Stability of salts and complexes of humic acids

Základem práce je studium vlivu přítomnosti kovů inkorporovaných do struktury huminových látek při tepelné zátěži za přítomnosti vzdušného kyslíku. Pro tyto účely byla použita lignitická huminová kyselina, u které byl nejprve retitračně-vodivostní metodou stanoven počet vazných míst, tj. karboxylových skupin. Smícháním s roztoky sodných a měďnatých iontů byly získány koncové produkty s různými stupni nasycení zjištěných vazných míst. Pro zhodnocení termooxidační stability byla provedena termogravimetrická analýza a diferenční kompenzační kalorimetrie. Výsledky přinášejí nový pohled na reaktivitu huminové kyseliny s kovovými ionty v kapalné fázi, poukazují na možný vznik „porézní“ struktury sodných humátů a jejich schopnost retence vody.The ground of this work lies in the study of influence of metal ions incorporated onto the structure of humic substances during thermal stress in the presence of air oxygen. For these purposes, lignitic humic acid was used. The amount of binding sites, i.e. carboxylic groups, was determined by retitration-conductometric method. Mixing the humic acid with solutions of sodium and cupric ions gave the final products with different saturation degrees of detected binding sites. For the evaluation of thermooxidative stability, thermogravimetric analysis and differential scanning calorimetry were performed. The results bring new view upon the reactivity of humic acid with metal ions in the liquid state, indicate possible formation of “porous” structure of sodium humates and their water-retention ability.

Towards a radiocarbon chronology of the Late-Glacial: Sample selection strategies

This paper outlines a dating program designed to test the reproducibility of radiocarbon dates on different materials of Late-Glacial age (plant macrofossils, fossil beetle remains, and the "humic" and "humin" chemical fractions of limnic sediments) using a combination of radiometric (beta counting) and accelerator mass spectrometry (AMS) techniques. The results have implications for the design of sampling strategies and for the development of improved dating protocols, both of which are important if a high-precision C-14 chronology for the Late- Glacial is to be achieved

Study of Hydrophobic Domains in Humic Acids

Fyzikálně-chemická povaha hydrofobních domén huminových kyselin byla studována z několika hledisek. K objasnění významu fluorescenčních spekter byly vzorky podrobeny sekvenční frakcionaci, která pomohla k částečnému objasnění vlivu vodorozpustných složek, volných a vázaných lipidů na optické vlastnosti huminových kyselin. Výsledky naznačily, že fluorescenční píky tradičně přiřazované superpozici jednotlivých struktur jsou spíše důsledkem agregačních vlastností huminových molekul tvořících vlivem hydrofobního efektu zdánlivě vysoce aromatické struktury. Dále pak bylo zjištěno, že na optických vlastnostech huminových kyselin mají podíl i molekuly, které nemají primárně fluoroforní nebo chromoforní vlastnosti. Tento pohled je v souladu s teorií supramolekulárního uspořádání huminových kyselin. Dále byly studovány agregace, konformační chování a termodynamická stabilita huminových kyselin pomocí metody vysoce rozlišovací ultrazvukové spektroskopie. Bylo prokázáno, že huminové kyseliny mají schopnost agregovat už od velmi nízkých koncentrací (The nature of hydrophobic domains in humic acids was studied from different points of view. To shed light on the meaning of fluorescent spectra, the measured samples underwent the sequential extraction which partially revealed the role of water-soluble components, free and bond lipids in optical properties of humic acids. The results indicated that the fluorescence peaks traditionally attributed to the superposition of individual chemical structures are rather a result of aggregation properties of humic molecules and hydrophobic effect driving aromatic molecules together forming aggregates apparently large molecular weight. Further, it seems that there is a significant influence of non-fluorophores and non-chromophores on the optical properties of humic acids. Results are consistent with the theory on supramolecular structure of humic acids. Next, the aggregation, conformational behaviour and thermodynamic stability of humic acids were studied by high resolution ultrasonic spectroscopy. It was demonstrated that humic molecules are able to interact and form aggregates at very low concentration (

Experimental studies for the detection of protein in trace amounts

Organic cyanine dye for detection of protein in trace amounts - dye reaction mechanism, methods of eliminating inorganic compound reaction with dye, and detection of humic aci

