GROUND-BASED MEASUREMENTS OF NOX AND TOTAL REACTIVE OXIDIZED NITROGEN(NOY) AT SABLE ISLAND, NOVA-SCOTIA, DURING THE NARE 1993 SUMMER INTENSIVE

Measurements of NO, NO2, and total reactive oxidized nitrogen (NOy) we re added to ongoing measurements of aerosols, CO, and O-3 at Sable Isl and (43 degrees 55'N,'60 degrees 01'W), Nova Scotia, during the North Atlantic Regional Experiment (NARE) 1993 summer intensive. Ambient lev els of NOx and NOy were found to be highly variable, and elevated leve ls can be attributed to the transport of polluted continental air or p resumably to relatively fresh emissions from sources upwind (e.g., shi p traffic). The median values for NOx and NOy are 98 and 266 parts per trillion by volume (pptv), respectively. A multiday pollution episode occurred during which elevated NOx and NO were observed with enhanced levels of O-3, CO, and condensation nuclei. Air masses of recent trop ical marine origin characterized by low and constant levels of O-3 and CO were sampled after Hurricane Emily. The correlation between ozone and CO is reasonably good, although the relation is driven by the sing le pollution episode observed during the study. The correlation of O-3 with NOy and with NOy-NOx is complicated by the presumed NOy removal processes in the marine boundary layer. Examination of the radiosonde data and comparisons of the surface data with those obtained on the ov erflying aircraft provide clear indications of vertical stratification above the site.