Trace metal enrichments in waters of the Gulf of Cadiz, Spain

Journal Article · Thu Aug 01 04:00:00 EDT 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90095-M· OSTI ID:6967717

Geen, A van; Boyle, E A ^[1]; Moore, W S ^[2]

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1. Massachusetts Institute of Technology, Cambridge (United States)
2. Univ. of South Carolina, Columbia (United States)

Dissolved Cu, Cd, and Zn concentrations in continental shelf waters of the Gulf of Cadiz are much higher than reported for other coastal areas. Direct observations of the metal enrichments in this region were made in March-April 1986 and October 1986; indirect observations (in the Alboran Sea) suggest similar enrichments occurred in June 1982 and September 1980, and it is probable that these enrichments are a persistent feature of the region. Zinc concentrations varied by more than two orders of magnitude between Atlantic water entering the Strait of Gibralter ([lt]1 nmol/kg) and Spanish shelf water (up to 160 nmol/kg). Copper and cadmium were also highly enriched in Spanish shelf water (up to 47 and 1.3 nmol/kg, respectively), and concentrations of these metals varied co-linearly with Zn. Metal:metal and metal:salinity relationships immediately west of the Strait of Gibraltar show that variations in the composition of surface water can be described by conservative mixing of three sources: (1) metal-depleted surface Atlantic water, (2) Spanish shelf water, highly enriched in Cu, Cd, and Zn, and (3) subsurface North Atlantic Central Water, enriched in Cd and slightly enriched in Ni. Although metal concentrations increase systematically with decreasing salinity over the Spanish shelf, Iberian rivers cannot account for the Cu, Cd, and Zn enrichments. One mechanism that may enhance metal fluxes from shelf sediments is a coastal 'metal trap' driven by an estuarine-type circulation pattern and biological production along the Iberian coast. This process is illustrated here by a simple box model; if this process occurs along the whole Iberian peninsula, Cd enrichments could be sustained against the considerable advective metal sink through the Strait of Gibraltar.

• OSTI ID: 6967717
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 55:8; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540310 -- Environment
Aquatic-- Basic Studies-- (1990-)
58 GEOSCIENCES
580000* -- Geosciences
ATLANTIC OCEAN
CADMIUM
CHEMICAL COMPOSITION
CHEMISTRY
COMPARATIVE EVALUATIONS
COPPER
DEVELOPING COUNTRIES
ECOLOGICAL CONCENTRATION
ELEMENTS
EUROPE
EVALUATION
HYDROGEN COMPOUNDS
METALS
OXYGEN COMPOUNDS
SALINITY
SEAS
SEAWATER
SPAIN
SURFACE WATERS
TRANSITION ELEMENTS
WATER
WATER CHEMISTRY
ZINC