Organic nitrogen in rain and aerosol in the eastern Mediterranean atmosphere: An association with atmospheric dust

[1] From March through early May of 2000, rain and bulk aerosol samples were collected at a coastal site on the eastern Mediterranean Sea at Erdemli, Turkey, and analyzed for nitrogen (N) species, including nitrate (NO3 ), nitrite (NO2 ), ammonium (NH4 ), watersoluble organic N, urea, and dissolved free amino acids. Other ions were also analyzed, including Ca, Mg, K, Na, Cl , and SO4 2 . Water-soluble organic N was found to contribute 17% and 26% of the total water-soluble N in rain and aerosols, respectively. Organic N concentrations within rain and aerosols exhibited statistically significant linear relationships to Ca ion (Rsqr 0.75, P < 0.05), suggesting a relationship to calcite (CaCO3) in atmospheric dust. Kinematic trajectory analyses indicated the origin of winds from arid regions, mainly in northern Africa, in 70% of the aerosols sampled. Earth Probe/ Total Ozone Mapping Spectrometer aerosol index data also confirmed the influence of atmospheric dust in the region on days when Ca concentrations were elevated, and trajectory analyses suggested northern Africa as a source region. The combined ion, trajectory, and aerosol index data suggest that organic N is associated with atmospheric dust in this region. Urea N and amino N represented a small percentage of the organic N fraction. In rain and aerosols, urea represented 11% and <1%, respectively, of the total organic N. While amino N contributed minimally to organic N totals ( 1% of total organic N in aerosols), the individual amino acids contributing 75% of amino N were indicative of biological organisms. Further research is needed to decipher the influence from biology and gas phase adsorption of anthropogenically derived water-soluble organics on organic N totals.