| Measurements of the major reactive nitrogen oxides including NO, NO2, HNO3, particulate nitrate, PAN and NO y, as well as O3 and supporting meteorology, were made at a high elevation site (845 masl) in the rural eastern townships of Quebec, Canada from February 1998 to August 1999. Concentrations of NOx and NOy exhibited a distinct seasonal cycle with monthly median mixing ratios in Winter (NOx 1--2.9 ppbv; NOy 1.9--3.6 ppbv) that were more than a factor of 2 greater than in summer (NOx 0.5 ppbv; NOy 1.5 ppbv). The decrease in NOx levels in the warmer months was coincident with increases in monthly median HNO 3 and PAN concentrations (HNO3 0.46--0.65 ppbv; PAN 0.41--0.5 ppbv). Seasonal partitioning indicated that NOx was the dominant fraction of NOy during winter (>78%) with contributions from HNO3 and PAN of 8--19% and 4--10% respectively. In summer, the NOx portion of NOy was lower at 35%, while HNO3 and PAN composed 25--30% and 13--26% respectively. A substantial portion of NOy was unaccounted for during the warmer months. (Abstract shortened by UMI.)... |
