Jiri Kucerik - Profile on Academia.edu (original) (raw)
Papers by Jiri Kucerik
Characterization of lignin monomers in low rank coal humic acids using the derivatization/reductive cleavage method
Organic Geochemistry, 2010
Traditional CuO oxidation and thermochemolysis with tetramethylammonium hydroxide are the two mai... more Traditional CuO oxidation and thermochemolysis with tetramethylammonium hydroxide are the two main methods for lignin characterization in gymnosperm wood, and in soils and sediments formed from degraded gymnosperm wood, or for assessing the supply of terrestrial organic matter to marine sediments. In some cases, the overall lignin yield and the compound ratios used as plant source proxies have been found
Structure and properties of humic and fulvic acids. I. Properties and reactivity of humic acids and fulvic acids
Journal of Polymer Materials
The aim of this part is to characterize of HA and FA on the basis of their ability to form comple... more The aim of this part is to characterize of HA and FA on the basis of their ability to form complexes with inorganic and organic molecules capable to cause the effect of crosslinking. The characterization and properties of HA and FA and differences between these two groups of compounds were summarized. Their reactivity with transition elements was investigated by EPR spectroscopy. The properties of HA and FA in more details were studied by FTIR spectroscopy. With aid of semiempirical version of INDO method parameterized for compounds of transition elements the interaction energies were calculated. Obtained results were discussed and compared.
Practical application of thermogravimetry in soil science
Journal of Thermal Analysis and Calorimetry, 2013
ABSTRACT Soil samples collected in South America, North America and West Siberia were measured by... more ABSTRACT 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.
Land use effects on carbon quality and soil biological properties in Eutric Cambisol
Acta Agriculturae Scandinavica, Section B - Soil & Plant Science, 2011
The choice of prospective type of farming requires knowledge about the specific relationships tha... more The choice of prospective type of farming requires knowledge about the specific relationships that exist between farm management practices and base environmental conditions. Nowadays the protection of soil organic carbon is one of the main tasks, because organic carbon in addition to soil fertility can act in elimination of soil contamination and carbon sequestration. Field experiments were focused on the
Journal of Thermal Analysis and Calorimetry, 2007
Humic acids represent a complicated mixture of miscellaneous molecules formed as a product of mos... more Humic acids represent a complicated mixture of miscellaneous molecules formed as a product of mostly microbial degradation of dead plant tissues and animal bodies. In this work, lignite humic acids were enriched by model compounds and the model-free method suggested by imon was used to evaluate their stability over the whole range of conversions during the first thermooxidative degradation step. The kinetic parameters obtained were used to predict the stability at 20 and 180°C, respectively, which served for the recognition of processes induced by heat and those naturally occurring at lower temperatures. Comparison of the conversion times brought a partial insight into the kinetics and consequently into the role of individual compounds in the thermooxidative degradation/stability of the secondary structure of humic acids. It has been demonstrated that aromatic compounds added to humic acids, except pyridine, increased stability of humic acids and intermediate chars. The same conclusion can be drawn for acetic and palmitic acids. Addition of glucose or ethanol decreased the overall humic stability; however, the char of the former showed the highest stability after 40% of degradation.
Journal of Thermal Analysis and Calorimetry, 2006
The thermal and thermooxidative behavior of sodium salt of hyaluronic acid (HA) and its n-hexyl, ... more The thermal and thermooxidative behavior of sodium salt of hyaluronic acid (HA) and its n-hexyl, n-decyl, n-tetradecyl and n-hexadecyl ether derivatives having an equal degree of substitution have been studied by means of differential scanning calorimetry (DSC) and thermogravimetry (TG). Derivatives were prepared by a substitution of H atom at the OH bound to the sixth C of N-acetyl-D-glucosamin of HA unit by n-hexyl, n-decyl, n-tetradecyl and n-hexadecyl chains. Both thermal and thermooxidative degradation of HA and derivatives resulted in multistep process. The main interest of this work was focused on processes occurring in the course of the first decomposition step. Experimental DSC data showed lower stability of derivatives and, remarkably lower heat evolution in comparison with original HA. On the other hand, TG measurement recorded lower mass loss for derivates which indicated appearance of new types of crosslinking reactions. Oxidative stability was evaluated by means of DSC that provided the induction period and the protection factor determination. Derivates showed remarkably lower stability in comparison with original HA; comparing each other, the highest oxidation stability showed n-decyl and n-tetradecyl derivates.
