MEASUREMENTS OF PAN IN THE POLLUTED BOUNDARY-LAYER AND FREE TROPOSPHERE USING A LUMINOL-NO2 DETECTOR COMBINED WITH A THERMAL CONVERTER

Peroxyacetyl nitrate (PAN, CH3C(O)O2NO2) has been measured in the poll uted boundary layer and free troposphere by thermal conversion to nitr ogen dioxide (NO2) followed by detection of the decomposition product with a Scintrex LMA-3 NO2-luminol instrument. Following laboratory tes ts of the efficiency of PAN conversion and investigations of possible interferences, the technique was evaluated at the West Beckham TOR (Tr opospheric Ozone Research) Station near the north Norfolk coast in Eas tern England between September 1989 and August 1990. PAN measured by t he new technique was reasonably well correlated with PAN recorded usin g electron capture gas chromatography (EC/GC). PAN was also well corre lated with ozone (O-3) in the summer months. Spring and autumn episode s of simultaneously high concentrations of PAN and O-3 were examined i n conjunction with air parcel back-trajectories and synoptic- and loca l-scale meteorology in a study of the sources of photooxidants on the east coast of England. Spring-time measurements of PAN made in the fre e troposphere in a light aircraft at altitudes up to 3.1 km showed the presence of 0.54 and 0.26 ppbv PAN in polar maritime and mid-latitude oceanic air masses, respectively. The technique is particularly suite d to airborne applications because potential interferences are minimis ed and the frequency of measurements is higher than generally achieved with EC/GC methods.