Enhanced wintertime oxidation of VOCs via sustained radical sources in the urban atmosphere.
Enhanced wintertime oxidation of VOCs via sustained radical sources in the urban atmosphere.
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DOI：
10.1016/j.envpol.2021.116563
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发表时间：
2021-01
影响因子：
8.9
通讯作者：
R. Sommariva;L. Crilley;S. Ball;R. Cordell;L. Hollis;W. Bloss;P. Monks
中科院分区：
文献类型：
--
作者：
R. Sommariva;L. Crilley;S. Ball;R. Cordell;L. Hollis;W. Bloss;P. Monks
白天的大气氧化化学通常被认为主要由通过光解源形成的OH自由基驱动。在本文中，我们研究如何，在冬季光解过程是缓慢的，氯化学可以有显着的影响，在城市边界层的氧化过程。硝酰氯（ClNO 2）的光解提供了氯原子的重要来源，这增强了挥发性有机化合物（VOCs）的氧化和大气污染物的产生。我们提出了一组观测ClNO 2和HONO在英格兰中部的城市位置在2014年12月和2016年2月。虽然HONO的直接排放和原位化学形成持续了一整天，但ClNO 2仅在夜间形成，通常在中午完全光解。我们的数据表明，在冬季，ClNO 2通常持续到白天，混合比高于10-20 ppt（平均）。此外，白天HONO（> 65 ppt）的相对较高的混合比率提供了一整天的OH自由基的强源。ClNO 2和HONO的联合作用导致从日出到日落持续产生Cl和OH自由基，形成额外的臭氧、PAN、含氧VOCs和二次有机气溶胶。我们表明，自由基源，如ClNO 2和HONO可以导致一个令人惊讶的光活性的城市大气在冬季，因此应该包括在大气化学模型。
Daytime atmospheric oxidation chemistry is conventionally considered to be driven primarily by the OH radical, formed via photolytic sources. In this paper we examine how, during winter when photolytic processes are slow, chlorine chemistry can have a significant impact on oxidative processes in the urban boundary layer. Photolysis of nitryl chloride (ClNO 2) provides a significant source of chlorine atoms, which enhances the oxidation of volatile organic compounds (VOCs) and the production of atmospheric pollutants. We present a set of observations of ClNO 2 and HONO made at urban locations in central England in December 2014 and February 2016. While direct emissions and in-situ chemical formation of HONO continue throughout the day, ClNO 2 is only formed at night and is usually completely photolyzed by midday. Our data show that, during winter, ClNO 2 often persists through the daylight hours at mixing ratios above 10–20 ppt (on average). In addition, relatively high mixing ratios of daytime HONO (> 65 ppt) provide a strong source of OH radicals throughout the day. The combined effects of ClNO 2 and HONO result in sustained sources of Cl and OH radicals from sunrise to sunset, which form additional ozone, PAN, oxygenated VOCs, and secondary organic aerosol. We show that radical sources such as ClNO 2 and HONO can lead to a surprisingly photoactive urban atmosphere during winter and should therefore be included in atmospheric chemical models.