Cadmium in northeast Pacific waters 1

Northeast Pacific water was collected by five different methods and the Cd in it was preconcentrated by both chelex‐ion exchange and chelation‐organic extraction techniques. All sampling and preconcentration methods yielded essentially the same data. Cadmium was very significantly correlated with phosphate and nitrate at all depths and it appears that the resulting equations, ng Cd · liter −1 = −3.6 + 34.9 ( µ mol PO 4 · liter −1 ) and ng Cd · liter −1 = 5.1 + 2.45 ( µ mol NO 3 · liter −1 ), can be used to predict oceanic Cd values. Cadmium concentrations are lowest in nutrient‐depleted surface waters (4.5 ± 0.4 ng · liter −1 ) and greatest (125 ng Cd · liter −1 ) at the depths of the PO 4 and NO 3 maxima. Hence, Cd has one of the highest deep enrichment:surface depletion ratios (≃30) yet observed. Cadmium and phosphorus are also correlated in microplankton, and it is apparent that these organisms and their organic remains are a dominant factor in the biogeochemical cycling of this element.