Observations of OH and HO 2 radicals in coastal Antarctica

• Main Authors: Bloss, W. J., Lee, J. D., Heard, D. E., Salmon, R. A., Bauguitte, S. J.-B., Roscoe, H. K., Jones, A. E.
• Other Authors: School of Chemistry Leeds, University of Leeds, British Antarctic Survey (BAS), Natural Environment Research Council (NERC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Antarctic; Austral; Halley Research Station; Antarc*; Antarctica
• Online Access: https://hal.science/hal-00302613; https://hal.science/hal-00302613/document; https://hal.science/hal-00302613/file/acpd-7-2893-2007.pdf

International audience OH and HO 2 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 HO 2 measured following chemical conversion through addition of NO. The mean radical levels were 3.9×10 5 molecule cm ?3 for OH, and 0.76 ppt for HO 2 (ppt denotes parts per trillion, by volume or pmol mol ?1 ). Typical maximum (local noontime) levels were 7.9×10 5 molecule cm ?3 and 1.50 ppt for OH and HO 2 respectively. The main sources of HO x were photolysis of O 3 and HCHO, with potentially important but uncertain contributions from HONO and higher aldehydes. Of the measured OH sinks, reaction with CO and CH 4 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 CH 3 O 2 -HO 2 -OH conversion in this environment, with associated ozone destruction.