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Identifier

000350387

Title

Οργανικό άζωτο στη ατμόσφαιρα : ειδοχαρακτηρισμός, πηγές και ρόλος στον βιογεωχημικό κύκλο του αζώτου

Alternative Title

Organic nitrogen in atmosphere : chemical characterization, sources and the role in the biochemical cycle of nitrogen

Author

Βιολάκη, Καλλιόπη

Thesis advisor

Μιχαλόπουλος, Νικόλαος

Abstract

The chemistry and the sources of water-soluble organic nitrogenous compounds have been poorly studied, although are considered as an important piece of biogeochemical cycle of nitrogen. Many organic nitrogenous compounds play an important role to the oxidation capacity of the atmosphere such as peroxyacetyl nitrate (PAN) and related alkyl nitrates (RONO2). Nitro-PAH is subject to research attention because of their toxicity while alkyl amines are precursor for SOA formation. Additionally urea and amino acids are considered particularly bioavailable to aquatic ecosystems, enhancing the importance of atmospheric deposition of WSON to marine ecosystem. Goal of this study is to understand the role of WSON in the atmospheric nitrogen cycle, including the sources and the chemical composition of WSON fraction. During this study, size segregated atmospheric particles have been collected from North and South Hemisphere. Comparing the concentration levels of atmospheric WSON in fine mode in both Hemispheres, concluded that ten-fold higher was the estimated concentration in N. Hemisphere enhanced the important role of anthropogenic origin of organic nitrogenous compounds. On the other hand in remote marine areas in S. Hemisphere much substantial was the role of atmospheric WSON because the absence of Inorganic Nitrogen increases the contribution of WSON to TDN. Additionally, important role to the atmospheric concentration levels of WSON play the marine bloom areas since the intense biological activity produce organic nitrogenous compounds. This natural source of WSON seems to be the same order with anthropogenic activities in fine particles. Another important source of WSON particularly in coarse atmospheric particles is the dust. It was estimated that approximately 2.9±1.0 Tg Ν yr^-1 of organic nitrogenous compounds were transferred from the Sahara desert. This quantity is comparable with the Inorganic nitrogen that produced naturally by lightning. Atmospheric deposition of water-soluble N-containing organic compounds has been measured in the Eastern Mediterranean during a four years period. Almost 23% and 38.6% of TDN deposition flux in the area attributed to WSON for wet and dry deposition respectively. The concentrations of WSON are associated strongly with the meteorological patterns encountered in the area. Furthermore, the estimated fluxes of WSON depend not only on the amount of rain but also on the air mass origin since the influence of anthropogenic emissions on WSON levels (E/NE winds) could be of comparable importance with the natural sources i.e dust (SW/S winds). Additionally, the fraction of WSON can also participate in the neutralisation of the atmospheric acidity. Atmospheric deposition of WSON was mainly governed by dry deposition as 78% of total WSON is deposited through this pathway. Thus during summer when the water column stratification prevails, the impact of atmospheric deposition to the marine environment is maximized. Finally, 20-30% of the new production due to atmospheric nitrogen deposition can be attributed to water-soluble organic N-containing compounds in E. Mediterranean basin. Krom et al. (2004) estimated that 70% of the nitrogen budget in the Eastern Mediterranean is due to atmospheric deposition of DIN. As WSON can provide nitrogen in bioavailable form, atmospheric deposition of both DIN and WSON can account for up to 90% of the nitrogen budget in areas far form the continental slope highlighting the important role of atmospheric deposition in the biogeochemical nitrogen cycle in the Eastern Mediterranean. Among organic nitrogenous compounds analyzed in the E. Mediterranean were urea, amines (dimethylamine & trimethylamine) and free amino acids. Furthermore, the presence of urea in coarse mode attributed to dust and the average concentration was estimated 1.0±2.0 nmol N m-3. The average concentration of urea in fine mode was estimated 2.2±3.0 nmol N m^-3, while it was found statistical significant correlation with ammonium ions, indicating same sources as both are end products of mammals metabolism. The average concentration of free amino acids in fine atmospheric particles in E. Mediterranean was estimated 0.8±1.3 nmol N m^-3 and the average percentage contribution to WSON was 3.8%, while the most abundant free amino acid was glycine with 66% percentage contribution to total free amino nitrogen. Only dimethylamine was detected with average concentration in fine mode 0.20±0.81 nmol N m^-3 and average percentage contribution to WSON 0.91%.

Language

Greek

Subject

WSON

Ανατολική Μεσόγειος

Λεπτά και Αδρά Σωματίδια

Χημική Ταυτοποίηση WSON

Issue date

2009-05-21

Collection

School/Department--School of Sciences and Engineering--Department of Chemistry--Doctoral theses

Type of Work--Doctoral theses