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


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Mace K., Kubilay N., Duce R.

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, vol.108, 2003 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 108
  • Publication Date: 2003
  • Doi Number: 10.1029/2002jd002997
  • Title of Journal : JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
  • Keywords: atmospheric dust, organic nitrogen, nitrogen cycling, Mediterranean Sea, Sahara, SAHARAN DUST, DEPOSITION, PHYTOPLANKTON, BACTERIA, INPUTS, UREA, SEA

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 (NO3-), nitrite (NO2-), ammonium (NH4+), water-soluble organic N, urea, and dissolved free amino acids. Other ions were also analyzed, including Ca2+, Mg2+, K+, Na+, Cl-, and SO42-. Water-soluble organic N was found to contribute similar to17% and similar to26% of the total water-soluble N in rain and aerosols, respectively. Organic N concentrations within rain and aerosols exhibited statistically significant linear relationships to Ca2+ ion (R(sqr)similar to0.75, 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 Ca2+ 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 similar to 11% and <1%, respectively, of the total organic N. While amino N contributed minimally to organic N totals (similar to1% of total organic N in aerosols), the individual amino acids contributing similar to75% 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.