A potential source of organic pollutants into the northeastern Atlantic: the outflow of the Mediterranean deep-lying waters through the Gibraltar Strait.
Small and large-size particles were collected in the water column (50-3000 m) of a Northeastern Atlantic area where deep Mediterranean waters, outflowing through the Strait of Gibraltar, are incorporated at mid-depth. Particles collected by water filtration (0.7 micron pore size) and by vertical hauls of a neuston net (50 microns mesh size) were analyzed for organic pollutants, namely aliphatic and aromatic hydrocarbons, and organochlorine compounds. Small-size particles represented the largest bulk of particulate organic carbon as well as of hydrophobic organic pollutants. Surface concentrations of n-alkanes [C14-C35), aromatic hydrocarbons (12 parent compounds), PCBs (7 congeners), and DDTs (DDT + DDE) were, respectively, in the range of 50-63 ng/L, 23-68 pg/L, 8-13 pg/L, and 0.05-1.7 pg/L. These concentrations showed a general decrease with depth, particularly significant in the upper 200 m, consistently with the POC contents. Compositional changes with depth were also evident in small-size particles and included the depletion of low molecular weight n-alkanes and low chlorinated PCB congeners as well as a decrease of the fossil to pyrolytic PAHs ratio. Unusual increases of concentrations were observed at mid-depths (900-1100 m), indicating additional particle inputs, either by in-situ formation or by advective transport from the Mediterranean. The latter was recognized because small-size particles within these water veins exhibited distribution patterns out of the vertical sequence and similar to those of deep Mediterranean waters. An input of 8 and 0.5 tons per year of the above PAH and PCB compounds, respectively, has tentatively been calculated as the contribution of these Mediterranean waters to the Northeastern Atlantic.
Martí
S
S
Department of Environmental Chemistry, CID-CSIC, Jordi Girona Salgado, 18-26, E-08034-Barcelona, Spain.
Bayona
J M
JM
Albaigés
J
J
D001267:Atlantic Ocean; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000032:analysis*; D008522:Mediterranean Sea; D009930:Organic Chemicals / Q000032:analysis; D010316:Particle Size; D011078:Polychlorinated Biphenyls / Q000032:analysis*; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
D004785:Environmental Pollutants; D009930:Organic Chemicals; D011084:Polycyclic Aromatic Hydrocarbons; D014874:Water Pollutants, Chemical; D011078:Polychlorinated Biphenyls