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Selenium is an anthropogenic contaminant of concern in estuaries on the NSW coast. Experiments have been performed to elucidate the processes controlling selenium remobilisation from contaminated sediments. Measurements of redox potential and pH were made in sediments taken from Lake Macquarie with different populations of infaunal organisms. Depending on the feeding mechanisms and mobility of the organisms, bioturbation causes a degree of deepening of the oxidised conditions in the sediment. Thermodynamic simulations of the solubility of selenium in estuarine porewaters predict a mobilisation of the contaminant under such conditions. Preliminary experiments involving exposure of contaminated reduced sediment to oxidising porewater resulted in the mobilisation of selenium species that were strongly bound to the sediment.