Comparison of the partitioning of trace metals in the Humber and Mersey estuaries

Studies into the partitioning of trace metals between the dissolved phase and suspended solids have been performed on two major UK estuaries, the Mersey and the Humber. Aqueous phase trace metal concentrations were determined, along with partitioning data (Kp) determined from both laboratory equilibration experiments and by chemical leaching techniques. Dissolved trace metals in the Humber essentially exhibited conservative behaviour (or a slight positive deviation). In the Mersey, however, removal of zinc, chromium, and, in particular, copper and cadmium occurred in the low salinity region. Sequential extraction data gave an indication of the nature of trace metal bindings to suspended sediment, and revealed total extractable trace metals on the Mersey suspended sediment to be a factor of two greater than that found in the Humber. Similarly, partition coefficients in the Mersey were approximately an order of magnitude greater than in the Humber. Chloro-complexation was shown to control the partitioning of cadmium within estuaries. Copper, however, exhibited a distinct trend of increasing Kp with increasing salinity.