Huang Xiaojuan, Zhang Junke, Zhang Wei, Tang Guiqian, Wang Yuesi
Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu, 610225, China.
Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 611756, China.
Environ Pollut. 2021 Dec 15;291:118195. doi: 10.1016/j.envpol.2021.118195. Epub 2021 Sep 16.
Controlling ammonia (NH) emissions has been proposed as a strategy to mitigate haze pollution. To explore the role of NH in haze pollution in Sichuan Basin, where agricultural activities are intense, hourly in situ data of NH, as well as nitric acid and secondary inorganic aerosols (SIAs) were gathered in Chengdu from April 2017 to March 2018. We found that NH had an annual mean concentration of 9.7 ± 3.5 (mean ± standard deviation) μg m, and exhibited seasonal variations (spring > summer > autumn and winter) due to changes in emission sources and meteorological conditions (particularly temperature). Chengdu's atmosphere is generally NH-sufficient, especially in the warm seasons, implying that the formation of SIAs is more sensitive to the availability of nitric acid. However, an NH "sufficient-to-deficient" transition was found to occur during winter pollution periods, and the frequency of NH deficiency increased with the aggravation of pollution. Under NH-deficient conditions, the nitrogen oxidation ratio increased linearly with the increase in free NH, implying that NH contributes appreciably to the formation of nitrate and thus to high PM loadings. No relationships of NH with fossil fuel combustion-related pollutants were found. The NH emissions from farmland and livestock waste in the suburbs of Chengdu and regional transport from west of Chengdu probably contribute to the occurrence of high PM loading in winter and spring, respectively. These results suggest that to achieve effective mitigation of PM in Chengdu, local and regional emission control of NH and NOx synergistically would be effective.
控制氨（NH₃）排放已被提议作为减轻雾霾污染的一项策略。为探究在农业活动密集的四川盆地NH₃在雾霾污染中的作用，于2017年4月至2018年3月在成都收集了NH₃以及硝酸和二次无机气溶胶（SIAs）的每小时现场数据。我们发现，NH₃的年平均浓度为9.7±3.5（平均值±标准差）μg/m³，并且由于排放源和气象条件（特别是温度）的变化呈现出季节性变化（春季＞夏季＞秋季和冬季）。成都的大气总体上NH₃充足，尤其是在温暖季节，这意味着SIAs的形成对硝酸的可用性更为敏感。然而，发现在冬季污染期间会出现NH₃从“充足到不足”的转变，并且NH₃不足的频率随着污染加剧而增加。在NH₃不足的条件下，氮氧化率随游离NH₃的增加呈线性增加，这意味着NH₃对硝酸盐的形成有显著贡献，从而对高PM负荷有显著贡献。未发现NH₃与化石燃料燃烧相关污染物之间存在关联。成都郊区农田和畜禽粪便的NH₃排放以及成都以西的区域传输可能分别导致了冬季和春季高PM负荷的出现。这些结果表明，要在成都有效减轻PM，协同控制当地和区域的NH₃和NOₓ排放将是有效的。
