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

• Published in: Applied Geochemistry
• Main Authors: De Vleeschouwer, François, Lanoe, Brigitte Van Vliet, Fagel, Nathalie
• Format: Article in Journal/Newspaper
• Language: English
• Published: Pergamon Press - An Imprint of Elsevier Science 2008
• Subjects: Iceland; peat; tephra; Physical; chemical; mathematical & earth Sciences; Earth sciences & physical geography; Physique; chimie; mathématiques & sciences de la terre; Sciences de la terre & géographie physique; Hekla
• Online Access: https://orbi.uliege.be/handle/2268/23305; https://orbi.uliege.be/bitstream/2268/23305/1/FDV%20peat%20iceland%20AG%202008%20OCR.pdf; https://doi.org/10.1016/j.apgeochem.2008.10.006

peer reviewed 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. (c) 2008 Elsevier Ltd. All rights reserved.