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Sirvi Autor "Krumins, J." järgi

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  • Pisipilt
    Kirje
    A comparative study of the properties of industrially produced humic substances
    (2020) Klavins, M.; Upska, K.; Viksna, A.; Bertins, M.; Ansone-Bertina, L.; Krumins, J.
    Humic substances (HSs) are produced industrially in large quantities from low rank coal, weathered coal, peat, also from soils, composts and other sources. Considering that the applications of industrially produced HSs also include food, pharmaceutical applications and environmental technologies, it is important to evaluate their composition and quality and to identify their sources. The aim of the present study is to compare the properties of industrially produced HS samples. HSs were characterised using spectroscopic and other methods. For the identification of origin of HSs, different methods can be used, such as elemental analysis and ratios of light stable isotopes. The results of the study indicate that many industrially produced HSs are of poor quality (low concentration of basic substance, admixture of undesirable substances, pollutants, no quality indications). In this situation, rigorous quality control should be implemented, providing detailed characteristics of the product. The composition of materials suggested for agricultural applications has not been analysed much. Most of the studied materials were designated as HAs, followed by fulvic acids (FAs) and HSs. However, an analysis of the humic matter types indicates that the majority of substances offered on the market are in fact mixtures of HAs and FAs; so, it would be more appropriate to designate them as HSs or their salts. This study identifies the main quality problems of industrially produced humic substances: 1) lack of strict quality indicators, 2) absence of indication of source materials/origins of HSs.
  • Pisipilt
    Kirje
    What happens to peat during bog fires? Thermal transformation processes of peat organic matter
    (2020) Ozols, V.; Silamikele, I.; Kalnina, L.; Porshnov, D.; Arbidans, L.; Krumins, J.; Klavins, M.
    Bog fires are a serious natural phenomena. Major increase in the number of fires has happened during the last decades due to bog transformation into agricultural lands, accidents and human activities. During bog fires the peat is exposed to high temperatures due to which chemical transformation and even mineralisation of peat can occur. The aim of the study was to analyse the impacts of the bog fires on the bog as an ecosystem, advance the understanding and knowledge of fire impact on peat and humic matter properties and application possibilities. As the material for the study peat samples from burnt sites and thermally treated peat were used. To reveal peat transformation during bog fires, thermogravimetric analysis of peat samples were done, where amounts of bitumens, humic acids and mineral matter were estimated. During bog fires thermal modification of peat properties takes place, resulting in full mineralisation of peat and release of mineral substances. Bog fires lead to development of peat char, bitumens and significant changes in structure and properties of peat humic acids. However, from perspective of application of peat as a substrate and from perspective of impacts on the bog ecosystems, the effects are negligible.