1. Department
of Geochemistry, Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen, Denmark
2. Center
for Permafrost (CENPERM), Department of Geosciences and Natural Resource
Management, University of Copenhagen, Copenhagen, Denmark
3. Departamento
de Química, Universidade Federal de Santa Maria, 97105-900 Santa Maria, Rio Grande do Sul, Brazil