Detection and Identification of Microplastics in Freshwater Samples and their Toxicological Impact on Daphnia Pulex, A Model Organism for Freshwater

Sana, Asma

Abstract

Plastics have become an indispensable part of modern life due to their
exceptional characteristics and versatility. Their use spans across various industries.
At the beginning of plastic industry, the GPP was around 2 million tons, which
reached approximately 368 million tons in 2019. However, these plastic products
once consumed, are abandoned in environment, and enters waste stream,
forming “Plastic Pollution”. Despite being given much attention on its safe disposal
and recycling’ it is getting difficult to cope with plastic pollution. Particularly, when
the abandoned microplastic objects undergo various degradation processes, they
are converted into micro or nano plastics. Various studies suggested their
increased toxicological effects with reduced plastic particle size. Given the
importance of microplastic pollution, the present study investigated freshwater
(from river Mersey) for detection and identification of microplastics using light
microscopy, fluorescence microscopy and micro-Raman spectroscopy. Followed
by this, experiments were conducted to evaluate the toxicological impact of
microplastics (Low density poly-ethylene LDPE and Polyethylene terephthalate PET)
on model invertebrate Daphnia pulex at physiological as well as molecular level.
Finally, the study evaluated the potential of microwave assisted thermal treatment
on degradation of PET microplastic particles under varied pH conditions. The results
confirm the presence of microplastics in studied water samples but at very low
concentration (0.01%). The toxicity of both studied microplastic types was seen in
Daphnia in terms of reduced reproductive activity, irregular heart rate and high
mortality (100% mortality observed for PE+Pb and <60% for PET+Fe and PE+Fe
treatment groups) . The RNA expression analysis further validates the findings of
bioassay. Upregulated expression of oxidative stress related genes (SOD,
Vitellogenin and apolipoproteins), down regulation of development and
reproductive pathway related genes indicates the compromised health condition
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of Daphnia under microplastic exposure. The degradation of PET microplastic
particles was observed under microwave assisted thermal treatment which
reduces their potential to adsorb heavy metals and reduced toxicity impact.

Citation

Sana, A. (2024). Detection and Identification of Microplastics in Freshwater Samples and their Toxicological Impact on Daphnia Pulex, A Model Organism for Freshwater. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Apr 11, 2024
• Publicly Available Date: May 26, 2024
• Award Date: Apr 25, 2024