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Thorsten Dittmar - One of the best experts on this subject based on the ideXlab platform.

  • Inefficient microbial production of refractory Dissolved Organic Matter in the ocean.
    Nature communications, 2015
    Co-Authors: Helena Osterholz, Jutta Niggemann, Helge-ansgar Giebel, Meinhard Simon, Thorsten Dittmar
    Abstract:

    The extent to which the microbial carbon pump contributes to the generation of marine refractory Dissolved Organic Matter (RDOM) remains a Matter of debate. Here, the authors report results from a 3-year mesocosm study, and show that most of the microbial DOM is different from RDOM in the ocean.

  • Biogeochemical interpretations of colored Dissolved Organic Matter optical signatures
    2014
    Co-Authors: Aron Stubbins, Robert G. M. Spencer, Paul J. Mann, Thorsten Dittmar, Jutta Niggemann, Robert M. Holmes, James W. Mcclelland, Paul A. Del Giorgio, Yves T. Prairie, Jean-françois Lapierre
    Abstract:

    The optical properties of colored Dissolved Organic Matter (CDOM) in surface waters are visible from space and observable throughout the water column in real time using in situ sensors. Due to their ease of measurement, CDOM optical properties are used as proxies for the quantity, quality and processing of Dissolved Organic Matter (DOM) in natural waters. This talk will focus upon the use of these optical signatures to provide insight into the cycling of DOM. Examples will include the use of color to estimate quantitative fluxes and the molecular composition of Organics in natural waters.

  • Molecular Fractionation of Dissolved Organic Matter with Metal Salts
    Environmental science & technology, 2012
    Co-Authors: Thomas Riedel, Harald Biester, Thorsten Dittmar
    Abstract:

    Coagulation of Dissolved Organic Matter (DOM) by hydrolyzing metals is an important environmental process with particular relevance, e.g., for the cycling of Organic Matter in metal-rich aquatic systems or the flocculation of Organic Matter in wastewater treatment plants. Often, a nonremovable fraction of DOM remains in solution even at low DOM/metal ratios. Because coagulation by metals results from interactions with functional groups, we hypothesize that noncoagulating fractions have a distinct molecular composition. To test the hypothesis, we analyzed peat-derived Dissolved Organic Matter remaining in solution after mixing with salts of Ca, Al, and Fe using 15 T Electrospray Ionization Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FT-ICR-MS). Addition of metals resulted in a net removal of DOM. Also a reduction of molecular diversity was observed, as the number of peaks from the ESI-FT-ICR-MS spectra decreased. At DOM/metal ratios of ∼9 Ca did not show any preference for distinct mol...

Klaus Kaiser - One of the best experts on this subject based on the ideXlab platform.

  • Cycling downwards – Dissolved Organic Matter in soils
    Soil Biology & Biochemistry, 2012
    Co-Authors: Klaus Kaiser, Karsten Kalbitz
    Abstract:

    Abstract Dissolved Organic Matter has been recognized as mobile, thus crucial to translocation of metals, pollutants but also of nutrients in soil. We present a conceptual model of the vertical movement of Dissolved Organic Matter with soil water, which deviates from the view of a chromatographic stripping along the flow path. It assumes temporal immobilization (sorptive or by co-precipitation), followed by microbial processing, and re-release (by desorption or dissolution) into soil water of altered compounds. The proposed scheme explains well depth trends in age and composition of Dissolved Organic Matter as well as of solid-phase Organic Matter in soil. It resolves the paradox of soil Organic Matter being oldest in the youngest part of the soil profile – the deep mineral subsoil.

  • cycling downwards Dissolved Organic Matter in soils
    Soil Biology & Biochemistry, 2012
    Co-Authors: Klaus Kaiser, Karsten Kalbitz
    Abstract:

    Abstract Dissolved Organic Matter has been recognized as mobile, thus crucial to translocation of metals, pollutants but also of nutrients in soil. We present a conceptual model of the vertical movement of Dissolved Organic Matter with soil water, which deviates from the view of a chromatographic stripping along the flow path. It assumes temporal immobilization (sorptive or by co-precipitation), followed by microbial processing, and re-release (by desorption or dissolution) into soil water of altered compounds. The proposed scheme explains well depth trends in age and composition of Dissolved Organic Matter as well as of solid-phase Organic Matter in soil. It resolves the paradox of soil Organic Matter being oldest in the youngest part of the soil profile – the deep mineral subsoil.

