CONTINUOUS HOURLY ANALYSIS OF C2-C10 NONMETHANE HYDROCARBON COMPOUNDS IN URBAN AIR BY GC-FID

An integrated system that quantitatively measures speciated C2-C-10 hydrocarbons and other volatile organic chemicals VOCs) down to the sub-parts-per-billion range is described. Ambient air was collected for up to 55 min of each hour into a holding canister, enabling a time-integrated sample to be taken without the use of solid sorbent traps or excessive cryogen. Subsequent analysis, using both cryotrapping and cryofocusing steps to produce high-resolution gas chromatograms, with either flame ionization (GC-FID) or mass selective (GC-MSD) detection, allowed for quantitation and identification of sampled non-methane hydrocarbons (NMHCs) on a single capillary column. Under the chromatographic conditions used, the total analysis time of 1 h enabled concurrent sampling and analysis of the previously collected sample in a continuous, automated mode. The use of this system at a field site, during a 6-week field study in Atlanta, GA, as part of the Southern Oxidant Research Program on Ozone Non-Attainment is described. Consideration of the standard operating procedures developed, the calibration of the systems, and the validation of the data set is given. Illustration of advantages of this method is provided by some preliminary results of the NMHC analyses at a semiurban site (Lost Mountain, Marietta, GA), showing that the dominant single hydrocarbon for much of the study was isoprene.