Zubaidi, Shahad Khaldoon Abdulameer Al
(2021)
The Short Term Study Of Polylactic Acid Microplastics Uptake By
Eudrilus Eugeniae.
Masters thesis, Universiti Sains Malaysia.
Abstract
Non-degradable fossil-based microplastics can inhibit the growth of soil flora and fauna, and can cause serious environmental damage. Potential alternatives to fossil-based plastics are biopolymers, such as polylactic acid (PLA), which degrade over time and does not give negative impact to the environment. In this study, the biodegradation of PLA was evaluated by observing the changes in biomass of earthworms Eudrilus eugeniae and the microplastics concentration in the vermicast of the worms. The earthworms were fed with cow dung mixed with PLA for 16 days at concentrations of 0%, 10%, 30%, 60%, and 80% w/w dry weight. A 0% worm mortality rate for all PLA concentrations was obtained during the 16 days feeding period. However, the microplastic had significantly influenced the earthworms’ weight (one way ANOVA, p=0.00027), ingestion (one way ANOVA, p= 0.037), and efficiency (one way ANOVA, p= 0.0348), especially at the concentration of 80% PLA. The earthworms fed with 80% PLA had the lowest weight gain (17.74%) and growth rate (0.47±0.00g/day) but the highest ingestion rate (3.01±0.05g/g. day). Meanwhile, the earthworms in 30% and 80% treatments had the highest efficiency of 97.48% and 91.10 %, respectively. This could have been caused by the effects of PLA on the earthworms’ digestion mechanisms. The cast concentration factor (CF) and the feed's organic matter concentration were the highest at 0.9 and 90% for the treatment with 10% of PLA microplastics, respectively.
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