Development and Deployment of an Airborne Gas Chromatography/Mass Spectrometer to Measure Tropospheric Volatile Organic Compounds

Airborne Volatile Organic Compounds are present throughout the atmosphere in a wide variety of species. An airborne Gas Chromatography/Mass Spectrometer was developed to measure these compounds in places otherwise inaccessible for ground- or ship-based instruments. The instrument was �tted to the UK FAAM BAe-146 Atmospheric Research Aircraft, and deployed on a number of campaigns. By the end of the project, the instrument was capable of making measurements that compared extremely well to other systems, meaning the proof of concept was successful. During the SAMBBA campaign, vertical pro�les of biogenic and anthropogenic species were determined from the ground, up to 8000 m. These showed the extent to which di�erent compounds (for example CO, benzene) were able to escape the planetary boundary layer and enter the free troposphere. Isoprene, however, with a much shorter lifetime of 0.5 hours, was primarily constrained to the boundary layer. Additionally, an analysis of biomass burning emissions was compared to those in literature. In particular the CO:VOC ratio was compared, with some species exhibiting very close comparisons, and others showing very di�erent ratios leading to the conclusion that the CO:VOC ratio for some compounds is highly dependent on the species of trees. Measurements from the CAST campaign determined the extent to which naturally occurring halogenated species can travel from their source at the ocean surface, up to the lower stratosphere, a�ecting ozone levels. A comparison was also conducted with 3 other aircraft systems, for which the GC/MS was in good agreement. Finally, ights were conducted around the North Sea Oil and gas �elds to determine background levels of compounds, in case of further leaks from natural gas extraction. Whilst the GC/MS could not identify speci�c plumes, calculations were performed to enhance the readings, showing very di�erent levels of benzene emitted, which was dependent on the rig type.