Drivers and food web effects of Gonyostomum semen blooms

The flagellate Gonyostomum semen forms dense late-summer blooms in humic lakes and is a nuisance to swimmers because it forms a slimy coat on the skin, causing irritation in sensitive individuals. Increasing occurrence and bloom incidence of G. semen has been reported during recent decades, but it is not clear which factors affect the distribution and bloom formation of this alga. Large cell size, ejection of long, slimy threads (trichocysts), and nighttime migration to the hypolimnion may limit grazing on G. semen by herbivorous zooplankton, resulting in a decreased coupling between phytoplankton and higher trophic levels during blooms. The studies included in this thesis investigate which factors affect G. semen occurrence and bloom formation and how G. semen blooms affect the community composition and trophic interactions in boreal, humic lakes. The occurrence of G. semen has increased between 1995 and 2010, especially in southern Sweden. Bloom incidence and total biomass did not increase continually, but fluctuated among years and peaked in the middle of the study period. Temperature and length of the growing season affected the occurrence and, to a lesser extent, bloom formation of G. semen, but local factors such as pH and water colour were more important for bloom formation. More lakes may become suitable habitats with the ongoing increase in water colour and increasing temperatures may result in a more frequent occurrence and bloom formation of G. semen. Blooms resulted in a shift in zooplankton assemblages toward predominance by small cladocerans, which were not able to feed on G. semen but instead fed more on heterotrophic food resources, supporting the hypothesis of a reduced coupling between phytoplankton and zooplankton. Zooplankton assemblages predominated by small animals feeding on low-quality resources may reduce the food quality for planktivorous fish. Instead, the invertebrate predator C. flavicans appeared to benefit from G. semen blooms, as indicated by its high abundance in bloom-lakes. Calanoid copepods and a large cladoceran fed efficiently on G. semen in the laboratory, indicating that there is, however, some trophic coupling between G. semen and higher trophic levels. This supports the use of biomanipulation of fish communities for controlling G. semen blooms

Structural characterization of humic acids, extracted from sewage sludge during composting, by thermochemolysis–gas chromatography–mass spectrometry

Thermochemolysis coupled with gas chromatography and mass spectrometry were applied to determine the structure of humic acids (HA) extracted from a sewage sludge and straw mixture at different steps of composting. The HA extracted from sludge mixture released various compounds, such as mono-, di-, tri-methoxy (alkyl) benzene and (alkyl) benzoic acids, which originated from lignin like derivatives of phydroxyphenyl, guiaicyl and syringyl units. In addition, other aromatic non-lignin derived structures were found along with series of branched C15, linear C16, C18 fatty acid methyl esters. The follow-up of various lignin-derived units during composting shows a decrease in phydroxyphenyl type-compounds (C) after the stabilisation phase. In parallel the more oxidized units, derived from guaiacyl (G) and syringyl (S) units, corresponding mainly to methylated derivatives of cafeic acids, protocatechuic acids, gallic acids and aldehydes, significantly increased in comparison with the other aromatic structures. Various ratios commonly used as parameters to determine the degree of lignin decomposition during humification were followed to monitor the chemical structure changes of the HA extracted from sludge mixture during composting. In the present case, the S/G ratio did not present significant changes during composting. The acid/aldehyde ratio was supervised using the ratio of gallic acids to gallic aldehyde methylated derivatives and showed an increase from 0.73 to 2.13 after the stabilisation phase but a decrease to 0.93 at the end of composting. This evolution may be explained by the increase of acid-containing derivatives following the intense oxidation of lignin side-chains during the stabilisation phase. But, the decrease of the acid/aldehyde ratio during the maturation phase could be attributed to a decrease in acid units by polymerisation of benzoic acid type-compounds through ester/ether linkages. The follow up of six families of compounds of similar chemical structures during composting showed a decrease of lignin-type compounds C6–C3 and that C6–C1 units predominated in the humic acid isolated from end compost sludge. The fatty acid methyl esters showed an increase in the intermediate phase of composting probably originating from the activities and tissues of microorganisms, which are numerous during the process. The final decrease in the amount of fatty acids may be explained by the death of most of the microbial population at the end of composting typified by a low respiratory rate. The index of Shannon-Weaver (Ish) remained constant at about 3 in course of composting indicating the neoformation of HA from subunits of similar chemical nature. A similitude index (Sij, S0 i j) showed a split between 30 and 90 days of composting indicating a change in the rate of neoformation of HA after a stabilisation phase. Afterwards, the rate of HA neoformation varied linearly with the duration of composting

