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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: Science of the Total Environment, 01 December 2015, Vol.535, pp.3-19
    Description: Engineered inorganic nanoparticles (EINP) from consumers' products and industrial applications, especially silver and titanium dioxide nanoparticles (NP), are emitted into the aquatic and terrestrial environments in increasing amounts. However, the current knowledge on their environmental fate and biological effects is diverse and renders reliable predictions complicated. This review critically evaluates existing knowledge on colloidal aging mechanisms, biological functioning and transport of Ag NP and TiO NP in water and soil and it discusses challenges for concepts, experimental approaches and analytical methods in order to obtain a comprehensive understanding of the processes linking NP fate and effects. Ag NP undergo dissolution and oxidation with Ag S as a thermodynamically determined endpoint. Nonetheless, Ag NP also undergo colloidal transformations in the nanoparticulate state and may act as carriers for other substances. Ag NP and TiO NP can have adverse biological effects on organisms. Whereas Ag NP reveal higher colloidal stability and mobility, the efficiency of NOM as a stabilizing agent is greater towards TiO NP than towards Ag NP, and multivalent cations can dominate the colloidal behavior over NOM. Many of the past analytical obstacles have been overcome just recently. Single particle ICP-MS based methods in combination with field flow fractionation techniques and hydrodynamic chromatography have the potential to fill the gaps currently hampering a comprehensive understanding of fate and effects also at a low field relevant concentrations. These analytical developments will allow for mechanistically orientated research and transfer to a larger set of EINP. This includes separating processes driven by NP specific properties and bulk chemical properties, categorization of effect-triggering pathways directing the EINP effects towards specific recipients, and identification of dominant environmental parameters triggering fate and effect of EINP in specific ecosystems (e.g. soil, lake, or riverine systems).
    Keywords: Transport ; Aggregation ; Analytics ; Environment ; Aging ; Ecotoxicology ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 3
    Language: English
    In: Journal of Thermal Analysis and Calorimetry, 2014, Vol.118(2), pp.1169-1182
    Description: Physicochemical aging of soil organic matter is assured by the dynamic character of weak interactions stabilizing its supramolecular structure. However, aging is difficult to monitor, due to low organic matter content in most soils and relatively large time constants. In order to overcome those problems, a model soil, sapric histosol, was exposed to the accelerated aging after a short heating event to 110 °C, and its thermal characteristics were monitored over several months. Classical and temperature modulated differential scanning calorimetry, microcalorimetry and solid-state NMR were used to elucidate the character of involved transitions. The heating event caused separation of an initially broad transition into two processes; a melting, which showed almost no response on the previous heating and a step transition, which is associated with the disruption of water molecule bridges (WaMB) between molecular segments of organic matter. Both processes are preceded by a preparatory phase, starting at subambient temperatures, in which aliphatic domains probably recrystallize and water molecules condensate forming WaMB stabilizing the physical structure of sapric histosol. The aliphatic moieties showed a particular behavior reflected in higher imperfection in crystallite structure upon slow cooling, which was attributed to their interaction with surrounding porous and heterogeneous structures. The results show that soil organic matter aging, considered as a natural process driven by thermodynamic principles, is caused by successive development of WaMB. This is potentially accompanied by recrystallization of aliphatic structures and both processes lead to higher physicochemical stability of soil organic matter.
    Keywords: Soil organic matter ; Aging ; Water molecule bridges (WaMB) ; Lipids ; Modulated DSC ; C CPMAS NMR
    ISSN: 1388-6150
    E-ISSN: 1588-2926
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  • 4
    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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  • 5
    Language: English
    In: Environmental Chemistry, 2015, Vol.13(1), p.50-57
    Description: The mobility of soil organic matter and water molecules has a strong influence on the availability of fertilisers as well as on the fate of pollutants in soil. Magnetic resonance techniques identified two regimes of mobility change on the molecular level occurring on a timescale of 1 year after initially heating the sample. The results can help to understand the effect of soil type and water content for agricultural use and soil protection.
