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COMPARISON OF NONMETHANE ORGANIC COMPOUND CONCENTRATIONS DATA COLLECTED BY TWO METHODS IN ATLANTA
Citation:
Shreffler, J. COMPARISON OF NONMETHANE ORGANIC COMPOUND CONCENTRATIONS DATA COLLECTED BY TWO METHODS IN ATLANTA. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-94/241 (NTIS PB94170123).
Description:
The Clean Air Act Amendments of 1990, Title 1, call for "enhanced monitoring" of ozone, which is planned to include measurements of atmospheric non-methane organic compounds (NMOC's). MOC concentration data gathered by two methods in Atlanta, Georgia during July and August 1990 are compared in order to assess the reliability of such measurements in an operational setting. uring that period, automated gas chromatography (GC) Systems (FIELD systems) were used to collect NMOC continuously as one-hour averages. In addition, canister samples of ambient air were collected on an intermittent schedule for quality control purposes and analyzed by laboratory GC (the LAB system). ata from the six-site network included concentrations of nitrogen oxides (Nox), carbon monoxide (CO), ozone, total NMOC (TNMOC), and 47 identified NMOC's. egression analysis indicates that the average TNMOC concentration from the LAB system is about 50 percent higher than that from the FIELD system, and that the bulk of the difference is due to unidentified NMOCs recorded by the LAB system. lso, there are substantial uncertainties in predicting a single FIELD TNMOC concentration from a measured LAB concentration. or individual identified TNMOCs, agreement is poor for many olefins that occur at low concentrations but may be photochemically important. egressions of TNMOC against CO and NOx lead to the conclusion that the larger unidentified component being reported by the LAB system is not closely related to local combustion or automotive sources.