Airborne measurements of formaldehyde employing a high-performance tunable diode laser absorption system

Formaldehyde (CH2O) is a ubiquitous component of both the remote atmosphere as well as the polluted urban atmosphere. This important gas-phase intermediate is a primary emission product from hydrocarbon combustion sources as well as from oxidation of natural hydrocarbons emitted by plants and trees. Through its subsequent decomposition, formaldehyde is a source of reactive hydrogen radicals, which control the oxidation capacity of the atmosphere. Because ambient CH2O concentrations attain levels as high as several tens of parts-per-billion (ppbv) in urban areas to levels as low as tens of parts-per-trillion (pptv) in the remote background atmosphere, ambient measurements become quite challenging, particularly on airborne platforms. The present paper discusses an airborne tunable diode laser absorption spectrometer, which has been developed and refined over the past 6 years, for such demanding measurements. The results from a recent study will be presented.