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AIR QUALITY MONITORING IN ATLANTA WITH THE DIFFERENTIAL OPTICAL ABSORPTION SPECTROMETER
Citation:
Conner, T. AND R. Stevens. AIR QUALITY MONITORING IN ATLANTA WITH THE DIFFERENTIAL OPTICAL ABSORPTION SPECTROMETER. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/D-91/086 (NTIS PB91191239), 1991.
Description:
During July and August of 1990, a differential optical absorption spectrometer (DOAS) made by OPSIS Inc. was used to measure gaseous air pollutants over three separate open paths in Atlanta, GA. ver path 1 (1099 m) and path 2 (1824 m), ozone (O3), sulfur dioxide (SO2), nitrogen dioxide (NO2), nitrous acid (HNO2), formaldehyde (HCHO), benzene, toluene, and o-xylene were measured. itric oxide (NO) and ammonia (NH3) were monitored over path 3 (143 m). he data quality and data capture depended on the compound being measured and the path over which it was measured. enzene, toluene, and o-xylene concentrations measured over path 2, which crossed over an interstate highway, were higher than concentrations measured over path 1, implicating emissions from vehicles on the highway as a significant source of these compounds. ederal Reference Method (FRM) instruments were located near the DOAS light receivers and measurements of O3, NO2 and NO were made concurrently with the DOAS. orrelation coefficients greater than 0.85 were obtained between the DOAS and FRM's; however, there was a significant difference between the mean values obtained by the two methods for NO. ifferences in the mean values obtained by the two methods for O3 resulted from large discrepancies at low concentrations. A gas chromatograph for measuring volatile organic compounds was operated next to the FRM's. orrelation coefficients of about 0.66 were obtained between the DOAS and GC measurements of benzene and o-xylene. However, the correlation coefficient between the DOAS and GC measurements of toluene averaged only 0.15 for the two DOAS measurement paths. he lack of correlation and other factors indicate the possibility of a localized source of toluene near the GC. n general, disagreements between the two measurement methods could be caused by atmospheric inhomogeneities or interferences in the DOAS and other methods.
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AIR QUALITY MONITORING IN ATLANTA WITH THE DIFFERENTIAL OPTICAL ABSORPTION SPECTROMETER