Trace metal distribution in Baltic Sea ferromanganese concretions: inferences on accretion rates

The usually high concentrations of Zn, Pb, Cd, and Cu in the most recently accreted portions of ferromanganese nodules from the western Baltic Sea are thought to reflect increased metal input due to anthropogenic mobilization. If so, the point of increase represents a time horizon within the structure of the nodule. Similar trace metal distributions of radiometrically dated sediments from the same area suggest that the ferromanganese nodules have grown in thickness between 0.02 and 0.16 mm yr^?1. From this growth rate anthropogenic Zn flux to the nodule surface was calculated to be 80 mg m^?2 yr^?1.