Reactive halogens in a simulated volcanic plume

火山气体排放在局部和全球范围内对大气化学具有重要意义。火山羽流中活性卤素化学的发现为火山的动力学过程带来了新的见解，甚至可能与火山喷发潜力有关。对活性卤素物种（如BrO、OClO、ClO）的研究在最近取得了很大进展，进行了大量的实地研究，但揭示了有关责任机制和影响环境参数（如羽流气体和气溶胶成分、相对湿度、潜在NOX排放的作用）的许多不确定性。这些参数对卤素活化的作用和影响（在火山羽流中从卤化物到活性卤素物种（RHS）的转化对于解释结果是必不可少的，例如（1）在得出关于岩浆过程的结论方面，基于BrO/SO2比率的喷发预测，或（2）在它们的大气影响方面，例如臭氧破坏汞的氧化，减少甲烷寿命等。在这个项目中，我们希望通过在受控条件下研究简化的火山羽流（SiO2和硫酸气溶胶，H2O，CO2，SO2，HCl，HBr），进一步了解火山羽流中的卤素化学。测量将在拜罗伊特大学的特氟隆烟雾室中进行，在那里可以很容易地安装所有必要的测量技术。RHS（BrO、ClO、OClO）将通过白色多反射池测量，CE-DOAS和其他卤素物质（Br 2、Cl 2、HOBr和BrCl）将通过FAPA-MS（流动大气压余辉质谱法）测量。将通过标准分析仪监测SO2、CO2、NOX和O3，并使用过滤器和撞击器对颗粒进行采样，用于随后的IC和SEM-EDX（扫描电子显微镜-能量色散X射线检测器）分析，以获得颗粒上吸收的卤素信息。这些技术的结合提供了探索卤素活化中所涉及的非均相反应的作用的可能性，这代表了目前对火山研究缺乏了解。特别是，将在四个项目阶段内研究（1）NOX和O3、（2）初始HCl/HBr比率、（3）相对湿度和（4）颗粒成分（朝向更复杂的真实的火山“灰”）对活性卤素化学（包括溴爆炸机理）的影响。在化学箱模型CAABA/MECCA的支持下，将对观测结果进行评估，并将其置于更大的背景下，以更好地理解自然过程。

Volcanic gas emissions are of importance for atmospheric chemistry in a local and with a varying extent in a global scale. The discovery of reactive halogen chemistry in volcanic plumes brought new insights in the dynamic processes of volcanos and may even be correlated with their eruption potential. The investigation of reactive halogen species (e.g. BrO, OClO, ClO) made great progress in the recent past, with numerous field studies that were conducted, but revealed many uncertainties concerning the responsible mechanism and influencing environmental parameters (e.g. plume gas and aerosol composition, relative humidity, role of potential NOX emissions). The role and influence of these parameters on halogen activation (conversion from halides to reactive halogen species (RHS) in volcanic plumes is essential for interpretations of the results e.g. (1) in terms of drawing conclusions about magmatic processes, eruption forecasting based on BrO/SO2 ratios, or (2) in terms of their atmospheric impact for instance ozone destruction oxidation of mercury, reduced methane life time etc.. In this project we want to take a step forward in the understanding of the halogen chemistry in volcanic plumes by investigating a simplified volcanic plume (SiO2 and sulfuric acid aerosols, H2O, CO2, SO2, HCl, HBr) under controlled conditions. The measurements will be conducted in a Teflon smog chamber at the University of Bayreuth, where all necessary measurement techniques can be easily installed. RHS (BrO, ClO, OClO) will be measured by a White multi-reflection cell and CE-DOAS and other halogen species (Br2, Cl2, HOBr and BrCl) by FAPA-MS (Flowing Atmospheric-Pressure Afterglow Mass Spectrometry). SO2, CO2, NOX and O3 will be monitored by standard analyzers and particles will be sampled with a filter and an impactor for subsequent IC and SEM-EDX (Scanning Electron Microscope - Energy Dispersive X-ray Detector) analysis to gain information on the halogens absorbed on the particles. The combination of these techniques gives the possibility to explore the role of the heterogeneous reactions involved in halogen activation, representing a current lack of understanding in volcanic research. In particular, the influence of (1) NOX and O3, (2) initial HCl/HBr ratio, (3) relative humidity, and (4) the particle composition (towards more complex real volcanic "ash") on the reactive halogen chemistry (including the bromine explosion mechanism) will be investigated within four project phases. Supported by the chemical box model CAABA/MECCA, the observations will be evaluated and placed into a larger context to better understand natural processes.