    Keywords: Organic Matter ; Transition Temperatures ; Geochemistry ; Aging ; Soils ; Calorimetry ; Peat ; Bridges ; Organic Matter ; Heating ; Aging ; Networks ; Calorimetry ; Soil Organic Matter ; Dynamics ; Peat ; Structures ; Methods and Instruments;
    ISSN: 1448-2517
    E-ISSN: 1449-8979
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  • 6
    Article
    Article
    Schaumann, Gabriele E. ; Allan PhilippeauthorUniversitt Koblenz-Landau, Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, Fortstr., D- Landau, Germany ; Mirco BundschuhauthorUniversitt Koblenz-Landau, Institute for Environmental Sciences, Group of Ecotoxicology and Environment, Fortstr., D- Landau, GermanySwedish ; [et al.]
    Language: English
    In: 2015
    Keywords: Shr ; Ros ; Titanium Dioxide ; Pvp ; Aas ; Nom ; Xas ; Af4 ; Ecotoxicology ; Hdc ; Hydrodynamics ; Mals ; Thermodynamics ; Chromatography ; Environmental Factors ; Einp ; Pss ; Edx ; Sec ; Ft-Ir ; Sem ; Hmw ; Dom ; Cpe ; Industrial Applications ; Transport ; Uvvis ; Cations ; Sed-Fff ; Nanoparticles ; Fractionation ; Environment ; Aging ; Dls ; Lmw ; Lakes ; Ecosystems ; Ccc ; Analytics ; Exafs ; Sers ; Dlvo ; Tem ; Cdi ; Eps ; Etp ; Mspe ; Ijp ; Oes ; Nanosilver ; Environmental Fate ; Scd ; Bet ; Silver ; Physicochemical Properties ; Oxidation ; Aggregation ; Prediction ; Bioactive Properties ; Soil Water ; Fff ; Pzc ; Afm ; Icp ; Tof-Sims ; Xanes ; Dna ; Xrd
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 7
    Language: English
    In: PLoS ONE, 01 January 2013, Vol.8(6), p.e65359
    Description: It is assumed to be common knowledge that multivalent cations cross-link soil organic matter (SOM) molecules via cation bridges (CaB). The concept has not been explicitly demonstrated in solid SOM by targeted experiments, yet. Therefore, the requirements for and characteristics of CaB remain unidentified. In this study, a combined experimental and molecular modeling approach was adopted to investigate the interaction of cations on a peat OM from physicochemical perspective. Before treatment with salt solutions of Al(3+), Ca(2+) or Na(+), respectively, the original exchangeable cations were removed using cation exchange resin. Cation treatment was conducted at two different values of pH prior to adjusting pH to 4.1. Cation sorption is slower (〉〉2 h) than deprotonation of functional groups (〈2 h) and was described by a Langmuir model. The maximum uptake increased with pH of cation addition and decreased with increasing cation valency. Sorption coefficients were similar for all cations and at both pH. This contradicts the general expectations for electrostatic interactions, suggesting that not only the interaction chemistry but also spatial distribution of functional groups in OM determines binding of cations in this peat. The reaction of contact angle, matrix rigidity due to water molecule bridges (WaMB) and molecular mobility of water (NMR analysis) suggested that cross-linking via CaB has low relevance in this peat. This unexpected finding is probably due to the low cation exchange capacity, resulting in low abundance of charged functionalities. Molecular modeling demonstrates that large average distances between functionalities (∼3 nm in this peat) cannot be bridged by CaB-WaMB associations. However, aging strongly increased matrix rigidity, suggesting successive increase of WaMB size to connect functionalities and thus increasing degree of cross-linking by CaB-WaMB associations. Results thus demonstrated that the physicochemical structure of OM is decisive for CaB and aging-induced structural reorganisation can enhance cross-link formation.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 8
    Language: English
    In: Journal of Plant Nutrition and Soil Science, June 2018, Vol.181(3), pp.453-461
    Description: Two previous studies suggested that part of the cation sorption sites in soil organic matter with low exchange capacity have to be considered as “lonely”, ., too far from each other to allow direct cross‐linking by bivalent cations. The objective of this contribution was to understand the mechanisms controlling structural rigidity and physicochemical aging of the SOM (soil organic matter) and the role of water molecule bridges (WaMB) therein. For this, we evaluated the matrix rigidity of an organic surface layer of a Haplic Podzol on a quantitative basis, by assessing WaMB transition temperature () directly after treatment with bivalent cations (Mg, Ca, or Ba) and after eight weeks of aging. Cation loading as well as