1. Environmental
Research Institute, School of Science, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand
2. Department
of Chemistry and Centre for Trace Element Analysis, University of Otago, PO Box 56, Union Place, Dunedin, New Zealand
3. Department of Mathematics & Statistics, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand