Integrated Chemistry of Ozone in the Atmosphere (ICOZA)

对流层臭氧是一种重要的大气污染物，对人体健康、农作物和植被都有危害。它是大气氧化剂的主要前体，引发排放到大气中的大多数活性气体的降解，并且本身就是一种重要的温室气体。由于这种在大气化学和空气污染方面的核心作用，了解、预测和管理对流层臭氧水平的能力是大气科学研究的一个关键目标。这一目标很难实现，因为臭氧是一种二次污染物，是在氮氧化物和阳光的存在下，由大气中挥发性有机化合物的复杂氧化形成的，臭氧产生的时间尺度是这样的，就地化学过程、沉积和输送的组合控制着臭氧水平。所有这些因素的不确定性影响了用于预测当前和未来臭氧水平的数值模式的准确性，从而阻碍了制定减轻臭氧暴露的最佳空气质量政策。在这里，我们将通过测量当地的化学臭氧生成速率来解决这个问题，并（首次）测量当地大气臭氧生成速率对氮氧化物和挥发性有机化合物水平的响应——直接确定臭氧生成机制。我们将在现有的测量大气臭氧生成速率的仪器的基础上实现这一目标（由NERC技术概念验证拨款资助，并在最近的ClearfLo“伦敦清洁空气”NERC城市大气科学计划中部署）。除了直接测量臭氧生成，通过干扰环境化学条件（例如，通过向采样气流中添加氮氧化物或挥发性有机化合物），并测量这种变化对测量的臭氧生成速率的影响外，还可以直接确定臭氧控制制度（氮氧化物与挥发性有机化合物限制的程度）。在这个项目中，我们将开发现有的臭氧生成仪器，使其包括这种能力，并通过与大型模拟室中VOC氧化产生的臭氧进行比较，以及通过测量系统内关键氧化剂OH自由基及其前体来验证测量结果。然后，我们将应用该仪器将测量的臭氧产出率与使用其他观测和模型方法计算的臭氧产出率进行比较，并在两种截然不同的环境中描述臭氧控制制度的特征：在欧洲大城市的流出处（在英国WAO的韦伯恩大气观测站），以及在农村大陆位置（在德国南部HPB的霍亨佩森堡）。在WAO，我们将把测量的臭氧产出率与通过同时测量HO2和RO2自由基（使用一种新开发的方法来区分这些密切相关的物种）计算的臭氧产出率进行比较，并与使用受限光化学盒模型模拟的臭氧产出率进行比较。我们将比较臭氧生成速率对氮氧化物的依赖性与基于对其他化学物质的观测而采用指标方法预测的结果。在HPB上，我们将重点关注臭氧生成速率对voc的依赖，并评估臭氧生成模式预测中的误差，这些误差是由于未测量的VOCs的存在而产生的。该项目将开发和演示一种新的测量方法，并应用它来提高我们对大气化学处理基本方面的理解。未来的应用具有相当大的潜力，既可以支持大气科学研究，也可以作为一种重要的空气质量工具，与现有的测量和建模方法一起，为最有效的排放控制提供信息，以减少特定地点的臭氧产生。在臭氧暴露导致全球作物减产7 - 12%（小麦）、6 - 16%（大豆）和3 - 4%（水稻）的背景下，这是一个重要的社会和科学目标。

Tropospheric ozone is an important air pollutant, harmful to human health, agricultural crops and vegetation. It is the main precursor to the atmospheric oxidants which initiate the degradation of most reactive gases emitted to the atmosphere, and is an important greenhouse gas in its own right. As a consequence of this central role in atmospheric chemistry and air pollution, the capacity to understand, predict and manage tropospheric ozone levels is a key goal for atmospheric science research. This goal is hard to achieve, as ozone is a secondary pollutant, formed in the atmosphere from the complex oxidation of VOCs in the presence of NOx and sunlight, and the timescale of ozone production is such that a combination of in situ chemical processes, deposition and transport govern ozone levels. Uncertainties in all of these factors affect the accuracy of numerical models used to predict current and future ozone levels, and so hinder development of optimal air quality policies to mitigate ozone exposure. Here, we will address this problem by measuring the local chemical ozone production rate, and (for the first time) perform measurements of the response of the local atmospheric ozone production rate to NOx and VOC levels - directly determining the ozone production regime. We will achieve this aim by building upon an existing instrument for the measurement of atmospheric ozone production rates (funded through a NERC Technology Proof-of-Concept grant, and deployed in the recent ClearfLo "Clean Air for London" NERC Urban Atmospheric Science programme). In addition to directly measuring ozone production, by perturbing the ambient chemical conditions (for example, through addition of NOx or VOCs to the sampled airflow), and measuring the effect of this change upon the measured ozone production rate, the ozone control regime (extent of NOx vs VOC limitation) may be directly determined. Within this project, we will develop our existing ozone production instrument to include this capability, and validate the measurements, through comparison with ozone production from VOC oxidation in a large simulation chamber, and by measurement of the key oxidant OH radicals, and their precursors, within the system. We will then apply the instrument to compare the measured ozone production rates with those calculated using other observational and model approaches, and to characterise the ozone control regime, in two contrasting environments: In the outflow of a European megacity (at Weybourne Atmospheric Observatory, WAO, in the UK), and in a rural continental location (at Hohenpeissenberg, HPB, in southern Germany). At WAO, we will compare the measured ozone production rate with that calculated through co-located measurements of HO2 and RO2 radicals (using a newly developed approach to distinguish between these closely related species), and with that simulated using a constrained photochemical box model. We will compare the NOx-dependence of the ozone production rate with that predicted using indicator approaches, based upon observations of other chemical species. At HPB, we will focus upon the VOC-dependence of the ozone production rate, and assess the error in model predictions of ozone production, which arise from the presence of unmeasured VOCs.The project will develop and demonstrate a new measurement approach, and apply this to improve our understanding of a fundamental aspect of atmospheric chemical processing. Future applications have considerable potential both to support atmospheric science research, but also as an important air quality tool, alongside existing measurement and modelling approaches, to inform the most effective emission controls to reduce ozone production in a given location. In the context of global crop yield reductions arising from ozone exposure of 7 - 12 % (wheat), 6 - 16 % (soybean) and 3 - 4 % (rice), this is an important societal as well as scientific goal.