Analysis of non-methane hydrocarbons in air samples collected aboard the CARIBIC passenger aircraft

Abstract

Abstract. The CARIBIC project (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) is a long-term monitoring program making regular atmospheric measurements from an instrument container installed monthly aboard a passenger aircraft. Typical cruising altitudes of the aircraft allow for the study of the free troposphere and the extra-tropical upper troposphere as well as the lowermost stratosphere. CARIBIC measurements include a number of real time analyses as well as the collection of aerosol and whole air samples. These whole air samples are analyzed post-flight for a suite of trace gases, which includes non-methane hydrocarbons (NMHC).The NMHC measurement system and its analytical performance are described here. Precision was found to vary slightly by compound, and is less than 2% for the C 2 -C 6 alkanes and ethyne, and between 1% and 6% for C 7 -C 8 alkanes and aromatic compounds. Preliminary results from participation in a Global Atmospheric Watch (WMO) VOC audit indicate accuracies within the precision of the system. Limits of detection are 1 pptv for most compounds, and up to 3 pptv for some aromatics. These are sufficiently low to measure mixing ratios typically observed in the upper troposphere and lowermost stratosphere for the longer-lived NMHC, however, in air samples from these regions many of the compounds with shorter lifetimes (<5 days) were frequently below the detection limit. Observed NMHC concentrations span several orders of magnitude, dependent on atmospheric region and air mass history, with concentrations typically decreasing with shorter chemical lifetimes.

Comparison between CARIBIC Aerosol Samples Analysed by Accelerator-Based Methods and Optical Particle Counter Measurements

“…The particles of the atmospheric aerosol have a broad spectrum of sources, where the anthropogenic contribution often can be difficult to quantify due to influences from natural sources at background conditions (Andreae and Rosenfeld, 2008). Despite being trace constituents of the atmosphere, particles are of considerable concern, such as adverse health effects and premature deaths (Pope III and Dockery, 2006) and climate change (IPCC, 2013), where in the latter case the direct and indirect effects of atmospheric particles can act as to mask the climate impact of greenhouse gases (Schwartz et al, 2010).…”

Characterization of non-methane hydrocarbons in Asian summer monsoon outflow observed by the CARIBIC aircraft

“…Also housed in the instrument container are systems for the collection of aerosol and whole-air samples, which are analyzed upon return to the laboratory, and it is the analysis of NMHCs in the whole air samples that forms the basis of the work presented here. Detailed descriptions of CARIBIC sample collection and NMHC measurements can be found in Schuck et al (2009) and Baker et al (2010), respectively, and will only be described briefly here.…”

A growing threat to the ozone layer from short-lived anthropogenic chlorocarbons

“…Samples were collected within 50 m of the sea and only when the prevailing winds were from the sea, minimising the impact of any local emissions. The CARIBIC aircraft samples were collected in 2.7 L glass flasks at a pressure of 4.5 bar using a two-stage 11932 D. E. Oram et al: A growing threat to the ozone layer metal bellows pumping system (Brenninkmeijer et al, 2007;Baker et al, 2010).…”