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Constraints on the Sources and Production Mechanisms of Dissolved Organic Matter in Soils from Molecular Biomarkers

Abstract : Spatio-temporal modifications of the composition of dissolved organic matter (DOM) from a wetland in an agricultural catchment were investigated using thermally assisted hydrolysis and methylation with tetramethylammonium hydroxide coupled to gas chromatography and mass spectrometry (THM-GC–MS). The results were compared with previous data acquired on the same samples using ultraviolet spectroscopy and the stable C isotope ratio. The correlation between molecular markers and bulk-scale descriptors validated the use of THM-GC–MS to investigate the fate of DOM in soils. Molecular proxies, including lignin markers, tannin markers, carbohydrates, and fatty acids, were classified into plant-derived and microbial markers. At the beginning of the hydrologic year, associated with the recharge period, the DOM composition was similar along the depth profile and >70% of the analyzed markers were from plant-derived origins. The rise in the water table was associated with a shift from vertical to horizontal water flow due to water saturation and resulted in a clear vertical heterogeneity, i.e., a varying composition throughout the profile. In the surface horizons, the proportion of plant-derived markers remained >70%, while in the deep horizon this proportion was <30%. Last, the lowering of the water table resulted in the homogenization of the DOM composition along the depth profile.
Keywords : GEOF
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Submitted on : Thursday, December 4, 2014 - 1:30:36 PM
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Laurent Jeanneau, Anne Jaffrézic, Anne-Catherine Pierson-Wickmann, Gérard Gruau, Thibault Lambert, et al.. Constraints on the Sources and Production Mechanisms of Dissolved Organic Matter in Soils from Molecular Biomarkers. Vadose Zone Journal, Soil science society of America - Geological society of America., 2014, 13 (7), 9 p. ⟨10.2136/vzj2014.02.0015⟩. ⟨insu-01090923⟩



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