High As concentrations occur in certain United Kingdom estuaries as a result of mineralization and associated processes including mining and metal refining. Analyses of dissolved and particulate As, carried out in estuaries of differing contamination, indicate that As is readily precipitated with Fe during mixing at the freshwater–seawater interface. This gives rise to significant correlations between the two elements in suspended and bottom sediments. More than 80% of the As entering Restronguet Creek, the most contaminated of the estuaries studied, is retained by estuarine sediments, which consequently act as sinks for riverine inputs and limit transport of dissolved species to coastal waters. However, the behavior of As in different estuaries varies with the physicochemical conditions present and the nature of the source. Most significantly, remobilization of sediments is recognized as a feature affecting the cycling of As in the Tamar Estuary.
