Microplastics and pesticides often share the same agricultural soils, but scientists are still uncovering how these pollutants interact. A new study shows that aging can turn tiny polyvinyl chloride, or PVC, microplastics into more effective sorbents for the fluorinated pesticide fluensulfone, potentially increasing pesticide retention in soil.
The researchers examined pristine and artificially aged PVC microplastics with particle sizes of 1 and 150 micrometers. They focused on fluensulfone, a fluorinated nematicide used to control plant parasitic nematodes, and investigated how particle size, aging, water chemistry, soil, and another pesticide influenced its behavior.
"Our findings show that microplastics should not be viewed simply as passive particles in agricultural soils," said corresponding author Xiaoyun Li. "As PVC particles become smaller and weathered, their surfaces change in ways that can create new opportunities for fluorinated pesticides to bind and remain in the soil environment."
The strongest effects appeared in the smallest aged particles. Oxidative aging roughened PVC surfaces, increased porosity, and introduced oxygen-containing functional groups. These changes created more chemically active and heterogeneous binding sites. For 1 micrometer PVC particles, aging increased the maximum sorption capacity for fluensulfone from about 292 to 344 micrograms per gram and substantially increased sorption affinity.
The researchers found evidence that the interaction cannot be explained by conventional hydrophobic attraction alone. Instead, the results point to fluorine-sensitive interfacial interactions, particularly hydrogen bonding involving fluorine and oxygen-containing surface groups, together with polar interactions and pore-assisted retention. Changes in chlorine-containing regions of aged PVC may also make a secondary contribution.
Environmental chemistry further changed the behavior of the pesticide. Fluensulfone sorption increased steadily as pH rose from 4 to 12. Calcium ions also promoted sorption, increasing uptake by roughly 30% to 35% in some treatments. In contrast, sodium, chloride, and nitrate generally reduced sorption. Humic acid, a common component of natural organic matter, enhanced fluensulfone retention but showed relatively little dependence on concentration.
Importantly, the researchers also tested systems containing agricultural soil. Soil organic matter remained the dominant sink for fluensulfone, but PVC microplastics provided additional binding sites rather than simply competing with soil.
Aged 1 micrometer PVC particles accounted for approximately 30% to 35% of the total retained fluensulfone in some soil systems, while increasing overall pesticide sorption by roughly 12% to 33%. Their contribution also grew as the amount of PVC increased.
Interactions became even more complex when another pesticide, spirotetramat, was introduced. While spirotetramat reduced fluensulfone sorption in simplified binary systems, it enhanced fluensulfone retention in soil containing aged PVC, highlighting how multiple contaminants can reshape interfacial processes in real environmental settings.
The findings suggest that aged and fine PVC microplastics may increase the persistence of fluorinated pesticides in agricultural soils and influence their mobility, bioavailability, and environmental risk.
The researchers emphasize that future pesticide fate and risk assessments may therefore need to consider microplastics as chemically active supplementary sorbents, particularly as environmental weathering continuously changes their surface properties.
===
Journal reference: Li A, Hou Y, Gao S, Li X, Gao S, et al. 2026. Size and aging-driven interactions between fluensulfone and PVC microplastics: the key role of fluorine-sensitive interactions. Environmental and Biogeochemical Processes 2: e017 doi: 10.48130/ebp-0026-0011
https://www.maxapress.com/article/doi/10.48130/ebp-0026-0011
===
About the Journal:
Environmental and Biogeochemical Processes (e-ISSN 3070-1708) is a multidisciplinary platform for communicating advances in fundamental and applied research on the interactions and processes involving the cycling of elements and compounds between the biological, geological, and chemical components of the environment.
