Aircraft Measurements of Nitrogen Dioxide and Peroxyacyl Nitrates Using Luminol Chemiluminescence with Fast Capillary Gas Chromatography

Fast capillary gas chromatography with luminol detection has been used to make airborne measurements of nitrogen dioxide (NO2) and peroxyacetyl nitrate (PAN). The analysis system allows for the simultaneous measurement of NO2 and peroxyacyl nitrates (PANs) with time resolution of less than 1 min, an improvement of a factor of 4−5 over previously reported methods using electron capture detection. Data presented were taken near Pasco, Washington, in August 1997, during a test flight onboard the U.S. Department of Energy G-1 aircraft. We report measurements of NO2 in the boundary layer in a paper mill plume and a plume from a grass fire, in addition to analyses for free tropospheric NO2 and PAN. Ratios of PAN/NO2 were observed to increase with altitude (decreasing temperature) and to reach values of 2−4 above the boundary layer, consistent with the thermal equilibrium of the peroxyacetyl radical and NO2 with PAN. Estimates for the peroxyacetyl radical in the continental free troposphere, calculated from this equilibrium, were found to be in the range of 104−105 molecules per cubic centimeter. These results demonstrate the application of this approach for airborne measurements of NO2 and PAN in a wide range of field study scenarios.