Particulate metals in five major North Sea estuaries

Suspended sediment samples collected from the North Sea and during axial surveys of five major North Sea estuaries (Humber, Thames, Scheldt, Weser, Elbe) have been analysed in a consistent manner for leachable metals, specific surface area and carbon.
Particulate trace metal (Co, Cr, Cu, Ni, Pb and Zn) concentrations were similar in each estuary and estimates of fluxes to the North Sea based on an empirically derived prediction equation therefore reflected catchment size. Concentrations generally decreased seawards as a result of mixing of riverborne sediment of high metal concentration with material of marine origin of relatively low metal concentration, although in the Humber, substantial anthropogenic inputs at high salinities were responsible for more ambiguous distributions.
In contrast, profiles and concentrations of Fe and Mn, implicated as being important to particle surface and compositional properties, exhibited significant yet explicable inter-estuarine variability (e.g. Humber during winter: Fe = 12·0 mg g−1, Mn = 0·99 mg g−1; Elbe during summer: Fe = 6·6 mg g−1, Mn = 3·08 mg g−1).
Comparable data such as these serve as valuable baselines for any future international long-term water quality monitoring programme of European estuaries.