Microplastics in sediments: A systematic review structured through reproducible analytical pipelines

Area of Science:

• Environmental Science
• Analytical Chemistry

Background:

• Microplastic research is rapidly growing, but methodological inconsistencies in sediment studies limit data comparability.
• Variability in sampling, preparation, detection, and identification methods poses challenges for accurate microplastic quantification.

Purpose of the Study:

• To systematically review current microplastic analysis methods in sediment studies.
• To identify key areas for methodological harmonization to improve data comparability.

Main Methods:

• A systematic literature review of 3290 records, selecting 37 sediment-focused studies (marine and freshwater).
• Analysis of methods using a Reproducible Analytical Pipelines (RAPs) framework, covering sampling, preparation, detection, and polymer identification.

Main Results:

• Wide variation in sampling techniques (grab samplers, corers) and lower size detection limits (<0.1 mm to 1 mm).
• Near-universal use of density separation (mostly sodium chloride), with limited use of denser media.
• μFTIR is the dominant polymer identification technique, with limited use of Raman spectroscopy for smaller particles.

Conclusions:

• While some methods show convergence, significant divergence persists in critical analytical parameters.
• Harmonization efforts should prioritize standardizing sampling, density separation media, and polymer identification techniques for microplastic sediment analysis.