Influence of contact duration on sediment-associated copper fractionation and bioavailability

Frequent utilization of copper formulations as aquatic herbicides and algaecides can lead to potentially elevated sediment-copper concentrations. This research investigated relationships between copper fractionation (through sequential extractions) and bioavailability in three reservoir sediments over a 60 d contact duration. Copper was initially associated with exchangeable, carbonate, and oxidizable fractions for copper-amended sediments; and redistributed to the reducible and oxidizable fractions after 60 d. Hyalella azteca mortality declined over time for organisms exposed to copper-amended reservoir sediments, indicating concomitant declines in sediment copper bioavailability. Comparisons between sequential extractions and organism responses indicated that bioavailability was primarily associated with the exchangeable fraction. Results of this research indicated fractionation and bioavailability of amended copper in sediments were influenced by contact duration along with sediment and overlying water characteristics. The influence of contact duration on copper bioavailability in sediments is important for assessing potential risks incurred by repeated applications of copper-containing algaecides in reservoirs.