| This research was designed to measure total water-soluble organic N, as well as the contribution of urea and dissolved free amino acids, in rain, aerosols, and ice cores collected from a variety of global locations. In addition to site-specific studies, a UV photo-oxidation method for the determination of total water-soluble nitrogen was evaluated and methods to determine urea and dissolved free amino acids in dilute solutions were developed. Global study sites included (1) a background marine sampling station located at Cape Grim, Tasmania, Australia; (2) a biomass burning region of the Amazon Basin, Brazil; (3) a desert dust influenced atmospheric sampling tower located at Erdemli, Turkey; (4) a cattle feedyard located in Parmer County, Texas; and (5) ice cores from southern Greenland (Dye 2) and the Tibetan plateau (Dasuopu, India). The combined data suggest that the sea surface, biomass burning, vegetation, atmospheric dust, and domestic animals are likely sources of the water-soluble organic N fraction measured in rain and atmospheric aerosols. In samples collected from atmospheric dust, background vegetation, and oceanic influenced areas, organic N represented ∼20% of total water-soluble N. In areas influenced by domestic animals and biomass burning, organic N represented ∼45% of the total water-soluble N. For all areas except the site in Australia, urea and dissolved free amino acids made up <20% of the total water-soluble organic N. In Australian rain, amino acids were found to contribute ∼50% of the total water-soluble organic N. The ice core from Greenland exhibited statistically significant increases for organic N during the time period analyzed (1750–1950), while concentrations in the Tibetan plateau ice core did not increase significantly. The combined findings from all data sites analyzed suggest an anthropogenic influence on organic N totals in the global atmosphere. This anthropogenic influence will likely increase in the coming decades. |