The role of various compounds in humic acids stability studied by TG and DTA
Journal of Thermal Analysis and Calorimetry, 2006
Simultaneous DTA/TG technique has been used to study the influence of various model compounds (ar... more Simultaneous DTA/TG technique has been used to study the influence of various model compounds (aromatics, organic acids, alkanes, ketone, heterocyclic and sterole) on the thermo-oxidative behavior of lignite humic acids. As a measure of stability the shift of the onset temperature of the exothermic degradation peak has been used. Further, the ratio of mass loss recorded in the high and
Correlation of humic substances chemical properties and their thermo-oxidative degradation kinetics
Journal of Thermal Analysis and Calorimetry, 2009
Application of the Arrhenius equation as the temperature function in modeling of the degradation ... more Application of the Arrhenius equation as the temperature function in modeling of the degradation kinetics of humic substances brought a high positive Pearson correlation coefficient with the carbon content and a reasonable negative correlation with the oxygen content. Ratio C/H indicating the aromaticity degree of humic samples did not show any significant correlation. Relatively high value of correlation coefficients provided also O + N and ratios C/(O + N) and C/O, respectively. In contrast, H, N content and natural and heat generated free radical content and their ratio gave substantially lower correlation coefficients. The latter indicates that free radicals are probably not the main reason of the collapse of the secondary structure of humic substances leading to their degradation.
Journal of Thermal Analysis and Calorimetry, 2000
Differential scanning calorimetry (DSC) and thermogravimetry (TG) studies of humic acids (HA) seq... more Differential scanning calorimetry (DSC) and thermogravimetry (TG) studies of humic acids (HA) sequentially extracted at pH 7, 8, 9 and 10 by phosphate and pyrophosphate buffers have been carried out. Supplement information were provided by elementary analysis and FTIR spectroscopy to characterize and evaluate in details the thermooxidative behavior of HA fractions. The exothermic DSC profiles of the HA samples extracted by phosphate buffers or by pyrophosphates were shifted to lower temperatures in comparison with the original sample and showed narrow distribution of humic molecules. Experimental data showed dependency of HA fraction composition on the pH used during extraction. DSC experimental data showed 1 endothermic and from 2-5 exothermic peaks associated with mass loss recorded by TG measurement. Higher degree of aliphaticity observed on samples extracted at lower pH did not remarkably affect the DSC peak temperature of the first decomposition step associated with aliphatic moieties and functional groups decomposition and recombination reactions. On the other hand, such dependency was observed in higher temperature range where destruction of aromatic structures took part. The behavior of HA samples (even after separation of specific fractions) showed high complexity of system, which resulted in complicated physical and chemical processes occurred during thermooxidation. Observed stability and released heat were affected by many factors, among them evaporation of volatile part of humic matter and a slight contribution of weak interactions among humic molecules were considered.
Poultry manure (PM) chars were obtained at different temperatures and charring times. Chemical−ph... more 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) 13C NMR
spectroscopy and thermal analysis. CPMAS 13C 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.
Interactions between cations and natural organic matter (NOM) are central for the stability of or... more Interactions between cations and natural organic matter (NOM) are central for the stability of organic matter, formation of supramolecular NOM structure, formation of organo-mineral associations, soil aggregation and binding of organic contaminants. The effect of multivalent cations on environmental functionalities of NOM strongly depends on the relative importance between intramolecular complexation and intermolecular cross-linking, the degree of which will be determined by the spatial arrangement of the hydrophilic functional groups in NOM. This literature review seeks to evaluate the current state of the art regarding the relevance of intermolecular crosslinks via bridges of multivalent cations. Cross-linking has been suggested to explain among others aggregate stability, retarded dissolved organic matter release, reduced organic matter (OM) solubility as well as increase in degree and nonlinearity of sorption or organic chemicals to NOM. Although the crosslinking mechanism has been suggested in numerous studies, it has not yet been verified directly. The dynamics of the intermolecular cross-links, their persistence as well as their interplay with OM and their influence on stability and bioavailability of organic chemicals is up to now unknown. The major challenge in this context is the development of a suitable combination of experimental and instrumental techniques and relating the results to molecular and physicochemical models on the basis of targeted combination of spectroscopic, molecular modelling and thermoanalytical methods.
