Distributions and fluxes of non-detrital particulate Fe, Mn, Cu, Zn in the Humber coastal zone, U.K.

Samples of suspended particulate matter (SPM) were collected at an anchor station at the mouth of the Humber Estuary and in the Humber-Wash coastal zone (U.K.) during the winter (1988), spring (1990) and summer (1990). Non-detrital particulate trace metals (Fe, Mn, Cu and Zn) were determined in the SPM following digestion with 1M HCl. Concentrations of non-detrital particulate trace metals were higher at the anchor station than in the coastal waters, suggesting dilution of metal-polluted estuarine SPM with natural SPM originating from erosion of the adjacent coastline. The distribution of non-detrital Fe and Zn in the coastal waters could be explained in terms of the Humber Estuary being a primary source, whereas for non-detrital Mn and Cu, the estuarine source was less significant because of their participation in biogeochemical processes. A hydrodynamic model of the Humber-Wash region was used to quantify the fluxes of dissolved and non-detrital trace metals into and out of the Humber Plume. The calculations showed that 0–10% of Fe, 5–70% of Mn, 40–100% of Cu and 30–100% of Zn were transported in the dissolved phase. Interpretation of the mass balances showed that the additional source of non-detrital particulate trace metals was sediment resuspension, whereas important sources of dissolved trace metals were porewater infusions and, for Mn, photochemically induced dissolution of particulate Mn. The trace metal sinks were the sedimentation of particulate matter and adsorption from solution. The flux estimates were used to evaluate the likely impact of dissolved and non-detrital trace metals on the wider North Sea.