WP16 Sediment Quality Assessment
Wednesday, 16 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(JON-1117-765882) Influence of contact duration on sediment-associated copper bioavailability.

Jones, R.¹, Hassan, S.², Rodgers, Jr., J.¹, ¹ Clemson University² University of Georgia

ABSTRACT- Sediment quality guidelines theoretically predict potential risks of sediment-associated contaminants based on laboratory observed correlations between contaminant concentrations and biotic responses. Inconsistencies in accuracy and precision of SQGs may be due in part to derivation of criteria using data in which recently-amended sediment was used, as opposed to sediment having sufficient contact time to achieve equilibrium. The objective of this study was to compare concentration-response relationships of Hyalella azteca (Saussure)over time in three copper-amended sediments with varying characteristics. Three nontoxic, field-collected sediments (identified as A, B, and C) were amended with copper sulfate to concentrations of 100, 1000, 1500, 1750, 2000, and 2250 mg Cu/kg (dry weight) above background. Responses of H. azteca were measured in 10-d static non-renewal toxicity experiments. Organisms were exposed to amended sediments at 48-h, 14-d, 28-d, 42-d, and 60-d intervals, following copper sulfate amendment. Inductively coupled plasma-mass spectrometry was used to measure sediment-copper concentrations. A decline in toxicity over time was observed for all sediments. Partial mortality was observed in the highest concentrations of each sediment after a 42-d interval. Sediment-A had a lower instantaneous binding capacity for copper and exhibited the largest change in potency, while sediment-B and sediment-C had higher initial binding capacities and toxicity decreased to a lesser extent. Growth of surviving amphipods was not significantly affected in any experiment. Organism survival was dependent on amended-copper concentrations, duration of contact between copper and sediment, and sediment characteristics. SQGs may inaccurately estimate the potential for toxicity from site to site over time, and to accurately assess the bioavailability of sediment-associated copper, toxicity testing should be conducted. Results provide insight into the role of sediments in altering the bioavailability of copper when applied in as a pulse exposure, such as the case in algaecide applications.

Key words: sediment, contact duration, toxicity, sediment quality guidelines