Nitrogen oxides in the Arctic troposphere

In order to characterize these compounds in the arctic troposphere, ground-level concentrations of total reactive nitrogen (NOy) and NO were determined over an extended period at a site near Barrow, Alaska. A high-sensitivity instrument developed for this purpose was used in three measurement campaigns: summer 1988, spring 1989, and March-December 1990. During the 1990 campaign, the detection limit for NO was 3-10 pptv and the NOy uncertainty was ±26%. A screening algorithm was applied to the data to eliminate effects from local (Barrow) sources, and the remaining data were divided into background periods and events. Evidence indicates that the springtime arctic NOy reservoir was primarily composed of stable removal-resistant species, including PAN and other organic nitrates. PAN decomposition as temperatures rose in late spring likely caused an observed pulse of NO to ∼35 pptv (maximum hourly average); hourly-average NO concentrations were otherwise generally < 8 pptv. NOx production from PAN decomposition due to the onset of spring or southward advection may affect springtime O3 levels both in the Arctic and in the northern mid-latitudes. NOy and O3 concentrations were positively correlated during summer, possibly indicating long-range transport of both and/or the presence of a mid-tropospheric NOy reservoir combined with a stratospheric O3 source