Dynamics of particulate trace metals in the tidal reaches of the Ouse and Trent, UK

Samples of suspended particulate matter (SPM) have been collected in the ti dal reaches of the Ouse and Trent over seven surveys covering the annual cy cle of riverine conditions. Settling experiments were carried out on water samples to differentiate permanently suspended particulate material (PSPM) from temporarily suspended particulate material (TSPM), The results indicat ed that PSPM, additional to the riverine component, was created within the turbidity maximum zone (TMZ) during tidal resuspension. The PSPM varied bet ween 10% and 50% of the total SPM and could be transported quasi-conservati vely down-estuary, The concentrations of particulate Cd, Fe, and Zn (availa ble to 1M HCl) mere determined in PSPM and TSPM, as well as samples of the bulk SPM. The trace metal concentrations in PSPM were seasonally variable a nd generally higher than in TSPM, which had relatively constant concentrati ons. The trace metal concentrations in PSPM and TSPM were used to develop a two-component, particle mixing model, which was applied to the interpretat ion of the bulk SPM concentrations of Cd and Zn. It is postulated that as t he PSPM encounters the salinity gradient labile Cd and Zn desorb from the p articles. On the basis of these results an additional mechanism for generat ing estuarine maxima in dissolved trace metals has been proposed. (C) 1999 Elsevier Science Ltd. All rights reserved.