Quantification and evaluation of atmospheric ammonia emissions with different methods: a case study for the Yangtze River Delta region, China

• Main Authors: Y. Zhao, M. Yuan, X. Huang, F. Chen, J. Zhang
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-04-01
• Series: Atmospheric Chemistry and Physics
• Online Access: https://www.atmos-chem-phys.net/20/4275/2020/acp-20-4275-2020.pdf

<p>To explore the effects of data and method on emission estimation, two inventories of <span class="inline-formula">NH₃</span> emissions of the Yangtze River Delta (YRD) region in eastern China were developed for 2014 based on constant emission factors (E1) and those characterizing agricultural processes (E2). The latter derived the monthly emission factors and activity data integrating the local information of soil, meteorology, and agricultural processes. The total emissions were calculated to be 1765 and 1067&thinsp;Gg with E1 and E2, respectively, and clear differences existed in seasonal and spatial distributions. Elevated emissions were found in March and September in E2, attributed largely to the increased top dressing fertilization and to the enhanced <span class="inline-formula">NH₃</span> volatilization under high temperature, respectively. A relatively large discrepancy between the inventories existed in the northern YRD with abundant croplands. With the estimated emissions 38&thinsp;% smaller in E2, the average of simulated <span class="inline-formula">NH₃</span> concentrations with an air quality model using E2 was 27&thinsp;% smaller than that using E1 at two ground sites in the YRD. At the suburban site in Pudong, Shanghai (SHPD), the simulated <span class="inline-formula">NH₃</span> concentrations with E1 were generally larger than observations, and the modeling performance was improved, indicated by the smaller normalized mean errors (NMEs) when E2 was applied. In contrast, very limited improvement was found at the urban site JSPAES, as E2 failed to improve the emission estimation of transportation and residential activities. Compared to <span class="inline-formula">NH₃</span>, the modeling performance for inorganic aerosols was better for most cases, and the differences between the simulated concentrations with E1 and E2 were clearly smaller, at 7&thinsp;%, 3&thinsp;%, and 12&thinsp;% (relative to E1) for <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="6ca56caa63735c5009fe6b299c1a126b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-4275-2020-ie00001.svg" width="24pt" height="15pt" src="acp-20-4275-2020-ie00001.png"/></svg:svg></span></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"><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="70c2dca1cdebf0791ac6d03f5c421763"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-4275-2020-ie00002.svg" width="29pt" height="17pt" src="acp-20-4275-2020-ie00002.png"/></svg:svg></span></span>, and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</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="8a872e45f44a0fc3c08e466e371cfb3a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-4275-2020-ie00003.svg" width="25pt" height="16pt" src="acp-20-4275-2020-ie00003.png"/></svg:svg></span></span>, respectively. Compared to the satellite-derived <span class="inline-formula">NH₃</span> column, application of E2 significantly corrected the overestimation in vertical column density for January and October with E1, but it did not improve the model performance for July. The <span class="inline-formula">NH₃</span> emissions might be underestimated with the assumption of linear correlation between <span class="inline-formula">NH₃</span> volatilization and soil pH for acidic soil, particularly in warm seasons. Three additional cases, i.e., 40&thinsp;% abatement of <span class="inline-formula">SO₂</span>, 40&thinsp;% abatement of <span class="inline-formula">NO_<i>x</i></span>, and 40&thinsp;% abatement of both species, were applied to test the sensitivity of <span class="inline-formula">NH₃</span> and inorganic aerosol concentrations to precursor emissions. Under an <span class="inline-formula">NH₃</span>-rich condition, estimation of <span class="inline-formula">SO₂</span> emissions was detected to be more effective on simulation of secondary inorganic aerosols compared to <span class="inline-formula">NH₃</span>. Reduced <span class="inline-formula">SO₂</span> would restrain the formation of (<span class="inline-formula">NH₄</span>)<span class="inline-formula">₂</span><span class="inline-formula">SO₄</span> and thereby enhance the <span class="inline-formula">NH₃</span> concentrations. To improve the air quality more effectively and efficiently, <span class="inline-formula">NH₃</span> emissions should be substantially controlled along with <span class="inline-formula">SO₂</span> and <span class="inline-formula">NO_<i>x</i></span> in the future.</p>