Marine scavenging: Trace metal adsorption by interfacial sediment from MANOP Site H

Abstract

The adsorption of thirteen trace metals from seawater was studied on interfacial sediment from MANOP site H. The adsorption data indicate a long (~20 day) equilibration time for most metals, an increase in adsorption with an increase in pH and particle concentration, a dependence of adsorption on total metal concentration at high adsorption densities, and a lack of correlation between metal binding ability and metal hydrolysis in solution.

Apparent equilibrium binding constants normalized to the total number of available sites on the solid were determined for metal binding with the interfacial sediment. The binding constants indicate that the affinity sequence for metal interactions with the interfacial sediment is: Pb > Fe > Sn ≳ Co≈ Mn > Cu > Be > Sc ≳ Zn > Ni > Cd ≳ Ba > Cs at pH 7.82 in seawater.

A comparison of the binding constants for suspended particles, interfacial sediment, and surface sediment indicate that the composition of particles influences the binding ability of the particles. Biogenic particles tend to bind most metals more strongly than lithogenic or authigenic particles.

Based on limited data, there is a strong positive correlation between the measured binding constants and the observed partitioning of metals between sediment and seawater.