Abstract:
Low concentrations of dissolved copper have been shown to adversely
affect the olfactory system of endangered salmonids, impairing their ability to avoid
predators and likely increasing predation. It is believed that only the free ionic
(Cu2+
free) and weakly complexed forms are bioavailable to organisms; these forms
typically account for a small fraction of the total dissolved copper. To determine the
threat of copper to salmonids, the speciation of copper in aqueous environments is
essential. Copper speciation has been examined in freshwater, seawater, estuaries, and
rainwater. However, no such studies have focused on stormwater, a major source of
dissolved copper in natural water bodies. To bridge this gap in knowledge,
competitive ligand exchange – adsorptive cathodic stripping voltammetry (CLEACSV)
techniques developed for seawater were adapted to stormwater. CLE-ACSV
is unique among speciation techniques in that it allows the characterization of the
ligands in the system as well as free copper concentrations. Major alterations of
seawater CLE-ACSV techniques include the shift to a lower pH (6.80) and the
addition of an electrolyte to increase solution ionic strength to 0.05M. The results of
this research show that free copper concentrations at the monitored sites ranges from
10−13.49 to 10−6.74 M. Additionally, free copper concentrations are best correlated with
dissolved copper and hardness levels. Ligand concentrations correlate with dissolved
organic carbon (DOC) measurements and (along with copper-ligand stability
constants) vary widely within and between sites. Finally, modeled Cu2+
free
concentrations overestimate analytically determined concentrations.
