1. Department of Environmental Science and Analytical Chemistry, Stockholm University, Svante Arrhenius väg 8, SE-10691 Stockholm, Sweden
2. Department of Environmental Science, Arctic Research Centre, Aarhus University, Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark
3. Department of Environmental Research and Monitoring, Swedish Museum of Natural History, PO
Box 50007, SE-10405 Stockholm, Sweden
4. Department of Bioscience, Arctic Research Centre, Aarhus University, Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark