Contrasting behaviour of trace metals in the Scheldt estuary in 1978 compared to recent years

摘要: Abstract Dissolved and particulate trace metals (Cu, Cd, Pb, Zn, Ni, Fe Mn) measured at six stations along the Scheldt estuary in October/November 1978 are compared with more recent data. Based on Ca content suspended matter, three distinct geochemical regions could be distinguished: upper (salinity 1–7) dominated by fluvial mud, mid-estuary 7–17) where composition of matter remained relatively constant, lower marine mud prevailed. Re-suspension sediments is major factor controlling particles upstream region. Anoxic conditions prevailed part extending to a salinity 15 1978, while present seaward boundary anoxic water body located less saline waters. Furthermore, present-day metal load much than 1978. As consequence changed situation, maxima dissolved concentrations redox-sensitive mid/lower have moved as well, which affects re-distribution pattern. In zone, exchange processes between fractions were strongly redox regulated, Mn excellent examples. Iron was removed from phase early stages mixing resulting an increase leachable `non-residual' fraction 2 3.5%. Due its slower kinetics, removal solution occurred oxygen increased. Cu, Cd Zn contrary mobilised during estuarine mixing. External inputs lesser extent resulted their concentrations. Calculated K d (distribution coefficient) values used assess redistribution investigated metals. existence estuary, importance determining demonstrated. The sequence (Fe, Pb > Cu significantly different that (Fe Cd). Thus, such dynamic single metal-specific cannot describe processes.