Science, Technology and Engineering

Environmental Geoscience

Honours Projects

Determination of Cadmium in North-Central Victorian Rivers by Potentiometric Stripping Analysis

Steven McGrath

The technique of Potentiometric Stripping Analysis (PSA) has been shown to be both accurate and reproducible in determining the concentration of trace levels of cadmium in environmental media (ie. River water and the mineral acid digests of sediments). Optimisation of the PSA instrumentation achieved a detection limit for Cd (0.3 mg/L) superior to that reported for the other analytical instruments encountered in this study - ICP-MS (0.2 mg/L) and flame-ASS (4 mg/L) - by nearly a factor of 10 and 100 respectively. The major draw-back encountered by the PSA technique was the length of time required for an accurate determination (in the vicinity of 2 hours per sample)

Application of the optimised PSA instrument to water and sediment samples from the Loddon, Avoca and Campaspe rivers revealed cadmium levels in both environmental media were below the suggested guidelines for ecosystem protection. Therefore, these rivers are currently free from pollution by cadmium. In addition, the results of this study supplement the post-1997 cadmium data collected by the EPA for these rivers. The combination of this data is in direct contradiction to the 1996 EPA bulletin that proposed an increasing trend in cadmium in the river waters of all three waterways. However, assuming the FSM data referred to in the bulletin were the result of sample contamination occurring during AWT's solvent extraction procedure, the report and indeed the pre-1997 FSN cadmium data are both inaccurate. Therefore, there may never have been a problem with cadmium in these rivers in the past either. In addition, the results of the current study were found to be consistent with similar studies performed in both Australian and overseas waterways.