MEASUREMENTS OF NOX AND NOY CONCENTRATIONS AND FLUXES OVER ARCTIC TUNDRA

Measurements of the atmospheric concentrations of NO, NO2, total NO(y) and O3 were made on a 12-m tower in a tundra bog ecosystem in southwestern Alaska during the growing season (July-August) of 1988. Typical concentrations of NO(x) and NO(y) were 10-15 pptv, and 130-200 pptv, respectively, lower than at other remote continental sites. Anthropogenic influences were small at this site during this time of year, but significant enhancements in NO(x) and NO(y) concentrations were observed from distant biomass fires. Measurements of NO(x) and O3 Vertical profiles, in combination with eddy correlation measurements of O3 flux (Jacob et al., this issue (b), provide an estimate of the NO(x) emission rate from the surface to the atmosphere, 0.13(+/-O.05) x 10(9) molecules cm-2 s-1. Direct (eddy correlation) measurements of the flux of total NO(y) were made for the first time, indicating a downward flux of NO(y) at all times of day, with maximum deposition of 2.5(+/-0.9) x 10(9) molecules cm-2 s-1 in the afternoon. Deposition of HNO3 appears to dominate the atmosphere/surface exchange of NO(y). The mean dry deposition rate of NO(y) to the tundra was 1.8(+/-1.0) x 10(9) molecules cm-2 s-1, about half as large as the wet deposition rate of NO3- (Talbot et al., this issue). The impact of wet tundra ecosystems on regional and global atmospheric chemistry is discussed in light of these results.