title: Temporal and spatial variability of chemical and isotopic composition of soil solutions from cambisols - field study and experiments.
abstract: The chemical and isotopic composition of soil solutions is highly relevant for environmental and forensic tasks. We investigated interstitial solutions from soil horizons of three cambisols in Styria (Austria). The soils consisted mainly of quartz, feldspar and clay minerals with a vertical variability. Two soil solution fractions from meso-, macro- and micropores (m) and micropores only (μ) were extracted at two subsequent hydraulic pressure steps corresponding to matrix potentials of up to pF 5.43 and from 5.43 to 5.73, respectively. While solute concentrations indicated diverse distribution in soil solution fractions m and μ, heavy stable hydrogen and oxygen isotopes of H2O (-92.5‰<δ2H<-34.4‰; -11.9‰<δ18O<-4.0‰, VSMOW) are clearly enriched in the μ versus m fractions. Principal component analysis on the hydrochemical data set indicates that the intensity of the overall silicate weathering is higher in autumn versus spring, whereas the anthropogenic impact on weathering behaves inversely. The anthropogenic impact is related to seasonal variability of nitrification of N-fertilizers. In consequence of evaluated signals for overall silicate weathering about three-fourths of the soil solutions sampled in autumn indicated elevated total dissolved solid concentration vs. those in spring accompanied with washing out solutes from the soil cover following precipitation events in autumn before sampling. Isotopic shift of soil solutions from the local meteoric water line in spring obviously followed an evaporation trend because of less precipitation and high evaporation before sampling. Experimentally simulated evaporation of soil samples confirmed the observed isotopic evaporation trend. Wetting experiments indicated the infiltration of water within minutes into the micropores of the soils. Exchange of water molecules between micro-, meso- and macropores is an almost instantaneous process and soil solutions in micropores are not as isolated from the soil water system as it was formerly suggested, e.g. for plant uptake. Highly dynamic and complex mechanisms in the gas-water-solid system of soils have to be considered for the application of elemental and isotope proxies related to environmental, forensic and agricultural tasks.
authors.affiliation: Institute of Applied Geosciences, Graz University of Technology, Rechbauerstraße 12, 8010 Graz, Austria.
authors.forename: Walter
authors.initials: W
authors.lastname: Schön
authors.affiliation: Institute of Technology and Testing of Building Materials, Graz University of Technology, Inffeldgasse 24, 8010 Graz, Austria.
authors.forename: Florian
authors.initials: F
authors.lastname: Mittermayr
authors.affiliation: Institute of Water, Energy and Sustainability, Joanneum Research, Elisabethstraße 18, 8010 Graz, Austria.
authors.forename: Albrecht
authors.initials: A
authors.lastname: Leis
authors.affiliation: Department of Dental Medicine and Oral Health, Medical University of Graz, Billrothgasse 4, 8010 Graz, Austria.
authors.forename: Irene
authors.initials: I
authors.lastname: Mischak
authors.affiliation: Institute of Applied Geosciences, Graz University of Technology, Rechbauerstraße 12, 8010 Graz, Austria. Electronic address: martin.dietzel@tugraz.at.
authors.forename: Martin
authors.initials: M
authors.lastname: Dietzel
mesh_terms: D001317:Austria; D003903:Deuterium / Q000032:analysis*; D004784:Environmental Monitoring; D010103:Oxygen Isotopes / Q000032:analysis*; D012987:Soil / Q000737:chemistry*
chemical_list: D010103:Oxygen Isotopes; D012987:Soil; D003903:Deuterium
keywords: Cambisol; Evaporation; Matrix potential; Soil solution; Stable hydrogen and oxygen isotopes