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  • 1
    Language: English
    In: Journal of Thermal Analysis and Calorimetry, 2013, Vol.113(3), pp.1103-1111
    Description: Soil samples collected in South America, North America and West Siberia were measured by thermogravimetry to verify the connection between mass losses and soil respiration represented by the rate and amount of carbon dioxide measured under laboratory conditions. It was demonstrated that linear correlation between those parameters is a common feature for soils originating from different climatic and geographic regions. Significant coefficients of determination were observed in temperature areas corresponding to the moisture evaporation and degradation of soil organic matter (SOM). It was concluded that the correlations are the consequences of soil-forming processes mediated by microorganisms over a long time period. The comparison of experimental data with earlier results showed that disturbance of those processes causes the decrease in observed correlations. The subtraction of thermal mass losses of incubated and non-incubated soils revealed the change in water holding character in all samples, which was ascribed to the transformation of SOM and its water-holding properties during the incubation. In contrast, the changes in thermal mass losses above 200 °C showed that this area reflects the specificity of biological transformation of each soil sample. Further, applied approach and obtained results indicate the necessity of very gentle soil sample preparation and especially gentle air drying to get comparable results about intrinsic soils’ features in different regions.
    Keywords: Soil ; Thermogravimetry ; Respiration ; Soil microbiological activity ; Soil forming processes
    ISSN: 1388-6150
    E-ISSN: 1572-8943
    E-ISSN: 15882926
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  • 2
    Language: English
    In: Chemosphere, January 2013, Vol.90(2), pp.789-795
    Description: ► Reactivity of DOM strongly depends on its concentration. ► Different parts of total compressibility play role at different concentrations. ► Progressive dilution causes weakening of the aggregate’s stability. ► H-bonds and aromaticity are responsible for main phase transitions in diluted DOM. ► DOM exhibits structural hysteresis under fluctuating temperature. Humic substances play an important role in many environmental processes such as sequestration and transport of hydrophobic compounds. The supramolecular character of humic substances imparts high flexibility of the aggregates associated with their variable reactivity under different conditions. In this study, heat-induced transitions and character of the hydration shell of sodium salts of humic and fulvic acids originating from various sources were investigated using ultrasonic velocimetry in the temperature interval from 5 to 90 °C. Results clearly showed differences in stability and characteristics of the hydrated states at concentrations above and below 1 g L with the exception of Pahokee peat fulvic acids. It has been concluded that predominantly the relaxation part of the adiabatic compressibility plays an important role below 1 g L in contrast to both relaxation and intrinsic parts of the compressibility being important at higher concentrations. Dilution brought several temperature induced transitions which were investigated with respect to composition of all investigated humic substances. Correlation analysis revealed that the transition around 17 °C is associated with disruption of H-interactions whereas the transition around 42 °C depends on the aromaticity. Comparison of cooling and heating records revealed hysteresis in the structural relaxation resembling the behavior of physically stabilized hydrogels. Results indicated a difference in the conformation and therefore reactivity of dissolved humic substances in the dependence on temperature and thermal history. It has been hypothesized that this may play an important role in the transport and sequestration of hydrophobic pollutants by dissolved organic matter.
    Keywords: Dissolved Organic Matter ; Humic Substances ; Hydration ; Hysteresis ; Transport and Sequestration ; Ultrasonic Spectroscopy ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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  • 3
    Language: English
    In: Langmuir : the ACS journal of surfaces and colloids, 09 October 2018, Vol.34(40), pp.12174-12182
    Description: Adsorption is the main mechanism of capturing water in soil organic matter (SOM) under arid conditions. This process is governed by hydrophilic sites, which are gradually bridged via water molecule bridges (WaMB). Until now, the link between WaMB and other types of water molecules occurring in SOM during sorption has not been systematically investigated. In this work, we compared the formation and stability of WaMB simultaneously with the total water content, strength of water binding, and kinetics of water sorption in a vacuum-dried model SOM (sapric histosol) exposed to different relative water pressures. The same parameters were then determined in SOM exposed to reduced relative pressures. The adsorption resulted in an adsorption isotherm with a Langmuir-like part below a relative pressure of 0.5 and a Brunauer-Emmett-Teller-like isotherm at higher relative pressures. The WaMB formation was observed at a relative pressure of 0.32, which represented the pressure at which Langmuir-like part reached a plateau. The binding energy showed a linear decrease with an increasing pressure; the slope increased at a relative pressure of 0.46. Reduction of relative pressures above 0.46 showed that the water content remained constant, but the binding energy was lowered. In contrast, below a relative pressure of 0.46, the water content decreased, but the binding energy was not changed. The results indicate that in SOM exposed to different relative pressures, water exists in three types: first, it is strongly bound to primary sorption sites (Langmuir-like), second, it occurs in the form of WaMB water, which bridges functional groups and where predominates water-water interactions, and third, it occurs in the form of phase water, which is located in larger pores similar to the pure water phase. The latter either surrounds the WaMB and destabilizes it or, for higher water content, links individual WaMB and successively reduces their stabilizing effect. Formation of phase water leads to swelling processes including plasticizing effects and potential volume changes of SOM. Accordingly, the results suggest that at lower water relative pressures WaMB stabilizes the SOM structure, whereas at higher water relative pressures, it influences the formation of phase water and thereby the total water content in SOM.
