Nutrient and metal content of water, sediment and soils amended with bauxite residue in the catchment of the Peel Inlet and Harvey Estuary, Western Australia

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Agriculture Ecosystems and Environment


phosphorus, leachates, Peel-Harvey, eutrophication, bauxite residue, soil amendment


The Peel Inlet and Harvey Estuary in Western Australia are susceptible to algal blooms fed by phosphorus in run-off. The surrounding catchment is dominated by sandy soils which do not retain phosphorus. Bauxite residue, the alkaline by-product from the extraction of alumina from bauxite with caustic soda, has been applied to the soil to increase the phosphorus retention and improve the soil. This study examines the effectiveness of bauxite residue in retaining phosphorus and also the impact of bauxite residue on other water quality parameters. Water, sediment and soils from sites amended or not amended with bauxite residue were analysed to establish the effect of bauxite residue and the background levels of heavy metals. Bauxite residue was applied at 20tha(-1) to 1600ha of a 4300ha catchment and the phosphorus concentration in drainage water dropped by more than 30% in the first year. A 32ha sandy catchment was treated with 80th(-1) of bauxite residue and it maintained a 75% lower phosphorus concentration of phosphorus than an adjacent untreated catchment over a period of four years. The phosphorus concentration in the effluent from a domestic sewage treatment plant was reduced by an average of 88% over two years after infiltration through a sand bed amended with bauxite residue, No difference was detected between the water quality of catchments amended with bauxite residue and comparable catchments, based on concentrations of a number of heavy metals. High levels of heavy metals were found in some areas unrelated to bauxite residue, mainly in the downstream receiving waters of the catchment. This was probably related to by-products of combustion and motor vehicle emissions. (C) 1997 Elsevier Science B.V.