Aerosols and precipitations collected over Sardinia are mainly controlled by two end-members: Saharan and European. European background aerosols in Sardinia show a 3 to 25-fold decrease in EFcrust values for Cd, Zn, Pb, and Cr compared with coastal stations in the Western Mediterranean. Partitioning of total atmospheric deposition between the soluble and the insoluble phases shows that Al, Si, Fe and Pb originating from the atmosphere are mostly in the insoluble form. For Ca, Cd, Cr metals the dissolved fraction represents 50-90 % of the total input. Aerosol dissolution experiments performed at particle concentrations ranging from 3 to 300 mg l-1 show Cd and Pb exhibiting low solubility at the high mass particle concentration. Solubility of Pb increases with the EFcrust values and the finest grain-size of the aerosols (<1µm), and is less affected by pH. Al and Fe solubilities appear to be mainly controlled by the particulate load. Dissolution of both metals decreases significantly from 30% (13 % for Fe) at aerosol loads lower than 5 mg l-1, to less than 1% for both metals, at total aerosol concentrations greater than 50 mg l-1, which are encountered during Saharan transport. Fluxes (dry +wet) of metals at Sardinia show that ~ 30% for Cd and Pb, to more than 80 % for Fe and Al are due to Saharan contribution.
|Titolo:||Role of desert aerosol in metal fluxes in the Mediterranean area.|
|Data di pubblicazione:||1999|
|Appare nelle tipologie:||2.1 Articolo su rivista |