cation type influenced matrix rigidity. Ba induced the most rigid matrix and Mg the weakest, which is in line with their binding strength in terms of Langmuir coefficient. The matrix rigidity increased with the cross‐linking activity, which is the product of loading and Langmuir constant of the respective cation. The aging process, however, was slowed down by the initial matrix rigidity, and the rigidity of the aged matrix decreased with increasing Langmuir constant. The degree of aging increased with increasing hydration enthalpy of the cation and decreased with increasing cation loading. Thus, directly after cation treatment, direct cross‐links by multivalent cations were most relevant, but WaMB increasingly gained influence on the matrix rigidity during aging. The untreated sample revealed a considerable number of WaMB, resulting in a fairly rigid and strongly cross‐linked matrix which, however, flexibly reacts on external influences like change in cation concentration or relative humidity. With these findings, the ideas on the relevance of indirect CaB‐WaMB associations between distant sorption sites for the rigidity and flexibility of the OM matrix as proposed in previous studies were confirmed on a mechanistic basis in this study.
    Keywords: Aging ; Cation Bridges ; Cross‐Linking ; Soil Organic Matter ; Water Molecule Bridges
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 9
    Description: Boden ist unter Feldbedingungen einer Dynamik von Temperatur und Feuchte ausgesetzt. Dadurch werden Quellungs- und Schrumpfungsprozesse sowie Veränderungen in den Oberflächeneigenschaften der organischen Bodensubstanz induziert, die nur in den seltensten Fällen vollständig reversibel sind. Von diesen Veränderun-gen werden direkte Auswirkungen auf das Sorptions- und Transportverhalten organischer Schadstoffe erwartet. Trotz dieser Bedeutung sind die zugrunde liegenden Prozesse bis heute noch weitgehend unverstanden. Ziel dieser Arbeit war es, die organische Bodensubstanz, basierend auf der Modell-vorstellung als amorphe Matrix, von einem neuen Blickwinkel zu beschreiben. Mit Hilfe der in der Bodenchemie noch wenig bekannten Methoden der 1H-NMR-Relaxometrie und Differential Scanning Kalorimetrie wurden ihre Wasserbindung und Matrixeigenschaften charakterisiert. Im Zentrum stand die Charakterisierung des Glasübergangsverhaltens und der physikalischen Alterung sowie deren Beeinflus-sung durch Wasser, Feuchtebedingungen und Temperatur. Die organische Bodensubstanz zeigt sowohl typisches als auch irreversibles Glas-übergangsverhalten, wobei Wasser in antagonistischer Weise als kurzfristig wirken-der Weichmacher und langfristig wirkender Hartmacher fungiert. Die zugrunde liegenden Strukturrelaxationsprozesse äußern sich in einer langsamen physikochemi-schen Alterung der organischen Matrix über einen Zeitraum von mindestens sechs Monaten. Änderungen in den Feuchtebedingungen führen zu einer Beschleunigung und teilweisen Umkehrung der Alterung. Hystereseeffekte als typisches Merkmal amorpher Stoffe wurden bei Matrixeigenschaften und bei Wasseraufnahme und -abgabe beobachtet. Quellungsprozesse führen zu einer... ; Under field conditions, soil is subjected to temperature and moisture dynamics. These induce swelling and shrinking as well as changes in the surface characteristics of soil organic matter, which are not fully reversible. These changes are expected to affect sorption and transport of organic contaminants. Despite this relevance, the underlying processes are still only scarcely understood. The objective of this research were to describe soil organic matter from a new viewpoint considering it as amorphous matrix. Water binding and matrix properties were characterized with 1H-NMR-Relaxometry and Differential Scanning Calorimetry, both of which represent young methods in the field of soil chemistry. We characterized the glass transition behavior and physical and physicochemical aging of soil organic matter and their interplay with water, moisture conditions and temperature. Soil organic matter reveals typical as well as atypical glass transition behavior, where water acts in antagonistic way as short-term plasticizer and long-term antiplasticizer. The processes of structural relaxation express in physicochemical aging of the organic matrix, and lasts for at least six months. Fluctuations and changes of moisture conditions accelerated or reversed the aging process. We observed hysteresis for water absorption as well as matrix properties, and swelling most probably results in a change...
