Dry atmospheric fluxes of trace metals (Al, Fe, Mn, Pb, Cd, Zn, Cu) over the Levantine Basin: A refined assessment

The current work presents dry deposition fluxes of trace metals to the Southern and Northern Levantine Basin of the Eastern Mediterranean Sea. The dry depositional inputs were calculated taking into account (i) the spatial gradients in metal aerosol concentrations across the Levantine Basin (using concentrations from two location, Erdemli, Turkey and Tel Shikmona, Israel over a 3 year sampling period), (ii) the air mass origins, (iii) air mass temporal influence across the north and south Levantine basins and (iv) fine/coarse elemental aerosol size mass distributions allowing the use of new elemental settling velocities. Two distinct airflow sectors were defined at each site; North (N) and southwest (SW), having different temporal influences at each site (the temporal ratio of SW:N was 1.85 and 0.43 at Tel Shikmona and Erdemli, respectively). Temporal airflow weighted aerosol concentrations were then calculated for each site. The applied settling velocities calculated using size fractioned aerosol samples (n=227) collected from Erdemli and from the literature, yielded higher (compared to previous work) settling velocities for Cu, Pb, and Zn being 1.1, 0.8 and 0.9 cm s^-1, respectively. Total dry deposition fluxes for the crustal elements (Al, Fe and Mn) were consistent with previous studies for the region; however, Cu, Pb, and Zn were much higher, in part, due to the larger adopted settling velocities. Using sequential leach data, the "exchangeable" as well as total elemental dry inputs were presented for both the north and south Levantine basins. Comparison with limited literature wet deposition would suggest that the dry deposition pathway is a more significant input for Cu, Pb, and possibly Al and Fe. The "exchangeable" dry atmospheric inputs of Pb, Cu and Cd to the southern basin were orders of magnitude greater than dissolved riverine inputs. A similar comparison could not be made for the northern basin owing to absence of riverine input data.