TITLE: COMPOSITION OF WATER AND SOLVENT EXTACTABLE ORGANIC MATTER IN TWO
WETTABLE AND WATER REPELLENT URBAN SOILS
Jennifer Langbein1, Gabriele Schaumann2
1 Tu Berlin, Institute of Environmental Technology, Department of Environmental Chemistry, KF3,
Straße des 17. Juni 135, D-10623 Berlin, Germany, jennylangbein@hotmail.com
2 Universität Koblenz-Landau, Institute of Sciences, Department of Chemistry, Section Organic and
Environmental Chemistry, Universitätsstr. 1 56072 Koblenz, Schaumann@uni-koblenz.de
Soil water repellency is a worldwide problem, which is currently under intensive research from physical
and chemical viewpoint. The molecular principles responsible for hydrophobicity are not fully
understood. There has been some research done to identify the compounds causing water repellency
(Doerr et al 2005, Horne 2000). New findings show that the surface tension of aqueous soil extracts
differs between wettable and water repellent soil samples (Hurraß, Schaumann 2005). This points to
differences in the composition of amphiphilic substances, which therefore could also be responsible
for the water repellency.
The objective of this study was to isolate and characterize amphiphilic substances like long chain fatty
acid and their amides, long chain alcohols etc. These molecules are able to reduce the surface
tension. The soil samples are neighbouring pairs of a water repellent and a wettable soil, taken from
an inner city park (Tiergarten) and an old sewage field (Buch) in Berlin.
The samples have been extracted with water and isopropanol/ammonia. The extracts were purified,
further separated and analysed with gas chromatography – mass spectrometry. Before and after the
extraction, soil-water contact angle and WDPT of the soil sample were determined, and surface
tension in an aqueous extract was measured with the De Nuoy Ring Method.
Preliminary results show different extract compositions, depending on whether the soil was wettable or
water repellent. The extracts of water repellent soils consist of larger amounts of fatty acids, alcohols
and similar compounds, while the extracts of hydrophilic soils contain more compounds with oxygen
and aromatic substances. The composition of the compounds and the effect of the extraction on the
soil surface characteristics will be presented and discussed in this contribution.
Keywords: amphiphilic substances, SOM, water repellency, GC-MS, column extraction
Doerr, S.H., P. Douglas, C.P. Morley, C.T. Llewellyn, K.A. Mainwaring, C. Haskins, L. Johnsey, C.J.
Ritsema, F. Stagnitti, A.J.D. Ferreira, A.K. Ziogas, A.K. 2004 Organic compounds associated with
water repellency in sandy soils. In: Huang, P.M., Violante, A. & Bollag, J.-M. (Eds) Soil Abiotic & Biotic
Interactions & the Impact on the Ecosystem & Human Welfare. Part V - Rhizosphere Processes,
Chapter 20. Science Publishers, Enfield, USA., 444pp. ISBN 1-57808-344-3/ September 2005
Horne, D.J., McIntosh, J.C. 2000. Hydrophobic compounds in sands in New Zealand – extraction,
characterisation and proposed mechanisms for repellency expression. Journal of Hydrology 231-232
(special issue: ”Water Repellency in soils”): 35 – 46
Hurraß, J., Schaumann, G.E. 2006. Properties if soil organic matter and aqueous extracts of actually
water repellent and wettable soil samples. Geoderma: DOI:10.1016/j.geoderma.2005.05.012