CHEMICAL AND PHYSICAL PROCESSES CONTROLLING THE CHEMICAL COMPOSITION OF SUSPENDED MATERIAL IN THE RIVER TAY ESTUARY

The chemical composition (Al, Si, Ti, K, Ca, Mg, P, Org. C, Fe and Mn) of suspended material in the Tay Estuary and River Tay have been measured to determine the relation between river and estuary material and chemical reactions which may be occurring during estuarine mixing. Variations in the ratios of Fe Al, Mn Al, Ti >Al, etc., with salinity and suspended load during a tidal station suggest that sedimentological and hydrological processes, rather than chemical ones, are responsible for the observed compositional changes. This interpretation is confirmed by laboratory mixing experiments which also contradict published reports of Fe and Mn desorption in estuaries. Measurements of suspended matter composition will not easily determine whether desorption or adsorption of element occurs when river-borne suspended material enters the saline environment. A tentative conclusion on the River Tay study is that the suspended matter in the Tay Estuary results from the input of material at times of high suspended loads and of high river water discharge. © 1979.