Publication date: 15 December 2016
Source:Geoderma, Volume 284
Author(s): Alexander Jäger, Marko Bertmer, Gabriele E. Schaumann
The impact of low water contents on the molecular mobility of soil organic matter (SOM) and its most frequent components was investigated. Combined 1H, 2H, and 13C solid-state nuclear magnetic resonance (NMR) techniques allow for an advanced insight into mechanisms of water uptake under defined atmospheres and its effect on SOM segment mobility. The major individual organic components of two peats, a gleyic podsol and a number of model substances (cutin, suberin, wood and cellulose) were distinguished with respect to their contribution to the 1H and 13C NMR spectra. Water molecules and mobile polymer constituents of SOM contribute to the mobile fraction in 1H NMR wide line spectra. Poly(methylene), being most probably part of amphiphilic molecules, have been identified as SOM components that are mobilized in the presence of water. Even though being of hydrophobic nature, water acts as a plasticizer on such long chain aliphatic soil components. Differential scanning calorimetry measurements of SOM samples support this insight in terms of a thermal step transition. Based on our findings, comparison of experimental results from different soils with varying water contents and soil composition should consider mobility effects of both, aliphatic moieties as well as polar moieties of SOM.
Source:Geoderma, Volume 284
Author(s): Alexander Jäger, Marko Bertmer, Gabriele E. Schaumann
