SEMICONTINUOUS METHOD FOR MONITORING SO2 AT LOW PARTS-PER-TRILLION CONCENTRATIONS

A technique is described for low parts-per-trillion (ppt) detection of SO2 with high temporal resolution compared to current filter sampling methods. A sulfur chemiluminescence detector, equipped with a quartz burner chamber and a sample probe with a critical orifice, was used as a single detector to analyze SO2 in ambient air by alternately cyclin g the sample airstream through a SO2 denuder. The method provides one SO2 concentration reading every 10 min. The limits of detection and qu antitation were found to be 20 and 70 pptv, respectively. Results from field measurements at a remote site on the south rim of the Grand Can yon during November 1998 are presented, and they indicate a highly var iable distribution of SO2 from the limit of detection to near 2 ppbv.