A new technique for the selective measurement of atmospheric peroxy radical concentrations of HO 2 and RO 2 using a denuding method

Abstract

A technique for the selective measurement of atmospheric HO 2 and RO 2 using peroxy radical chemical amplification coupled to laser-induced fluorescence NO 2 detection (PERCA-LIF) is demonstrated. By pulling the air through a filled pre-inlet advantage can be taken of the higher heterogeneous loss rate of HO 2 relative to CH 3O 2. Pre-inlet conditions have been found where ca. 90% of HO 2 was removed whereas the comparable CH 3O 2 loss was 15%. The dependence of loss rate on humidity and peroxy radical concentration has been investigated. When using glass beads as the surface for peroxy radical removal, the influence of the relative humidity on the removal efficiency becomes negligible. It may therefore be possible to apply this technique to the measurement of absolute concentrations of solely RO 2 as well as the sum of HO 2 and RO 2. The practical utility of the PERCA-LIF coupled to a denuder has been demonstrated with atmospheric measurements. © Author(s) 2010.