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Updated: Aug 5, 2025
Protocol for Microplastics Sampling on the Sea Surface and Sample Analysis
Published on: December 16, 2016
Comparative evaluation of the carbonyl index of microplastics around the Japan coast
Murat Celik1, Haruka Nakano2, Keiichi Uchida1
1Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan.
Abstract:
The carbonyl index (CI) of polyethylene and polypropylene microplastics (MPs) (2950 particles) collected in coastal waters around Japan was investigated. The CI of MPs was calculated by the specified area under band technique. The mean MP CI in all samples (regardless of shape and color) was 0.69 ± 0.34 and 0.70 ± 0.34 for polyethylene and polypropylene, respectively, and there was no significant difference in the color or shape of the MPs. The polyethylene, white, and fragment MPs CI was negatively (p < 0.05) correlated with the major length of the MPs. Large MPs with relatively little deterioration were distributed along the west coast of the Sea of Japan, whereas small MPs were distributed along the east coast. Our findings of this gradual change in the deterioration of MPs, based on geographical distribution, are in accordance with literature CI-size and MP degradation hypotheses.
Insights
The carbonyl index (CI) of microplastics (MPs) in Japanese coastal waters was analyzed. MP degradation varied geographically, with larger, less degraded plastics found on the west coast and smaller, more degraded ones on the east coast.
Area of Science:
- Environmental Science
- Polymer Science
- Marine Biology
Background:
- Microplastics (MPs) are a growing environmental concern.
- Assessing the degradation state of MPs is crucial for understanding their environmental fate.
- Polyethylene and polypropylene are common plastic types found as marine debris.
Purpose of the Study:
- To investigate the carbonyl index (CI) of polyethylene and polypropylene microplastics collected from Japanese coastal waters.
- To determine if MP shape, color, or size correlates with degradation.
- To analyze the geographical distribution of MP degradation.
Main Methods:
- Collected 2950 microplastic particles from coastal waters around Japan.
- Calculated the carbonyl index (CI) using the specified area under band technique.
- Analyzed the correlation between CI, MP characteristics (shape, color, size), and geographical location.
Main Results:
- The mean CI for polyethylene and polypropylene MPs was 0.69 ± 0.34 and 0.70 ± 0.34, respectively.
- No significant difference in CI was observed based on MP shape or color.
- A negative correlation was found between the CI of polyethylene, white, and fragment MPs and their major length.
- Larger MPs with less deterioration were found along the west coast of the Sea of Japan, while smaller MPs were found along the east coast.
Conclusions:
- MP degradation shows a geographical gradient along the Japanese coast.
- MP size is a significant factor influencing degradation, with larger MPs exhibiting less deterioration.
- Findings align with existing hypotheses on CI-size relationships and MP degradation patterns.
