Nickel, cadmium, and copper in the northeast Pacific off the coast of Washington1,2

Abstract

The distributions of nickel, cadmium, and copper have been determined in northeast Pacific waters off the coast of Washington. Nickel concentrations average 5.5 nmol·kg‒1 at the surface and 10 nmol·kg‒1 in deep water. Although nickel shows a dual covariance with phosphate and dissolved silicon, a strong concentration gradient away from the coast cannot be explained by variations in the nutrient concentrations alone; an additional source in the sediments is suggested. The geochemistry of cadmium is controlled by the biological cycling of organic matter. Concentrations are depleted to levels of 0.1 nmol·kg‒1 at the surface but increase to a maximum of 1.27 nmol·kg‐1 at the depth of the phosphate and nitrate maxima. Cd‐phosphate and Cd‐nitrate correlations are significantly different in nearshore and offshore waters. Copper shows no correlation with the nutrients. An apparent surface maximum may result from the upwelling and offshore advection of Cu‐rich shelf water. Copper is rapidly stripped from subsurface waters but is then returned to bottom waters via a flux of dissolved copper from the sediments.