Measurements of alkyl and multifunctional organic nitrates at a rural site in Ontario

Abstract

Measurements of alkyl and multifunctional organic nitrates were conducted at a rural site in Ontario during periods with varying levels of photochemical activity. On August 6 and August 21–23, 1992, a total of 17 organic nitrates (12 C3‐C6 alkyl nitrates, 4 C2‐C4 hydroxynitrates and 1,2‐dinitrooxybutane) were quantitatively determined in atmospheric samples. The sum of the organic nitrate concentrations was found to be correlated with ozone and ranged from 12 to 140 parts per trillion (volume). The total concentration of organic nitrates measured contributed from 0.5 to 3.0% to the total odd nitrogen species. On average, the alkyl nitrates represented 82%, the hydroxynitrates 16%, and the dinitrate 2% of the total measured organic nitrates. Unidentified organic nitrate peaks determined from an organic nitrate selective detector were found to contribute an additional 0.25% to the total odd nitrogen budget. The distribution of alkyl and hydroxy nitrates measured was found to be reasonably consistent with computed relative production rates, for photochemically active air masses. Although the inclusion of the multifunctional organic nitrates does not significantly change the measured contribution of these species to NOy, it is shown that the isoprene nitrates may contribute as much as the combined contribution of all the measured organic nitrates.