Local Atmospheric Ozone Production Perturbation Instrument - Proof of Concept

臭氧是低层大气中的主要污染物，已知对人类健康、生态系统、植被和某些材料有害。臭氧是在氮氧化物（NOx）存在下VOC（挥发性有机化合物）在大气中降解的结果。由于臭氧是一种二次污染物，臭氧水平的控制并不简单，臭氧的产生速率与NOx和VOC水平呈高度非线性关系。详细的大气化学模型可用于为减少臭氧的空气质量战略提供信息，但模型预测、排放控制和臭氧生成率之间的联系很难评估，因为现场臭氧生成、当地化学效应和迁移等因素的结合都会导致特定地点臭氧水平的变化。此外，即使是最详细的模型（或测量）也不能包含所有的大气过程（或物种），模型机制有待于不断发展。该项目的目的是测试一种直接测量当地大气臭氧产生率及其对化学和物理条件的依赖性的新方法。通过扰动环境化学条件（例如，通过添加NOx或VOC），并测量扰动对当地臭氧产生率的影响，该技术将允许直接评估空气质量策略的有效性（并确定当地生产与运输的重要性）。通过比较测量（和扰动）的臭氧生产率与使用大气模型预测，我们对潜在的化学过程的理解可能会受到考验。基本方法是将环境空气采样到反应器中，停留时间为几分钟，暴露于环境光或去除紫外线成分的环境光。在前者中，臭氧的产生与在环境大气中一样继续，而在后者中，通过排除紫外线来关闭臭氧产生的化学过程，从而可以确定臭氧基线。通过比较离开每个反应器的臭氧水平（严格地说，O3 + NO2），可以推导出原位臭氧产生速率。通过向采样气流中添加试剂，可以研究扰动对环境条件的影响，并且可以建立VOC与NOx控制的程度。通过用受控的光谱分布人为地照射腔室，可以测试驱动臭氧产生的不同化学机制的重要性。该项目将为一种新的方法提供概念验证数据，以进行扰动臭氧产生率测量。这项技术的未来发展将使大气测量，这将提高我们的理解率，最有效的控制，大气臭氧的生产。这种测量对大气科学家、决策者和空气质量工作者将有很大用处。

Ozone is a major pollutant in the lower atmosphere, known to be harmful to human health, ecosystems, vegetation and certain materials. Ozone is produced as a consequence of the atmospheric degradation of VOCs (Volatile Organic Compounds) in the presence of oxides of nitrogen (NOx). As ozone is a secondary pollutant, control of ozone levels is not straightforward, with ozone production rate showing a highly non-linear dependence upon NOx and VOC levels. Detailed atmospheric chemistry models may be used to inform air quality strategies for ozone abatement, however the link between model predictions, emission controls and ozone production rates is hard to evaluate, as a combination of in situ ozone production, local chemical effects and transport all contribute to variations in ozone levels at a given site. Moreover, even the most detailed models (or measurements) cannot incorporate all atmospheric processes (or species), and model mechanisms are subject to ongoing development. The aim of this project is to test a new approach to directly measure the local atmospheric ozone production rate, and its dependence upon chemical and physical conditions. By perturbing the ambient chemical conditions (for example, through addition of NOx or VOCs), and measuring the effect of the perturbation upon the local ozone production rate, this technology will allow the efficacy of air quality strategies to be directly evaluated (and the importance of local production vs. transport determined). By comparing the measured (and perturbed) ozone production rate with that predicted using atmospheric models, our understanding of the underlying chemical processes may be tested. The fundamental approach will be to sample ambient air into reactors with residence times of a few minutes, exposed to either ambient light or ambient light with the UV component removed. In the former, ozone production continues as in the ambient atmosphere, while in the latter, the ozone production chemistry is switched off by excluding UV light, allowing an ozone baseline to be determined. By comparing the ozone levels exiting each reactor (strictly, O3 + NO2), the in situ ozone production rate may be deduced. By adding reagents to the sampled airstream, the effects of perturbations to the ambient conditions may be investigated and the extent of VOC vs. NOx control may be established. By illuminating the chambers artificially with a controlled spectral distribution, the importance of different chemical mechanisms driving ozone production may be tested. The project will deliver proof-of concept data for a new approach to perform perturbed ozone production rate measurements. Future development of this technology will enable atmospheric measurements which will improve our understanding of the rate of, and most efficient controls upon, atmospheric ozone production. Such measurements will be of considerable use to atmospheric scientists, policy makers and air quality practitioners.