Systematic development of extraction methods for quantitative microplastics analysis in soils using metal-doped...

Area of Science:

• Environmental Science
• Analytical Chemistry
• Soil Science

Background:

• Current microplastic (MP) analysis methods in soils lack harmonization and consistency across different soil types.
• Standardized and robust extraction and quantification techniques are crucial for accurate environmental monitoring.

Purpose of the Study:

• To develop and validate a versatile workflow for microplastic extraction and quantification adaptable to various soil compositions.
• To address challenges in isolating MPs from complex soil matrices, particularly recalcitrant organic matter.

Main Methods:

• Utilized PET MPs spiked with an inorganic tracer (Indium) for quantitative recovery assessment via ICP-MS.
• Investigated soil subgroups (sand, silt, clay, organic matter) to tailor extraction methods.
• Developed a novel biotechnological method (3-F-Ultra) using Fenton and CAZymes to remove organic matter.
• Implemented Nile Red staining and a Deep Learning-based image analysis tool (calculating Filter Clearness Index - FCI) for non-metal-doped MPs.

Main Results:

• Achieved high MP recovery rates (88% for fragments, 74% for fibers) in standard soils.
• The developed 3-F-Ultra method effectively removed lignocellulosic organic matter.
• The Filter Clearness Index (FCI) averaged 0.75, indicating efficient filtering.
• Demonstrated the workflow's adaptability across different soil types.

Conclusions:

• The proposed workflow offers a harmonized and adaptable approach for microplastic analysis in diverse soil environments.
• This method enhances the accuracy and reliability of microplastic quantification in environmental sampling campaigns.
• The study provides a foundation for improved understanding and standardization of soil microplastic research.