Observations of OH and HO2 radicals in coastal Antarctica

• Main Authors: S. J.-B. Bauguitte, H. K. Roscoe, D. E. Heard, R. A. Salmon, J. D. Lee, W. J. Bloss, A. E. Jones
• Format: Article
• Language: English
• Published: Copernicus Publications 2007-08-01
• Series: Atmospheric Chemistry and Physics
• Online Access: http://www.atmos-chem-phys.net/7/4171/2007/acp-7-4171-2007.pdf

OH and HO₂ radical concentrations have been measured in the boundary layer of coastal Antarctica for a six-week period during the austral summer of 2005. The measurements were performed at the British Antarctic Survey's Halley Research Station (75° 35' S, 26° 19' W), using the technique of on-resonance laser-induced fluorescence to detect OH, with HO₂ measured following chemical conversion through addition of NO. The mean radical levels were 3.9×10⁵ molecule cm^−3 for OH, and 0.76 ppt for HO₂ (ppt denotes parts per trillion, by volume). Typical maximum (local noontime) levels were 7.9×10⁵ molecule cm^−3 and 1.50 ppt for OH and HO₂ respectively. The main sources of HO_x were photolysis of O₃ and HCHO, with potentially important but uncertain contributions from HONO and higher aldehydes. Of the measured OH sinks, reaction with CO and CH₄ dominated, however comparison of the observed OH concentrations with those calculated via the steady state approximation indicated that additional co-reactants were likely to have been present. Elevated levels of NO_x resulting from snowpack photochemistry contributed to HO_x cycling and enhanced levels of OH, however the halogen oxides IO and BrO dominated the CH₃O₂ – HO₂ – OH conversion in this environment, with associated ozone destruction.