Authors: V Chardot G Echevarria M Gury S Massoura J L Morel
Publish Date: 2007/05/05
Volume: 293, Issue: 1-2, Pages: 7-21
Abstract
A serpentinised harzburgite outcrop located in the Vosges Mountains hosts a population of the Nihyperaccumulator Thlaspi caerulescens J C Presl A complete study was undertaken to relate the variability of Ni availability along the ultramafic toposequence to pedogenesis soil mineralogy and functioning with XRay Diffraction Transmission Electron Microscope observations coupled with Isotopic Exchange Kinetics and diethylenetriamine pentaacetic acid extraction of Ni The soil profiles ranging from Dystric Cambisol to Hypermagnesic Hypereutric Cambisol were distributed unevenly along the toposequence probably due to geochemical variability of the bedrock and also complex quaternary erosion features The richest soils were characterised by slight mineral weathering leading to Ni Cr and Fe accumulation in the B horizons whereas the lowest saturated soils had very lowmetal contents Most soil minerals were inherited from the parent materials and there were only few traces of formation of secondary minerals Primary minerals eg serpentine chlorite contained low Ni concentrations 02 whereas neoformed goethite mainly in the B horizons of the richest soils contained up to 43 Ni Ni was probably sorbed onto amorphous Fe oxy−hydroxide particles oxalate extraction rather than incorporated within the crystal lattice of goethite Ni availability in the B horizon of Hypereutric Cambisols was extremely high and so was the oxalate extractable Fe At the toposequence level there was a high level of Ni availability in the least weathered soils and a very lowavailability level in the more intensively weathered soils strongly acidic pH Ni availability was unexpectedly positively correlated to pH and was controlled by soil mineralogy and Nibearing mineral phases Ni hyperaccumulation above 1000 mg kg−1 by native T caerulescens was only reached in the Nirich soils as a consequence of the local edaphic factors Ni uptake by T caerulescens is strongly regulated by Ni availability in soils and therefore related to pedogenesisThe study was funded by a grant from the Fédération de Recherche “EauSolTerre” INPLUHPCNRSINRA of Nancy France The authors would especially like to thank Dr Jafaar Ghambaja and Philippe Lambert for the TEM and XRD analyses and interpretation and Hélène Molins for her valuable help in field and lab work
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