Sediment-borne contaminants in rivers discharging into the Humber estuary,UK

As part of a project to characterise and quantify the volume of sediments w hich comprise the Holocene (10,000 years to present) fill of the Humber Est uary, a study was undertaken to determine the geochemistry and heavy minera logy of bed sediments in the river systems that discharge into the estuary. A total of 19 sediment samples in the Trent and Ouse river systems were ta ken for analysis, Contamination was evaluated by comparison of the sample g eochemistry with that of the appropriate catchment (using existing data), a nd by evaluation of the proportion of anthropogenic heavy minerals (includi ng natural minerals which have been mobilised by mining) in the sediment sa mple. Heavy metals fall into two groups with different patterns of distribu tion. Pb-Zn concentrations are greatest in catchments and rivers draining t he Pennine orefields. Levels of these metals remain high between source are as and the Humber Estuary suggesting that large quantities are trapped in s ediments stored within the fluvial systems. By way of contrast other heavy metals, associated with manufacturing industry, such as Cu and Co, have hig h concentrations near source cities, but decrease rapidly in amount down th e river systems because of dilution by other sediments. The differing behav iour of mining and industrial related contaminants is generally reflected b y the heavy minerals. Concentrations of gangue minerals, such as barytes an d fluorite, are generally highest in rivers draining mining areas;'furnace' materials, such as slags are highest in industrialised rivers such as the Aire and the Don, The anthropogenic origin of all the contaminants is illus trated by comparison of the catchment and river sediment geochemistry and h eavy mineralogy with that of early Holocene fluvially-derived sediments cor ed in boreholes drilled in the present Humber Estuary. The findings of the study corroborate those of others focused on water chemistry and floodplain sediments (Neal et al,, 1996, 1997; Macklin ef nl,, 1997). However, the co mparison of pre-existing data on catchment geochemistry with a limited numb er of river samples, as demonstrated here, provides a fast and cost effecti ve tool for the determination of contamination characteristics in ri,er sys tems. (C) 1999 NERC. Published by Elsevier Science Ltd. All rights reserved .