Long term mobilisation of chemical elements in tephra-rich peat (NE Iceland)

• Published in: Applied Geochemistry
• Main Authors: de Vleeschouwer, François, van Vliet-Lanoë, Brigitte, Fagel, Nathalie
• Other Authors: Unité de Recherche Argiles et Paléoclimats, Université de Liège, Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Processus et bilan des domaines sédimentaires (PBDS), Université de Lille, Sciences et Technologies-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2008
• Subjects: [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; Hekla; Iceland
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-00338740; https://hal-insu.archives-ouvertes.fr/insu-00338740/document; https://hal-insu.archives-ouvertes.fr/insu-00338740/file/FDV%20peat%20iceland%20AG%202008%20OCR.pdf; https://doi.org/10.1016/j.apgeochem.2008.10.006

International audience This paper presents geochemical profiles of a tephra-bearing minerotrophic peat column from NE-Iceland obtained using various elemental analyses of the solid phase and the pore water. The influence of tephra grain size, thickness and composition of each tephra on the peat geochemistry was investigated. Interpretations are supported by a statistical approach, in particular by autocorrelation, and by microscopy observations. Minerotrophic peat geochemistry may be strongly dependent upon post-depositional mobilization and possible leaching of elements as demonstrated by Fe and trace metal concentration profiles. Chemical elements, and more specifically potentially harmful metals, can be slowly leached out of volcanic falls during their weathering and re-accumulate downwards. It is emphasised that a tephra deposit can act as an active geochemical barrier, blocking downward elemental movements and leading to the formation of enriched layers. In this study, the formation of poorly amorphous Fe phases above the Hekla 3 tephra is shown. These poorly crystalline Fe phases scavenged Ni.