Microplastic metrology: Current techniques, best practices, and recommendations for environmental analysis
Masura, J.; Ho, D. (2025). Microplastic metrology: Current techniques, best practices, and recommendations for environmental analysis, in: Shumway, S.E. et al. Plastics in the sea: occurrence and impacts. pp. 25-68. https://dx.doi.org/10.1016/b978-0-12-822324-6.00011-6
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| Keywords |
Pretreatment
Sampling
Standardization
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| Author keywords |
Microplastic; Nanoplastic; Environmental matrices; QA/QC; Polymer identification |
| Abstract |
Microplastics (synthetic polymers 1 μm to 5 mm (MP)) are an emerging contaminant in the natural environment, posing risks to terrestrial organisms, marine ecosystems, and even human health. The ocean environment acts as a significant sink for MP, threatening the stability of ecosystems across trophic level communities. The widespread prevalence and complex impact of MP across diverse matrices have made comprehensive scientific exploration particularly challenging. The physical and chemical variability of plastics, coupled with their presence in a multiple environmental matrices (air, water, soil), has necessitated diverse approaches to surveying their presence and impacts; however, the lack of standardization in methodologies—from sampling, to pretreatment, and analysis—has resulted in inconsistent and incomparable findings, hindering research into the source, fate and transport, and policy development for MP in the environment. This meta-analysis sought to summarize the current techniques, and provide best practices and recommendations for environmental analysis of MP, and reviewed peer-reviewed publications up to August 2024, focusing on microplastic metrology, with an emphasis on sampling, pretreatment, quantification, and identification of microplastics in the marine environment. Three matrices–air, water, and solids–were analyzed, with subgroups defined by varying levels of turbidity. Sampling methods included passive deposition for air, active pumping, volume reducing and bulk sampling for water, selective direct extraction, and pressurized fluid extraction for solids. Pretreatment employed inorganic separations using salts of varying densities and natural organic matter (NOM) degradation using acids, alkalis, oxidizing agents, and enzymes. Analytical tools were evaluated on their ability to quantify MP and identify the polymer types, including optical imaging, spectroscopic analysis, thermal analysis, and electroanalysis. Refinement in research techniques is ongoing, with a critical need for greater speed, sensitivity, and objectivity to identify MP from NOM, and to detect smaller particles, nanoplastics (<1 nm). Advanced machine learning and artificial intelligence offer significant potential to enhance data selection and comparison, enabling the generation of more accurate, objective, and standardized MP datasets. Robust quality assurance and quality control (QA/QC) protocols are essential to mitigate contamination and ensure accurate representation of MP in studies. Since exposure to fibers and extremely small polymers are inevitable, field blanks must be used and quantified. Field work, sample preparation, and analysis should prioritize minimizing environmental contamination from the atmosphere, materials, and working environment. Large-scale harmonization of spatial and temporal monitoring efforts is urgently needed, alongside the recognition of the limitations of instrumentation for detecting fractions smaller than microplastics. Future research should embrace the open-source framework that emphasizes transparency, collaboration, and integration of diverse perspectives to advance methodological consistency and data accessibility. |
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