1. Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden
2. Norwegian Institute for Water Research (NIVA), Gaustadalléen 21,
NO-0349 Oslo, Norway
3. Department
of Systems Ecology, Stockholm University, SE-106 91 Stockholm, Sweden
4. Norwegian Geotechnical Institute (NGI), P.O. Box 3930 Ullevål Stadion,
NO-0806 Oslo, Norway
5. Department
of Aquatic Sciences
and Assessment, Swedish University of Agricultural Sciences (SLU), Box 7050, SE-750 07 Uppsala, Sweden