Diurnal HO₂ cycles at clean air and urban sites in the troposphere

Abstract

HO₂ concentrations have been determined at two Oregon sites for continuous periods of 36 to 48 hours, using fluorescence assay with gas expansion. At the sea level coastal site (45degN 124degW), NNW winds prevailed during daytime, and a point measurement of very low total nonmethane hydrocarbon concentration indicated the presence of remote tropospheric air of oceanic origin. At the urban site, HO₂ was determined during moderately low ozone pollution levels. At both sites, maximum daily [HO₂] was in the range of 1-2times10⁸ cm⁻³ under clear-sky conditions, with an estimated overall uncertainty of 40%.