking University site (PKUERS), a site representative of Beijing. We
present a study of the effects of aerosols on two key photolysis
frequencies, <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">O<sup>1</sup>D</span>) and <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">NO<sub>2</sub></span>). Both <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">O<sup>1</sup>D</span>) and <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">NO<sub>2</sub></span>)
display significant dependence on aerosol
optical depth (AOD; 380 nm) with a non-linear negative
correlation. With the increase in AOD, the slopes of photolysis frequencies
vs. AOD decrease, which indicates that the capacity of aerosols to reduce the
actinic flux decreases with AOD. The absolute values of slopes are equal to
4.2–<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">6.9</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="0cd2a175176a99d89576103a2b76705c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-9413-2019-ie00001.svg" width="51pt" height="14pt" src="acp-19-9413-2019-ie00001.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">3.4</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">3</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="f52695db51dbd8e6f14a67c3bc298744"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-9413-2019-ie00002.svg" width="51pt" height="14pt" src="acp-19-9413-2019-ie00002.png"/></svg:svg></span></span> s<span class="inline-formula"><sup>−1</sup></span> per AOD unit for
<span class="inline-formula"><i>j</i></span>(<span class="inline-formula">O<sup>1</sup>D</span>) and <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">NO<sub>2</sub></span>) respectively at a solar zenith angle (SZA) of 60<span class="inline-formula"><sup>∘</sup></span> and AOD
smaller than 0.7, both of which are larger than those observed in a similar,
previous study in the Mediterranean. This indicates that the aerosols in
Beijing have a stronger extinction effect on actinic flux than
absorptive dust aerosols in the Mediterranean. Since the photolysis
frequencies strongly depended on the AOD and the SZA,
we established a parametric equation to quantitatively evaluate the effect
of aerosols on photolysis frequencies in Beijing. According to the
parametric equation, aerosols lead to a decrease in seasonal mean
<span class="inline-formula"><i>j</i></span>(<span class="inline-formula">NO<sub>2</sub></span>) by 24 % and 30 % for summer and winter, respectively, and
a corresponding decrease in seasonal mean <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">O<sup>1</sup>D</span>) by 27 % and 33 %,
respectively, compared to an aerosol-free atmosphere (AOD <span class="inline-formula">=0</span>). Based on
an observation campaign in August 2012, we used a photochemical box model
to simulate the ozone production rate (<span class="inline-formula"><i>P</i></span>(<span class="inline-formula">O<sub>3</sub></span>)). The simulation results
shows that the monthly mean daytime net ozone production rate is reduced by
up to 25 % due to the light extinction of aerosols. Through further
in-depth analysis, it was found that particulate matter concentrations
maintain a high level under the condition of high concentrations of ozone
precursors (volatile organic compounds, VOCs, and <span class="inline-formula">NO<sub><i>x</i></sub></span>), which inhibits the production of ozone to a large
extent. This phenomenon implies a negative feedback mechanism in the
atmospheric environment of Beijing.</p> |
| first_indexed | 2024-12-19T22:35:42Z |
| format | Article |
| id | doaj.art-4db595a4c1db4695902e028fbf78aa15 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-19T22:35:42Z |
| publishDate | 2019-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-4db595a4c1db4695902e028fbf78aa152022-12-21T20:03:12ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242019-07-01199413942910.5194/acp-19-9413-2019The impact of aerosols on photolysis frequencies and ozone production in Beijing during the 4-year period 2012–2015W. Wang0X. Li1M. Shao2M. Shao3M. Hu4L. Zeng5Y. Wu6T. Tan7State Joint Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, ChinaState Joint Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, ChinaState Joint Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, ChinaInstitute for Environmental and Climate Research, Jinan University, Guangzhou 511443, ChinaState Joint Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, ChinaState Joint Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, ChinaState Joint Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, ChinaState Joint Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China<p>During the period 2012–2015, photolysis frequencies were