Chapter 10 - Zinc in the Ocean

Abstract

Reported concentrations of zinc in seawater vary widely, probably due both to variability in concentrations actually present and to sample contamination. Zinc and iron often seem to co-occur in seawater samples. The concentrations of zinc in seawater are anomalously high. A large fraction of the zinc entering the oceans of the world is derived from aerial deposition. Between 11,000 and 60,000 metric tons of dissolved and particulate zinc is deposited from the air into the ocean each year. An additional 6,000 tons of dissolved zinc enters the oceans each year in river flows. Flux rates of zinc from the atmosphere vary widely in different geographic regions. Zinc concentrations in estuaries and coastal waters frequently are much higher than those in the ocean, with concentrations often as high as 4 μg/L and occasionally as high as 25 μg/L. A large fraction of the zinc in contaminated and uncontaminated sediments is residual, rendering it non-bioavailable. The residual zinc may be associated with the mineral lattice of clays or with a variety of heavy minerals.