Chemistry of Halogen Oxides in the Troposphere: Comparison of Model Calculations with Recent Field Data

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• 作者：Jochen Stutz ; Kai Hebestreit ; Bj?rn Alicke and Ulrich Platt
• 关键词：atmospheric ozone ; halogen oxides ; tropospheric photochemistry
• 刊名：Journal of Atmospheric Chemistry
• 出版年：1999
• 出版时间：1999
• 年：1999
• 卷：34
• 期：1
• 页码：65-85
• 全文大小：641 KB

文摘

Reactive halogen species (RHS = X, XO, HOX, OXO; X = Cl, Br, I) are known to have an important influence on the chemistry in the polar boundary layer (BL), where they are responsible for ozone depletion events in spring. Recent field campaigns at Mace Head, Ireland, and the Dead Sea, Israel, identified for the first time iodine oxide (IO) at mixing ratios of up to 6.6 ppt and 90 ppt bromine oxide (BrO), respectively, by DOAS also at lower latitudes. These results intensified the discussion about the role of the RHS in the mid-latitude BL.Photochemical box model calculations show that the observed IO mixing ratios can destroy ~0.45 ppb ozone per hour. This is comparable to the rates of the known O₃-loss processes in the boundary layer. The model studies also reveal that IO, at these levels, has a strong influence on the BL photochemistry, increasing the OH/HO₂- and the NO₂/NO - ratios. In combination these changes lead to a reduction of the photochemical ozone formation, which - in addition - reduces ozone mixing ratios by up to 0.15 ppb/h.