    Keywords: Naturwissenschaften Und Mathematik ; Alterung ; Glasübergang ; Organische Bodensubstanz ; Quellung ; Wasser ; Aging ; Glass Transition ; Soil Organic Matter ; Swelling ; Water
    Source: DataCite
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  • 10
    Description: Viele ökologisch wichtige Aspekte der organischen Bodensubstanz (OBS), wie die Sorption von organischen Verbindungen und die Wasseraufnahme-Kinetik, lassen sich nur mit Hilfe einer makromolekularen Betrachtungsweise der humosen Substanzen erklären. Es ist bekannt, dass die Konformation des makromolekularen OBS-Netzwerks stark vom Wasserstatus des Bodens beeinflusst wird. Die zugrunde liegenden Prozesse, wie die Art der Wasserbindung und die daraus resultierenden Effekte für die Starrheit der organischen Bodenmatrix, werden bisher jedoch nur unzureichend verstanden. Im Mittelpunkt dieser Dissertation stand die Charakterisierung der Wechselwirkungen zwischen der festen OBS und Wasser. Einerseits wurde der Wasseraufnahmeprozess humoser Bodenproben untersucht. Dabei wurden vor allem Unterschiede des Benetzungsvorgangs zwischen wasserabweisenden und benetzbaren Proben und mögliche Einflussfaktoren für Benetzungshemmung im Boden betrachtet. Andererseits wurde für 102 Bodenproben von unterschiedlichen Standorten das Glasübergangsverhalten der OBS, das sehr genau die Art der Wasserbindung widerspiegelt, untersucht. Sowohl die Ergebnisse der Benetzungsversuche als auch die der Glasübergangsuntersuchungen stützen die makromolekulare Vorstellungsweise der humosen Substanzen. In 52 der 102 Bodenproben wurden zwei Arten von Glasübergängen festgestellt: Ein klassischer Glasübergang lässt sich nur in wasserfreien Proben beobachten. Der andere Übergangstyp ist stark vom Wasserstatus der OBS abhängig und zeichnet sich durch einen nur langsam reversierenden Charakter aus, was der klassischen Definition von Glasübergängen widerspricht. Die... ; Several ecologically relevant aspects of soil organic matter (SOM), like the sorption of organic compounds and the water uptake kinetics, can only be explained in terms of the macromolecular structure of the humic substances. It is known that the conformation of the macromolecular SOM network is distinctly affected by the water status in soil. But, the underlying processes, as the way of water binding and the resulting effects on the rigidity of the organic soil matrix, are still insufficiently understood. This thesis focused on the characterization of the interactions between solid SOM and water. On the one hand, the hydration process of humous soil samples was studied. Especially, differences in the wetting process of water repellent and wettable samples and possible factors of influence for soil water repellency were investigated. On the other hand, the glass transition behavior of SOM, which sensitively reflects the way of water bonding, was examined for a set of 102 soil samples from different locations. The results of the wetting experiments as well as of the study of the glass transition behavior strongly support the macromolecular view of humic substances. In 52 out of the 102 soil samples, two types of glass transitions were detected:...
    Keywords: Naturwissenschaften Und Mathematik ; Alterung ; Benetzungshemmung ; Glasübergang ; Organische Bodensubstanz ; Quellung ; Aging ; Glass Transition ; Soil Organic Matter ; Swelling ; Water Repellency
    Source: DataCite
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