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  • 1
    Language: English
    In: Science of the Total Environment, 01 December 2015, Vol.536, pp.1045-1051
    Description: To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1016/j.scitotenv.2015.07.064 Byline: Martin Wiesmeier [wiesmeier@wzw.tum.de] (a,*), Rico Hubner (b), Ingrid Kogel-Knabner (a,c) Keywords Soil organic carbon; Climate change; Net primary productivity; Soil C input Highlights * C stocks in agricultural soils may be largely affected by climate change. * It is assumed that C stocks would increase due to an assumed increase of NPP. * However, crop statistics indicate stagnating yields of major crops since the 1990s. * Concurrently stagnating C inputs would lead to C decreases in the long-term. * Indications for declining agricultural C stocks were already found. Abstract The carbon (C) balance of agricultural soils may be largely affected by climate change. Increasing temperatures are discussed to cause a loss of soil organic carbon (SOC) due to enhanced decomposition of soil organic matter, which has a high intrinsic temperature sensitivity. On the other hand, several modeling studies assumed that potential SOC losses would be compensated or even outperformed by an increased C input by crop residues into agricultural soils. This assumption was based on a predicted general increase of net primary productivity (NPP) as a result of the CO.sub.2 fertilization effect and prolonged growing seasons. However, it is questionable if the crop C input into agricultural soils can be derived from NPP predictions of vegetation models. The C input in European croplands is largely controlled by the agricultural management and was strongly related to the development of crop yields in the last decades. Thus, a glance at past yield development will probably be more instructive for future estimations of the C input than previous modeling approaches based on NPP predictions. An analysis of European yield statistics indicated that yields of wheat, barley and maize are stagnating in Central and Northern Europe since the 1990s. The stagnation of crop yields can probably be related to a fundamental change of the agricultural management and to climate change effects. It is assumed that the soil C input is concurrently stagnating which would necessarily lead to a decrease of agricultural SOC stocks in the long-term given a constant temperature increase. Remarkably, for almost all European countries that are faced with yield stagnation indications for agricultural SOC decreases were already found. Potentially adverse effects of yield stagnation on the C balance of croplands call for an interdisciplinary investigation of its causes and a comprehensive monitoring of SOC stocks in agricultural soils of Europe. Author Affiliation: (a) Lehrstuhl fur Bodenkunde, Department fur Okologie und Okosystemmanagement, Wissenschaftszentrum Weihenstephan fur Ernahrung, Landnutzung und Umwelt, Technische Universitat Munchen, 85350 Freising-Weihenstephan, Germany (b) Lehrstuhl fur Strategie und Management der Landschaftsentwicklung, Department fur Okologie und Okosystemmanagement, Wissenschaftszentrum Weihenstephan fur Ernahrung, Landnutzung und Umwelt, Technische Universitat Munchen, 85350 Freising-Weihenstephan, Germany (c) Institute for Advanced Study, Technische Universitat Munchen, Lichtenbergstr. 2a, 85748 Garching, Germany * Corresponding author. Article History: Received 23 April 2015; Revised 12 July 2015; Accepted 13 July 2015 (miscellaneous) Editor: D. Barcelo
    Keywords: Soil Organic Carbon ; Climate Change ; Net Primary Productivity ; Soil C Input ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 2
    Language: English
    In: Science of the Total Environment, 01 July 2018, Vol.628-629, pp.906-918
    Description: We compared synchrotron-based C near-edge X-ray absorption fine structure (NEXAFS) and CPMAS C nuclear magnetic resonance (NMR) spectroscopy with respect to their precision and accuracy to quantify different organic carbon (OC) species in defined mixtures of soil organic matter source compounds. We also used both methods to quantify different OC species in organic surface horizons of a Histic Leptosol as well as in mineral topsoil and subsoil horizons of two soils with different parent material, stage of pedogenesis, and OC content (Cambisol: 15–30 OC mg g , Podzol: 0.9–7 OC mg g ). CPMAS C NMR spectroscopy was more accurate and precise (mean recovery of different C functional groups 96–103%) than C NEXAFS spectroscopy (mean recovery 92–113%). For organic surface and topsoil samples, NMR spectroscopy consistently yielded larger O-alkyl C percentages and smaller alkyl C percentages than C NEXAFS spectroscopy. For the Cambisol subsoil samples both methods performed well and showed similar C speciation results. NEXAFS spectroscopy yielded excellent spectra with a high signal-to-noise ratio also for OC-poor Podzol subsoil samples, whereas this was not the case for CPMAS C NMR spectroscopy even after sample treatment with HF. Our results confirm the analytical power of CPMAS C NMR spectroscopy for a reliable quantitative OC speciation in soils with 〉10 mg OC g . Moreover, they highlight the potential of synchrotron-based C NEXAFS spectroscopy as fast, non-invasive method to semi-quantify different C functional groups in soils with low C content (0.9–10 mg g ).
    Keywords: Direct Non-Invasive Soc Speciation ; Method Comparison ; Soil Organic Matter ; C Functional Groups ; Organic Surface Soil ; Mineral Soil ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 3
    Language: English
    In: Science of the Total Environment, 1992, Vol.117, pp.393-401
    Description: Dissolved organic matter (DOM) can act as a sorbent for organic chemicals in soils and natural waters. Therefore, distribution of an environmental chemical in soil is determined by a three compartment system of bulk soil matrix, water, and colloidal or dissolved organic matter. In the present study we demonstrate the binding of a new herbicide to DOM. Ultrafiltration techniques allowed the separation of two dissolved fractions of the free herbicide and the herbicide bound to DOM. Ion composition and pH exert a decisive influence on the sorption processes. An effective sorption isotherm is calculated, which takes into account the sorption onto DOM. Implications of the results on the movement of the herbicide in soils are discussed.
