Sophie Gangloff
Peter Stille Marie-Claire Pierret Tiphaine WeberFrançois Chabaux. Characterization and evolution of dissolved organic matter in acidic forest soil and its impact on the mobility of major and trace elements (case of the Strengbach watershed).Geochimica et Cosmochimica ActaVolume 130 1 April 2014 Pages 21–41
Abstract
Dissolved Organic Carbon (DOC) plays an important role in the behavior of major and trace elements in the soil and influences their transfer from soil to soil solution. The first objective of this study is to characterize different organic functional groups for the Water Extractable Organic Carbon (WEOC) fractions of a forest soil as well as their evolution with depth. The second objective is to clarify the influence of these organic functional groups on the migration of the trace elements in WEOC fractions compared to those in the soil solution obtained by lysimeter plates. All experiments have been performed on an acidic forest soil profile (five depths in the first meter) of the experimental spruce parcel in the Stengbach catchment.
The Infra-red spectra of the freeze-dried WEOC fractions show a modification of the molecular structure with depth i.e. a decrease of the polar compounds such as polysaccharides and an increase of the less polar hydro-carbon functional groups with a maximum value of the aromaticity at 30 cm depth. A Hierarchical Ascending Classification (HAC) of the evolution of Water Extractable Chemical Elements (WECE) with the evolution of the organic functional groups in the organic matter (OM) enriched soil compartments permits recognition of relationships between trace element behavior and the organic functional group variations. More specifically Pb is preferentially bound to the carboxylic acid function of DOC mainly present in the upper soil compartment and rare earth elements (REE) show similar behavior to Fe V and Cr with a good affinity to carboxy-phenolic and phenolic groups of DOC. The experimental results show that heavy REE compared to light REE are preferentially bound to the aromatic functional group. This different behavior fra