Observations of OH and HO₂ radicals in coastal Antarctica

W. J. Bloss (1) , J. D. Lee (1) , D. E. Heard (1) , R. A. Salmon (2) , S. J.-B. Bauguitte (2) , H. K. Roscoe (2) , A. E. Jones (2)

1 School of Chemistry [Leeds]
2 BAS - British Antarctic Survey

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.

Domaines: Océan, Atmosphère

W. J. Bloss, J. D. Lee, D. E. Heard, R. A. Salmon, S. J.-B. Bauguitte, et al.. Observations of OH and HO₂ radicals in coastal Antarctica. Atmospheric Chemistry and Physics, 2007, 7 (16), pp.4171-4185. ⟨hal-00296310⟩