Improved Instrumentation for Near-Real-Time Measurement of Reactive Hydrocarbons, NO2, and Peroxycyl Nitrates

The measurement of reactive hydrocarbons and associated nitrogen oxides, NO2 and PANs, is of key importance to unraveling the complex chemistries involved in photochemical oxidant formation and nighttime chemistry driven by nitrate radical. Recent work has demonstrated that chemiluminescent reactions of ozone with hydrocarbons (and the temperature dependence of the reactions) can be used as a means of detecting a wide variety of organic compounds in the gas phase with comparable to or sensitivity better than that of the conventional flame ionization detection method. We have implemented a new design built an instrument to evaluate this approach for the monitoring of olefins. This instrument makes use of a computer-controlled photon counting system with a reaction chamber operated at room temperature. Signals are compared to those for an ethene standard to estimate relative reactivity. The instrument will be described in detail, along with a new version of a luminol-based chemiluminescence detection system with fast gas chromatography for measurement of NO2 and PANs. These two instruments have been combined on one instrument rack for field use on both ground-based and aircraft platforms. Data presented show the response times of the instruments and indicate applications for examining reactive hydrocarbon emissions from both vegetation and anthropogenic sources.