HR: 1330h
AN: A32A-0125    [PDF]
TI: Atlantic Ocean Measurements of Low Molecular Weight Alkyl Nitrates
AU: * Dahl, E E
EM: edahl@uci.edu
AF: University of California, Irvine Department of Earth System Science, 1212 Croul Hall, Irvine, CA 92697 United States
AU: Saltzman, E S
EM: esaltzma@uci.edu
AF: University of California, Irvine Department of Earth System Science, 1212 Croul Hall, Irvine, CA 92697 United States
AB: The surface oceans appear to be a source of low molecular weight alkyl nitrates to the atmosphere. These compounds are converted by photolysis to NOx, and may contribute to ozone production in remote regions. The mechanism(s) of production of oceanic alkyl nitrates in surface seawater are currently unknown. Laboratory studies suggest that the reaction of peroxy radicals with nitric oxide in seawater may provide a near-surface source of these compounds. These precursors originate from the photolysis of dissolved organic matter and nitrite. Depth profiles of alkyl nitrates in the North Atlantic Ocean (Chuck et al. 2002) show elevated concentrations of alkyl nitrates below the photic zone, suggesting that non-photochemical mechanisms are also likely. We have recently completed a series of alkyl nitrate (C1-C3) depth profiles and shipboard incubation experiments in the north Atlantic, on a cruise track from Reykjavik, Iceland to Natal, Brazil (A16N2003; R/V Brown). The northernmost stations (45-50N), exhibited alkyl nitrate maxima in the mixed layer, and a positive correlation between alkyl nitrates and nitrite. In the tropics and subtropics, alkyl nitrate maxima were below the mixed layer, and alkyl nitrates correlated with nitrate. Shipboard deck irradiation studies demonstrated photochemical production of alkyl nitrates in waters that correlated with the initial nitrite concentration. Addition of nitrite stimulated production to extremely high levels, suggesting that NO, rather than peroxy radicals, is the limiting reactant in these waters. Overall, the distribution of alkyl nitrates suggests that both photochemical and microbial sources of alkyl nitrate may occur.
DE: 0315 Biosphere/atmosphere interactions
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
DE: 4820 Gases
DE: 4852 Photochemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting