Uniting Global Efforts to Combat Microplastic Pollution in Agricultural Soils: A Call for Harmonized Protocols and Collaborative Action

Microplastics (MP), defined as plastic particles ranging from 1 to 5000 µm, have become a significant environmental concern due to the drastic increase in plastic use. Agricultural soils are highly susceptible to MP contamination from both direct and indirect sources such as plasticulture, biosolids application, irrigation systems, and atmospheric deposition. These contaminants disrupt soil physical and biological functions, altering porosity, water retention, and microbial communities essential for nutrient cycling, ultimately impairing plant productivity. MPs also act as vectors for associated pollutants, raising concerns about their transfer to the food chain and potential health risks. Despite these critical impacts, agricultural soils have received far less attention than aquatic systems.

The global diversity of soil types poses challenges to the development of standardized protocols for sampling, extraction, and analysis of MPs. Existing methods often lack reproducibility and comparability across regions, hindering effective management strategies. To address these challenges, a harmonized, globally applicable framework is needed. This framework should consider soil properties and ensure reliable identification and quantification of MPs through standardized procedures for sampling, density separation, and polymer-specific analysis, while accounting for particle size and shape. Such protocols will provide a reliable foundation for MP monitoring in soils, while remaining adaptable for diverse research applications.

The Soil and Water Management & Crop Nutrition Laboratory (SWMCNL) in Seibersdorf, in collaboration with international experts, has conducted research on MPs. This includes soil incubation experiments using isotopes to monitor organic matter stability and MP degradation. Additionally, methods for extracting MPs from various soil types, including both conventional and biodegradable plastics, area being developed and tested. Recent work has focused on preparing protocols based on methods from the MINAGRIS project, in collaboration with Coordinated Research Project (CRP) experts. These protocols integrate density separation, organic matter removal, and microscopic analysis and provide improved MP recovery rates, particularly for particles larger than 300 µm. Additionally, emphasis was placed on determining the isotopic changes of δ¹³C by EA-IRMS due to the extraction procedure. This is to support research involving carbon isotopes, such as in incubation experiments. These methodological advances are important steps towards establishing a robust and scalable Standard Operating Procedure (SOP) for MP research in soils.

Furthermore, in collaboration with the International Network on Soil Pollution (INSOP) from FAO, we aim to develop global working groups focused on MP extraction, identification and quantification of MPs in soil. INSOP’s overall aim is to stop soil pollution and achieve the global goal of zero pollution, covering assessment and remediation, as well as impacts on the environment and human health. INSOP also aims to strengthen technical capacities, legislative frameworks, and promotes the exchange of experiences and technologies for sustainable soil management and remediation.

Aligned with the UN Plastics Treaty, this initiative aims to enhance Member States’ technical capacities to address soil pollution and provide tools for evidence-based policymaking. By integrating harmonized monitoring protocols with adaptable research frameworks, we can better understand MP impacts on agricultural soils and support global efforts to mitigate plastic pollution.