Solid state nuclear magnetic resonance spectroscopy in the evaluation of soil organic matter changes following thermal variations
Soil organic matter (SOM) is an ubiquitous, complex material which is produced by the degradation... more Soil organic matter (SOM) is an ubiquitous, complex material which is produced by the degradation of plant tissues and animal bodies. It is the major indicator of soil quality since it is directly involved in the maintenance of soil fertility, prevention of erosion and desert encroachment and provision of suitable environment for biological activity. Organic matter is an important driving
Solid state NMR spectroscopy in the evaluation of the conformational changes of humic substances as affected by thermal variations
Soil organic matter (SOM) is an ubiquitous, complex material which is produced by the degradation... more Soil organic matter (SOM) is an ubiquitous, complex material which is produced by the degradation of plant tissues and animal bodies. It is the major indicator of soil quality since it is directly involved in the maintenance of soil fertility, prevention of erosion and desert encroachment and provision of suitable environment for biological activity. Organic matter is an important driving
SURFACE AND SOLUTION BEHAVIOR OF SURFACTANTS PRODUCED FROM LIGNITE HUMIC ACIDS
Fresenius Environmental Bulletin
Analytical and physical-chemical techniques, such as elemental analysis, FTIR, surface tension (S... more Analytical and physical-chemical techniques, such as elemental analysis, FTIR, surface tension (ST) measurement, high performance size exclusion chromatography (HPSEC) and high resolution ultrasonic spectroscopy (HRUS) were combined in order to assess the surface activity of lignite sodium humic acids salts (humates). Humates were obtained from parental and modified South Moravian lignite pre-treated either by oxidation or by small organic acids. It was shown that unlike common surfactants, humates dissolved in water do not exhibit the critical micelle concentration and form micelle-like aggregates also in diluted solutions. As revealed by HRUS, the aggregation and/or reconformation of humic aggregates in solution takes up to ten minutes; in contrast, the ST measurements showed long-term stabilization associated with a slow decrease in ST of the solution. Correlation with results of HPSEC indicated that the surface activity of lignite humates is caused predominantly by aggregates wi...
SpringerPlus, 2014
The positive effect of humic acids on the growth of plant roots is well known, however, the mecha... more The positive effect of humic acids on the growth of plant roots is well known, however, the mechanisms and role of their physical structure in these processes have not been fully explained yet. In this work, South-Moravian lignite was oxidized by means of nitric acid and hydrogen peroxide to produce a set of regenerated humic acids. The elemental composition, solid state stability and solution characteristics were determined and correlated in vitro with their biological activity. A modified hydroponic method was applied to determine the effects of their potassium salts on Zea mays seedlings roots with respect to the plant weight, root length, root division, and starch and protein content. The relations between the determined parameters were evaluated through Principal Component Analysis and Pearson's correlation coefficients. The results indicated that the most important factor determining the biological activity of South-Moravian lignite potassium humates is related to the nature of self-assemblies, while the chemical composition had no direct connection with the root growth of Zea mays seedlings. It was demonstrated a controlled processing that provided humic substances with different chemical and physicochemical properties and variable biological activity.
