CHEMICAL PARTITIONING AND BIOAVAILABILITY OF LEAD AND NICKEL IN AN ESTUARINE SYSTEM

Sediments, water, and biota of an estuarine system were analyzed for c oncentrations of lead and nickel. Sediments were sequentially extracte d to obtain the different chemically extractable fractions (exchangeab le, carbonate bound, Fe/Mn-oxide bound, organically bound, and residua l fractions) of these metals. Concentrations of these metals in the so ft tissue of an estuarine bivalve Villorita cyprinoides var. cochinens is were correlated with the concentrations of these metals present in the various sediment fractions, dissolved, and particulate phases in w ater. The degree of correlation between these various environmental va riables and biological factors was considered as the index of bioavail ability. Metal concentrations in the soft tissue and particulate phase of water were divided by the corresponding concentrations in the diss olved phase in water to obtain the bioconcentration ratio (BCR) and me tal partitioning ratio (MPR), respectively. These ratios were found to be useful in quantifying the metal bioavailability. The relationship between other biological factors and environmental variables is also p resented and discussed.