1. Department of Geography and Environmental Sciences, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa
2. Department of Water and Sanitation, Resource Quality Information Services (RQIS), Roodeplaat, Pretoria, South Africa
3. School of Chemical Sciences, Technical University of Kenya, Nairobi, Kenya
4. Department of Chemistry, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa