A study of metal contaminant availability in sediments

Of the many different chemical extraction or digestion procedures that have been proposed to quantify metal contamination, partial acid extractions are probably the best overall compromise between selectivity, sensitivity, precision and cost. The extent to which measured metal concentrations relate to the anthropogenic fraction that is bioavailable is controversial, but is one of the desired outcomes of an assessment or prediction of biological impact. As part of a survey on metal contamination in a coastal lagoon, we wanted to identify an extraction protocol that would allow a reasonable definition of the anthropogenic bioavailable fraction in sediment samples. From a kinetic study of the 1M HCl- extraction of two test sediments, we concluded that a 24 h extraction time allows the equilibrium dissolution of relatively labile metal contaminants.