Trace Metal Sources for the Atlantic Inflow to the Mediterranean Sea.

摘要

Copper, Cadmium and Zinc, concentrations over a 40 km long portion of the Spanish continental shelf are an order of magnitude higher than enrichments generally found in coastal water. All samples were analyzed with a simple device which automates the pre-concentration of Cu, Nickel, Cd, Zn and from seawater and fresh water by bis (2-hydroxyethyl) - dithiocarbamate-metal complex retention on a hydrophobic column. Enrichments observed over the Spanish shelf are sufficient to influence the composition of the Mediterranean because Spanish coastal water is entrained in the inflow to the Alboran Sea. Trace metal and ancillary data for 172 samples from the Gulf of Cadiz collected in April and October '86 confirm that Spanish shelf water dominates Cu, Cd and Zn fluxes through the Strait of Gibraltar. A shelf 'metal-trap' mechanism is presented in order to reconcile the magnitude of observed metal enrichments with their geographical distribution and seasonal variability. A simple box model of the metal-trap indicates this mechanism must be operating over the whole length of the Iberian Atlantic coast (rather than the Gulf of Cadiz only) in order to support the important metal sink through the Strait of Gibraltar. The three water masses originating in the Atlantic and entering the Alboran Sea through the Strait of Gibraltar are (1) Atlantic surface water, (2) North Atlantic Central Water and (3) Spanish shelf water, based on salinity and Cu, Ni, Cd and Zn concentrations. Theses. (aw)