Peroxy radical measurements by ethane-nitric oxide chemical amplification and laser-induced fluorescence during the IRRONIC field campaign in a forest in Indiana

Abstract

Peroxy radicals were measured in a mixed deciduous forest atmosphere in Bloomington, Indiana, USA, during the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC) during the summer of 2015. Total peroxy radicals ([XO2] = [HO2]+s[RO2]) were measured by a newly developed technique involving chemical amplification using nitric oxide (NO) and ethane (C2H6) followed by NO2 detection by cavity-attenuated phase-shift spectroscopy (hereinafter referred to as ECHAMP-Ethane CHemical AMPlifier). The sum of hydroperoxy radicals (HO2) and a portion of organic peroxy radicals ([HO* >inf>2>/inf>] U D [HO2]+sai [RiO2], 0 > a > 1) was measured by the Indiana University (IU) laser-induced fluorescence-fluorescence assay by gas expansion instrument (LIF-FAGE). Additional collocated measurements include concentrations of NO, NO2, O3, and a wide range of volatile organic compounds (VOCs) and meteorological parameters. XO2 concentrations measured by ECHAMP peaked between 13:00 and 16:00 local time (LT), with campaign average concentrations of 41±15 ppt (1s) at 14:00 LT. Daytime concentrations of isoprene averaged 3:6±1:9 ppb (1s), whereas average concentrations of NOx ([NO]C[NO2]) and toluene were 1.2 and 0.1 ppb, respectively, indicating a low impact from anthropogenic emissions at this site.