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Influence of biodegradable polymers microplastics on properties of soil organic matter
Denková, Pavla ; Řezáčová, Veronika (referee) ; Kučerík, Jiří (advisor)
The microplastics contamination is an issue observed in all environmental compartments. Currently, the trend is to replace the synthetic polymers by biodegradable ones, which are expected to degrade faster due to omnipresent microorganisms. However, this assumption may not correspond with the reality. In nature, biodegradation can last long or not whatsoever and the microparticles of biodegradable polymers can remain in soil the same way as particles of synthetic polymers. The effect of microparticles of biodegradable polymers on soil´s biota has already been studied, but the effect on the properties of soil and water in the soil has not been elucidated yet. This thesis deals with the influence of microparticles of biodegradable plastics on the physico-chemical properties of soil organic matter, especially on the behavior of water in the soil system under arid and semiarid conditions. Microparticles of poly(R-3-hydroxybutyrate), abbreviated as P3HB, were used as a model biodegradable polymer and were introduced into the soil in various concentrations. To determine the evaporation enthalpy of water and stability of water bridges that affect (stabilize) the physical and chemical structure of soil organic matter Differential Scanning Calorimetry (DSC) was used. Simultaneously was also measured their effect on water holding capacity of soil organic matter. Under experimental conditions, P3HB microplastics were found to reduce evaporation enthalpy, which facilitates drying of soil organic matter. Nevertheless, their effect on final water holding capacity was relatively low. Besides, we observed a negative effect on the stability of water molecule bridge that connect segments of soil´s organic components. Thus, P3HB microparticles in soil could pose a risk due to their influence on the water retention mechanism in soil under arid and semiarid conditions.
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Hydration of biochar prepared by using microwave pyrolysis of municipal sludge
Miklasová, Marta ; Komendová, Renata (referee) ; Kučerík, Jiří (advisor)
Microwave pyrolysis represents a possible solution of municipal sludge disposal. One of the final products of pyrolysis is amorphous porous carbon material called biochar, which can be used in agriculture as a soil amendment. As a rule, biochar is hydrophobic, but its addition can lead to an increase in water holding capacity. However, reasons of this improvement cannot be explained only by its high porosity. This thesis aims to contribute to the understanding the interactions between biochar and water under various environmental-relevant conditions such as direct water addition method and water adsorption from ambient air at different relative humidity. The thermo-analytical methods are common for investigation of the relationship between water and organic materials. One of these methods, differential scanning calorimetry, was used in this thesis. The first experiment was focused on measuring of melting enthalpy of freezable water in biochar pores. The results reflect the influence of pore size and properties of ice structure. The extrapolation of concentration dependence to zero enthalpy was used to determine non-freezing water (0,13–0,15 mg·mg-1 biochar), which reflects microporosity of the biochar. The second experiment was focused on the determination of evaporation enthalpy of water from biochar, which is a measure of the strength of water binding in biochar. This value indirectly reflects the mechanisms of the intake and release of water by biochar. Comparing the results for bound and pure water showed that in biochar is water bound weaker about 10–20 %. This led to conclusion that biochar binds water relatively weakly and the water exchange between biochar and soil is fast, despite the biochar hydrophobicity.
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Influence of biodegradable polymers microplastics on properties of soil organic matter
Denková, Pavla ; Řezáčová, Veronika (referee) ; Kučerík, Jiří (advisor)
The microplastics contamination is an issue observed in all environmental compartments. Currently, the trend is to replace the synthetic polymers by biodegradable ones, which are expected to degrade faster due to omnipresent microorganisms. However, this assumption may not correspond with the reality. In nature, biodegradation can last long or not whatsoever and the microparticles of biodegradable polymers can remain in soil the same way as particles of synthetic polymers. The effect of microparticles of biodegradable polymers on soil´s biota has already been studied, but the effect on the properties of soil and water in the soil has not been elucidated yet. This thesis deals with the influence of microparticles of biodegradable plastics on the physico-chemical properties of soil organic matter, especially on the behavior of water in the soil system under arid and semiarid conditions. Microparticles of poly(R-3-hydroxybutyrate), abbreviated as P3HB, were used as a model biodegradable polymer and were introduced into the soil in various concentrations. To determine the evaporation enthalpy of water and stability of water bridges that affect (stabilize) the physical and chemical structure of soil organic matter Differential Scanning Calorimetry (DSC) was used. Simultaneously was also measured their effect on water holding capacity of soil organic matter. Under experimental conditions, P3HB microplastics were found to reduce evaporation enthalpy, which facilitates drying of soil organic matter. Nevertheless, their effect on final water holding capacity was relatively low. Besides, we observed a negative effect on the stability of water molecule bridge that connect segments of soil´s organic components. Thus, P3HB microparticles in soil could pose a risk due to their influence on the water retention mechanism in soil under arid and semiarid conditions.
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Hydration of biochar prepared by using microwave pyrolysis of municipal sludge
Miklasová, Marta ; Komendová, Renata (referee) ; Kučerík, Jiří (advisor)
Microwave pyrolysis represents a possible solution of municipal sludge disposal. One of the final products of pyrolysis is amorphous porous carbon material called biochar, which can be used in agriculture as a soil amendment. As a rule, biochar is hydrophobic, but its addition can lead to an increase in water holding capacity. However, reasons of this improvement cannot be explained only by its high porosity. This thesis aims to contribute to the understanding the interactions between biochar and water under various environmental-relevant conditions such as direct water addition method and water adsorption from ambient air at different relative humidity. The thermo-analytical methods are common for investigation of the relationship between water and organic materials. One of these methods, differential scanning calorimetry, was used in this thesis. The first experiment was focused on measuring of melting enthalpy of freezable water in biochar pores. The results reflect the influence of pore size and properties of ice structure. The extrapolation of concentration dependence to zero enthalpy was used to determine non-freezing water (0,13–0,15 mg·mg-1 biochar), which reflects microporosity of the biochar. The second experiment was focused on the determination of evaporation enthalpy of water from biochar, which is a measure of the strength of water binding in biochar. This value indirectly reflects the mechanisms of the intake and release of water by biochar. Comparing the results for bound and pure water showed that in biochar is water bound weaker about 10–20 %. This led to conclusion that biochar binds water relatively weakly and the water exchange between biochar and soil is fast, despite the biochar hydrophobicity.
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