Field Measurement of In-Cloud Sulfur Dioxide Oxidation

对流层二氧化硫的反应和去除通过多种途径发生。主要的气相反应路径，与羟基自由基，被认为是二氧化硫的半衰期为7-14天的特征。在气溶胶表面、雾霾和云滴上的反应导致云和降水水中硫酸盐的直接产生。实验室动力学数据表明，溶解的二氧化硫与过氧化物和臭氧的水相反应是二氧化硫从大气中去除的最有效途径。为了补充实验室数据，也因为需要了解对流层云中产生氧化硫的过程，实地研究被认为是大气化学研究的重要目标。如果要预测降水组成，了解氧化剂和二氧化硫转化为硫酸的过程是必不可少的。溶解在云滴中的二氧化硫的氧化被认为受到几个因素的影响，这些因素使得很难将实验室研究的含水二氧化硫氧化推断到自然云系统。在这项研究中，将进行一套独特的实验，旨在测量地形云中二氧化硫向硫酸盐的转化。这些测量将与使用实验室推导的速率常数和云成分测量作为输入参数的详细云化学模型进行比较。实验策略是从地面发电机向云中释放二氧化硫脉冲，并在山顶天文台进行羽流探测时收集云水作为冰霜沉积物。该实验设计已经过测试，并表明能够产生可用的结果。在二氧化硫释放期间，将使用惰性示踪剂的几个较短脉冲来测量羽流传输时间。

Reactions and removal of tropospheric sulfur dioxide occur via a variety of pathways. The dominant gas phase reaction path, with the hydroxyl radical, is thought to be characterized by a sulfur dioxide half-life of 7-14 days. Reaction on aerosol surfaces, and in haze and cloud droplets results in the direct production of sulfate in cloud and precipitation water. Laboratory kinetic data suggest that aqueous phase reactions of dissolved sulfur dioxide with peroxides and ozone are the most efficient pathway by which sulfur dioxide is removed from the atmosphere. To complement laboratory data, and because of the need to understand processes which produce oxidized sulfur species in tropospheric clouds, field studies are recognized as important objectives of atmospheric chemistry research. Knowledge of the oxidants and processes responsible for the conversion of sulfur dioxide to sulfuric acid are essential if predictions of precipitation composition are to be made. The oxidation of sulfur dioxide dissolved in cloud droplets is thought to be affected by several factors which make it difficult to extrapolate laboratory studies of aqueous sulfur dioxide oxidation to natural cloud systems. In this research a set of unique experiments designed to measure the conversion of sulfur dioxide to sulfate in orographic clouds will be carried out. These measurements will be compared to a detailed cloud chemistry model using laboratory derived rate constants and cloud composition measurements as input parameters. The experimental strategy is to release pulses of sulfur dioxide into the cloud from a ground based generator and to collect cloud water as a rime ice deposit during plume detection at the mountain top observatory. This experimental design has been tested and shown to be capable of producing usable results. Plume transport times will be measured using several shorter pulses of an inert tracer during the sulfur dioxide releases.