Nitrogen isotope analysis of ammonium and glycine

Stable isotope techniques can be used as a tool in nitrogen cycling studies of different ecosystems. The studies are based on measurement of the heavy (15N)- to- light (14N) isotopic ratios of nitrogen in different biospheric pools. Isotope ratio mass spectrometry (IRMS) is the most precise technique to use for analysis of nitrogen isotopic ratios. This thesis deals with the development of methods for compound-specific nitrogen isotope analysis of ammonium and glycine in aqueous solutions and soil extracts using Gas Chromatography - Combustion (GC-C) - IRMS. For ammonium, three different techniques were developed: equilibrium headspace analysis, solid phase microextraction (SPME) and the purge and trap (P & T) technique, which were all based on conversion of ammonium to ammonia with subsequent separation of ammonia for analysis. In the SPME and P & T approaches, custom-made absorbents were used for pre-concentration, followed by thermal desorption into the GC-C-IRMS system. For the equilibrium headspace technique, high precision measurements of the nitrogen isotopic ratio were obtained for concentrations above 420 mg N L-1. With further improvements and the use of suitable equipment, the method has the potential to be used for solutions containing ammonium in the low mg N L-1 range. The SPME technique increased the sensitivity by a factor of » 3 compared to the headspace technique, but was less precise. In addition, the NafionÒ material used for absorption showed a memory effect in the desorption step. With the P & T technique a large variation in the measured isotopic value was observed (using solutions containing 2 mg N L-1) which was due to a non-quantitative thermal desorption. However, with further improvements, the P & T technique has the potential to be used for samples containing below 1.0 µg N, which is a much lower amount than that possible with any method used today. A method for determination of the nitrogen isotopic ratio in free glycine in soil extracts was also developed. By a combination of sample pre-concentration and Isotope Dilution Mass Spectrometry (IDMS), it was possible to determine isotopic ratio in soil extracts with a glycine concentration of only 3 µM (0.042 mg N L-1). The precision obtained was sufficient for use with tracer studies and was higher by an order of magnitude than the precision obtained with conventional GC-MS

Forecasting wind speed data by using a combination of ARIMA model with single exponential smoothing

Wind serves as natural resources as the solution to minimize global warming and has been commonly used to produce electricity. Because of their uncontrollable wind characteristics, wind speed forecasting is considered one of the best challenges in developing power generation. The Autoregressive Integrated Moving Average (ARIMA), Simple Exponential Smoothing (SES) and a hybrid model combination of ARIMA and SES will be used in this study to predict the wind speed. The mean absolute percentage error (MAPE) and the root mean square error (RMSE) are used as measurement of efficiency. The hybrid model provides a positive outcome for predicting wind speed compare to the single model of ARIMA and SES

Immobilization of lectin preparations from Moringa oleifera seeds in inert supports for water purification

Humic acids are linked to the formation of carcinogenic disinfection by-products upon chlorination of drinking water. In this work the first focus was tocharacterize the affinity of protein preparations obtained from Moringa oleifera seeds (extract, E, fraction, 0-60F and M.oleifera lectin, MoL) to bind humic acids. The second focus was to select a suitable support to immobilize MoL and to assess humic acid removal from water in a packed bed column. Specific hemagglutinating activity (SHA) decreased by 94 % for both E and MoL and by 50 % for 0-60F in the presence of a commercial humic acid. Humic acid-MoL precipitation bands were observed in the diffusion gel. Both results indicate humic acid-lectin binding. Carbohydrates, potassium and calcium ions as well as pH va-lues affected the SHA of MoL. Ahumic acid removal of 30.4 mg/g (expressed as mass of humic acid per mass of support) was obtained in a column packed with sepharose immobilized MoL receiving a 20 mg/L of carbon humic acid solution

Sorption of Aldrich Humic Acids onto Hematite: Insights into Fractionation Phenomena by Electrospray Ionization with Quadrupole Time-of-Flight Mass Spectrometry

International audienceSorption induced fractionation of purified Aldrich humic acid (PAHA) on hematite is studied through the modification of electrospray ionization (ESI)quadrupole time-of-flight (QToF) mass spectra of supernatants from retention experiments. The ESI mass spectra show an increase of the “mean molecular masses” of the molecules that constitutes humic aggregates. The low molecular weight fraction (LMWF; m/z ≤ 600 Da) is preferentially sorbed compared to two other fractions. The resolution provided by ESI-QToF mass spectrometer in the low-mass range provided evidence of further fractionation induced by sorption within the LMWF. Among the two latter fractions, the high molecular weight fraction (HMWF; m/z ≈ 1700 Da) seems to be more prone to sorption compared to the intermediate molecular weight fraction (IMWF; m/z ≈ 900 Da). The IMWF seems to be more hydrophilic as it should be richer in O, N and alkyl C from the proportion of even mass, and poorer in aromatic structures from mass defect analysis in ESI mass spectra