Microplastics are increasingly common in agricultural landscapes, where they can enter soil through degraded greenhouse coverings, mulch films, irrigation water, sewage sludge and atmospheric deposition. Because these particles can remain in the environment for decades, researchers have questioned whether they might accumulate contaminants and transport them through soil, groundwater or food-production systems. The concern is particularly significant in regions where reclaimed wastewater is used to irrigate crops.

The study focused on linear low-density polyethylene, a flexible plastic widely used in agricultural films. Researchers buried fragments of previously used polyethylene mulch film in three different Israeli agricultural soils and allowed them to remain underground for 20 months. This approach was designed to reproduce environmental aging under realistic conditions rather than relying solely on accelerated laboratory treatments, which can produce surface changes that do not fully reflect what occurs in the field.

When the scientists recovered the plastic fragments, the particles had clearly changed. Natural organic matter from the soil had accumulated on their surfaces, forming a coating known as an environmental or soil-derived corona. Such coatings can alter surface chemistry, wettability and the availability of binding sites. In theory, these changes could increase the particles’ capacity to attract hydrophobic organic molecules, leading to stronger sorption and potentially allowing microplastics to act as mobile carriers of pollution.

To test that possibility, the researchers examined the interaction between the aged polyethylene and 48 organic contaminants commonly detected in reclaimed wastewater used for agricultural irrigation. The chemical set included pesticides, pharmaceuticals and other wastewater-associated compounds with different molecular properties. The team measured both sorption, the process by which contaminants attach to a surface, and desorption, the process by which they are released back into the surrounding environment.

The results challenged the assumption that aging automatically makes polyethylene microplastics more chemically active. For approximately 90 percent of the tested compounds, soil aging caused little or no meaningful change in the amount of contaminant associated with the plastic. Overall, the compounds interacted only weakly with the polyethylene and could be released relatively easily. That pattern indicates that the plastic did not permanently trap most of the chemicals or become a substantially more powerful contaminant carrier over time.

The researchers also found that the largest changes to the plastic surfaces occurred during the first year of burial. After that initial period, the particles became comparatively stable, suggesting that the formation of the organic coating reached a plateau. Surprisingly, differences among the three soils—including their organic matter and clay content—had little influence on how the polyethylene aged or how it interacted with the contaminants. This does not mean soil properties are unimportant; rather, it suggests that the soil matrix itself may dominate contaminant behavior more strongly than the aged plastic particles.

“Soil, not the plastic, remains the main factor influencing the environmental fate of these chemicals,” said Dr. Evyatar Ben Mordechay, one of the study’s researchers. Soil minerals, clay surfaces and native organic matter provide an enormous and chemically diverse network of binding sites. Compared with that complex matrix, the surface area and sorption capacity of polyethylene microplastics may be relatively minor, particularly when the particles are present at environmentally realistic concentrations.

The findings do not make microplastics harmless. Polyethylene fragments remain persistent pollutants, can accumulate in agricultural soils and may affect soil structure, organisms and ecosystem processes through other mechanisms. The study examined one plastic type, and different polymers, additives, particle sizes, shapes and weathering histories could behave differently. Even so, the research offers a more precise picture of their role in contaminant transport: for aged polyethylene in agricultural soils, the plastic appears to play a secondary part, while the soil itself continues to control the movement, retention and release of most organic pollutants.

Subject of Research: Cells
Article Title: Aging of polyethylene microplastics in agricultural soils has minimal effect on sorption and desorption of wastewater-derived organic contaminants
Web References: https://doi.org/10.1016/j.seh.2026.100207
References: Soil & Environmental Health, DOI: 10.1016/j.seh.2026.100207
Image Credits: Raz Lev

Keywords: Soil science, surface chemistry, environmental sciences, pollution, environmental chemistry, plastics, wastewater, microplastics, agricultural soils, organic contaminants

Microplastics, often defined as plastic particles smaller than 5 millimeters, have undergone extensive scrutiny in marine systems, yet their occurrence and fate in soil have remained inadequately quantified. Conventional extraction techniques for microplastics from soil frequently struggle due to the physical and chemical complexities inherent in soil samples, which contain varying organic matter content, mineral compositions, and moisture levels. This complexity is exacerbated when attempting to retrieve weathered synthetic microcapsules, whose altered surface chemistry and density can hinder isolation. The pioneering extraction method detailed in this study leverages modified oil-based solvents tailored to dislodge both pristine and aged polyurea microcapsules, alongside polyethylene microplastics, from soil matrices with unprecedented efficiency.

Critically, the use of modified oil solvents targets the hydrophobic characteristics of microplastic particles, exploiting their affinity for non-polar solvents while leaving the majority of soil constituents relatively unperturbed. This nuanced leverage of chemical affinities allows for selective extraction that circumvents the aggressive physical disruptions or harsh chemical treatments typical of previous methodologies. By optimizing the solvent composition and contact parameters, the researchers enhance the detachment of microplastic particles, thus increasing yield and preserving particle integrity—imperative for subsequent analyses, whether spectroscopic or microscopic.