Dynamics of water solutions of natural polysaccharides by fast field cycling nmr relaxometry
Cryobiology studies the effect of low temperatures on living systems such as microorganisms and p... more Cryobiology studies the effect of low temperatures on living systems such as microorganisms and plants. In particular, plants growing in cold or frozen environments can survive such extreme conditions due to the cold hardening process. Hardening is a three step process during which, first, translocation of polysaccharides to the plant roots affects water structure in the cell-soil surface. For this
International Journal of Pharmaceutics, 2014
Physical and chemical structure of paclitaxel (PTX) was studied after its incorporation into poly... more Physical and chemical structure of paclitaxel (PTX) was studied after its incorporation into polymeric micelles made of hyaluronic acid (HA) (M w = 15 kDa) grafted with C6 or C18:1 acyl chains. PTX was physically incorporated into the micellar core by solvent evaporation technique. Maximum loading capacity for HAC6 and HAC18:1 was determined to be 2 and 14 wt.%, respectively. The loading efficiency was higher for HAC18:1 and reached 70%. Independently of the derivative, loaded HA micelles had spherical size of approximately 60-80 nm and demonstrated slow and sustained release of PTX in vitro. PTX largely changed its form from crystalline to amorphous after its incorporation into the micelle's interior. This transformation increased PTX sensitivity towards stressing conditions, mainly to UV light exposure, during which the structure of amorphous PTX isomerized and formed C3À ÀC11 bond within its structure. In vitro cytotoxicity assay revealed that polymeric micelles loaded with PTX isomer had higher cytotoxic effect to normal human dermal fibroblasts (NHDF) and human colon carcinoma cells (HCT-116) than the same micelles loaded with non-isomerized PTX. Further observation indicated that PTX isomer influenced in different ways cell morphology and markers of cell cycle. Taken together, PTX isomer loaded in nanocarrier systems may have improved anticancer activity in vivo than pure PTX.
Organic Geochemistry, 2007
The potential of high resolution ultrasonic analysis (HRUS) in humic acid colloidal properties re... more The potential of high resolution ultrasonic analysis (HRUS) in humic acid colloidal properties research has been demonstrated. Sodium salts of humic acids from soil and lignite showed similar behaviour, supporting the hypothesis that, at both neutral and alkaline pH, they aggregate from very low concentration. The same conclusion can be reached for solutions at high ionic strength. We tried to
Lignite pre-treatment and its effect on bio-stimulative properties of respective lignite humic acids
Soil Biology & Biochemistry, 2009
Humic acids originating from South-Moravian lignite were subjected to a comparative study with th... more Humic acids originating from South-Moravian lignite were subjected to a comparative study with the aim to assess the alteration of their physico-chemical properties after various lignite pre-treatments. Physical modification was achieved with two organic acids, such as acetic acid and citric acid and chemical modification by nitric acid and hydrogene peroxide in various concentrations. Elemental analysis, solid-state NMR, GC–MS analysis
Thermochimica Acta, 2011
The processes of hyaluronan (HYA) drying and hydration were studied using differential scanning c... more The processes of hyaluronan (HYA) drying and hydration were studied using differential scanning calorimetry. In the first approach the isoconversional Kissinger-Akahita-Sunose (KAS) method was applied in order to determine actual activation energies of evaporation of pure water and water from concentrated HYA solutions. Since the evaporation is a single-step process, the activation energies for pure water provided results consistent with tabulated values of evaporation enthalpies. In the course of water evaporation from hyaluronan solution a break in increasing enthalpy followed by a decrease below 0.34 g of water per 1 g of HYA was observed. This result confirmed earlier observation that at this particular water content evaporation from hyaluronan is compensated by heat evolution associated with the formation of new bonds in hyaluronan supramolecular structure. Subtraction of water evaporation enthalpy from enthalpies obtained for HYA concentrated solution provided a possibility to extrapolate the evaporation enthalpies to the concentration (approximately 2 g of water per 1 g of HYA) at which free water is not present any longer and only bound water starts being evaporated from the HYA solution. Similar results were obtained in the second approach in which using slightly modified "traditional" freezing/thawing experiment, melting enthalpy of ice was plotted against water fraction in HYA. It was found out that the melting enthalpy of ice exponentially increases from 0.8 up to 2 g of water per g of hyaluronan where it reaches and keeps the melting enthalpy of hexagonal ice. It was shown that both approaches can serve as alternatives providing an additional insight into the state of water and biopolymers in highly concentrated solutions.
