Formation mechanisms of nitrous acid (HONO) during the haze and non-haze periods in Beijing, China.
Formation mechanisms of nitrous acid (HONO) during the haze and non-haze periods in Beijing, China.
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DOI：
10.1016/j.jes.2021.09.013
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发表时间：
2022-02
影响因子：
6.9
通讯作者：
Deng Lin;Shengrui Tong;Wenqian Zhang;Weiran Li;Fangjie Li;Chenhui Jia;Gen Zhang;Meifang Chen;Xinran Zhang;Zhen Wang;Maofa Ge;Xiang He
中科院分区：
文献类型：
--
作者：
Deng Lin;Shengrui Tong;Wenqian Zhang;Weiran Li;Fangjie Li;Chenhui Jia;Gen Zhang;Meifang Chen;Xinran Zhang;Zhen Wang;Maofa Ge;Xiang He
亚硝酸（HONO）作为羟基自由基（OH）的重要前体物，在大气化学中起着重要的作用。2017年4月14日至28日，在北京城市站点进行了HONO和相关空气污染物的观测。在观察过程中，HONO浓度出现两个明显的峰值。相反，颗粒物浓度在第一阶段（阶段Ⅰ）显著高于第二阶段（阶段Ⅱ）。通过对两个时段HONO排放源的比较发现，机动车直接排放是两个时段夜间HONO的主要来源，尤其是在第二时段。NO2的非均相反应是Ⅰ期的主要来源，而NO与OH的均相反应则是Ⅱ期夜间更为关键的来源。在白天，NO2的非均相反应是一个重要的污染源，并且在第Ⅰ时段，未知污染源（P未知）与NO2、PM2.5、NO2 × PM2.5之间具有良好的相关系数（R2）。此外，在白天以太阳辐射和OH自由基作为未知源时，未知P与NO2和OH的光解速率（JNO2 × OH）的相关系数在第Ⅰ期为0.93，在第Ⅱ期为0.95。这些良好的相关系数表明，未知源释放的HONO与太阳辐射和OH自由基的变化密切相关。
As an important precursor of hydroxyl radical (OH), nitrous acid (HONO) plays a significant role in atmospheric chemistry. Here, an observation of HONO and relevant air pollutants in an urban site of Beijing from 14 to 28 April, 2017 was performed. Two distinct peaks of HONO concentrations occurred during the observation. In contrast, the concentration of particulate matter in the first period (period Ⅰ) was significantly higher than that in the second period (period Ⅱ). Comparing to HONO sources in the two periods, we found that the direct vehicle emission was an essential source of the ambient HONO during both periods at night, especially in period Ⅱ. The heterogeneous reaction of NO 2 was the dominant source in period Ⅰ, while the homogeneous reaction of NO with OH was more critical source at night in period Ⅱ. In the daytime, the heterogeneous reaction of NO 2 was a significant source and was confirmed by the good correlation coefficients (R 2) between the unknown sources (P unknown) with NO 2, PM 2.5, NO 2× PM 2.5 in period Ⅰ. Moreover, when solar radiation and OH radicals were considered to explore unknown sources in the daytime, the enhanced correlation of P unknown with photolysis rate of NO 2 and OH (J NO 2× OH) were 0.93 in period Ⅰ, 0.95 in period Ⅱ. These excellent correlation coefficients suggested that the unknown sources released HONO highly related to the solar radiation and the variation of OH radicals.