    ISSN: 07437463
    E-ISSN: 1520-5827
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  • 4
    Language: English
    In: Analytical chemistry, 07 August 2018, Vol.90(15), pp.8793-8799
    Description: The use of plastic materials in daily life, industry, and agriculture can cause soil pollution with plastic fragments down to the micrometer scale, i.e., microplastics. Quantitative assessment of microplastics in soil has been limited so far. Until now, microplastic analyses in soil require laborious sample cleanup and are mostly restricted to qualitative assessments. In this study, we applied thermogravimetry-mass spectrometry (TGA-MS) to develop a method for the direct quantitative analysis of poly(ethylene terephthalate) (PET) without further sample pretreatment. For this, soil samples containing 1.61 ± 0.15 wt % organic matter were spiked with 0.23-4.59 wt % PET bottle recyclate microplastics. dl-Cysteine was used as the internal standard (IS). Sample mixtures were pyrolyzed with a 5 K min ramp (40-1000 °C), while sample mass loss and MS signal intensity of typical PET pyrolysis products were recorded. We found MS signal intensities linearly responding to microplastic concentrations. The most-promising results were obtained with the IS-corrected PET pyrolysis product vinylbenzene/benzoic acid ( m/ z = 105, adj. R = 0.987). The limits of detection and quantification were 0.07 and 1.72 wt % PET, respectively. Our results suggest that TGA-MS can be an easy and viable complement to existing methods such as pyrolysis or thermogravimetry-thermal desorption assays followed by gas chromatography/mass spectrometry detection or to spectral microscopy techniques.
    Keywords: Microplastics ; Quantitative-Analysis ; Pyrolysis ; Terephthalate ; Soil-Pollution ; Soil-Analysis ; Ground-Samples ; Mass-Reduction ; Cysteine ; Benzoic-Acid ; Agricultural-Industry ; Fragment ; Organic-Medium ; Detection-Limit ; Thermogravimetric-Analysis ; Spectral-Technique ; Mikroplastik ; Quantitative Analyse ; Pyrolyse ; Terephthalat ; Bodenverschmutzung ; Bodenanalyse ; Bodenprobe ; Massenverringerung ; Cystein ; Benzoesäure ; Agrikultur ; Fragment ; Organisches Material ; Nachweisgrenze ; Thermogravimetrie ; Spektralverfahren ; Engineering ; Chemistry;
    ISSN: 00032700
    E-ISSN: 1520-6882
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  • 5
    Language: English
    In: The journal of physical chemistry. A, 30 March 2017, Vol.121(12), pp.2367-2376
    Description: Water molecules in soil organic matter (SOM) can form clusters bridging neighboring molecular segments (water molecule bridges, WaMBs). WaMBs are hypothesized to enhance the physical entrapment of organic chemicals and to control the rigidity of the SOM supramolecular structure. However, the understanding of WaMBs dynamics in SOM is still limited. We investigated the relation between WaMBs stability and the physicochemical properties of their environment by treating a sapric histosol with various solvents and organic chemicals. On the basis of predictions from molecular modeling, we hypothesized that the stability of WaMBs, measured by differential scanning calorimetry, increases with the decreasing ability of a chemical to interact with water molecules of the WaMBs. The interaction ability between WaMBs and the chemicals was characterized by linear solvation energy relationships. The WaMBs stability in solvent-treated samples was found to decrease with increasing ability of a solvent to undergo H-donor/acceptor interactions. Spiking with an organic chemical stabilized (naphthalene) or destabilized (phenol) the WaMBs. The WaMBs stability and matrix rigidity were generally reduced strongly and quickly when hydrophilic chemicals entered the soil. The physicochemical aging following this destabilization is slow but leads to successive WaMBs stabilization and matrix stiffening.
