| Surveys of the Mersey estuary in north-west
England were undertaken near the mouth of the estuary in the region known as the
Mersey Narrows. Tidal fluxes of suspended and dissolved matter, particularly
heavy metals, through the Mersey Narrows were investigated. This paper gives
results of conducting four intensive cross-sectional surveys of the Narrows,
during which currents, salinities, turbidity and water samples were obtained
systematically at numerous positions, throughout selected tidal cycles. Over 300
water samples per survey were analysed to yield suspended and dissolved
concentrations of the elements As, Cd, Cr, Cu, Hg, Ni, Pb and Zn, at all states
of the tide. Suspended solids, concentrations and salinities were also measured.
Suspended particulates account for the majority of each element present, except
for cadmium, which was present in roughly equal dissolved and suspended
fractions. From the tidal current and water quality data, calculations were made
of hour-by-hour fluxes of each component, to show the detailed ebb and flow of
heavy metals and the net tidal transport of each component. Although some
differences between landward transport on the flood tide and seaward transport
on the ebb were not significant, the more definite results consistently showed a
seawards net transport. For spring tides of high tidal range, there was an
indication of an opposite tendency, reducing the seawards transport or even
reversing it, for certain suspended components.
Keywords: Mersey estuary, surveys, tidal flux, dissolved metals, particulate metals,
salinity, suspended particulate matter, suspended solids |