During the summer of 1991, simultaneous measurements of O3, NO, NO2, and SO2 were obtained by an open path differential optical absorption spectrometer (DOAS) and conventional point methods at two sites (one urban and one rural) in the central Piedmont of North Carolina. The monitoring was conducted as part of the Southern Oxidant Study (SOS) program. In addition, the DOAS was configured to measure HNO2, NH3 HCHO, benzene, toluene, and p-xylene. The DOAS measurements were each integrated over a one minute period and the full set of measurements was obtained over a seven minute cycle time. NO and NH3 were measured over a 200 meter folded path. The remaining gases were measured over a 400 meter folded path. Additional point measurements included continuous measurements of NOy, H2O2, and integrated measurements of speciated hydrocarbons, aldehydes, and HNO3. This paper examines the relationship between the path integrated, and point measurements of O3, NO, NO2, and SO2.
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