Exploring the drivers of the increased ozone production in Beijing in summertime during 2005–2016
<p>In the past decade, average PM<span class="inline-formula"><sub>2.5</sub></span> concentrations decreased rapidly under the strong pollution control measures in major cities in China; however, ozone (<span class="inline-formula">O<sub>...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-12-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/20/15617/2020/acp-20-15617-2020.pdf |
| Summary: | <p>In the past decade, average PM<span class="inline-formula"><sub>2.5</sub></span> concentrations decreased rapidly
under the strong pollution control measures in major cities in China;
however, ozone (<span class="inline-formula">O<sub>3</sub></span>) pollution emerged as a significant problem. Here we examine a unique (for China) 12-year data set of ground-level <span class="inline-formula">O<sub>3</sub></span> and precursor concentrations collected at an urban site in Beijing (PKUERS, campus of Peking University), where the maximum daily 8 h average (MDA8) <span class="inline-formula">O<sub>3</sub></span> concentration and daytime <span class="inline-formula">O<sub><i>x</i></sub></span> (<span class="inline-formula">O<sub>3</sub>+NO<sub>2</sub></span>) concentration in August increased by <span class="inline-formula">2.3±1.2</span> ppbv (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>+</mo><mn mathvariant="normal">3.3</mn><mo>±</mo><mn mathvariant="normal">1.8</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="b582e1e37f5014bd16cb2a8a8cc0a132"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-15617-2020-ie00001.svg" width="52pt" height="10pt" src="acp-20-15617-2020-ie00001.png"/></svg:svg></span></span> %) yr<span class="inline-formula"><sup>−1</sup></span> and <span class="inline-formula">1.4±0.6</span>
(<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>+</mo><mn mathvariant="normal">1.9</mn><mo>±</mo><mn mathvariant="normal">0.8</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="87a37ea378aa54100288ae60112cc605"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-15617-2020-ie00002.svg" width="52pt" height="10pt" src="acp-20-15617-2020-ie00002.png"/></svg:svg></span></span> %) yr<span class="inline-formula"><sup>−1</sup></span>, respectively, from 2005 to 2016. In
contrast, daytime concentrations of nitrogen oxides (<span class="inline-formula">NO<sub><i>x</i></sub></span>) and the OH reactivity of volatile organic compounds (VOCs) both decreased
significantly. Over this same time, the decrease of particulate matter (and
thus the aerosol optical depth) led to enhanced solar radiation and
photolysis frequencies, with near-surface <span class="inline-formula"><i>J</i>(NO<sub>2</sub>)</span> increasing at a rate of <span class="inline-formula">3.6±0.8</span> % yr<span class="inline-formula"><sup>−1</sup></span>. We use an observation-based box model to analyze the combined effect of solar radiation and ozone precursor changes on ozone production rate, <span class="inline-formula">P(O<sub>3</sub>)</span>. The results indicate that the ratio of the rates of decrease of VOCs and <span class="inline-formula">NO<sub><i>x</i></sub></span> (about 1.1) is inefficient in reducing ozone production in Beijing. <span class="inline-formula">P(O<sub>3</sub>)</span> increased during the decade due to more rapid atmospheric oxidation caused to a large extent by the decrease of particulate matter. This elevated ozone production was driven primarily by increased actinic flux due to PM<span class="inline-formula"><sub>2.5</sub></span> decrease and to a lesser extent by reduced heterogeneous uptake of <span class="inline-formula">HO<sub>2</sub></span>. Therefore, the influence of PM<span class="inline-formula"><sub>2.5</sub></span> on actinic flux and thus on the rate of oxidation of VOCs and <span class="inline-formula">NO<sub><i>x</i></sub></span>
to ozone and to secondary aerosol (i.e., the major contributor to
PM<span class="inline-formula"><sub>2.5</sub>)</span> is important for determining the atmospheric effects of
controlling the emissions of the common precursors of PM<span class="inline-formula"><sub>2.5</sub></span> and ozone
when attempting to control these two important air pollutants.</p> |
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| ISSN: | 1680-7316 1680-7324 |