- Title
- Micro-nanoplastics in freshwater ecosystem: an ecotoxicological and molecular assessment
- Creator
- Afrose, Sania
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2023
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Global-scale exposure and often irresponsible use make plastics a significant threat for the planet. Globally, the rate plastics enter the environment has doubled to 44 million tonnes a year since 2019, accumulating in aquatic environments such as lakes, rivers and oceans, and this is expected to triple by 2060. Upon entering the environment, plastics age and weather to be transformed into smaller microplastics (MP < 5 mm) and nanoplastics (NPs, < 1 µm). Size is one of the most important properties of micro-nanoplastics (MNPs) as the chemical and physical properties of polymers alter with the decreasing of particle size. Their fate and behaviour also change due to the decreasing MNP size. Their small size not only makes them more readily bioavailable to aquatic organisms, including those in freshwater, but it also increases the capacity for organic and inorganic pollutant ad/absorption to their surfaces. A major concern surrounding MNPs is ingestion by freshwater organisms and that these pollutants, along with associated chemicals will enter to organs and tissues. There is a paucity of information on the existence of MNPs and their fate and behaviour in freshwater. Due to ageing and weathering, MNPs undergo a degradation process, increasing the abun-dance of NPs in the environment. Not only is very little known about NPs fresh-water environments, due to lack of sound methods for extraction and detection but al-so, which size NPs will be more bioavailable has yet to be investigated. Consequently, we highlight a significant knowledge gap regarding MNP occurrence, their fate, and behaviour in freshwater as well as their trophic transfer to aquatic biota and associated toxicity. The specific research objectives were to; (I) develop baseline information on the occurrence, and characteristics of MNPs in the Australian freshwater environment; develop proper methods for NPs extraction from environmental water sample and pol-ymer detection; (II) investigate long-term ageing and weathering impact on common plastic polymers in surface water of freshwater environments (III) metagenomic role responsible for biodegradation of common MPs in freshwater; and (IV) investigate in-direct ingestion of NPs to aquatic organism and toxicity of different sizes NPs to de-termine their bioavailability and impact on biota depending on size. A series of sequential investigations were used to achieve these research objectives and generate valuable environmentally relevant data on the physicochemical properties of long-term weathered MPs. The methodical approach consisted of desktop-based re-search, field surveys and controlled field experiments, analytical chemistry, statistical analysis, and modelling. Chapter 2 summarises existing information on MNPs and their potential risk in terms of bioavailability and toxicity due to their size and highlights the need to assess the risk of MNPs in freshwater environments. Chapter 3 reports the oc-currence, abundance, and characteristics of MPs in surface water of Australian fresh-water environments along with the existence of NPs. Chapter 4 employs an advanced analytical approach to investigate long-term ageing and weathering of microplastics in freshwater environments. Experimental findings demonstrate that long-term ageing and weathering processes modify the physical and chemical properties of the surface and bulk phase of exposed MPs, leading to slow environmental degradation and the release of small plastic particles (<1 μm). Finding also provide valuable information on bacterial assemblage patterns in long-term aged polymers which were attributed to dif-ferences in bacterial niche selection between polymer types. Chapter 5 explores the accumulation of different sizes NPs by fish upon indirect ingestion of NPs treated Ar-temia and investigated size dependant tissue translocation and toxicological impact. Findings indicated that smaller size facilitated the translocation of NPs to the fish body which impact on body via DNA damage, elevated Superoxide Dismutase production and the alteration of metabolites. Finally, the significance and limitations of the key findings are discussed in Chapter 6, in terms of their contribution to the current state of MPs research and the future research priorities. This thesis demonstrates that the occurrence of MNPs in Australian freshwater pose an immense risk to wildlife. The degradation of MPs in freshwater induced by ageing and weathering and their capacity to release not only in situ NPs but also pathogens (at-tached biofilm over the time) pose additional threats. This study also demonstrated that NPs are translocated to organs and become bioavailable to triggering toxicological threats. Their bio-transfer through direct ingestion in food chain can facilitate further risk of biomagnification and eventually cause a threat to human health. Future research into the role of MNPs as vectors for toxic chemical mixtures to aquatic organisms and food webs is urgently needed to preserve freshwater biodiversity and safeguard valua-ble food resources.
- Subject
- microplastics; nanoplastics; freshwater; emerging contaminants
- Identifier
- http://hdl.handle.net/1959.13/1504804
- Identifier
- uon:55576
- Rights
- This thesis is currently under embargo and will be available from 24.07.2024 Copyright 2023 Sania Afrose
- Language
- eng
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