MEASUREMENT OF ALKYL NITRATES AT CHEBOGUE POINT, NOVA-SCOTIA DURING THE 1993 NORTH-ATLANTIC REGIONAL EXPERIMENT (NARE) INTENSIVE

Measurements of six alkyl nitrates, methyl-, ethyl-, 1-propyl-, 2-prop yl-, 2-butyl, and 3-pentyl nitrates, and two peroxycarboxylic nitric a nhydrides, peroxyacetic nitric anhydride (PAN) and peroxypropionic nit ric anhydride (PPN) were made at Chebogue Point, Nova Scotia, during t he 1993 North Atlantic Regional Experiment campaign. The correlation o f alkyl nitrates (RONO2) with carbon monoxide makes it clear that the chemistry at this site is being driven by continental emissions, since RONO2 compounds are known to be by-products of HC-NO, photochemistry. Comparison of the ratios of alkyl nitrates to their parent hydrocarbo ns to that of 2-butyl nitrate/butane showed significant deviations fro m trends predicted from rate constants, branching ratios, and loss rat es. For ethyl nitrate this deviation is likely due to a combination of many additional pathways to the intermediate peroxy radical from the decomposition of larger alkoxy radicals. The propyl nitrates showed tr ends that differed from one another; 2-propyl nitrate was a factor of 2 to 3 higher than predicted, while 1-propylnitrate was a factor of 8 to 10 higher than predicted. The trend of 3-pentyl nitrate/pentane was relatively close (about 50% lower) to the predicted trend. The relati onship between PAN and PPN showed unexpectedly high ratios of PPN to P AN in air masses coming from the south and west of the site, implying a slight local source of PPN.