    Keywords: Humus – Research ; Organic Compounds – Chemical Properties ; Polar Molecules – Chemical Properties;
    ISSN: 10895639
    E-ISSN: 1520-5215
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  • 6
    Language: English
    In: Journal of agricultural and food chemistry, 26 February 2014, Vol.62(8), pp.1912-8
    Description: Poultry manure (PM) chars were obtained at different temperatures and charring times. Chemical-physical characterization of the different PM chars was conducted by cross-polarization magic angle spinning (CPMAS) (13)C NMR spectroscopy and thermal analysis. CPMAS (13)C NMR spectra showed that the chemical composition of PM char is dependent on production temperature rather than on production duration. Aromatic and alkyl domains in the PM chars obtained at the lowest temperatures remained unchanged at all heating times applied for their production. The PM char obtained at the highest temperature consisted only of aromatic structures having chemical nature that also appeared invariant with heating time. Thermogravimetry revealed differences in the thermo-oxidative stability of the aromatic domains in the different PM chars. The PM char produced at the highest temperature appeared less stable than those produced at the lowest temperatures. This difference was explained by a protective effect of the alkyl groups, which are still present in chars formed at lower temperature. The analysis of the chemical and physicochemical character of poultry manure chars produced at different temperatures can increase understanding of the role of these materials in the properties and behavior of char-amended soils.
    Keywords: Charcoal -- Chemistry ; Manure -- Analysis
    ISSN: 00218561
    E-ISSN: 1520-5118
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  • 7
    Language: English
    In: Journal of Thermal Analysis and Calorimetry, 2013, Vol.113(3), pp.1177-1185
    Description: The hydration of cellulose, chitosan, schizophyllan, hyaluronan, and carboxymethyl cellulose was studied using differential scanning calorimetry (DSC). In the first part, the classical freezing/thawing approach was used to determine the amount of non-freezing water. The inconsistency in enthalpies obtained during crystallization and melting of freezable water was discussed with respect to the DSC experimental conditions. Our interpretation questions the recent conclusions about competitive processes occurring during melting which are hypothesized to influence the determined melting enthalpy. In the second part, the hydration and drying were studied using the evaporation enthalpy of water. The dry mass normalized dependency of vaporization enthalpy on water content confirmed an abrupt break at low water content in hyaluronan sample which was attributed to the sudden appearance of a parallel process taking part during the drying. The rest of polysaccharide samples showed only a linear decrease in evaporation enthalpy. The renormalization of enthalpies by the water content revealed the increase in evaporation enthalpy with decreasing water content in most samples which was ascribed to the strong interaction between polysaccharide and water. The exceptions were carboxymethyl cellulose which showed a decrease in evaporation enthalpy. This indicates the existence of a simultaneous process occurring during drying, but unlike in hyaluronan, the processes do not appear abruptly but accompany the evaporation in the wide concentration range. Comparison of determined hydration numbers showed that part of non-freezing water in hyaluronan is not bound to sorption sites but occurs presumably in small temporary pores. In contrast, water-soluble schizophyllan forms temporary pores as well but presumably with higher dimension and the non-freezing water is formed mostly by water molecules interacting with sorption sites.