Characterization of lignin monomers in low rank coal humic acids using the derivatization/reductive cleavage method
Organic Geochemistry, 2010
Traditional CuO oxidation and thermochemolysis with tetramethylammonium hydroxide are the two mai... more Traditional CuO oxidation and thermochemolysis with tetramethylammonium hydroxide are the two main methods for lignin characterization in gymnosperm wood, and in soils and sediments formed from degraded gymnosperm wood, or for assessing the supply of terrestrial organic matter to marine sediments. In some cases, the overall lignin yield and the compound ratios used as plant source proxies have been found
Structure and properties of humic and fulvic acids. I. Properties and reactivity of humic acids and fulvic acids
Journal of Polymer Materials
The aim of this part is to characterize of HA and FA on the basis of their ability to form comple... more The aim of this part is to characterize of HA and FA on the basis of their ability to form complexes with inorganic and organic molecules capable to cause the effect of crosslinking. The characterization and properties of HA and FA and differences between these two groups of compounds were summarized. Their reactivity with transition elements was investigated by EPR spectroscopy. The properties of HA and FA in more details were studied by FTIR spectroscopy. With aid of semiempirical version of INDO method parameterized for compounds of transition elements the interaction energies were calculated. Obtained results were discussed and compared.
Practical application of thermogravimetry in soil science
Journal of Thermal Analysis and Calorimetry, 2013
ABSTRACT Soil samples collected in South America, North America and West Siberia were measured by... more ABSTRACT 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.
Land use effects on carbon quality and soil biological properties in Eutric Cambisol
Acta Agriculturae Scandinavica, Section B - Soil & Plant Science, 2011
The choice of prospective type of farming requires knowledge about the specific relationships tha... more The choice of prospective type of farming requires knowledge about the specific relationships that exist between farm management practices and base environmental conditions. Nowadays the protection of soil organic carbon is one of the main tasks, because organic carbon in addition to soil fertility can act in elimination of soil contamination and carbon sequestration. Field experiments were focused on the
Journal of Thermal Analysis and Calorimetry, 2007
Humic acids represent a complicated mixture of miscellaneous molecules formed as a product of mos... more Humic acids represent a complicated mixture of miscellaneous molecules formed as a product of mostly microbial degradation of dead plant tissues and animal bodies. In this work, lignite humic acids were enriched by model compounds and the model-free method suggested by imon was used to evaluate their stability over the whole range of conversions during the first thermooxidative degradation step. The kinetic parameters obtained were used to predict the stability at 20 and 180°C, respectively, which served for the recognition of processes induced by heat and those naturally occurring at lower temperatures. Comparison of the conversion times brought a partial insight into the kinetics and consequently into the role of individual compounds in the thermooxidative degradation/stability of the secondary structure of humic acids. It has been demonstrated that aromatic compounds added to humic acids, except pyridine, increased stability of humic acids and intermediate chars. The same conclusion can be drawn for acetic and palmitic acids. Addition of glucose or ethanol decreased the overall humic stability; however, the char of the former showed the highest stability after 40% of degradation.
Journal of Thermal Analysis and Calorimetry, 2006
The thermal and thermooxidative behavior of sodium salt of hyaluronic acid (HA) and its n-hexyl, ... more The thermal and thermooxidative behavior of sodium salt of hyaluronic acid (HA) and its n-hexyl, n-decyl, n-tetradecyl and n-hexadecyl ether derivatives having an equal degree of substitution have been studied by means of differential scanning calorimetry (DSC) and thermogravimetry (TG). Derivatives were prepared by a substitution of H atom at the OH bound to the sixth C of N-acetyl-D-glucosamin of HA unit by n-hexyl, n-decyl, n-tetradecyl and n-hexadecyl chains. Both thermal and thermooxidative degradation of HA and derivatives resulted in multistep process. The main interest of this work was focused on processes occurring in the course of the first decomposition step. Experimental DSC data showed lower stability of derivatives and, remarkably lower heat evolution in comparison with original HA. On the other hand, TG measurement recorded lower mass loss for derivates which indicated appearance of new types of crosslinking reactions. Oxidative stability was evaluated by means of DSC that provided the induction period and the protection factor determination. Derivates showed remarkably lower stability in comparison with original HA; comparing each other, the highest oxidation stability showed n-decyl and n-tetradecyl derivates.
