An eight-step method for analyzing microplastics in a soil ecosystem

In today's world, plastics are widely used due to their favorable properties and affordability. However, the widespread use of these non-biodegradable materials makes them a waste management nuisance and a global environmental concern. It is estimated that by 2050, around 12 billion metric tons of plastic waste will end up in landfills.

Plastics that enter the soil undergo intense weathering and breakdown, resulting in microplastics (MPs) or plastic fragments as small as 5mm. These MPs accumulate in soil, altering their chemical and biological properties and increasing the threat of plastic pollution. Not only do these MPs endanger soil health, they also affect soil organisms and pollute plants, jeopardizing the integrity of the entire food chain.

Given the recent focus on microplastic pollution in soil, a systematic, comprehensive and standardized procedure for sampling, extraction and analysis of soil MPs is still lacking. Current analytical methods for soil MPs are generally modified versions of existing marine research that rarely acknowledge the inherent complexities of soil ecosystems.

To address this research gap, Prof. A group led by Yong Sik Ok has now critically evaluated current analytical approaches for soil MPs and proposed a new, comprehensive, eight-step methodology for analyzing MPs in soil.

Prof. Ok is Chair and Program Director of the Sustainable Waste Management (APRU SWM) Program for the Association of Pacific Rim Universities (APRU), President of the International ESG (Environment, Social and Governance) Association (IESGA) and President of the International Society of Trace Element Biogeochemistry (ISTEB), since 2018. A highly cited researcher.

Prof. Elaborating further on their research. Oke says, „In a world grappling with the increasing challenges of plastic pollution, our critical assessment provides important insights that can provide significant support to global industries in line with the United Nations' Sustainable Development Goals (SDGs) and ESG principles.”

The article was Published in Critical Reviews in Environmental Science and Technology.

In this work, Prof. Oke and his team emphasize the importance of soil sampling, homogenization, and bulk dispersion and examining soil physicochemical and biological properties before analyzing soil MPs. Based on their analysis, the team recommended a comprehensive eight-step methodology for analyzing soil MPs.

These steps include 1) careful planning of soil sampling; 2) collecting representative samples; 3) processing of samples including drying and sieving; 4) characterizing the soil to determine its physicochemical and biological properties; 5) Pre-cleaning of the soil before separating the MPs from it; 6) separation of MPs from the clay and organic components of the soil; 7) Visual or chemical identification of MPs and finally 8) Calculation of MPs per kg of dry soil.

In this methodology, each step recognizes the importance of considering soil-specific properties, understanding how these may interfere with MP analysis, and overcoming these interferences and other methodological challenges.

This new method provides a streamlined approach to analyzing soil MPs, ensuring accuracy, precision, reliability and quality assurance, and minimizing potential sources of error or contamination.

Also, this method is easy to reproduce under different settings. Interestingly, the implications of this method extend beyond the scientific community. This systematic approach facilitates data and research comparison and improves scientific understanding, which promotes international collaboration and knowledge sharing and supports policy development to manage MP pollution.

„Our proposed eight-step method serves as a basis for developing standardized methods for analyzing soil MPs. Such globally accepted standards can be aligned with regulations under the United Nations Environment Program and used to develop international agreements to manage plastic waste.”

„Furthermore, our methodology could prove to be a valuable tool for industries, policy makers and researchers around the world committed to combating plastic pollution and protecting the environment, in particular,” concludes Professor Oke.