Persistent Organic Pollutants in Mediterranean Seawater and Processes Affecting Their Accumulation in Plankton
Résumé
The Mediterranean and Black Seas are unique
marine environments subject to important anthropogenic pressures
due to riverine and atmospheric inputs of organic pollutants.
Here, we report the results obtained during two
east-west sampling cruises in June 2006 and May 2007 from
Barcelona to Istanbul and Alexandria, respectively, where water
and plankton samples were collected simultaneously. Both
matrixes were analyzed for hexaclorochyclohexanes (HCHs),
hexachlorobenzene (HCB), and 41 polychlorinated biphenyl
(PCB) congeners. The comparison of the measured HCB and
HCHs concentrations with previously reported dissolved phase
concentrations suggests a temporal decline in their concentrations since the 1990s. On the contrary, PCB seawater concentrations
did not exhibit such a decline, but show a significant spatial variability in dissolved concentrations with lower levels in the open
Western and South Eastern Mediterranean, and higher concentrations in the Black, Marmara, and Aegean Seas and Sicilian Strait.
PCB and OCPs (organochlorine pesticides) concentrations in plankton were higher at lower plankton biomass, but the intensity of
this trend depended on the compound hydrophobicity (KOW). For the more persistent PCBs and HCB, the observed dependence of
POP concentrations in plankton versus biomass can be explained by interactions between air-water exchange, particle settling,
and/or bioaccumulation processes, whereas degradation processes occurring in the photic zone drive the trends shown by the more
labile HCHs. The results presented here provide clear evidence of the important physical and biogeochemical controls on POP
occurrence in the marine environment.