The role of various compounds in humic acids stability studied by TG and DTA
Journal of Thermal Analysis and Calorimetry, 2006
Simultaneous DTA/TG technique has been used to study the influence of various model compounds (ar... more Simultaneous DTA/TG technique has been used to study the influence of various model compounds (aromatics, organic acids, alkanes, ketone, heterocyclic and sterole) on the thermo-oxidative behavior of lignite humic acids. As a measure of stability the shift of the onset temperature of the exothermic degradation peak has been used. Further, the ratio of mass loss recorded in the high and
Correlation of humic substances chemical properties and their thermo-oxidative degradation kinetics
Journal of Thermal Analysis and Calorimetry, 2009
Application of the Arrhenius equation as the temperature function in modeling of the degradation ... more Application of the Arrhenius equation as the temperature function in modeling of the degradation kinetics of humic substances brought a high positive Pearson correlation coefficient with the carbon content and a reasonable negative correlation with the oxygen content. Ratio C/H indicating the aromaticity degree of humic samples did not show any significant correlation. Relatively high value of correlation coefficients provided also O + N and ratios C/(O + N) and C/O, respectively. In contrast, H, N content and natural and heat generated free radical content and their ratio gave substantially lower correlation coefficients. The latter indicates that free radicals are probably not the main reason of the collapse of the secondary structure of humic substances leading to their degradation.
Journal of Thermal Analysis and Calorimetry, 2000
Differential scanning calorimetry (DSC) and thermogravimetry (TG) studies of humic acids (HA) seq... more Differential scanning calorimetry (DSC) and thermogravimetry (TG) studies of humic acids (HA) sequentially extracted at pH 7, 8, 9 and 10 by phosphate and pyrophosphate buffers have been carried out. Supplement information were provided by elementary analysis and FTIR spectroscopy to characterize and evaluate in details the thermooxidative behavior of HA fractions. The exothermic DSC profiles of the HA samples extracted by phosphate buffers or by pyrophosphates were shifted to lower temperatures in comparison with the original sample and showed narrow distribution of humic molecules. Experimental data showed dependency of HA fraction composition on the pH used during extraction. DSC experimental data showed 1 endothermic and from 2-5 exothermic peaks associated with mass loss recorded by TG measurement. Higher degree of aliphaticity observed on samples extracted at lower pH did not remarkably affect the DSC peak temperature of the first decomposition step associated with aliphatic moieties and functional groups decomposition and recombination reactions. On the other hand, such dependency was observed in higher temperature range where destruction of aromatic structures took part. The behavior of HA samples (even after separation of specific fractions) showed high complexity of system, which resulted in complicated physical and chemical processes occurred during thermooxidation. Observed stability and released heat were affected by many factors, among them evaporation of volatile part of humic matter and a slight contribution of weak interactions among humic molecules were considered.
Poultry manure (PM) chars were obtained at different temperatures and charring times. Chemical−ph... more 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) 13C NMR
spectroscopy and thermal analysis. CPMAS 13C 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.
Interactions between cations and natural organic matter (NOM) are central for the stability of or... more Interactions between cations and natural organic matter (NOM) are central for the stability of organic matter, formation of supramolecular NOM structure, formation of organo-mineral associations, soil aggregation and binding of organic contaminants. The effect of multivalent cations on environmental functionalities of NOM strongly depends on the relative importance between intramolecular complexation and intermolecular cross-linking, the degree of which will be determined by the spatial arrangement of the hydrophilic functional groups in NOM. This literature review seeks to evaluate the current state of the art regarding the relevance of intermolecular crosslinks via bridges of multivalent cations. Cross-linking has been suggested to explain among others aggregate stability, retarded dissolved organic matter release, reduced organic matter (OM) solubility as well as increase in degree and nonlinearity of sorption or organic chemicals to NOM. Although the crosslinking mechanism has been suggested in numerous studies, it has not yet been verified directly. The dynamics of the intermolecular cross-links, their persistence as well as their interplay with OM and their influence on stability and bioavailability of organic chemicals is up to now unknown. The major challenge in this context is the development of a suitable combination of experimental and instrumental techniques and relating the results to molecular and physicochemical models on the basis of targeted combination of spectroscopic, molecular modelling and thermoanalytical methods.
