A modified methodology for extraction and quantification of microplastics in soil.

Area of Science:

• Environmental Science
• Analytical Chemistry
• Soil Science

Background:

• Microplastic pollution (<5 mm) is a global concern, extensively studied in aquatic environments but poorly characterized in soils.
• Current analytical methods for soil microplastic quantification are challenging, requiring improved validation to reduce obscurities and biases.

Purpose of the Study:

• To develop an effective method for the extraction and quantification of microplastics from soil samples.
• To optimize density-dependent separation and organic matter removal for accurate microplastic recovery.

Main Methods:

• Tested various ratios of low-density (NaCl) and high-density (ZnCl2/NaBr) solutions for density-dependent separation.
• Evaluated different hydrogen peroxide (H2O2) soil-to-solution ratios for organic matter removal, with and without heating.
• Validated the method by spiking soil samples with microplastic particles of varying sizes (10-5000 μm).

Main Results:

• A combination of low- (1:6) and high-density (1:3) solutions achieved 95% recovery of spiked microplastics.
• Prior removal of organic matter facilitated 99% microplastic recovery.
• Validated method demonstrated high recovery rates (88-99%) for microplastics across different sizes.

Conclusions:

• The developed method, involving prior organic matter digestion and density-dependent separation, efficiently extracts and quantifies microplastics from soil.
• This validated approach enables accurate characterization of microplastics, including diverse shapes, sizes, colors, and polymer compositions, in field-collected soil samples.