Another notable aspect of this study is its focus on both pristine microplastics, which represent new or minimally degraded particles, and weathered counterparts that have experienced environmental aging processes. Weathering alters the physicochemical properties of microplastics, often introducing oxygen-containing functional groups and modifying surface morphology. These changes can influence not only the environmental behavior of microplastics but also their response to extraction solvents. The modified oil extraction technique effectively addresses these challenges by demonstrating robust performance across a spectrum of weathering states, suggesting versatile applicability for monitoring microplastic pollution under realistic environmental conditions.

The research also highlights the critical need for reliable extraction protocols capable of handling soil complexity and microplastic heterogeneity. Polyurea microcapsules, frequently leveraged for controlled-release applications in agriculture and industry, comprise a synthetic polymer network distinct from the more widespread polyethylene microplastics. Their detection and quantification in soils have been impeded by their unique chemical makeup and potential for surface degradation. By integrating solvent modifications that specifically enhance affinity for polyurea structures, the method achieves selective extraction without significant co-extraction of soil-derived interferences, thereby refining microplastic quantification accuracy.

This innovative approach heralds new opportunities for environmental monitoring programs seeking to benchmark terrestrial microplastic contamination levels accurately. Microplastics’ migration through soil profiles and potential uptake by plants, soil fauna, and microorganisms represent critical ecological pathways influencing ecosystem health and food security. By providing a robust tool for isolating these contaminants, the study indirectly supports risk assessment efforts that must consider exposure pathways grounded in precise contamination mapping.

Moreover, the scalability and adaptability of the modified oil extraction method spotlight its potential for widespread adoption in environmental laboratories. Unlike labor-intensive or equipment-heavy alternatives, this solvent-based technique offers a streamlined workflow conducive to high-throughput sample processing. Consequently, environmental scientists can more feasibly conduct large-scale surveys spanning diverse land-use types—from agricultural fields to urban soils—illuminating spatial variability and temporal dynamics of microplastic presence.

The emphasis on polyethylene microplastics underscores the persistent presence of this polymer, one of the most ubiquitous plastics worldwide, notorious for its environmental persistence and ecological impact. By demonstrating successful extraction from native soil samples, the study addresses a pressing gap in terrestrial microplastic research, which has often defaulted to marine or freshwater contexts. Understanding polyethylene’s terrestrial distribution and transformation informs policy measures targeting plastic waste management and environmental remediation.

In addition to environmental implications, the methodology carries relevance for analytical chemistry, particularly in the characterization of microplastic particles post-extraction. Preservation of particle morphology and chemical functionality enables integrated spectroscopic analyses, such as Fourier-transform infrared spectroscopy (FTIR) or Raman spectroscopy, which depend on representative sample integrity. This complementary analytical capability facilitates the identification of polymer types, weathering states, and potential additive residues, contributing multidimensional insights into pollution sources and degradation pathways.

Environmental fate studies predicated on accurate microplastic extraction data could elucidate degradation rates, bioavailability, and vector potential for co-contaminants such as heavy metals or persistent organic pollutants. The nuanced extraction approach detailed here therefore serves as a foundational technology underpinning interdisciplinary investigations spanning environmental chemistry, soil science, and ecotoxicology.

The study also encourages future exploration into refining solvent systems tailored to other polymer classes or composite materials embedded within soils, recognizing the heterogeneous nature of plastic pollution. Coupled with advances in instrumentation and image analysis, such developments could enable comprehensive pollutant profiling essential for holistic environmental stewardship.

It is worth noting that such methodological breakthroughs arrive at a critical juncture when global plastics production continues to soar, with emerging policy frameworks increasingly demanding transparent monitoring of plastic pollution reservoirs. Reliable data, enabled by improved extraction and detection methods, will be instrumental in shaping effective mitigation strategies and guiding circular economy initiatives aimed at curbing plastic waste generation.

Beyond environmental monitoring, the principles underpinning modified oil extraction hold potential translational value for other fields grappling with micro- and nano-scale particle isolation, including pharmaceutical sciences and materials engineering. The selective affinity-based approach exemplified here might inspire analogous protocols for isolating functionalized particles amid complex matrices, expanding the technique’s interdisciplinary footprint.

Importantly, this study also draws attention to the underexplored domain of synthetic polyurea microcapsules, prompting broader consideration of engineered nanomaterials’ environmental interactions. As these materials gain traction in diverse technological applications, understanding their life cycle, environmental persistence, and fate becomes paramount to balancing innovation with ecological safeguard.

In summary, the advancement of a modified oil extraction protocol capable of efficiently recovering both pristine and weathered synthetic polyurea microcapsules alongside polyethylene microplastics from soil constitutes a significant stride in microplastic research. This technique enhances detection capabilities within complex terrestrial environments, aids in pollution mapping, and supports broader environmental risk assessments. Its implications reverberate across scientific, regulatory, and societal domains confronted with the realities of plastic pollution in the Anthropocene.

Subject of Research: Microplastic extraction methods focusing on pristine and weathered synthetic polyurea microcapsules and polyethylene microplastics from soil matrices.

Article Title: Modified oil extraction of pristine and weathered synthetic polyurea microcapsules and polyethylene microplastics from soil.

Article References:

Teggers, EM., Heck, S., Meisterjahn, B. et al. Modified oil extraction of pristine and weathered synthetic polyurea microcapsules and polyethylene microplastics from soil.
Micropl.&Nanopl. 5, 21 (2025). https://doi.org/10.1186/s43591-025-00121-0

Image Credits: AI Generated