1. Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark
2. Department of Agricultural Sciences, The Royal Veterinary and Agricultural University (KVL), Højbakkegårds Allé 30, DK-2630 Tåstrup, Denmark
3. Department of Natural Sciences and Department of Ecology, KVL, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark