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Published on: May 10, 2013
The biodegradation of polylactic acid microplastic and their toxic effect after biofouling in activate sludge
Nik Nurhidayu Nik Mut1, Joorim Na2, Gwiwoong Nam2
1Division of Environmental Science and Ecological Engineering, Korea University, Seoul, 02841, Republic of Korea.
Abstract:
Biodegradable microplastics (MPs) can form biofilms through interactions with various microorganisms in aquatic system and can be exposed to organisms. This study first investigated biodegradability of polylactic acid (PLA) MPs and the characterization of PLA MPs before/after biofouling (4 weeks) and their toxic effects on the freshwater invertebrate Daphnia magna. The biodegradability rate of PLA MPs was up to 50% over 28 days, suggesting that even biodegradable MPs do not easily decompose under environmental conditions. Furthermore, biofouling of MPs led to an increase in size and, in the process, induced an additional functional peak in the PLA MPs. The exposure of biofouled MPs did not lead to a reduction in survival, reproduction, or growth during chronic exposure, nor did it cause feeding inhibition in juvenile (<4 days old) D. magna. However, pristine MPs significantly reduced survival, reproduction, and growth at concentrations of 5.0 mg L-1. Overall, pristine MPs caused inhibition of reproduction and growth and high mortality in D. magna, while the biofouling process did not induce these effects. Our findings highlight the complex interactions between MPs and biological components in aquatic environments, emphasizing the importance of considering biofouling dynamics when assessing the ecological impacts of biodegradable MPs.
Insights
Biodegradable polylactic acid microplastics (MPs) showed limited decomposition and altered characteristics after biofouling. Pristine MPs were toxic to Daphnia magna, but biofouled MPs were not, highlighting the impact of biofouling on MP ecological risk.
Area of Science:
- Environmental Science
- Ecotoxicology
- Materials Science
Background:
- Biodegradable microplastics (MPs) can interact with aquatic microorganisms, forming biofilms and posing exposure risks to organisms.
- Polylactic acid (PLA) is a common biodegradable plastic, but its environmental fate and ecological impact, especially after biofouling, require further investigation.
Purpose of the Study:
- To investigate the biodegradability of PLA MPs.
- To characterize PLA MPs before and after biofouling.
- To assess the toxic effects of pristine and biofouled PLA MPs on the freshwater invertebrate Daphnia magna.
Main Methods:
- Assessed PLA MP biodegradability over 28 days.
- Characterized PLA MPs using physical and chemical methods before and after 4 weeks of biofouling.
- Conducted chronic exposure toxicity tests of pristine and biofouled MPs on Daphnia magna, evaluating survival, reproduction, growth, and feeding.
Main Results:
- PLA MPs exhibited a biodegradability rate of up to 50% over 28 days, indicating slow decomposition in environmental conditions.
- Biofouling increased MP size and induced additional functional peaks, altering their characteristics.
- Pristine MPs significantly reduced Daphnia magna survival, reproduction, and growth at 5.0 mg L⁻¹, while biofouled MPs did not cause these adverse effects.
Conclusions:
- Even biodegradable MPs decompose slowly under environmental conditions.
- Biofouling significantly alters MP characteristics and mitigates their toxicity to Daphnia magna.
- Assessing the ecological impact of MPs necessitates considering biofouling dynamics and their complex interactions with biological components in aquatic environments.
