1. Department of Water and Environmental Studies, Linköping University, SE-581 83 Linköping, Sweden, Department of Environmental Assessment, Swedish University of Agricultural Sciences, P.O. Box 7050 SE-750 07 Uppsala, Sweden, Department of Environmental Chemistry, Wallenberg Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden, and Akzo Nobel Surface Chemistry AB, SE-444 85 Stenungsund, Sweden