  • Storm flow flushing in a structured soil changes the composition of Dissolved Organic Matter leached into the subsoil
    Geoderma, 2005
    Co-Authors: Klaus Kaiser, Georg Guggenberger
    Abstract:

    Abstract Dissolved Organic Matter increases typically in streams draining forested catchments during heavy rainstorms and snowmelt. Tracer methods and model calculations suggest that the storm flow flushing of Dissolved Organic Matter is either due to lateral near-surface flow, i.e. within the Organic forest floor, or preferential flow (funnelling) through the mineral soil. Both pathways should deliver forest floor-derived Dissolved Organic Matter to streams that is hardly changed because of little to no interaction with mineral soil material and microorganisms. Here, we investigated the effect of rain storm induced vertical flushing through the mineral soil on the composition of Dissolved Organic Matter in a structured Rendzic Leptosols under 90-year-old European beech ( Fagus sylvatica L.). During two rainstorm periods in autumn 1998 with elevated transport of Organic C, N, P and S from the forest floor into the subsoil, we sampled Dissolved Organic Matter in forest floor leachates (sampled by zero-tension plate lysimeters), subsoil solutions (sampled by suction cups at 90 cm depth) and subsoil seepage (sampled by zero-tension plate lysimeters at 90 cm depth). The chemical composition of Dissolved Organic Matter was characterised by fractionation with XAD-8 macroreticular resin, wet-chemical analyses of carbohydrates and lignin-derived phenols, and determination of the δ 13 C. During both rainstorm periods, all tested chemical features of Dissolved Organic Matter in forest floor leachate and subsoil seepage matched each other greatly. In contrast, Dissolved Organic Matter in soil solution contained smaller portions of XAD-8-adsorbable Organic C, less lignin-derived phenols, more carbohydrates and showed smaller δ 13 C values than that in forest floor leachates and subsoil seepage. These results suggest a rather direct transfer of Organic solutes from the forest floor into the subsoil and probably further to ground and surface waters during heavy rainstorms. Dissolved Organic Matter leaving the soil in heavy rainstorms by rapid water flow through macropores is likely less biodegradable, more UV-digestible and more reactive towards metals and Organic pollutants than that released from soil at low rainfall intensity by matric flow.

  • Dissolved Organic Matter sorption by mineral constituents of subsoil clay fractions
    Journal of Plant Nutrition and Soil Science, 2000
    Co-Authors: Klaus Kaiser, Wolfgang Zech
    Abstract:

    The retention of Dissolved Organic Matter in soils is mainly attributed to interactions with the clay fraction. Yet, it is unclear to which extent certain clay-sized soil constituents contribute to the sorption of Dissolved Organic Matter. In order to identify the mineral constituents controlling the sorption of Dissolved Organic Matter, we carried out experiments on bulk samples and differently pretreated clay-size separates (untreated, Organic Matter oxidation with H2O2, and Organic Matter oxidation with H2O2 + extraction of Al and Fe oxides) from subsoil horizons of four Inceptisols and one Alfisol. The untreated clay separates of the subsoils sorbed 85 to 95% of the Dissolved Organic Matter the whole soil sorbed. The sorption of the clay fraction increased when indigenous Organic Matter was oxidized by H2O2. Subsequent extraction of Al and Fe oxides/hydroxides caused a sharp decrease of the sorption of Dissolved Organic Matter. This indicated that these oxides/hydroxides in the clay fraction were the main sorbents of Dissolved Organic Matter of the investigated soils. Moreover, the coverage of these sorbents with Organic Matter reduced the amount of binding sites available for further sorption. The non-expandable layer silicates, which dominated the investigated clay fractions, exhibited a weak sorption of Dissolved Organic Matter. Whole soils and untreated clay fractions favored the sorption of ”hydrophobic” Dissolved Organic Matter. The removal of oxides/hydroxides reduced the sorption of the lignin-derived ”hydrophobic” Dissolved Organic Matter onto the remaining layer silicates stronger than that of ”hydrophilic” Dissolved Organic Matter. Sorption geloster organischer Substanz an mineralische Bestandteile der Tonfraktion von Unterbodenhorizonten Bindung an die Tonfraktion gilt als Hauptursache fur den Ruckgang der Gehalte an geloster organischer Substanz in der Bodenlosung wahrend deren Passage des Solums. Unklar ist allerdings, welchen Beitrag verschiedene Mineralbestandteile der Tonfraktion zur Sorption geloster organischer Substanz leisten. Wir haben deshalb die Sorption geloster organischer Substanz an Gesamtproben und unterschiedlich behandelten Proben der Tonfraktion (unbehandelt, nach Oxidation organischer Substanz mittels H2O2, nach Oxidation organischer Substanz + Extraktion pedogener Oxide) von Unterbodenhorizonten zweier Braunerden, zweier Pseudogleye und einer Parabraunerde untersucht. Die unbehandelte Tonfraktion war fur 85 bis 95% der Sorption geloster organischer Substanz der Gesamtboden verantwortlich. Oxidation der organischen Substanz in der Tonfraktion lies die Sorption von geloster organischer Substanz ansteigen. Die darauf folgende Extraktion pedogener Oxide hingegen verringerte die Sorption deutlich. Dies lasst vermuten, dass Oxide der Tonfraktion die wesentlichen Sorbenten fur geloste organische Substanz in Boden sind und dass ihre Belegung mit organischer Substanz die Sorption geloster organischer Substanz erschwert. Die nicht quellfahigen Schichtsilikate, die die untersuchten Tonfraktionen dominierten, zeigten dagegen nur eine sehr geringe Bindung geloster organischer Substanz. Gesamtboden wie auch die unbehandelten Tonfraktionen sorbierten bevorzugt „hydrophobe“ organische Substanz. Entfernen der Oxide verminderte die Sorption ligninburtiger „hydrophober“ geloster organischer Substanz an die verbliebenen Schichtsilikate starker als die Sorption „hydrophiler“ geloster organischer Substanz.

Helena Osterholz - One of the best experts on this subject based on the ideXlab platform.

Lars Lövgren - One of the best experts on this subject based on the ideXlab platform.

Colin A. Stedmon - One of the best experts on this subject based on the ideXlab platform.

  • Corrigendum: Turnover time of fluorescent Dissolved Organic Matter in the dark global ocean.
    Nature communications, 2016
    Co-Authors: Teresa S. Catalá, Isabel Reche, Antonio Fuentes-lema, Cristina Romera-castillo, Mar Nieto-cid, Eva Ortega-retuerta, Eva María Calvo, Marta Álvarez, Cèlia Marrasé, Colin A. Stedmon
    Abstract:

    Corrigendum: Turnover time of fluorescent Dissolved Organic Matter in the dark global ocean

  • Characterizing Dissolved Organic Matter fluorescence with parallel factor analysis: a tutorial
    Limnology and Oceanography: Methods, 2008
    Co-Authors: Colin A. Stedmon, Rasmus Bro
    Abstract:

    A sub-fraction of Dissolved Organic Matter fluoresces when excited with ultraviolet light. This property is used to quantify and characterize changes in Dissolved Organic Matter (DOM) in aquatic environments. Detailed mapping of the fluorescence properties of DOM produces excitation emission matrices (EEM), which are well suited to multi-way data analysis techniques (chemometrics). Techniques such as parallel factor analysis (PARAFAC) are increasingly being applied to characterize DOM fluorescence properties. Here, an introduction to the technique and description of the advantages and pitfalls of its application to DOM fluorescence is presented. Additionally a MATLAB based tutorial and toolbox specific to PARAFAC analysis of DOM fluorescence is presented.