OH clock determination by proton transfer reaction mass spectrometry at an environmental chamber
- 1Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland
- 2Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USA
- *now at: Department of Civil Architectural and Environmental Engineering, Drexel University, Philadelphia, PA, USA
- **now at: TSI GmbH, Particle Instruments, Aachen, Germany
Abstract. The hydroxyl free radical (OH) is the major oxidizing species in the lower atmosphere. Measuring the OH concentration is generally difficult and involves elaborate, expensive, custom-made experimental setups. Thus other more economical techniques, capable of determining OH concentrations at environmental chambers, would be valuable. This work is based on an indirect method of OH concentration measurement, by monitoring an appropriate OH tracer by proton transfer reaction mass spectrometry (PTR-MS). 3-pentanol, 3-pentanone and pinonaldehyde (PA) were used as OH tracers in α-pinene (AP) secondary organic aerosol (SOA) aging studies. In addition we tested butanol-d9 as a potential "universal" OH tracer and determined its reaction rate constant with OH: kbutanol-d9 = 3.4(±0.88) × 10−12 cm3 molecule−1 s−1. In order to make the chamber studies more comparable among each other as well as to atmospheric measurements we suggest the use of a chemical (time) dimension: the OH clock, which corresponds to the integrated OH concentration over time.