Chemical characterization of the inorganic fraction of aerosols and mechanisms of the neutralization of atmospheric acidity in Athens, Greece

E. T. Karageorgos (1) , S. Rapsomanikis (1) , P. Wåhlin (2)

1 Laboratory of Atmospheric Pollution and Pollution Control Engineering
2 ATMI - Department of Atmospheric Environment [Roskilde]

Mass concentration levels and the inorganic chemical composition of PM₁₀ (two fractions; PM_10?2.5 and PM_2.5) were determined during August 2003 and March 2004, in the centre of Athens, Greece. August 2003 monthly mean PM₁₀ mass concentration, at 5 m above ground, was 56 ?g/m³ and the EU imposed daily limit of 50 ?g/m³ was exceeded on 16 occasions. The corresponding monthly mean for March 2004 was 92 ?g/m³ and the aforementioned daily limit was exceeded on 23 occasions. The PM₁₀ (PM_10?2.5+PM_2.5) mass concentrations at 1.5 m above ground were found to be approximately 20% higher compared to the respective PM₁₀ measured at 5 m. Consequently, for a realistic estimation of the exposure of citizens to particulate matter, PM₁₀ sampling at a height of 1.5?3 m above ground, in the "breathing zone" is necessary. Such data are presented for the first time for the centre of Athens. In both campaigns, calcium was found to be the predominant component of the coarse fraction while crust-related aluminosilicates and iron were found to be the other major components of the same fraction. The above elements constitute the most important components of the fine fraction, together with the predominant sulphur. Toxic metals were found to be below the air quality limits and in lower concentrations compared to older studies, with the exception of Cu and V for which some increase was observed. Pb, in particular, appeared mostly in the fine fraction and in very low concentrations compared to studies dating more than a decade back. The major ions of the coarse fraction have been found to be Ca²⁺, NO₃^? and Cl^?, while SO₄^?2, Ca²⁺ and NH₄⁺ were the major ionic components of the fine fraction. The low molar ratio of NH₄⁺/SO₄^?2 indicated an ammonium-poor ambient air, where atmospheric ammonia is not sufficient to neutralize all acidity and the formation of NH₄NO₃ does not occur to a significant extend. Calcium predominated the coarse fraction and its good correlations with NO₃^? and SO₄^?2 indicated its role as an important neutralizing agent of atmospheric acidity in this particle size range. In the fine fraction, both Ca²⁺ and NH₄⁺ participate in the neutralizing processes with NH₄⁺ being the major neutralizing agent of SO₄^?2. Chloride depletion from NaCl or MgCl₂ was not found to occur to a significant extend. Total analyzed inorganic mass (elemental+ionic) was found to be ranging between approximately 25?33% of the total coarse particle mass and 35?42% of the total fine particle mass.

Domaines: Océan, Atmosphère

E. T. Karageorgos, S. Rapsomanikis, P. Wåhlin. Chemical characterization of the inorganic fraction of aerosols and mechanisms of the neutralization of atmospheric acidity in Athens, Greece. Atmospheric Chemistry and Physics Discussions, 2006, 6 (6), pp.12389-12431. ⟨hal-00302330⟩