Solid state nuclear magnetic resonance spectroscopy in the evaluation of soil organic matter changes following thermal variations
Soil organic matter (SOM) is an ubiquitous, complex material which is produced by the degradation... more Soil organic matter (SOM) is an ubiquitous, complex material which is produced by the degradation of plant tissues and animal bodies. It is the major indicator of soil quality since it is directly involved in the maintenance of soil fertility, prevention of erosion and desert encroachment and provision of suitable environment for biological activity. Organic matter is an important driving
Solid state NMR spectroscopy in the evaluation of the conformational changes of humic substances as affected by thermal variations
Soil organic matter (SOM) is an ubiquitous, complex material which is produced by the degradation... more Soil organic matter (SOM) is an ubiquitous, complex material which is produced by the degradation of plant tissues and animal bodies. It is the major indicator of soil quality since it is directly involved in the maintenance of soil fertility, prevention of erosion and desert encroachment and provision of suitable environment for biological activity. Organic matter is an important driving
SURFACE AND SOLUTION BEHAVIOR OF SURFACTANTS PRODUCED FROM LIGNITE HUMIC ACIDS
Fresenius Environmental Bulletin
Analytical and physical-chemical techniques, such as elemental analysis, FTIR, surface tension (S... more Analytical and physical-chemical techniques, such as elemental analysis, FTIR, surface tension (ST) measurement, high performance size exclusion chromatography (HPSEC) and high resolution ultrasonic spectroscopy (HRUS) were combined in order to assess the surface activity of lignite sodium humic acids salts (humates). Humates were obtained from parental and modified South Moravian lignite pre-treated either by oxidation or by small organic acids. It was shown that unlike common surfactants, humates dissolved in water do not exhibit the critical micelle concentration and form micelle-like aggregates also in diluted solutions. As revealed by HRUS, the aggregation and/or reconformation of humic aggregates in solution takes up to ten minutes; in contrast, the ST measurements showed long-term stabilization associated with a slow decrease in ST of the solution. Correlation with results of HPSEC indicated that the surface activity of lignite humates is caused predominantly by aggregates wi...
SpringerPlus, 2014
The positive effect of humic acids on the growth of plant roots is well known, however, the mecha... more The positive effect of humic acids on the growth of plant roots is well known, however, the mechanisms and role of their physical structure in these processes have not been fully explained yet. In this work, South-Moravian lignite was oxidized by means of nitric acid and hydrogen peroxide to produce a set of regenerated humic acids. The elemental composition, solid state stability and solution characteristics were determined and correlated in vitro with their biological activity. A modified hydroponic method was applied to determine the effects of their potassium salts on Zea mays seedlings roots with respect to the plant weight, root length, root division, and starch and protein content. The relations between the determined parameters were evaluated through Principal Component Analysis and Pearson's correlation coefficients. The results indicated that the most important factor determining the biological activity of South-Moravian lignite potassium humates is related to the nature of self-assemblies, while the chemical composition had no direct connection with the root growth of Zea mays seedlings. It was demonstrated a controlled processing that provided humic substances with different chemical and physicochemical properties and variable biological activity.
