Measurements of PAN in the polluted boundary layer and free troposphere using a luminol-NO detector combined with a thermal converter

Peroxyacetyl nitrate (PAN, CHC(O)ONO) has been measured in the polluted boundary layer and free troposphere by thermal conversion to nitrogen dioxide (NO) followed by detection of the decomposition product with a Scintrex LMA-3 NO-luminol instrument. Following laboratory tests of the efficiency of PAN conversion and investigations of possible interferences, the technique was evaluated at the West Beckham TOR (Tropospheric Ozone Research) Station near the north Norfolk coast in Eastern England between September 1989 and August 1990. PAN measured by the new technique was reasonably well correlated with PAN recorded using electron capture gas chromatography (EC/GC). PAN was also well correlated with ozone (O) in the summer months. Spring and autumn episodes of simultaneously high concentrations of PAN and O were examined in conjunction with air parcel back-trajectories and synoptic- and local-scale meteorology in a study of the sources of photooxidants on the east coast of England. Spring-time measurements of PAN made in the free 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 suited to airborne applications because potential interferences are minimised and the frequency of measurements is higher than generally achieved with EC/GC methods.