Characterisation of the photolytic HONO-source in the atmosphere simulation chamber SAPHIR
Characterisation of the photolytic HONO-source in the atmosphere simulation chamber SAPHIR
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DOI：
10.5194/acp-5-2189-2005
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发表时间：
2004-12
影响因子：
6.3
通讯作者：
F. Rohrer;B. Bohn;T. Brauers;D. Brüning;F. Johnen;A. Wahner;J. Kleffmann
中科院分区：
文献类型：
--
作者：
F. Rohrer;B. Bohn;T. Brauers;D. Brüning;F. Johnen;A. Wahner;J. Kleffmann
抽象的。二十多年来，HONO的形成一直被认为是模拟室中重要的OH自由基源。除了由NO2和吸附水的暗反应形成的非均相HONO外，还提出了一种光解源来解释模拟室实验中升高的反应性。然而，到目前为止，光解过程的机制还没有很好地理解。正如预期的那样，在新的大气模拟室SAPHIR内，在太阳照射下也观察到HONO和NOx的产生。这种光解HONO和NOx的形成进行了研究，在可重复的控制条件下，在大气中的其他痕量气体浓度与一个敏感的HONO仪器。结果表明，在SAPHIR室的光解HONO源不是由NO2反应，它是唯一的直接NOy源在光照条件下。此外，硝酸盐的光解，这是最近假设的观察到的光解HONO形成雪，地面和玻璃表面，可以排除在该室。一个光解HONO源的表面上的室提出了强烈依赖于湿度，光强度，和温度。一个经验函数描述了这些依赖关系，并再现了所观察到的HONO形成率在10%以内。结果表明，HONO的光解是SAPHIR室中典型对流层O3/H2O浓度的主要自由基源。在这些条件下，SAPHIR内部的HONO浓度与最近在环境空气中的观测结果相似。
Abstract. HONO formation has been proposed as an important OH radical source in simulation chambers for more than two decades. Besides the heterogeneous HONO formation by the dark reaction of NO2 and adsorbed water, a photolytic source has been proposed to explain the elevated reactivity in simulation chamber experiments. However, the mechanism of the photolytic process is not well understood so far. As expected, production of HONO and NOx was also observed inside the new atmospheric simulation chamber SAPHIR under solar irradiation. This photolytic HONO and NOx formation was studied with a sensitive HONO instrument under reproducible controlled conditions at atmospheric concentrations of other trace gases. It is shown that the photolytic HONO source in the SAPHIR chamber is not caused by NO2 reactions and that it is the only direct NOy source under illuminated conditions. In addition, the photolysis of nitrate which was recently postulated for the observed photolytic HONO formation on snow, ground, and glass surfaces, can be excluded in the chamber. A photolytic HONO source at the surface of the chamber is proposed which is strongly dependent on humidity, on light intensity, and on temperature. An empirical function describes these dependencies and reproduces the observed HONO formation rates to within 10%. It is shown that the photolysis of HONO represents the dominant radical source in the SAPHIR chamber for typical tropospheric O3/H2O concentrations. For these conditions, the HONO concentrations inside SAPHIR are similar to recent observations in ambient air.