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Article Dans Une Revue Journal of Geophysical Research: Atmospheres Année : 1999

Trend in total atmospheric deposition fluxes of Aluminium, iron and trace metals in the North western Mediterranean, over the past decade (1985-1997)

Céline Ridame
Cécile Guieu
Marie-Dominique Loÿe-Pilot
  • Fonction : Auteur

Résumé

The total atmospheric deposition on the north-western coast of Corsica (Pirio) was sampled for 2 years and concentration of Al, Cd, Cu, Fe, Mn, Ni, Pb and Zn were measured during that time period. The sampling station was chosen for its isolation from any local and regional contamination sources. The year-to-year variability of the total atmospheric deposition was found to be high (up to a factor of 2). Using Al as the crustal reference indicates that Pb, Cd and Zn are mainly associated with anthropogenic aerosols (> 85%) and Fe with crustal aerosols (> 70 %). However, our results indicate that the Saharan dust is a potential source of «natural» lead especially in the case of a major input of dust to the north-western Mediterranean. In order to determine the spatio-temporal variability of the trace metals over the north-western Mediterranean Sea, the observed fluxes are compared to those previously found in the past decade using the same methodology. The comparison indicates a relative homogeneity of Cu and Ni fluxes over the north-western Mediterranean and over the past decade. The decrease found in Al and Fe since 1985 (by a factor of 4 to 6) can be related to the decrease of the Saharan dust fallout. The limitation in the use of lead additives in gasoline could result in a decrease of the European atmospheric lead emissions of about a factor of 6 since 1985 and in a maximum decrease of the total atmospheric flux of 12 when taking into account the natural interannual variability of atmospheric deposition in this region. So the recorded decrease in the lead atmospheric flux since 1985 (~a factor of 30) reveals a slight local contamination at the previous Corsican station. In the case of Cd and Zn, there is a decrease by a factor of 30 and 23 respectively between the data obtained at La Tour du Valat (7/88-6/89) and those at Pirio (3/96-3/97); such a decrease cannot be the consequence of neither a reduction of emissions at the European scale (the factor being at most 4), nor the distance to the emissions sources. Hence, we confirm that Zn and Cd fluxes at la Tour du Valat and Zn fluxes at Cap Ferrat were not representative of a long-range transport to the Mediterranean but the result of a local/regional contamination. The large decrease observed for anthropogenic metals (Cd, Zn and Pb) results from a combination of the actual diminution of the concentrations due to the reduction of the emissions and the occurrence of local/regional contamination for some elements at some sampling sites.
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Dates et versions

hal-00166816 , version 1 (12-11-2020)

Identifiants

Citer

Céline Ridame, Cécile Guieu, Marie-Dominique Loÿe-Pilot. Trend in total atmospheric deposition fluxes of Aluminium, iron and trace metals in the North western Mediterranean, over the past decade (1985-1997). Journal of Geophysical Research: Atmospheres, 1999, 104 (23), pp.30127-30138. ⟨10.1029/1999JD900747⟩. ⟨hal-00166816⟩
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