Sediment Mobility and its Contribution to Trace Metal Cycling and Retention in a Macrotidal Estuary

Abstract

Measurements of trace metals in the dissolved, suspended particulate and sediment phases of the Tamar Estuary have been combined with observations of sediment and suspended particle mobility in an interpretation of metal cycling and retention processes within the system. Dissolved metal distributions indicate pronounced estuarine metal reactivity involving net removal onto suspended particles in the low salinity, high turbidity zone and net input from the sediment in the middle estuary. These processes are not reflected in the metal contents of suspended particulate material and superficial sediment, although the dissolved metal variations are a product of particle-water exchanges. This apparent anomaly is attributed to the magnitude of internal resuspendable particle fluxes within the system. Consequently, temporal and spatial variabilities in the composition of suspended particulate material and superficial sediment are determined by physical rather than chemical processes.