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  • 1
    Language: English
    In: Organic Geochemistry, 2011, Vol.42(8), pp.917-925
    Description: H wideline NMR spectra of soil samples offer the possibility to analyze soil material based on their proton mobility. Care has to be taken to remove unwanted signal contributions from the probe background. We demonstrate that unstructured wideline spectra can be analyzed quantitatively by a combination of a Gaussian line for rigid and a Lorentzian line for mobile protons. This is used to study effects of hydrogen-bonded water networks upon heat treatment for a series of different soil samples with varying water content as a contribution to study physical aging of soil organic matter (SOM). Results are combined with H projections from C 2D WISE (wideline separation) experiments representing solely the broad Gaussian line. Furthermore, for the first time applied to soils, H structural information from soil samples is obtained from 2D PMLG phase modulated Lee–Goldburg measurements under magic angle spinning (MAS). Low water contents improve the resolution of main functional groups significantly.
    Keywords: Geology
    ISSN: 0146-6380
    E-ISSN: 1873-5290
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  • 2
    Language: English
    In: Journal of Plant Nutrition and Soil Science, August 2018, Vol.181(4), pp.586-599
    Description: The presence and mutual interactions of soil organic matter (SOM) and clay particles are major factors determining soil structural stability. In the scope of agricultural management and environmental sustainability, it remains unclear how various mineral and organic matter (OM) fractions, OM–clay interactions and swelling processes in the interparticle space determine soil–water interactions and thus soil structural stability. To investigate this issue, we isolated the mineral and OM fractions of an agriculturally cultivated silty loam soil by soil density fractionation and assessed their hydration characteristics and effects on soil structural stability combining H‐NMR relaxometry, soil rheology and single wet‐sieving of soil aggregates. The results showed that agricultural management practices, in particular compost and ploughing, as well as various OM–clay interactions significantly affected soil–water interactions and soil structural stability. On the one hand, ploughing reduced soil structural stability by promoting clay swelling as a result of disrupted soil structures and reduced SOM content. On the other hand, compost treatment and reduced tillage increased soil structural stability. In all cases, soil density fractionation showed that compost‐derived particulate organic matter (POM) and mineral‐associated organic matter (MAOM) restricted clay swelling and resulted in a highly porous and mechanically stable soil matrix. In particular, POM increased soil structural stability by acting as nucleus for soil aggregation and by restricting clay swelling its presence as solid, granular interparticulate material. In contrast, MAOM seemed to restrict clay swelling clay surface covering and the formation of viscous interparticulate hydrogel structures.
    Keywords: Density Fractionation ; Gel Effect ; Nmr Relaxometry ; Rheology ; Wet‐Sieving
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 3
    Language: English
    In: Journal of Soils and Sediments, 2013, Vol.13(9), pp.1579-1588
    Description: Purpose: Nutrient release, soil wettability, water binding, and matrix rigidity of soil organic matter (SOM) can be affected by cross-links between segments of SOM, cations, and water molecule bridges (WaMB). Not all cation effects on SOM can be explained with the currently accepted idea that multivalent cations cross-link organic matter segments via direct cation bridges (CaB). The objective was to understand these interactions and their effect on SOM matrix rigidity and wettability. Materials and methods: We modified cation composition of two peats and an organic surface layer (OSL) using cation exchange resin to remove cations and solutions of Na super(+), Ca super(2+), or Al super(3+) to enrich samples with cations. SOM matrix rigidity was determined at 4 and 〉8 weeks after treatment via the WaMB transition temperature T*, using differential scanning calorimetry. Wettability was measured via sessile drop contact angle (CA). Results and discussion: The effect of cation removal on T* depended on cation exchange capacity and initial cation content. Cation addition to OSL increased T*. This effect increased with increasing cation loading and valency, and T* correlated with CA. Classical cross-linking can neither explain the higher heterogeneous matrix of Ca-treated than Al-treated samples nor the aging-induced convergence of T* for different cations and concentrations. The latter is likely due to interaction between CaB and WaMB in SOM. Conclusions: Associations of CaB and WaMB evolve slowly and form a supramolecular network in SOM. Those dynamic associations can fix molecular arrangements inducing water repellency and increase kinetic barriers for the release and uptake of water and nutrients from aged soil.
    Keywords: Cross-links ; Differential scanning calorimetry ; Matrix rigidity ; Multivalent cation ; Soil organic matter ; Water molecule bridges (WaMB) ; Water repellency
    ISSN: 1439-0108
    E-ISSN: 1614-7480
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  • 4
    Language: English
    In: Geochimica et Cosmochimica Acta, 2007, Vol.71(3), pp.691-702
    Description: Recent studies indicate that glassiness represents a characteristic feature of soil organic matter (SOM). It is however unknown, to which extent the transitions detected in humic substances and whole soil samples correspond to common models of synthetic polymers providing the theoretical basis for explaining their glass transition characteristics. Physical aging associated with structural relaxation of amorphous substances below their glass temperature is one fundamental basis for the glass transition behavior of synthetic polymers. According to the results of this study, aging processes also occur in SOM. In whole soil samples, this process can be observed by the shift of glass transition-like step transitions to higher temperatures within the time scale of years. Not only the structural relaxation of the macromolecular organic substances, but also interactions with water molecules, which may exhibit both plasticizing and antiplasticizing properties, influence the aging process of SOM. Especially under moistening or drying conditions, a differentiation between the effects of water and of alterations of the SOM structure in the course of time on the rigidity of the macromolecular network is difficult.
    Keywords: Geology
    ISSN: 0016-7037
    E-ISSN: 1872-9533
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  • 5
    Language: English
    In: Science of the Total Environment, 15 December 2015, Vol.538, pp.246-261
    Description: Terrestrial inputs into freshwater ecosystems are a classical field of environmental science. Resource fluxes (subsidy) from aquatic to terrestrial systems have been less studied, although they are of high ecological relevance particularly for the receiving ecosystem. These fluxes may, however, be impacted by anthropogenically driven alterations modifying structure and functioning of aquatic ecosystems. In this context, we reviewed the peer-reviewed literature for studies addressing the subsidy of terrestrial by aquatic ecosystems with special emphasis on the role that anthropogenic alterations play in this water–land coupling. Our analysis revealed a continuously increasing interest in the coupling of aquatic to terrestrial ecosystems between 1990 and 2014 (total: 661 studies), while the research domains focusing on abiotic (502 studies) and biotic (159 studies) processes are strongly separated. Approximately 35% (abiotic) and 25% (biotic) of the studies focused on the propagation of anthropogenic alterations from the aquatic to the terrestrial system. Among these studies, hydromorphological and hydrological alterations were predominantly assessed, whereas water pollution and invasive species were less frequently investigated. Less than 5% of these studies considered indirect effects in the terrestrial system e.g. via food web responses, as a result of anthropogenic alterations in aquatic ecosystems. Nonetheless, these very few publications indicate far-reaching consequences in the receiving terrestrial ecosystem. For example, bottom-up mediated responses via soil quality can cascade over plant communities up to the level of herbivorous arthropods, while top-down mediated responses via predatory spiders can cascade down to herbivorous arthropods and even plants. Overall, the current state of knowledge calls for an integrated assessment on how these interactions within terrestrial ecosystems are affected by propagation of aquatic ecosystem alterations. To fill these gaps, we propose a scientific framework, which considers abiotic and biotic aspects based on an interdisciplinary approach.
    Keywords: Aquatic–Terrestrial Subsidies ; Flood Events ; Hot Moments ; Hot Spots ; Biogeochemical Processes ; Environmental Chemicals ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 6
    Language: English
    In: Journal of Soils and Sediments, 2017, Vol.17(4), pp.901-916
    Description: To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1007/s11368-016-1584-1 Byline: Nisreen Tamimi (1), Gabriele E. Schaumann (1), Dorte Diehl (1) Keywords: Differential scanning calorimetry; Olive mill wastewater; Soil organic carbon; Soil organic matter; Thermal stability; Thermogravimetry Abstract: Purpose Application of olive mill wastewater (OMW) to soil may cause positive or negative effects. The present study aims at a better understanding of the fate of organic matter brought into soil by OMW application under different environmental conditions. Materials and methods Single OMW application to soil was conducted in spring, dry summer, summer with irrigation, and in winter. Two days and 18--24 months after the application, soil samples from two depths were analyzed for thermal soil organic matter (SOM) properties, total organic carbon, water-extractable dissolved soil organic carbon, and its specific ultraviolet absorbance at 254 nm. Results and discussion After winter and irrigated summer treatments, OMW was largely leached from the upper horizon within 2 days. Application in spring and summer dry initially increased the thermolabile fraction and the calorific value of SOM, however, in a different degree due to different transport, transformation, and immobilization mechanisms. At the long term, SOM content was still elevated after summer dry treatment. The reduction of the thermostable fraction in spring treatment indicates a priming effect of the labile OMW constituents. Conclusions Application in winter or with irrigation cannot be recommended for the investigated site. Under hot and dry conditions, SOM content increased most persistently due to stronger mineral-organic interactions. Favorable conditions for biodegradation during OMW application in spring reduced the effects on SOM quantity in the long term. However, a possible priming effect and the persistence of changes in thermal properties need to be further investigated for repeated applications. Author Affiliation: (1) Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, Universitat Koblenz-Landau, Fortstr. 7, 76829, Landau, Germany Article History: Registration Date: 19/10/2016 Received Date: 04/07/2016 Accepted Date: 19/10/2016 Online Date: 04/11/2016 Article note: Responsible editor: Zucong Cai
    Keywords: Differential scanning calorimetry ; Olive mill wastewater ; Soil organic carbon ; Soil organic matter ; Thermal stability ; Thermogravimetry
    ISSN: 1439-0108
    E-ISSN: 1614-7480
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  • 7
    Language: English
    In: Journal of Hydrology and Hydromechanics, 01 June 2016, Vol.64(2), pp.176-195
    Description: Environmental conditions play a major role for effects of olive mill wastewater (OMW) application to soil. Choosing a different season for OMW application than the commonly practiced winter, may help avoid negative effects. However, understanding...
    Keywords: Olive Mill Wastewater ; Soil Water Repellency ; Acidification ; Salinity ; Soluble Phenolic Compounds ; Leaching ; Geography
    E-ISSN: 0042-790X
    E-ISSN: 13384333
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  • 8
    Language: English
    In: Geoderma, 01 April 2017, Vol.291, pp.40-46
    Description: Crystalline aliphatic moieties in soil organic matter (SOM) have been under intensive investigation, but it is still unknown how they interact with organic chemicals in the unfractionated SOM. Our objective was to understand the changes in properties of soil aliphatic crystallites when being in contact with organic chemicals. For this, we treated an organic (sapric histosol) and a mineral soil (gleyic podzol) with phenol and naphthalene dissolved in different solvents. The crystallites were characterized in the unfractionated soil by their melting temperatures determined by differential scanning calorimetry (DSC) and by C CPMAS NMR spectra from the (33.0 ppm) and (30.0 ppm) signals. DSC identified two distinct types of crystalline domains differing in melting temperatures. Their reaction on solvent treatment and spiking allowed for the first time new insights into the nature of these domains in the unfractionated soil samples. Melting temperature and relative crystallinity were generally reduced by the presence of organic chemicals and solvent treatment, but in different way for each domain type. Thus, the domain types differ from each other in chemical nature. The domains melting at 68–75 °C (sapric histosol) responded similar to biopolymer residues and may originate from higher plants, while those melting at 82–93 °C (sapric histosol) and at 76–80 °C (gleyic podzol) responded similarly to lipids and are speculated to be of microbiological origin. These findings open new perspectives for the mechanistic analysis of sorption processes in soil. Aliphatic crystalline domains may have been underestimated with respect to their qualitative relevance for sorption processes in soil.
    Keywords: Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 9
    Language: English
    In: Journal of Soils and Sediments, 2015, Vol.15(1), pp.1-12
    Description: Byline: Daniela Gildemeister (1,2), George Metreveli (1), Sandra Spielvogel (3), Sabina Hens (1,4), Friederike Lang (5), Gabriele E. Schaumann (1) Keywords: Cation bridges; Cross-link; Differential scanning calorimetry; Dissolved organic matter; Glass transition; Water molecule bridges Abstract: Purpose Precipitation of dissolved organic matter (DOM) by multivalent cations is important for biogeochemical cycling of organic carbon. We investigated to which extent cation bridges are involved in DOM precipitation and how cross-links by cations and water molecule bridges (WaMB) stabilise the matrix of precipitated DOM. Materials and methods DOM was precipitated from the aqueous extract of a forest floor layer adding solutions of Ca(NO.sub.3).sub.2, Al(NO.sub.3).sub.3 and Pb(NO.sub.3).sub.2 with different initial metal cation/C (Me/C) ratios. Precipitates were investigated by differential scanning calorimetry before and after ageing to detect cation bridges, WaMB and restructuring of supramolecular structure. Results and discussion Twenty-five to sixty-seven per cent of the dissolved organic carbon was precipitated. The precipitation efficiency of cations increased in the order Ca〈Al〈Pb, while the cation content of precipitates increased in the order Pb〈Ca〈Al. The different order and the decrease in the WaMB transition temperature (T*) for Al/C〉3 is explained by additional formation of small AlOOH particles. Thermal analysis indicated WaMB and their disruption at T* of 53--65 [degrees]C. Like cation content, T* increased with increasing Me/C ratio and in the order Ca〈Pb〈Al for low Me/C. This supports the general assumption that cross-linking ability increases in the order Ca〈Pb〈Al. The low T* for high initial Me/C suggests less stable and less cross-linked precipitates than for low Me/C ratios. Conclusions Our results suggest a very similar thermal behaviour of OM bound in precipitates compared with soil organic matter and confirms the relevance of WaMB in stabilisation of the supramolecular structure of cation-DOM precipitates. Thus, stabilisation of the supramolecular structure of the DOM precipitates is subjected to dynamics in soils. Author Affiliation: (1) Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, Universitat Koblenz-Landau, Fortstr. 7, 76829, Landau, Germany (2) Umweltbundesamt, FG IV 2.2 Pharmaceuticals, Worlitzer Platz 1, 06844, Dessau-Ro[sz]lau, Germany (3) Department of Geography, Institute of Integrated Natural Sciences, Universitat Koblenz-Landau, Universitatsstr. 1, 56070, Koblenz, Germany (4) GN Dr. Netta Beratende Ingenieure und Geowissenschaftler, Bienengarten 3, 56072, Koblenz, Germany (5) Albert-Ludwigs-Universitat Freiburg, Institute of Forest Sciences, 79085, Freiburg i.Br., Germany Article History: Registration Date: 09/07/2014 Received Date: 02/04/2014 Accepted Date: 09/07/2014 Online Date: 30/07/2014 Article note: Responsible editor: Dong-Mei Zhou Electronic supplementary material The online version of this article (doi: 10.1007/s11368-014-0946-9) contains supplementary material, which is available to authorized users.
    Keywords: Cation bridges ; Cross-link ; Differential scanning calorimetry ; Dissolved organic matter ; Glass transition ; Water molecule bridges
    ISSN: 1439-0108
    E-ISSN: 1614-7480
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  • 10
    Language: English
    In: Geochimica et Cosmochimica Acta, 2006, Vol.70(12), pp.2957-2969
    Description: Hydration of organic coatings in soils is expected to affect the sorption of oxyanions onto hydrous Fe and Al oxides. We hypothesized that the hydration of polygalacturonate (PGA) coatings on alumina (Al O ) increases their permeability for phosphate. Pure and PGA-coated alumina were equilibrated in deionized water for 2 and 170 h at pH 5 and 20 °C before studying (i) their porosity with N gas adsorption and H NMR relaxometry, (ii) structural changes of PGA-coatings with differential scanning calorimetry (DSC), and (iii) the kinetics of phosphate sorption and PGA desorption in batch experiments. Scanning electron micrographs revealed that PGA molecules formed three-dimensional networks with pores ranging in size from 〈10 to several hundred nanometers. Our NMR results showed that the water content of intraparticle alumina pores decreased upon PGA sorption, indicating a displacement of pore water by PGA. The amount of water in interparticle alumina pores increased strongly after PGA addition, however, and was attributed to water in pores of PGA and/or in pores at the PGA-alumina interface. The flexibility of PGA molecules and the fraction of a PGA gel phase increased within one week of hydration, implying restructuring of PGA. Hydration of PGA coatings increased the amount of phosphate defined as instantaneously sorbed by 84%, showing that restructuring of PGA enhanced the accessibility of phosphate to external alumina surfaces. Despite the fact that the efficacy of phosphate to displace PGA was higher after 170 h than after 2 h, a higher phosphate surface loading was required after 170 h to set off PGA desorption. Our findings imply that the number of PGA chain segments directly attached to the alumina surface decreased with time. We conclude that hydration/dehydration of polymeric surface coatings affects the sorption kinetics of oxyanions, and may thus control the sorption and transport of solutes in soils.
    Keywords: Geology
    ISSN: 0016-7037
    E-ISSN: 1872-9533
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