[1] Macaulay Institute, Craigiebuckler, Aberdeen, AB15 8QH, United Kingdom
[2] Curtin Water Quality Research Centre, Department of Applied Chemistry, Curtin University, Perth, Australia
[3] Department of Geology, University of Leicester, Kingsley Dunham Centre, Keyworth, Nottingham, NG12 5GG, United Kingdom
[4] Micro- and Trace Analysis Centre, Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium