Abstract :
Distribution coefficients, KDs, are of fundamental significance to our understanding of geochemical and contaminant fluxes in estuaries and coastal waters. Based on a compilation of trace-metal data from laboratory partitioning experiments and field observations of KDs in estuaries, it is argued that the distributions of KDs in energetic, tidally influenced environments are controlled principally by variations in salinity and particle concentration. These effects are incorporated into a simple model driven by the partitioning in freshwater, the rate of change of KD with respect to salinity, the adsorbed concentrations of constituent on permanently suspended particles and a single resuspendable particle population, and the magnitude of resuspension. Using observed particle concentrations to define resuspension, and empirically calculating the remaining variables by non-linear regression analysis, the model was able to reproduce the distributions of KDs in several estuaries with reasonable success. The inability to reproduce distributions in other estuaries was attributed to subsidiary metal inputs, multiple resuspending populations of different chemical characteristics, and disequilibrium between sorbed and dissolved components.