    Keywords: Binding ; Water-Soluble Soil Humic Substance ; Herbicide ; Dissolved Organic Matter ; Ultrafiltration ; Ion Composition and Ph ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 4
    Language: English
    In: Science of the Total Environment, 2004, Vol.326(1), pp.225-237
    Description: There is growing concern about environmentally released man-made chemicals suspected to be responsible for a number of adverse effects on endocrine function in wildlife species and possibly also in humans. Sex hormones are of particular interest due to their regulatory role in developmental processes such as sexual differentiation. Endogenous hormones of human or animal origin as well as exogenous sex steroids used for contraception or as anabolics for farm animals are excreted and reach the environment. We investigated the transport of the synthetic growth promoters trenbolone (TbOH) and melengestrol acetate (MGA) in agricultural soil by means of column experiments with aggregated soil materials (Ap and Bt horizons of a Luvisol). Column effluent concentrations and depth profiles of TbOH and MGA were determined with sensitive enzyme immunoassay systems and HPLC (RP-18), respectively. All procedures were confirmed by liquid chromatography-mass spectrometry. Small amounts of TbOH and MGA passed the columns very quickly. However, both hormones exhibited a high affinity to the organic matter of both horizons leading to a high retardation within the upper layers of the soil columns. Although we cannot deduce whether hormones of animal origin reach the ground water under field conditions, our model experiments show that their transition can be presumed.
    Keywords: Trenbolone ; Melengestrol Acetate ; Agricultural Soil ; Sorption Isotherm ; Column Study ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 5
    Language: English
    In: Science of the Total Environment, 1992, Vol.117, pp.175-185
    Description: Resistant residues isolated from whole soils were subjected to analysis by solid-state CPMAS 13 C NMR and Curie-point pyrolysis-gas chromatography-mass spectrometry to delineate the nature of the resistant aliphatic components. These components constitute a major fraction of soil organic matter and associated humic substances and appear to be concentrated during soil formation initially by a process of selective preservation. Changes in the nature of these biomacromolecules with increasing depth and decomposition in the soil profile indicate that they are being altered significantly. The NMR data show that the aliphatic structures in forest soil organic matter can be assigned to mobile and rigid carbon moieties. The mobile and rigid carbon types are possibly associated with different types of macromolecules. One type are the polyesters cutin and suberin from leaves, barks and roots, the other is a resistant non-saponifiable aliphatic biomacromolecule derived from leaves and barks or microorganisms. At depth in the soil profile the mobile components are degraded but the rigid aliphatic biomacromolecules appear to be selectively preserved. However, the pyrolysis data indicate that these non-saponifiable aliphatic macromolecules bear no resemblance to the resistant aliphatic biomacromolecules in fresh leaf cuticles or microbial cell walls. This lack of resemblance is probably due to the fact the selective preservation of resistant, non-saponifiable plant or microbial macromolecules is not the dominant process leading to the accumulation of alkyl carbon moieties in forest soil organic matter. Alternatively, it seems possible that the structural differences observed between the alkyl carbon moieties in forest litter and humified soil horizons result from an increase in cross-linking during humification.
    Keywords: Humification ; Alkyl Carbon ; Forest Soils ; Cpmas 13c NMR ; Py-Gc(-MS) ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 6
    Language: English
    In: Science of the Total Environment, 1992, Vol.123, pp.121-131
    Description: The sorption behaviour of the new acidic herbicide quinmerac on a range of different synthetic and natural iron oxides was studied in order to determine the influence of pH and degree of crystallinity. The synthetic iron oxides chosen for the batch sorption experiments were 6-line ferrihydrite, goethite and hematite. In addition, natural soil substrates rich in iron oxides (cambic and spodic B horizons and ochreous sludge) were used for sorption experiments. The synthetic iron oxides were characterized by X-ray diffraction, transmission electron micrographs and by measuring their specific surface area. Sorption of quinmerac (p K a2 = 4.3) on both synthetic and natural ferrihydrite was linear up to the water solubility of the herbicide at low pH values. Sorption decreases with increasing pH. At pH 〉 5.5 no sorption was observed. Sorption decreases with increasing degree of crystallinity. The isotherms on the well crystallized oxides goethite and hematite indicated saturation of binding sites at quinmerac concentrations of 1.8 10 −3 mg g −1 (goethite) and 1.0 10 −3 mg g −1 (hematite). Sorption on the soil samples depends on both the content of weakly crystalline iron oxides and on organic carbon content.
    Keywords: Quinmerac ; Synthetic Iron Oxides ; Natural Iron Oxides ; Soils ; Organic Carbon Content ; Crystallinity ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 7
    Language: English
    In: Science of the Total Environment, 1992, Vol.113(1), pp.89-106
    Description: Forest soil organic matter contains a refractory alkyl-carbon component of unknown structure and composition. Soil samples obtained from different types of forest humus and from litter-bag experiments were examined by the complementary...
    Keywords: Forest Soils ; Organic Matter ; Humic Substances ; Alkyl Carbon, 13c NMR, Py-Gc(-MS) ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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