CHEMICAL AND ISOTOPIC COMPOSITION OF SOIL SOLUTIONS FROM CAMBISOLS IN STYRIA (AUSTRIA) – SEASONAL VARIATIONS AND EXPERIMENTS
Schön Walter (1) , Dietzel Martin (1), Leis Albrecht (2)
(1) Institute of Applied Geosciences, Graz University of Technology, Rechbauerstraße 12, 8010 Graz, Austria (2) Institute of Water, Energy and Sustainability, J
15:20 - 17:30 Thursday 24 October 2013 Foyer Alte Technik In most natural surroundings soil solutions are primary gained from the uptake of meteoric water. Subsequently infiltration, capillary exchange, bioresponse, evaporation etc. result in complex and individual gas-water-solid systems. Knowledge on the chemical and isotopic composition of soil solutions and its evolution is highly relevant for environmental and forensic studies, but respective systematic and combined field and experiment studies are rare. Hence we investigated the composition of solids and interstitial solutions of individual soil horizons for three sampled cambisols in Styria (Austria).
The soil solutions were separated from the soils by compaction method at hydraulic pressures of 27.4 and 54.9 MPa, corresponding to pF values of 5.43 and 5.73, respectively (Böttcher et al., 1996, modified). The soils consist mainly of quartz, chlorite, muscovite and plagioclase with minor amounts of kaolinite, vermiculite and smectite due to weathering processes without any carbonates and without significant vertical variability in composition. The soil solutions contain Ca2+, Na+, K+, Mg2+, NO3-, Cl- and SO42- ions in decreasing order of concentrations. The pH ranges from 5.8 to 7.8. δ18O and δ2H values vary from -11.9 to -4.0 ‰ and -90.4 to -34.4 ‰ respectively. In principal, solutes, δ18O and δ2H values are higher concentrated and isotopically heavier, respectively, at pF 5.73 vs. 5.43.
Concerning seasonal variations two sampling campaigns were carried out (April and October, 2012). δ18O and δ2H values from October plot on the local meteoric water line, whereas values from April indicate an evaporation trend. Current degrees of evaporation can be calculated for distinct horizons of the three soils according to the approach by Mittermayr et al. (2013). The evaporation approach was verified by evaporation lab experiments using the above soils at a given humidity and temperature.
Moreover wetting experiments using deionized water with high δ18O and δ2H values were conducted to observe changes regarding pH, ion content, δ18O and δ2H values of the interstitial solutions as a function of matrix potential. Field-related and experimental results are discussed with respect to the impact of seasonality, evaporation, wetting and matrix potential-related interstitial distribution of the isotope-geochemical compositions of the separated soil solutions.
References
BÖTTCHER, G., BRUMSACK, H.-J., HEINRICHS, H., POHLMANN, M., 1996, A new high-pressure squeezing technique for pore fluid extractions from terrestrial soils, Water Air and Soil Pollution 94, pp. 289-296
MITTERMAYR, F., BALDERMANN, A., KURTA, C., RINDER, T., KLAMMER, D., LEIS, A., TRITTHART, J., DIETZEL, M., 2013, Evaporation-a key mechanism for the thaumasite form of sulphate attack, Cement and Concret Research 49, 55-64
|
