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，这些氧化剂会降解排放到大气中的大多数活性气体，本身就是一种重要的温室气体。由于在大气化学和空气污染方面的这一中心作用，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，因为臭氧是大气中的一种二次污染物，在NOx和阳光的存在下由VOCs的复杂氧化形成，而且臭氧产生的时间尺度决定了臭氧水平是由就地化学过程、沉积和输送的组合决定的。所有这些因素中的不确定性都会影响用于预测当前和未来臭氧水平的数值模型的准确性，从而阻碍制定减少臭氧暴露的最佳空气质量政策。在这里，我们将通过测量本地化学臭氧产生率来解决这个问题，并(首次)测量本地大气臭氧产生率对NOx和VOC水平的响应--直接确定臭氧产生机制。我们将通过建立现有的测量大气臭氧产生率的仪器来实现这一目标(由NERC技术概念验证赠款资助，并在最近的ClearfLo“伦敦清洁空气”NERC城市大气科学计划中部署)。除了直接测量臭氧产生量外，还可以通过扰动周围的化学条件(例如，通过向采样气流中添加NOx或VOCs)，并测量这种变化对测量的臭氧产生率的影响，可以直接确定臭氧控制制度(NOx与VOC的限制范围)。在这个项目中，我们将开发我们现有的臭氧产生仪器，以包括这一能力，并通过在大型模拟室中与VOC氧化产生臭氧进行比较，以及通过测量系统中关键的氧化剂OH自由基及其前体来验证测量结果。然后，我们将使用该仪器将测量的臭氧产生率与使用其他观测和模型方法计算的臭氧产生率进行比较，并在两个不同的环境中描述臭氧控制制度：在欧洲特大城市的外流(在英国的韦伯恩大气天文台)和在大陆农村地区(在德国南部的霍恩佩森贝格，HPB)。在WAO，我们将把测量的臭氧产生率与通过共存测量HO2和RO2自由基计算的臭氧产生率进行比较(使用一种新开发的方法来区分这些密切相关的物种)，并与使用受约束的光化学盒子模型模拟的臭氧产生率进行比较。我们将基于对其他化学物种的观察，将臭氧产生率与NOx的依赖关系与使用指示器方法预测的结果进行比较。在HPB，我们将重点研究臭氧产生速率与VOC的关系，并评估由于存在未测量的VOC而导致的臭氧产生模型预测的误差。该项目将开发和演示一种新的测量方法，并将其应用于提高我们对大气化学处理的一个基本方面的理解。未来的应用具有相当大的潜力，既可以支持大气科学研究，也可以作为一个重要的空气质量工具，与现有的测量和建模方法一起，为减少特定地点的臭氧产生提供最有效的排放控制。在臭氧暴露于7-12%(小麦)、6-16%(大豆)和3-4%(水稻)的臭氧造成全球作物减产的背景下，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.