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Abstract: Plastics are based on organic polymers that are sensitive to the environment in which they find themselves and will gradually decay through a variety of chemical reactions. This process is of great importance for the transformation and persistence of microplastics (MPs) that pollute the environment. The rate of degradation depends on two major factors: Firstly, the intrinsic properties of the polymers, such as chemical structure, molecular weight, crystallinity and the presence of additives, fillers or reinforcement and secondly, the environment to which they are exposed. The degradation rate of plastic will vary in different environmental matrices like soil, freshwater, seawater, wastewater, land etc., as well as in diverse environmental conditions like UV radiation, temperature, humidity, the effect of pollutants etc. Plastic mainly undergoes two fundamental reactions: oxidation and hydrolysis and the chemical structure of the polymer and its additives plays a key role in the degradation mechanism of plastic. Polyolefins having a carbon-only main chain are resistant to hydrolysis but susceptible to oxidation, whereas polyesters and polyamides containing heteroatoms are sensitive to hydrolysis and much more resistant to oxidation. In the context of the present work, five different studies were done involving both naturally degraded plastic and accelerated weathering of plastics in the form of small particles, MPs. In the first study, natural degraded polyethylene (PE) and polypropylene (PP) samples with a life span of more than forty years were collected from the environment and their physiochemical properties were analysed. The results show that red coloured PE samples were more degraded as compared to blue coloured samples, indicating that pigment plays a key role in the degradation. The PP sample shows extreme surface degradation, leading to fragmentation and the generation of MPs. In the second study, the effect of hydrodynamic cavitation on MPs in waste water treatment plant sludge was evaluated. PE, PP, polyethylene terephthalate and polyamide were extracted from the sludge. It was found that hydrodynamic cavitation does not disintegrate the MPs, although it removes some toxic metals and shows cell disruption mechanisms. Other studies were done with accelerated weathered MPs, which include PE, PP and tire wear particles (TWP), that were treated in accordance with an ISO 4892 standard weathering procedure that mimics natural weathered conditions. In the third study, we used weathered PE films to evaluate the synergistic adsorption behaviour of two pollutants, namely triclosan (TCS) and methylparaben (MeP). It was found that weathered MPs adsorb more pollutants and the adsorption behaviour of TCS is enhanced in the presence of MeP. In the fourth study, the magnetic extraction of pristine and weathered PE and TWP particles was performed. The results confirmed that the magnetic VI extraction of weathered MPs is difficult as compared to pristine MPs as their surface becomes more hydrophilic with weathering. In the fifth study, the effect of weathering on the density of PE and PP was evaluated. We found that weathering enhances the density of polyolefins, which is one of the main reasons for the observed sinking of polyolefin MPs in water.
Keywords: accelerated weathering, aging, density, magnetic separation, pigment, plastic degradation, pollutants, polyethylene, polyolefin, polypropylene, sinking, tire wear particles, dissertations
Published in RUNG: 04.06.2024; Views: 11; Downloads: 0
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Keywords: hadronske interakcije, detektorji fluorescence, talni detektorji, Observatorij Pierre Auger
Published in RUNG: 16.05.2024; Views: 241; Downloads: 1
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Keywords: ESA, Aeolus, Aladin, Observatorij Pierre Auger, vetrni profili
Published in RUNG: 16.05.2024; Views: 231; Downloads: 2
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Keywords: radio measurement, kozmični žarki ekstremnih energij, observatory Pierre Auger
Published in RUNG: 31.01.2024; Views: 534; Downloads: 2
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Abstract: AugerPrime, the upgrade of the Pierre Auger Observatory, is nearing completion and the Observatory is now prepared to collect physics data after the commissioning of the new components. The Pierre Auger Observatory has demonstrated, based on the data collected thus far, the existence of the cutoff in the spectrum with high accuracy. However, the origin of this cutoff remains incompletely understood. The upgraded Observatory is designed to address the unresolved questions regarding the nature of the cosmic ray flux cutoff thanks to its capability to disentangle the muon and electromagnetic components of extensive air showers. Furthermore, the measurement of the muon component at ground level can verify the accuracy of hadronic interaction models currently used. This presentation will provide an overview of the status of the Observatory and the accurate commissioning done before the start of the physics run. Furthermore, we will present the initial data from Phase II data mainly dedicated to proving the continuity of operation of the Observatory from Phase I to Phase II.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, AugerPrime detector upgrade, Pierre Auger data
Published in RUNG: 24.01.2024; Views: 763; Downloads: 6
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