A prototype DOAS instrument was assembled to measure ambient concentration of Sulfur Dioxide (SO2). A folded-path configuration employing retroreflectors was chosen because of advantages in sensitivity and convenience in housing the transmitter and receiver together. The measurement path length was approximately 280m. Data gathering was performed during April, 2004. Since an NIST-traceable calibration gas was unavailable, the instrument was calibrated with the Opsis system (a commercial DOAS instrument located near the experiment). Results showed good agreement between the two instruments. The results were also compared to the SO2 measurements of the EMB (Environmental Management Bureau) located near the experiment site. The detection limit of the prototype instrument is estimated to be 1.4 ppb.
[Loyola Schools Review, 2005]