An Examination of Copper Speciation in Seawater

Abstract

The speciation of copper determines its chemical and biological interactions in the marine environment. Several methods have been employed in this work to examine the speciation of copper. The availability of total copper to measurement by anodic stripping voltammetry has been examined in coastal and open ocean waters in the Northwestern Atlantic Ocean. In deep waters approximately 75% of the total copper is detected by anodic stripping voltammetry. In near surface and coastal water greater than 90% of the total copper is bound in species that are not detected by ASV. The availability of copper in coastal waters for uptake on a chelating resin was also used to examine copper speciation. Between 20 and 50% of the dissolved copper in coastal water was not taken up by the chelating resin even after 100 hours of contact. It appears that a portion of the copper that is not available to the ASV measurement is available for uptake by the chelating resin. Stripping polarograms are plots of anodic stripping voltammetry peak heights against deposition potential. These plots can be used to examine trace metal speciation. Stripping polarograms for copper in seawater, or other chloride media, are complicated by the Cu(I) intermediate and do not give information about the complexation of Cu(II).