[1] Univ Florence, Dipartimento Sci Terra, I-50100 Florence, Italy
[2] Univ Autonoma Barcelona, Inst Ciencia & Tecnol Ambientals, Bellaterra 08193, Catalonia, Spain
[3] Vrije Univ Amsterdam, Fac Earth Sci, NL-1081 HV Amsterdam, Netherlands
[4] Univ Bremen, Fachbereich Geowissensch, D-28334 Bremen, Germany