title: Soil wettability can be explained by the chemical composition of particle interfaces - An XPS study.
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.
authors.affiliation: Institute of Soil Science, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany.
authors.forename: Susanne K
authors.initials: SK
authors.lastname: Woche
authors.affiliation: Institute of Soil Science, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany.
authors.forename: Marc-O
authors.initials: MO
authors.lastname: Goebel
authors.affiliation: Soil Science and Soil Protection, Martin Luther University Halle-Wittenberg, Von-Seckendorff-Platz 3, 06120 Halle (Saale), Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Mikutta
authors.affiliation: Laborgesellschaft für Umweltschutz mbH, Waldheimer Str. 1, 04746 Hartha, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schurig
authors.affiliation: Department for Environmental Biotechnology, Helmholtz Centre for Environmental Research, UFZ, Permoserstr. 15, 04318 Leipzig, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Kaestner
authors.affiliation: Institute of Soil Science, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Guggenberger
authors.affiliation: Institute of Soil Science, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Bachmann