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. 2017 Feb 17:7:42877.
doi: 10.1038/srep42877.

Soil wettability can be explained by the chemical composition of particle interfaces - An XPS study

Susanne K Woche  1 , Marc-O Goebel  1 , Robert Mikutta  2 , Christian Schurig  3 , Matthias Kaestner  4 , Georg Guggenberger  1 , Jörg Bachmann  1
Affiliations

Soil wettability can be explained by the chemical composition of particle interfaces - An XPS study

Susanne K Woche et al. Sci Rep. .

Abstract

Soil wettability (quantified in terms of contact angle, CA) is crucial for physical, chemical, and biological soil functioning. As the CA is determined by components present within the outmost nanometer of particles, this study applied X-ray photoelectron spectroscopy (XPS) with a maximum analysis depth of 10 nm to test the relationship between CA and surface elemental composition, using soil samples from a chronosequence where CA increased from 0° (0 yrs) to about 98° (120 yrs). Concurrently, as seen by XPS, C and N content increased and the content of O and the mineral-derived cations (Si, Al, K, Na, Ca, Mg, Fe) decreased. The C content was positively correlated with CA and least squares fitting indicated increasing amounts of non-polar C species with soil age. The contents of O and the mineral-derived cations were negatively correlated with CA, suggesting an increasing organic coating of the minerals that progressively masked the underlying mineral phase. The atomic O/C ratio was found to show a close negative relationship with CA, which applied as well to further sample sets of different texture and origin. This suggests the surface O/C ratio to be a general parameter linking surface wettability and surface elemental composition.

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Conflict of interest statement

The authors declare no competing financial interests.

Figures

Figure 1
Figure 1. Surface wetting properties in terms of contact angle (CA) as function of XPS-detected element content.
The lines represent linear regression fits. Significance levels: *P < 0.05; **P < 0.01; ***P < 0.001. The dotted lines added to the plots with no significant correlation (Na, Mg) indicate the general trend.
Figure 2
Figure 2. Relationship between surface O and C content (a, n = 55) and contact angle (CA) as function of the surface atomic O/C ratio (b, n = 48) for the chronosequence samples (red stars) and further sample sets differentiated by texture and origin (grey symbols).
The organoclay, i.e., the suite of bentonite samples treated with different amounts of hexadecylpyridiniumchloride, only is shown in the left graph. The lines represent linear and exponential regression fits. The coefficients of dtermination and significance levels in red refer to the chronosequence samples and the coefficients of determination and significance levels in cyan refer to all sample sets including the chronosequence samples. Significance level: ***P < 0.001.
Figure 3
Figure 3. Contact angle (CA) as function of the amount of non-polar C species (Cnp) (a; n = 48) and as function of the ratio between non-polar and polar C species (Cnp/Cp) (b; n = 48) for the chronosequence samples (red stars) and further sample sets differentiated by texture and origin (grey symbols).
The lines represent exponential regression fits. The coefficients of determination and significance levels in red refer to the chronosequence samples and the coefficients of determination and significance levels in cyan refer to all sample sets including the chronosequence samples. Significance level: ***P < 0.001.
See this image and copyright information in PMC

References

    1. Bachmann J., Deurer M. & Arye G. Modeling water movement in heterogeneous water-repellent soil: 1. Development of a contact angle–dependent water-retention model. Vadose Zone J. 6, 436–445 (2007).
    1. Young T. An essay on the cohesion of fluids. Philos. Trans. R. Soc. 95, 65–87 (1805).
    1. Doerr S. H., Shakesby R. A. & Walsh R. P. D. Soil water repellency: its causes, characteristics and hydro-geomorphological significance. Earth Sci. Rev. 51, 33–65 (2000).
    1. Ma’shum M.; Tate M. E.; Jones G. P. & Oades J. M. Extraction and characterization of water-repellent materials from Australian soils. J. Soil Sci. 39, 99–110 (1988).
    1. Chorover J., Kretzschmar R., Garcia-Pichel F. & Sparks D. L. Soil biogeochemical processes within the critical zone. Elements 3, 321–326 (2007).

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