DUAL-INLET CHEMICAL AMPLIFIER FOR ATMOSPHERIC PEROXY RADICAL MEASUREMENTS

The state-of-the-art of peroxy radical measurements using the techniqu e of chemical amplification has matured in recent years. The NCAR chem ical amplifier has been improved over previous versions by employing a dual-inlet system that allows more rapid switching between measuremen t and background modes. Further improvement is realized by the use of two NO2 detectors. The dual-inlet chemical amplifier (DICHAMP) employs two identical glass inlet reactor-NO2 detector combinations, one of w hich is operated in the background, while the other operates in the ra dical measurement mode. This instrument is less sensitive to fluctuati ons in ambient ozone than the single-channel version because of the co ntinuous monitoring of the background and background plus radical sign als. The single-inlet, dual-inlet with single-detector, and DICHAMP in struments are compared through theoretical calculations of the effect of noise at a given frequency and amplitude on retrieved radical level s, Laboratory experiments were conducted to support the theoretical re sults. Ambient radical concentrations were determined using these conf igurations to evaluate the performance under actual measurement condit ions.