Copper and nickel in settling particle collected with sediment trap in the western North Pacific

Abstract

Sequential methods to measure the concentrations of chemical elements in (1) acid soluble, (2) reducible, (3) oxidizable, (4) opal, and (5) refractory fractions of settling particles were developed. Concentrations of Cu and Ni of settling particles collected with HX-10 type sediment traps at 1.2 km and 4.8 km depths at 44°04′ N, 155°03′ E were measured by the methods. Copper was enriched in the reducible and oxidizable fractions, especially in the oxidizable fraction, both at 1.2 km and 4.8 km. The degree of vertical increase in Cu concentration of the oxide fraction is the largest among the five fractions. Nickel was most enriched in the oxide fraction with a concentration in the oxide fraction three times that of the oxidizable fraction. Nickel concentrations of the acid soluble and the reducible fractions decreased with depth. The results suggest that (1) Cu and Ni are incorporated in surface water into organic material and calcium carbonate particles, respectively, (2) organic material and calcium carbonate particles decompose in the water column, (3) Cu and Ni are regenerated from these particles, and (4) scavenging of Ni in intermediate and deep waters is not significant.