Atmospheric Occurrence and Deposition of Polychlorinated Dibenzo- p -Dioxins and Dibenzofurans (PCDD/Fs) in the Open Mediterranean Sea
Résumé
The overall objective of this work is to provide the first
evaluation of polychlorinated dibenzo-p-dioxins and dibenzofurans
(PCDD/Fs) occurrence and deposition to Mediterranean
open seawater. Σ2,3,7,8-PCDD/F air (gas+aerosol) concentrations
over the Mediterranean Sea ranged from 60 to1040
fg m-3. The highest value (1555 fg m-3) was measured in a
reference sample taken in the SW Black Sea. No consistent
trend regarding the diel cycle of PCDD/Fswasobserved.PCDD/
Fs transported to the open sea waters from continental areas
and across the Atlantic as well as ship emissions may be
significant sources to the open Mediterranean. Seawater
concentrations in the Mediterranean ranged from 42 to 64 fg
L-1. The Σ2,3,7,8-PCDD/F dry deposition fluxes in the
Marmara and Black Seas (210 kg year-1) are from 2 to 55
times higher than dry fluxes in the Mediterranean Sea (4-156
kg year-1). Analysis of estimated diffusive air-water fluxes
and air/water fugacity ratios show that a net volatilization of
some PCDD congeners is feasible. However, evidence of a
net absorption flux for the rest of PCDD/F is found. When both
atmospheric deposition processes are considered together
the open Mediterranean Sea is a net sink of PCDD/F, due to
the importance of dry deposition fluxes of aerosol-bound
PCDDFs.