    Keywords: Melting and crystallization ; Evaporation ; Hydration ; Drying ; Hyaluronan ; Schizophyllan ; Chitosan ; Cellulose
    ISSN: 1388-6150
    E-ISSN: 1572-8943
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  • 8
    Language: English
    In: Journal of Thermal Analysis and Calorimetry, 2016, Vol.123(3), pp.2441-2450
    Description: Growing demands for sustainable land use challenges the management of soil organic matter (SOM). Research on SOM stabilization mechanisms during the last decades opened access to new approaches of SOM assessment. This study tried to empower this trend with a focus on the interrelations between soil components including clay, organic carbon and bound water toward a unifying assessment for practical land use. Soil samples from different regions of the world were collected, air-dried, sieved and equilibrated to 76 % relative humidity prior to analysis. Thermogravimetry was applied to search for a relationship between thermal mass losses corresponding to soil components and mass losses on ignition (MLI) between 110 and 550 °C. The results refer to a predictability of MLI from thermal mass losses in two 10 °C temperature steps (TML), which are both closely correlated with the content of clay and soil organic carbon (SOC), respectively. We found a relationship MLI = 10 × TML130–140 °C + 25 × TML320–330 °C − 2 with R 2  = 0.98, applicable for soils with a wide range of properties. Using previous results, this equation can be rewritten as SOC = 0.48 × MLI–0.12 × clay + 0.2, which is similar to previously published relationship. The application of equation to plots with varying fertilization in long-term field experiments revealed deviations, which could be explained by different amounts of biologically degradable, non-humified, fresh organic residues or similar organic admixtures. This assumption was tested by application to untouched by human activity soils before and after laboratory incubation. The microbiological decay of SOM in incubated samples led to significantly lower differences of calculated and measured MLI, confirming a decrease in the amount of fresh organic matter. We conclude that thermogravimetry is applicable to study interrelations between soil components and to assess soil organic carbon content and quality.
    Keywords: Soil organic carbon ; Soil organic matter ; Clay ; Mass loss on ignition ; Thermogravimetry ; Water ; Soil fertility
    ISSN: 1388-6150
    E-ISSN: 1588-2926
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  • 9
    Language: English
    In: Analytical and Bioanalytical Chemistry, 2010, Vol.397(7), pp.3023-3028
    Description: Fast field cycling (FFC) NMR relaxometry has been used to study the conformational properties of aqueous solutions of hyaluronan (HYA) at three concentrations in the range 10 to 25 mg mL –1 . Results revealed that, irrespective of the solution concentration, three different hydration layers surround hyaluronan. The inner layer consists of water molecules strongly retained in the proximity of the HYA surface. Because of their strong interactions with HYA, water molecules in this inner hydration layer are subject to very slow dynamics and have the largest correlation times. The other two hydration layers are made of water molecules which are located progressively further from the HYA surface. As a result, decreasing correlation times caused by faster molecular motion were measured. The NMRD profiles obtained by FFC-NMR relaxometry also showed peaks attributable to 1 H– 14 N quadrupole interactions. Changes in intensity and position of the quadrupolar peaks in the NMRD profiles suggested that with increasing concentration the amido group is progressively involved in the formation of weak and transient intramolecular water bridging adjacent hyaluronan chains. In this work, FFC-NMR was used for the first time to obtain deeper insight into HYA–water interactions and proved itself a powerful and promising tool in hyaluronan chemistry.
    Keywords: FFC-NMR ; Relaxometry ; Correlation time ; Quadrupole interactions ; Hydration layer
    ISSN: 1618-2642
    E-ISSN: 1618-2650
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  • 10
    Language: English
    In: Environmental science & technology, 01 March 2016, Vol.50(5), pp.2210-6
    Description: Knowledge of structural dynamics of dissolved organic matter (DOM) is of paramount importance for understanding DOM stability and role in the fate of solubilized organic and inorganic compounds (e.g., nutrients and pollutants), either in soils or aquatic systems. In this study, fast field cycling (FFC) (1)H NMR relaxometry was applied to elucidate structural dynamics of terrestrial DOM, represented by two structurally contrasting DOM models such as Suwanee River (SRFA) and Pahokee peat (PPFA) fulvic acids purchased by the International Humic Substance Society. Measurement of NMR relaxation rate of water protons in heating-cooling cycles revealed structural hysteresis in both fulvic acids. In particular, structural hysteresis was related to the delay in re-establishing water network around fulvic molecules as a result of temperature fluctuations. The experiments revealed that the structural temperature dependency and hysteresis were more pronounced in SRFA than in PPFA. This was attributed to the larger content of hydrogel-like structure in SRFA stabilized, at a larger extent, by H-bonds between carboxylic and phenolic groups. Moreover, results supported the view that terrestrial DOM consist of a hydrophobic rigid core surrounded by progressively assembling amphiphilic and polar molecules, which form an elastic structure that can mediate reactivity of the whole DOM.
    Keywords: Benzopyrans -- Chemistry ; Soil -- Chemistry ; Water -- Chemistry
    ISSN: 0013936X
    E-ISSN: 1520-5851
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