Converting carbonyl index values in microplastics studies

Area of Science:

• Environmental Chemistry
• Polymer Science
• Analytical Chemistry

Background:

• Variability in carbonyl index (CI) calculation methods hinders direct comparison of microplastic oxidation levels across studies.
• Standardized CI values are crucial for accurate environmental monitoring and risk assessment of microplastics.

Purpose of the Study:

• To develop a unified methodology for converting carbonyl index (CI) values derived from different calculation methods.
• To enable consistent and reliable comparisons of microplastic oxidation states across diverse environmental studies.

Main Methods:

• Developed a polynomial regression model using spectral data from environmental microplastic samples.
• Employed five-fold cross-validation to determine the optimal model order and assess variance explanation (36%-84%).
• Applied the conversion methodology to existing CI data from Japanese coastal regions.

Main Results:

• The developed CI conversion methodology effectively unifies CI values from various calculation methods.
• Microplastics in Japan's southeast coastal regions exhibit higher oxidation levels compared to the west.
• The model demonstrates adaptability to CI calculation methods not explicitly included in the initial development.

Conclusions:

• The novel CI conversion methodology provides a standardized approach for microplastic oxidation assessment.
• Regional differences in microplastic oxidation in Japan are likely influenced by environmental exposure and retention times.
• This approach enhances the comparability of microplastic research globally and supports more accurate environmental impact assessments.