Photochemical production of oceanic alkyl nitrates

Atmospheric alkyl nitrates are important because they can account for a substantial portion (up to 80%) of the reactive odd nitrogen in the troposphere, hence playing a role in NOx and ozone cycling. Previous observations of methyl, ethyl, and propyl nitrates in the remote marine atmosphere suggested that the oceans are a source of alkyl nitrates to the troposphere. Oceanic alkyl nitrates have not been well studied and the origin of these alkyl nitrates is unknown. The goal of this dissertation was to examine the distribution of alkyl nitrates in the oceans and to investigate a possible photochemical source.; The mechanism proposed in this work for the formation of alkyl nitrates in the aqueous phase is the free radical reaction of alkyl peroxy radicals with nitric oxide (ROO + NO). ROO and NO are derived in seawater from the photolysis of dissolved organic matter and nitrite, respectively. Photochemical yield experiments indicated that the reaction produces alkyl nitrates with yields of up to 70%. Irradiations of open ocean seawater from the Pacific and Atlantic oceans were carried out in the field using natural sunlight. Alkyl nitrates were formed at environmentally significant rates that were highly dependent on nitrite concentration indicating that the reaction of ROO + NO is a viable source of surface ocean alkyl nitrates.; The relative abundances of surface ocean alkyl nitrates in the Pacific and Atlantic oceans indicated that photochemical production was a likely source of alkyl nitrates in the tropical oceans. However, alkyl nitrate maxima were sometimes observed below the mixed layer, suggesting that photochemical production is not the only source of alkyl nitrates in the oceans. Saturation anomaly measurements of alkyl nitrates in the tropical Pacific Ocean demonstrated that the ocean is the major source of C1--C3 alkyl nitrates to the troposphere in this region.