Formulated sediment as a reference and dilution sediment in definitive toxicity tests

Abstract

To accurately determine the relative potency of contaminated sediments that exhibit toxicity in screening tests, definitive toxicity tests are conducted by diluting test sediment with a nontoxic reference sediment of similar characteristics. To demonstrate the usefulness of formulated sediment as a reference and dilution sediment, the relative potency of a copper-contaminated sediment was assessed by diluting with a formulated sediment. Toxicity of sediment-bound copper was assessed by monitoring the survival of Ceriodaphnia dubia Richard, Daphnia magna Straus, Hyalella azteca Saussure, Chironomus tentans Fabricius, and Pimephales promelas Rafinesque. Organisms were exposed in static systems for 10 d using test sediment dilutions that produced mortality in range-finding tests. Formulated sediment served as a suitable control sediment, with organism survival ranging from 85–100%. Formulated sediment was prepared and matched ten of eleven characteristics of the field-collected test sediment. When used to dilute the copper-contaminated sediment, formulated sediment resulted in decreased concentrations of copper in sediment, pore water, and overlying water with concomitant increases in test dilution. Thus, formulated sediment served as a suitable reference and dilution sediment in this study. Evidence indicates that formulated sediments could be used in this capacity when suitable natural reference sediments are otherwise unavailable.