TY - THES A1 - Gogoi, Nayan jyoti T1 - Combined effects of microplastics and heavy metals: implications for soil microbial ecology N2 - There is substantial evidence that microplastic pollution and heavy metal contamination pose a significant threat to the health of soils and the functioning of ecosystems. However, little is known about the interactions between heavy metals and microplastics, as well as possible biological effects when the two are combined. It is possible that MPs and heavy metals can interact in soil, causing changes in their environmental behaviour, bioavailability, and potentially toxic properties, further posing ecological risks. Therefore, the objective of this study was to evaluate the individual and combined impacts of microplastics and heavy metals on soil chemical properties, microbial biomass, microbial activity, and microbial communities in soil treated with varying concentrations of these pollutants. In an incubation experiment, soil was amended with low-density polyethylene (LDPE) and a mixture of heavy metals (Zn, Cu, and Ni) in two concentrations (Low and High). Seven treatments (Control; MP-L; MP-H; HM-L; HM-H; MP+HM-L and MP+HM-H) were analysed in seven replications. The rate of microbial respiration was determined during incubation. Following incubation, soil pH, microbial biomass carbon (C), nitrogen (N), soil fluorescein diacetate hydrolytic activity, and the abundance of archaea, bacteria, and fungi were measured as well as the effects on inorganic nitrogen (NO3-, NH4+) were determined. It was found that no significant difference existed between the control treatment and LDPE treatment in terms of soil pH, FDAse activity, microbial biomass, microbial respiration, inorganic nitrogen, and abundance of archaea, bacteria, or fungi, regardless of the concentration of LDPE (0.6%, 1.2%). Heavy metal treatment did, however, result in a significant decrease in soil pH, NO3, and microbial respiration particularly at high concentrations (2.68 mg kg-1), compared with treatments with LDPE and a control, suggesting that HMs suppressed microbial activity. Additionally, HMs also reduced MBN and MBC, indicating their negative effect on microbial biomass. As a result of the combination of microplastics and heavy metals, microbial biomass, and microbial respiration decreased significantly when compared to either the control treatments or the microplastics alone treatment. Additionally, the combined treatment reduces NO3- and soil pH significantly compared to the control and sole microplastic treatment There was no significant effect observed in any treatment on the abundance of archaea or fungi, indicating that the presence of MP and/or HMs had no impact on their abundance. However, the MP+HM treatment resulted in a reduction in the number of bacteria. Using a two-factor statistical analysis, the effect of two concentrations (low and high) of microplastics and/or heavy metals on these soil parameters was further evaluated. According to these results, the concentrations of added microplastics and/or heavy metals (low and high) had no significant effect (p > 0.05) on any soil parameter except for soil pH (p < 0.05). Overall, the results indicate that the presence of heavy metals, either alone or combined with microplastics, had a detrimental effect on soil ecosystem. However, this study was limited to examining the short-term effects of these pollutants on soil microorganisms and their functioning. Additional research will be necessary to determine the long-term effects of these pollutants. Y1 - 2023 ER - TY - THES A1 - Rohlfing, Pauline T1 - Einfluss von Benzalkoniumchlorid auf die Selektion von Bakteriengemeinschaften und die Verbreitung von Resistenzgenen in mit Mikroplastik angereichertem Boden N2 - Die zunehmende Anreicherung anthropogener Mikroverunreinigungen in der Umwelt hat in jüngster Zeit verstärkte wissenschaftliche Aufmerksamkeit erhalten. Der steigende Eintrag von Mikroplastik in die Umwelt kombiniert mit der Ausbreitung von Resistenzgenen erfordert eine eingehende Analyse ihrer möglichen Interaktionen und Auswirkungen auf die Ökosysteme. In dieser Studie stand die Interaktion zwischen Mikroplastik, speziell HDPE, einem nicht biologisch abbaubaren Polymer, und PHBH, eine biologisch abbaubare Alternative, in Kombination mit Benzalkoniumchlorid im Fokus. Ziel war es, deren Einfluss auf die Gemeinschaftsstruktur von Bodenmikroorganismen und die Prävalenz von Antibiotikaresistenzgenen zu untersuchen. Unter Verwendung eines Mikrokosmos- Designs wurden organisch bewirtschaftete Bodenproben mit den vorgenannten Substanzen über drei und sechs Wochen inkubiert. Im Anschluss wurden die Biofilme auf den Mikropartikeln mittels qPCR und ddPCR analysiert, wobei die Abundanz von Bakterien, Pilzen und dem Klasse-1-Integron-Gen untersucht wurde. Die Ergebnisse können nicht bestätigen, dass Benzalkoniumchlorid die Verbreitung von Resistenzgenen oder mikrobielle Gemeinschaftsstrukturen beeinflusst. Im Gegensatz dazu wirkte PHBH als signifikanter Modulator, der die Vielfalt der Pilz- und Bakterientaxa im Biofilm verringerte, jedoch die Gesamtabundanz erhöhte. Vor dem Hintergrund dieser Befunde werden die potenziellen ökologischen Implikationen der Mikroplastikverschmutzung deutlich. Es betont die Notwendigkeit vertiefter Forschungen, um die komplexen Wechselwirkungen zwischen Mikroplastik und anderen anthropogenen Kontaminanten in terrestrischen Ökosystemen zu verstehen. N2 - The increasing accumulation of anthropogenic micropollutants in the environment has received greater scientific attention in recent years. The rise of microplastics in the environment combined with the spread of resistance genes requires an in-depth analysis of their potential interactions and impacts on ecosystems. This study focused on the interaction between microplastics, specifically HDPE, a non- biodegradable polymer, and PHBH, a biodegradable alternative, in combination with benzalkonium chloride. The aim was to investigate their influence on the community structure of soil microorganisms and the prevalence of antibiotic resistance genes. Using a microcosm design, organically managed soil samples were incubated with the aforementioned substances for three and six weeks. Subsequently, biofilms on the microparticles were analysed using qPCR and ddPCR method, with particular emphasis on the abundance of bacteria, fungi and the class 1 integron gene. The results cannot confirm that benzalkonium chloride influences the dissemination of resistance genes or microbial community structures. In contrast, PHBH acted as a significant modulator, reducing the diversity of fungal and bacterial taxa in the biofilm, but increasing overall abundance. Given these results, the potential ecological implications of microplastic pollution become apparent. It emphasises the need for deeper research to understand the complex interactions between microplastics and other anthropogenic contaminants in terrestrial ecosystems. Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1383-opus4-18573 ER -