THE PARTITIONING OF NITROGEN-OXIDES IN THE LOWER ARCTIC TROPOSPHERE DURING SPRING 1988

Surface observations of several nitrogen oxides in the Canadian high A rctic during the period March-April 1988 are reported. These include d ata on NO2, the inorganic nitrates HNO3 and particulate nitrate, and t he organic nitrates PAN and C3-C-7 alkyl-nitrates. It is found that th e organic nitrates make up 70-80% of the sum of the measured nitrogen oxides. Based on concurrently measured sulphur oxides, the period of o bservation was divided into two halves with the first half representin g less polluted, more aged air than the second. The preponderance of t he organic nitrates was less in the first period than the second. In c ontrast, there was little difference in the inorganic nitrates and NO2 concentrations. The dominant inorganic nitrate shifted from particula te nitrate in the first period towards gaseous HNO2 in the second. No correlation between the nitrates (inorganic or organic) and O3 was obs erved; although some indication of a positive correlation between NO2 and O3 has been reported earlier (Bottenheim et al., 1990). Possible e xplanations for these observations are proposed. A survey of other pot ential nitrogen oxides that may be present in the Arctic air but not m easured in these experiments suggests that the nitrogen oxides not mea sured here constitute a minor fraction of the total reactive nitrogen (NO(y)).