measured at the Peking University site (PKUERS), a site representative of Beijing. We present a study of the effects of aerosols on two key photolysis frequencies, <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">O<sup>1</sup>D</span>) and <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">NO<sub>2</sub></span>). Both <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">O<sup>1</sup>D</span>) and <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">NO<sub>2</sub></span>) display significant dependence on aerosol optical depth (AOD; 380 nm) with a non-linear negative correlation. With the increase in AOD, the slopes of photolysis frequencies vs. AOD decrease, which indicates that the capacity of aerosols to reduce the actinic flux decreases with AOD. The absolute values of slopes are equal to 4.2–<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">6.9</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="0cd2a175176a99d89576103a2b76705c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-9413-2019-ie00001.svg" width="51pt" height="14pt" src="acp-19-9413-2019-ie00001.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">3.4</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">3</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="f52695db51dbd8e6f14a67c3bc298744"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-9413-2019-ie00002.svg" width="51pt" height="14pt" src="acp-19-9413-2019-ie00002.png"/></svg:svg></span></span> s<span class="inline-formula"><sup>−1</sup></span> per AOD unit for <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">O<sup>1</sup>D</span>) and <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">NO<sub>2</sub></span>) respectively at a solar zenith angle (SZA) of 60<span class="inline-formula"><sup>∘</sup></span> and AOD smaller than 0.7, both of which are larger than those observed in a similar, previous study in the Mediterranean. This indicates that the aerosols in Beijing have a stronger extinction effect on actinic flux than absorptive dust aerosols in the Mediterranean. Since the photolysis frequencies strongly depended on the AOD and the SZA, we established a parametric equation to quantitatively evaluate the effect of aerosols on photolysis frequencies in Beijing. According to the parametric equation, aerosols lead to a decrease in seasonal mean <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">NO<sub>2</sub></span>) by 24 % and 30 % for summer and winter, respectively, and a corresponding decrease in seasonal mean <span class="inline-formula"><i>j</i></span>(<span class="inline-formula">O<sup>1</sup>D</span>) by 27 % and 33 %, respectively, compared to an aerosol-free atmosphere (AOD <span class="inline-formula">=0</span>). Based on an observation campaign in August 2012, we used a photochemical box model to simulate the ozone production rate (<span class="inline-formula"><i>P</i></span>(<span class="inline-formula">O<sub>3</sub></span>)). The simulation results shows that the monthly mean daytime net ozone production rate is reduced by up to 25 % due to the light extinction of aerosols. Through further in-depth analysis, it was found that particulate matter concentrations maintain a high level under the condition of high concentrations of ozone precursors (volatile organic compounds, VOCs, and <span class="inline-formula">NO<sub><i>x</i></sub></span>), which inhibits the production of ozone to a large extent. This phenomenon implies a negative feedback mechanism in the atmospheric environment of Beijing.</p>https://www.atmos-chem-phys.net/19/9413/2019/acp-19-9413-2019.pdf |
| spellingShingle | W. Wang X. Li M. Shao M. Shao M. Hu L. Zeng Y. Wu T. Tan The impact of aerosols on photolysis frequencies and ozone production in Beijing during the 4-year period 2012–2015 Atmospheric Chemistry and Physics |
| title | The impact of aerosols on photolysis frequencies and ozone production in Beijing during the 4-year period 2012–2015 |
| title_full | The impact of aerosols on photolysis frequencies and ozone production in Beijing during the 4-year period 2012–2015 |
| title_fullStr | The impact of aerosols on photolysis frequencies and ozone production in Beijing during the 4-year period 2012–2015 |
| title_full_unstemmed | The impact of aerosols on photolysis frequencies and ozone production in Beijing during the 4-year period 2012–2015 |
| title_short | The impact of aerosols on photolysis frequencies and ozone production in Beijing during the 4-year period 2012–2015 |
| title_sort | impact of aerosols on photolysis frequencies and ozone production in beijing during the 4 year period 2012 2015 |
| url | https://www.atmos-chem-phys.net/19/9413/2019/acp-19-9413-2019.pdf |
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