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

Abstract

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 (NO 3 − ), nitrite (NO 2 − ), ammonium (NH 4 + ), water‐soluble organic N, urea, and dissolved free amino acids. Other ions were also analyzed, including Ca 2+ , Mg 2+ , K + , Na + , Cl − , and SO 4 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 2+ ion (R sqr ∼ 0.75, P < 0.05), suggesting a relationship to calcite (CaCO 3 ) 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 2+ 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.