ZN AND CU REMOVAL KINETICS IN ESTUARINE WATERS

The time-dependent removal of dissolved Zn and Cu in the presence of suspended particles has been studied in the laboratory using conditions closely resembling the aquatic environment encountered in the Tamar Estuary. The metals were removed from both river water and low salinity waters and the uptake profiles were of an exponential form. The removal profiles were interpreted in terms of a reversible, heterogeneous, pseudo-first order reaction, for which the forward and reverse rate constants were evaluated. The forward rate constants for Zn were salinity dependent and varied between 0.08 h-1 and 0.61 h-1. In contrast, the rate constants for Cu ranged from 0.10 h-1 to 0.75 h-1 and in freshwater they were dependent on the suspended particle concentration. The reaction response times, τresp (defined as the time for the attainment of 63% of a new equilibrium), were 1 to 10 h for Zn and 1 to 8 h for Cu. These values were compared with calculated flushing times of the Tamar Estuary and a new interpretation of field observations of the non-conservative behaviour of dissolved Zn and Cu in the Tamar Estuary was evolved. © 1992 Academic Press Limited.