Geochemistry and related studies of Clyde Estuary sediments

Geochemical and related studies have been made of near-surface sediments from
the River Clyde estuary and adjoining areas, extending from Glasgow to the N, and W as far as
the Holy Loch on the W coast of Scotland, UK. Multibeam echosounder, sidescan sonar and shallow
seismic data, taken with core information, indicate that a shallow layer of modern sediment, often
less than a metre thick, rests on earlier glacial and post-glacial sediments. The offshore Quaternary
history can be aligned with onshore sequences, with the recognition of buried drumlins, settlement of
muds from quieter water, probably behind an ice dam, and later tidal delta deposits. The geochemistry
of contaminants within the cores also indicates shallow contaminated sediments, often resting on
pristine pre-industrial deposits at depths less than 1 m. The distribution of different contaminants with
depth in the sediment, such as Pb (and Pb isotopes), organics and radionuclides, allow chronologies
of contamination from different sources to be suggested. Dating was also attempted using microfossils,
radiocarbon and 210Pb, but with limited success. Some of the spatial distribution of contaminants
in the surface sediments can be related to grain-size variations. Contaminants are highest,
both in absolute terms and in enrichment relative to the natural background, in the urban and inner
estuary and in the Holy Loch, reflecting the concentration of industrial activity.