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

An integrated system that quantitatively measures speciated C2-C-10 hy drocarbons 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-integ rated sample to be taken without the use of solid sorbent traps or exc essive cryogen. Subsequent analysis, using both cryotrapping and cryof ocusing steps to produce high-resolution gas chromatograms, with eithe r flame ionization (GC-FID) or mass selective (GC-MSD) detection, allo wed for quantitation and identification of sampled non-methane hydroca rbons (NMHCs) on a single capillary column. Under the chromatographic conditions used, the total analysis time of 1 h enabled concurrent sam pling and analysis of the previously collected sample in a continuous, automated mode. The use of this system at a field site, during a 6-we ek field study in Atlanta, GA, as part of the Southern Oxidant Researc h Program on Ozone Non-Attainment is described. Consideration of the s tandard operating procedures developed, the calibration of the systems , and the validation of the data set is given. Illustration of advanta ges of this method is provided by some preliminary results of the NMHC analyses at a semiurban site (Lost Mountain, Marietta, GA), showing t hat the dominant single hydrocarbon for much of the study was isoprene .