Dynamics of water solutions of natural polysaccharides by fast field cycling nmr relaxometry
Cryobiology studies the effect of low temperatures on living systems such as microorganisms and p... more Cryobiology studies the effect of low temperatures on living systems such as microorganisms and plants. In particular, plants growing in cold or frozen environments can survive such extreme conditions due to the cold hardening process. Hardening is a three step process during which, first, translocation of polysaccharides to the plant roots affects water structure in the cell-soil surface. For this
International Journal of Pharmaceutics, 2014
Physical and chemical structure of paclitaxel (PTX) was studied after its incorporation into poly... more Physical and chemical structure of paclitaxel (PTX) was studied after its incorporation into polymeric micelles made of hyaluronic acid (HA) (M w = 15 kDa) grafted with C6 or C18:1 acyl chains. PTX was physically incorporated into the micellar core by solvent evaporation technique. Maximum loading capacity for HAC6 and HAC18:1 was determined to be 2 and 14 wt.%, respectively. The loading efficiency was higher for HAC18:1 and reached 70%. Independently of the derivative, loaded HA micelles had spherical size of approximately 60-80 nm and demonstrated slow and sustained release of PTX in vitro. PTX largely changed its form from crystalline to amorphous after its incorporation into the micelle's interior. This transformation increased PTX sensitivity towards stressing conditions, mainly to UV light exposure, during which the structure of amorphous PTX isomerized and formed C3À ÀC11 bond within its structure. In vitro cytotoxicity assay revealed that polymeric micelles loaded with PTX isomer had higher cytotoxic effect to normal human dermal fibroblasts (NHDF) and human colon carcinoma cells (HCT-116) than the same micelles loaded with non-isomerized PTX. Further observation indicated that PTX isomer influenced in different ways cell morphology and markers of cell cycle. Taken together, PTX isomer loaded in nanocarrier systems may have improved anticancer activity in vivo than pure PTX.
Organic Geochemistry, 2007
The potential of high resolution ultrasonic analysis (HRUS) in humic acid colloidal properties re... more The potential of high resolution ultrasonic analysis (HRUS) in humic acid colloidal properties research has been demonstrated. Sodium salts of humic acids from soil and lignite showed similar behaviour, supporting the hypothesis that, at both neutral and alkaline pH, they aggregate from very low concentration. The same conclusion can be reached for solutions at high ionic strength. We tried to
Lignite pre-treatment and its effect on bio-stimulative properties of respective lignite humic acids
Soil Biology & Biochemistry, 2009
Humic acids originating from South-Moravian lignite were subjected to a comparative study with th... more Humic acids originating from South-Moravian lignite were subjected to a comparative study with the aim to assess the alteration of their physico-chemical properties after various lignite pre-treatments. Physical modification was achieved with two organic acids, such as acetic acid and citric acid and chemical modification by nitric acid and hydrogene peroxide in various concentrations. Elemental analysis, solid-state NMR, GC–MS analysis
Thermochimica Acta, 2011
The processes of hyaluronan (HYA) drying and hydration were studied using differential scanning c... more The processes of hyaluronan (HYA) drying and hydration were studied using differential scanning calorimetry. In the first approach the isoconversional Kissinger-Akahita-Sunose (KAS) method was applied in order to determine actual activation energies of evaporation of pure water and water from concentrated HYA solutions. Since the evaporation is a single-step process, the activation energies for pure water provided results consistent with tabulated values of evaporation enthalpies. In the course of water evaporation from hyaluronan solution a break in increasing enthalpy followed by a decrease below 0.34 g of water per 1 g of HYA was observed. This result confirmed earlier observation that at this particular water content evaporation from hyaluronan is compensated by heat evolution associated with the formation of new bonds in hyaluronan supramolecular structure. Subtraction of water evaporation enthalpy from enthalpies obtained for HYA concentrated solution provided a possibility to extrapolate the evaporation enthalpies to the concentration (approximately 2 g of water per 1 g of HYA) at which free water is not present any longer and only bound water starts being evaporated from the HYA solution. Similar results were obtained in the second approach in which using slightly modified "traditional" freezing/thawing experiment, melting enthalpy of ice was plotted against water fraction in HYA. It was found out that the melting enthalpy of ice exponentially increases from 0.8 up to 2 g of water per g of hyaluronan where it reaches and keeps the melting enthalpy of hexagonal ice. It was shown that both approaches can serve as alternatives providing an additional insight into the state of water and biopolymers in highly concentrated solutions.