title: Comparing molecular composition of dissolved organic matter in soil and stream water: Influence of land use and chemical characteristics.
abstract: Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) was used to examine the molecular composition of dissolved organic matter (DOM) from soils under different land use regimes and how the DOM composition in the catchment is reflected in adjacent streams. The study was carried out in a small area of the Schwingbach catchment, an anthropogenic-influenced landscape in central Germany. We investigated 30 different soil water samples from 4 sites and different depths (managed meadow (0-5cm, 40-50cm), deciduous forest (0-5cm), mixed-coniferous forest (0-5cm) and agricultural land (0-5cm, 40-50cm)) and 8 stream samples. 6194 molecular formulae and their magnitude-weighted parameters ((O/C)w, (H/C)w, (N/C)w, (AI-mod)w, (DBE/C)w, (DBE/O)w, (DBE-O)w, (C#)w, (MW)w) were used to describe the molecular composition of the samples. The samples can be roughly divided in three groups. Group 1 contains samples from managed meadow 40-50cm and stream water, which are characterized by high saturation compared to samples from group 2 including agricultural samples and samples from the surface meadow (0-5cm), which held more nitrogen containing and aromatic compounds. Samples from both forested sites (group 3) are characterized by higher molecular weight and O/C ratio. Environmental parameters vary between sites and among these parameters pH and nitrate significantly affect chemical composition of DOM. Results indicate that most DOM in streams is of terrestrial origin. However, 120 molecular formulae were detected only in streams and not in any of the soil samples. These compounds share molecular formulae with peptides, unsaturated aliphatics and saturated FA-CHO/FA-CHOX. Compounds only found in soil samples are much more aromatic, have more double bonds and a much lower H/C ratio but higher oxygen content, which indicates the availability of fresh plant material and less microbial processed material compared to stream samples.
authors.affiliation: University Giessen, Animal Ecology & Systematic Zoology, Heinrich Buff Ring 29, D-35392 Giessen, Germany. Electronic address: anne-gret.seifert@allzool.bio.uni-giessen.de.
authors.forename: Anne-Gret
authors.initials: AG
authors.lastname: Seifert
authors.affiliation: Max Planck Institute for Biogeochemistry, POB 100164, 07701 Jena, Germany. Electronic address: vroth@bgc-jena.mpg.de.
authors.forename: Vanessa-Nina
authors.initials: VN
authors.lastname: Roth
authors.affiliation: Research Group for Marine Geochemistry (ICBM-MPI Bridging Group), Univ. of Oldenburg, Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl-von-Ossietzky-Str. 9-11, 26111 Oldenburg, Germany. Electronic address: thorsten.dittmar@uni-oldenburg.de.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Dittmar
authors.affiliation: Max Planck Institute for Biogeochemistry, POB 100164, 07701 Jena, Germany. Electronic address: gerd.gleixner@bgc-jena.mpg.de.
authors.forename: Gerd
authors.initials: G
authors.lastname: Gleixner
authors.affiliation: University Giessen, Landscape Ecology & Resources Management, Res Ctr BioSyst Land Use & Nutr IFZ, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany. Electronic address: lutz.breuer@umwelt.uni-giessen.de.
authors.forename: Lutz
authors.initials: L
authors.lastname: Breuer
authors.affiliation: University Giessen, Landscape Ecology & Resources Management, Res Ctr BioSyst Land Use & Nutr IFZ, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany. Electronic address: tobias.houska@umwelt.uni-giessen.de.
authors.forename: Tobias
authors.initials: T
authors.lastname: Houska
authors.affiliation: University Giessen, Animal Ecology & Systematic Zoology, Heinrich Buff Ring 29, D-35392 Giessen, Germany; Limnological River Station of the Max Planck Institute for Limnology, Schlitz, Germany. Electronic address: juergen.marxsen@allzool.bio.uni-giessen.de.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Marxsen
keywords: Carbon cycle; Catchment; Dissolved organic matter; Ion cyclotron resonance mass spectrometry; Land use; Soil carbon