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In Situ monitoring of NO3 radicals in a atmospheric chamber by cavity ring down spectroscopy

通过腔衰荡光谱法原位监测大气室中的 NO3 自由基

基本信息

批准号：
NE/F011326/1
负责人：
Paul Seakins
金额：
$ 3.81万
依托单位：
University of Leeds
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2008
资助国家：
英国
起止时间：
2008 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FF011326%2F1
关键词：
Situ monitoring NO3 radicals atmospheric

项目摘要

Atmospheric chambers have a vital role to play in the elucidation of reaction mechanisms for the troposphere. The highly instrumented reactor for atmospheric chemistry (HIRAC) constructed in the School of Chemistry under grant NE/C513493/1 is a 2 m3 stainless steel chamber capable of making measurements over a wide range of conditions. Uniquely for such a chamber it can measure OH and HO2 radical concentrations using a laser based technique. The principal behind HIRAC is to measure as many reactants, intermediates and products as possible in order to constrain the chemical models used to interpret and understand the results. All measurements are subject to potential systematic errors and therefore we consider it important to initially measure using two or more complimentary techniques (e.g. FTIR and GC). This is especially true for radical species, where the short lifetimes make measurements particularly taxing. We have demonstrated an ability to detect and monitor OH and HO2 (ACPD 2007, 7, 10687) and now seek to extend our measurement capability to the NO3 radical, an important nighttime oxidant. It is proposed to measure NO3 using cavity ring down spectroscopy (CRDS). This is an extremely sensitive technique, that unlike laser induced fluorescence (LIF), yields absolute concentrations. With CRDS we should have a detection limit of ~1 pptv, well below typical nighttime NO3 concentrations. Once constructed the CRDS system will be compared with a broadband cavity enhanced absorption spectrometer (BB-CEAS) via a collaboration with Dr Steve Ball and LIF (adapting our current system from OH detection). We will also test the technique by determining rate coefficients for the reaction of NO3 with ethanal, a reaction that is well characterised. Finally, we will apply the technique to the determination of the rate coefficients and product distributions to the reaction of NO3 with alkenes under atmospheric conditions. The rates of reaction are relatively fast and determination of the rate coefficient requires knowledge of the absolute NO3 concentrations (an advantage of CRDS over BB-CEAS and LIF). Products will be examined by GC and FTIR; knowledge of the temporal dependence of NO3 will be vital in constraining the chemical model used to extract quantitative branching ratios.

大气室在阐明对流层的反应机制方面起着至关重要的作用。根据NE/C513493/1拨款，在化学学院建造的高仪器化大气化学反应器（HIRAC）是一个2立方米的不锈钢室，能够在各种条件下进行测量。独特的是，它可以使用激光技术测量OH和HO2自由基浓度。HIRAC的主要目的是测量尽可能多的反应物、中间体和产物，以限制用于解释和理解结果的化学模型。所有的测量都受到潜在的系统误差的影响，因此我们认为使用两种或更多的互补技术（例如FTIR和GC）进行初步测量是很重要的。对于激进物种来说尤其如此，它们的生命周期很短，测量起来特别费力。我们已经展示了检测和监测OH和HO2的能力（ACPD 2007, 7, 10687），现在寻求将我们的测量能力扩展到NO3自由基，一种重要的夜间氧化剂。提出了用腔衰荡光谱（CRDS）测量NO3的方法。这是一种非常敏感的技术，与激光诱导荧光（LIF）不同，它产生绝对浓度。使用CRDS，我们应该有~1 pptv的检测限，远低于典型的夜间NO3浓度。一旦建成，CRDS系统将与宽带腔增强吸收光谱仪（BB-CEAS）进行比较，这是由Steve Ball博士和LIF（从OH检测中改进我们目前的系统）合作完成的。我们还将通过确定NO3与乙醇反应的速率系数来测试该技术，该反应具有很好的特征。最后，将该技术应用于常压条件下NO3与烯烃反应的速率系数和产物分布的测定。反应速率相对较快，速率系数的测定需要知道NO3的绝对浓度（CRDS相对于BB-CEAS和LIF的优势）。产品将通过气相色谱和红外光谱进行检测；了解NO3的时间依赖性对于限制用于提取定量分支比的化学模型至关重要。