1. Department
of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences,
Box 7050, SE-750 07 Uppsala, Sweden
2. Geological Survey of Sweden (SGU), Box 670, SE-751 28 Uppsala, Sweden
3. Department
of Chemistry, Umeå University, SE-901 87 Umeå, Sweden
4. Department
of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden