Combined proton NMR wideline and NMR relaxometry to study SOM-water interactions of cation-treated soils

Schaumann, Gabriele E.; Diehl, Dörte; Bertmer, Marko; Jaeger, Alexander; Conte, Pellegrino; Alonzo, G.; Bachmann, Jörg

doi:10.2478/johh-2013-0007

Cited by 35 publications

(40 citation statements)

References 59 publications

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“…The SOM composition can be determined in terms of organic matter functional groups using Fourier transform infrared (FTIR) spectroscopy (e.g., Demyan et al, 2012) or nuclear magnetic resonance (NMR) spectroscopy (e.g., Celi et al, 1997;Schaumann et al, 2013). The potential wettability of SOM was characterized by the ratio between the FTIR signal intensities of hydrophobic aliphatic C-H groups and hydrophilic C = O groups (Ellerbrock et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Droplet infiltration dynamics and soil wettability related to soil organic matter of soil aggregate coatings and interiors

Fér

Leue

Kodešová

et al. 2016

Journal of Hydrology and Hydromechanics

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Abstract:The organo-mineral coatings of soil aggregates, cracks, and biopores control sorption and macropore-matrix exchange during preferential flow, in particular in the clay-illuvial Bt-horizon of Luvisols. The soil organic matter (SOM) composition has been hypothesized to explain temporal changes in the hydraulic properties of aggregate surfaces. The objective of this research was to find relations between the temporal change in wettability, in terms of droplet infiltration dynamics, and the SOM composition of coated and uncoated aggregate surfaces. We used 20 to 40 mm sized soil aggregates from the Bt2 horizon of a Haplic Luvisol from loess that were (i) coated, (ii) not coated (both intact), and (iii) aggregates from which coatings were removed (cut). The SOM composition of the aggregate surfaces was characterized by infrared spectroscopy in the diffuse reflection mode (DRIFT). A potential wettability index (PWI) was calculated from the ratio of hydrophobic and hydrophilic functional groups in SOM. The water drop penetration times (WDPT) and contact angles (CA) during droplet infiltration experiments were determined on dry and moist aggregate samples of the three types. The decrease in the CA with time was described using the power function (CA(t) = at -b ). For dry aggregates, the WDPT values were larger for coated as compared to uncoated regions on the aggregate surfaces, and increased with increasing PWI value (R 2 = 0.75). The a parameter was significantly related to the WDPT (R 2 = 0.84) and to the PWI (R 2 = 0.64). The relations between the b parameter and the WDPT (R 2 = 0.61) and the PWI (R 2 = 0.53) were also significant. The WDPT values of wet soil aggregates were higher than those of dry aggregates due to high water contents, which limited the droplet infiltration potential. At the wet aggregate surfaces, the WDPT values increased with the PWI of the SOM (R 2 = 0.64). In contrast to dry samples, no significant relationships were found between parameters a or b of CA(t) and WDPT or PWI for wet aggregate surfaces. The results suggest that the effect of the SOM composition of coatings on surface wettability decreases with increasing soil moisture. In addition to the dominant impact of SOM, the wettability of aggregate surfaces could be affected by different mineralogical compositions of clay in coatings and interiors of aggregates. Particularly, wettability of coatings could be decreased by illite which was the dominant clay type in coatings. However, the influence of different clay mineral fractions on surface wettability was not due to small number of measurements (2 and 1 samples from coatings and interiors, respectively) quantified.

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Section: Introductionmentioning

confidence: 99%

Droplet infiltration dynamics and soil wettability related to soil organic matter of soil aggregate coatings and interiors

Fér

Leue

Kodešová

et al. 2016

Journal of Hydrology and Hydromechanics

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“…Recently, it was shown by the use of differential scanning calorimetry (DSC) that cross‐linking of molecular segments of SOM can occur either by water molecules [water molecule bridges (WaMB)], CaB or CaB‐WaMB associations ( Schaumann et al, ). Disruption of cross‐links in which WaMB are involved, causes softening of SOM matrix.…”

Section: Introductionmentioning

confidence: 99%

“…Thereby T* is interpreted as a measure of the matrix rigidity ( Schaumann and LeBoeuf , ), which is assumed to increase with the strength and number of cross‐links. Additionally, disruption of cross‐links results in an increase in structural mobility, which is reflected by narrowing of the proton nuclear magnetic resonance spectral peak after a heating event ( Schaumann et al, ). Therefore, DSC and 1 H NMR wide line spectroscopy are the major methods used to characterize the molecular rigidity in a WaMB‐stabilized matrix, and DSC is currently the only suitable one to quantify matrix rigidity ( Schaumann et al, ; Schaumann and Bertmer , ).…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the relevance of direct CaB is expected to increase with increasing pH on the cost of CaB‐WaMB‐associations and, thus, the extent of the aging process should decrease. Hints about the formation of CaB‐WaMB associations during aging were found in a study on cation‐treated SOM in a highly organic soil ( Schaumann et al., ). Beyond these hints, evidence for the mechanism of this aging process is still required.…”

Section: Introductionmentioning

confidence: 99%

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Cation binding in a soil with low exchange capacity: Implication for the structural rigidity of soil organic matter

Mouvenchery

Schaumann

2017

J. Plant Nutr. Soil Sci.

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Two previous studies suggested that part of the cation sorption sites in soil organic matter with low exchange capacity have to be considered as “lonely”, i.e., too far from each other to allow direct cross‐linking by bivalent cations. The objective of this contribution was to understand the mechanisms controlling structural rigidity and physicochemical aging of the SOM (soil organic matter) and the role of water molecule bridges (WaMB) therein. For this, we evaluated the matrix rigidity of an organic surface layer of a Haplic Podzol on a quantitative basis, by assessing WaMB transition temperature (T*) directly after treatment with bivalent cations (Mg2+, Ca2+, or Ba2+) and after eight weeks of aging. Cation loading as well as cation type influenced matrix rigidity. Ba2+ induced the most rigid matrix and Mg2+ the weakest, which is in line with their binding strength in terms of Langmuir coefficient. The matrix rigidity increased with the cross‐linking activity, which is the product of loading and Langmuir constant of the respective cation. The aging process, however, was slowed down by the initial matrix rigidity, and the rigidity of the aged matrix decreased with increasing Langmuir constant. The degree of aging increased with increasing hydration enthalpy of the cation and decreased with increasing cation loading. Thus, directly after cation treatment, direct cross‐links by multivalent cations were most relevant, but WaMB increasingly gained influence on the matrix rigidity during aging. The untreated sample revealed a considerable number of WaMB, resulting in a fairly rigid and strongly cross‐linked matrix which, however, flexibly reacts on external influences like change in cation concentration or relative humidity. With these findings, the ideas on the relevance of indirect CaB‐WaMB associations between distant sorption sites for the rigidity and flexibility of the OM matrix as proposed in previous studies were confirmed on a mechanistic basis in this study.

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“…Focusing on the hypothesis that multivalent cations have an impact on soil organic matter (SOM) matrix and surface characteristics, Schaumann et al (2013) treat peat and soil samples by solutions of NaCl, CaCl 2 , AlCl 3 , or with a cation exchange resin. From analysis of the 1 H wideline, they distinguish mobile water and water involved in water molecule bridges (WaMB) and find that a large part of cation bridges (CaB) between SOM functional groups are associated with WaMB.…”

Section: Leaching Of Somentioning

confidence: 99%

Editorial and preface to thematic issue on biohydrology

Lichner¹

2013

Journal of Hydrology and Hydromechanics

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Combined proton NMR wideline and NMR relaxometry to study SOM-water interactions of cation-treated soils

Cited by 35 publications

References 59 publications

Droplet infiltration dynamics and soil wettability related to soil organic matter of soil aggregate coatings and interiors

Droplet infiltration dynamics and soil wettability related to soil organic matter of soil aggregate coatings and interiors

Cation binding in a soil with low exchange capacity: Implication for the structural rigidity of soil organic matter

Editorial and preface to thematic issue on biohydrology

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