1. Department of Soil Sciences, PO Box 7014, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden
2. Department of Chemical Engineering and Technology, Royal Institute of Technology, SE 100 44 Stockholm, Sweden
3. Department of Inorganic Chemistry, Royal Institute of Technology, SE 100 44 Stockholm, Sweden
4. The Ragnar Sellberg Foundation for Waste Research and Development, Hogbytorp, SE 197 93 Bro, Sweden