Long-term measurements of atmospheric peroxyacetylnitrate (PAN) at rural sites in Ontario and Nova Scotia - Seasonal variations and long-range transport

The atmospheric behavior of peroxyacetylnitrate (PAN) at rural locations is studied using highly sensitive, automated gas chromatographic techniques to perform measurements at Longwoods, Ontario and Kejimkujik, Nova Scotia and two sites in northern Ontario. Periods of elevated PAN mixing ratio are found throughout the year, suggesting that significant photochemical activity can occur during wintertime. The results suggest that PAN maxima occur in fall and late winter/early spring. The magnitude of PAN maxima decreases with distance from the source region of influence. For all sites studied, PAN accounts for a significant fraction of the observed oxidized nitrogen species and appears to make an increasing contribution as the transport time from the source region increases.