Bioavailability and Analytical Measurement of Copper Residuals in Sediments

Analytical measurements are commonly used to screen for toxicity or lack of toxicity from sediment-associated copper. Comparisons of analytical measurements with toxicological responses can be useful for determining the practicality of analytical measurements for assessing the toxicity of copper in sediments. The purpose of this research was to determine the utility of method detection limits (MDLs; i.e., minimum concentration of an analyte such as copper that can be measured with 99 % confidence with a specific analytical method and matrix) to predict the bioavailability of copper in five different sediments. The specific objectives of this research were to (1) select and characterize five sediments with different characteristics, (2) amend and measure a range of copper concentrations in the five sediments to determine MDLs and bioavailability of copper amendments in those sediments, (3) discern relationships with sediment characteristics to MDLs and bioavailability of copper in the five sediments, and (4) compare MDLs and observed toxicity to Hyalella azteca Saussure as an indicator of copper bioavailability in the five sediments. The lowest copper concentrations that elicited an observable adverse effect ranged from 15 to 550 mg Cu/kg, and the MDLs ranged from 1.5 to 6 mg Cu/kg. The MDLs and measured copper concentrations were not adequately predictive of the bioavailability and toxicity of copper in the five sediments. No adverse effects were observed for H. azteca exposed for 10 days to the sediment from California with simultaneously extractable metals > acid-volatile sulfides. Since the lowest observed effects concentrations of copper in the five sediments ranged two orders of magnitude, the National Oceanic and Atmospheric Administration screening values (threshold and probable effect levels) were not predictive of H. azteca responses to the copper-amended sediments.