1. Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
2. Umeå Marine Sciences Centre, Umeå University, SE-910 20 Hörnefors, Sweden.
3. Department of Ecology and Environmental Science, Umeå University, SE-901 87 Umeå, Sweden.
4. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden.
5. Department of Environmental Sciences, Rutgers University, New Brunswick, NJ 08901, USA.
6. Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.