<title>Air quality monitoring with the differential optical absorption spectrometer</title>

Abstract

Measurements of gaseous air pollutants over three separate open paths in Atlanta, Georgia, conducted with a differential optical absorption spectrometer (DOAS) during July and August 1990 are reported. Over path 1 (1099 m) and path 2 (1824 m), O3, SO2, NO2, HNO2, HCHO, benzene, toluene, and o-xylene were measured. NO and NH3 were monitored over path 3 (143 m). Federal reference method (FRM) instruments were located near the DOAS light receivers, and measurements of O3, NO2, and NO were made concurrently with the DOAS. Correlation coefficients between the two measurement paths ranged from 0.87 for toluene to 0.99 for ozone. Comparisons between FRM and DOAS for O3, NO2, and NO showed good correlations but some differences in average concentrations, most notably for NO, whose FRM concentrations averaged less than 40 percent of the DOAS concentrations. The advantages of the DOAS system over traditional FRM systems are discussed.