Laboratory Studies of Halogen Heterogeneous Chemistry in the Troposphere

9627231 Abbatt在这个项目中，将进行涉及卤素物种的非均相过程的实验研究，这对确定对流层的光化学稳定状态很重要。大部分工作将集中在溴非均相化学方面，因为它与春季北极边界层臭氧消耗现象有关。要研究的特殊相互作用是HOBr、HBr、BrO和具有对流层颗粒表面的溴化有机物质的相互作用。这些实验的目的是更好地确定溴保持一种对气相臭氧破坏有活性的形式的机制，并确定无机溴的主要来源。由于观测表明在这些臭氧消耗事件期间存在大量活性氯，因此还将进行氯非均相化学研究，这可能是这一现象的一个组成部分。在实验上，这些研究将使用实验技术的组合来进行。气体表面吸收系数和反应概率将在本实验室最近建造的高压气溶胶流管和标准低压涂覆壁流管中进行测量。为了确定溴化物质在气相和凝聚相之间的分配，将使用质谱法测量溶解在溶液中的稳定物质的平衡蒸汽压，并测量薄膜对气相物质的物理吸收。最后，FTIR吸收光谱将用于监测气溶胶流管内气溶胶的相和组成。这些实验将在气溶胶成分、温度和相对湿度尽可能接近大气中普遍存在的条件下进行。＊＊＊

9627231 Abbatt In this project, experimental studies of heterogeneous processes involving halogen species important in determining the photochemical steady state of the troposphere will be performed. The majority of the work will focus upon aspects of bromine heterogeneous chemistry as it relates to the phenomenon of ozone depletion in the Arctic boundary layer in the springtime. Particular interactions to be studied are those of HOBr, HBr, BrO and brominated organic species with tropospheric particulate surfaces. The goal of these experiments is to better define the mechanism by which bromine is maintained in a form active towards gas-phase ozone destruction and to determine the dominant source of inorganic bromine. Motivated by observations which indicate large amounts of active chlorine during these ozone depletion events, studies of chlorine heterogeneous chemistry which may be an integral part of this phenomenon will also be carried out. Experimentally, these studies will be performed using a combination of experimental techniques. Gas-surface uptake coefficients and reaction probabilities will be measured both in a high pressure, aerosol flow tube recently constructed in this laboratory and in a standard low pressure, coated-wall flow tube. To determine the partitioning of brominated species between the gas and condensed phases, mass spectrometry will be used to measure the equilibrium vapor pressures of stable species dissolved in solutions and to measure the physical uptake of gas-phase species by thin films. Finally, FTIR absorption spectroscopy will be used to monitor the phase and composition of the aerosols within the aerosol flow tube. These experiments will be performed under conditions of aerosol composition, temperature and relative humidity which match as closely as possible those prevalent in the atmosphere. ***