Quantitative Study of SO2 and Reactive Halogen Chemistry in Volcanic Plumes by Imaging with a Novel Fabry-Pérot Camera Technique

以高时间分辨率(即以秒为时间尺度)对火山气体的二维(2D)分布进行成像，可以研究传统扫描方法无法获得的过程。这些措施包括：(1)在其固有时间尺度上直接可视化输运和湍流混合过程；(2)实时研究化学转变(例如，bbbro的形成)。此外，(3)可以分析痕量气体(如BrO和OClO)的空间梯度及其在羽流中的演化，从而可以推断化学过程的细节。目前，只有通过使用已被称为“SO2相机”的设备才能对火山SO2进行2D成像。它们依赖于在两个窄波长区域(由干涉滤光片定义)获取的相关图像。尽管近年来SO2相机的引入是火山气体研究的重大突破，但它们不适用于其他火山气体，也受到交叉干扰，例如对火山气溶胶的干扰。在此，我们提出了一种基于法布里-珀罗涉仪(FPI)的新型成像技术的开发和应用，该技术能够在高时间分辨率下几乎不受干扰地记录几种重要火山气体的空间分布。我们已经证明了它对SO2的实际适用性，并表明该技术具有对火山柱中的BrO和OClO进行成像的灵敏度和特异性。在拟议的项目中，我们打算建造用于对这三种气体进行成像的实用设备，并将这些设备应用于研究卤素自由基浓度的演变。这将对静止的除气和爆炸性羽流进行。任何其他已知的技术都不可能进行预期的研究。此外，这里提出的工作将构成未来将浮点喷射技术应用于一系列更多大气气体(例如IO、NO2、CH2O)的基础。

Imaging two dimensional (2D) distributions of volcanic gases with high time resolution (i.e. at time scales of seconds), allows to study processes which are not accessible to traditional scanning methods. These include: (1) to directly visualize transport and turbulent mixing processes at their intrinsic time scales and (2) to study chemical transformation (e.g. the formation ob BrO) in real time. Moreover, (3) spatial gradients of trace gases (e.g. of BrO and OClO) and their evolution in the plume can be analyzed, which allows to infer details of chemical processes.At present 2D imaging is possible only for volcanic SO2 by using devices which have become known as “SO2 cameras”. They rely on relating images acquired in two narrow wavelengths regions (defined by interference filters). While the introduction of SO2 cameras in recent years marked are a major breakthrough in volcanic gas research they are not applicable to other volcanic gases and also suffer from cross interferences, e.g. to volcanic aerosol.Here we propose the development and application of a novel, Fabry-Perot Interferometer (FPI) – based imaging technique capable of recording the spatial distributions of several important volcanic gases at high time resolution and virtually without interference. We already demonstrated its practical applicability for SO2 and showed that the technique has the sensitivity and specificity to also image BrO and OClO in volcanic plumes. Within the proposed project we intent to build practical devices for the imaging of these three gases and to apply the instruments to studies of the evolution of halogen radical concentrations. This will be done for quiescent degassing as well as for explosive plumes. The intended studies are not possible with any other known technique. In addition, the work proposed here will form the basis to apply the FPI technique to a range of further atmospheric gases (e.g. IO, NO2, CH2O) in the future.