Alkyl nitrates, nonmethane hydrocarbons, and halocarbon gases over the equatorial Pacific Ocean during SAGA 3

Latitudinal gradients were found for trace gases with predominantly anthropogenic sources, e.g., methylene chloride, tetrachloroethylene, and acetylene; higher concentrations in the North Pacific atmosphere decreased slowly across the Equator to the South Pacific. More stable gases, e.g. methyl chloride and methyl bromide, had no pronounced variation across the equator. A biogenic source of two organobromine compounds, bromoform and dibromochloromethane, was indicated by maximum mixing ratios of these species over the equator where indicators of biological productivity (e.g. chlorophyll) in the surface ocean water also maximized. Alkyl nitrates were found at levels higher than predicted from steady state calculations based on measured mixing ratios of hydrocarbons and NO. The measured levels of RONO₂ suggest long-range transport as one mechanism contributing to elevated concentrations of alkyl nitrates in the remote troposphere. However, the distributions of C₂ and C₃ alkyl nitrates over the equator were similar to the organobromine gases. The distribution suggests a possible oceanic source for alkyl nitrates to the atmosphere. -from Authors