Trace metal processes and fluxes in the humber plume: A focus on Pb and Zn

Abstract

This paper presents a critical review of the current state of knowledge of trace metal processes in the Humber plume, as illustrated by the marine chemistry of Pb and Zn. The data sources were abstracted from the U.K. Natural Environment Research Council North Sea Project CD ROM. Particulate and dissolved Pb and Zn were monitored, spatially and seasonally, at strategic locations within the coastal zone and over tidal cycles at an estuarine anchor station. Sediment box coring was also carried out and the samples used to determine the diffusional and resuspension fluxes of Pb and Zn. The mass balances within the plume show that there was considerable internal cycling of Pb and Zn. Dissolved Pb is adsorbed from solution and particulate Pb was deposited within the plume. Particulate Zn underwent sediment resuspension and dissolved Zn was adsorbed from solution. The distribution of Pb was influenced by atmospheric and benthic inputs, whereas Zn uptake and release by phytoplankton could be significant. The fluxes of Pb and Zn from the eastern boundary of the Humber plume to the North Sea were relatively minor compared to atmospheric inputs to the southern Bight and fluxes into the North Sea from the English Channel. The processes identified in the study are relevant to the development of coupled hydrodynamic-geochemical models for the generalised prediction of trace metal transport in coastal plumes.