Cooperative Institute for Research in Environmental Sciences

Science Rendezvous > Posters
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Measurement of Nitrogen Dioxide by CW Cavity Ring-Down Spectroscopy

Bill Dube’ 1,2, Eric Williams 1,2, Hendrik Fuchs 1,2, Brian Lerner 1,2, Rebecca Washenfelder 1,2, Nick Wagner 1,2, Steve Brown 2

ebecca Washenfelder1,2, Nick Wagner1,2, Steve Brown2 1 CIRES/University of Colorado, Boulder, CO 80309 2 NOAA/ESRL/CSD, 325 Broadway, Boulder, CO 80305

NO2 and NOx (=NO2+NO) measurements are essential for monitoring air-quality.Cavity ring-down spectroscopy (CRDS) is a highly sensitive technique to detect small concentrations of atmospheric trace gases such as NO2. Laser diode light sources enable the development of compact, light weighted instruments with minimal requirements for power and consumables. NO2 can be detected directly by absorption near 405,nm where ozone absorption and water absorption, which are the major concerns with respect to interferences, are small compared to that of NO2. Here, NOx is detected in a second cavity in addition to ambient NO2 by oxidation of ambient NO with excess ozone so that the sum of NO2 and NO is measured as NO2. This presentation will compare the performance of the CRDS instrument for NO and NO2 detection to standard instruments based on chemiluminescence for sensitivity, accuracy, linearity and dynamic range, and potential interferences using data from both laboratory and in-field comparisons.