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Microplastics: Pesticide sorption and efficiency
Summary
Tiny plastic particles in soil and water don't just sit there—they act like sponges that grab onto pesticides and antibiotics, changing how far these chemicals travel and how long they stick around in our environment. This matters because plastic pollution could be quietly making pesticide and antibiotic contamination worse or harder to predict in the food and water we rely on. The findings suggest that safety assessments for these chemicals should start factoring in microplastic pollution, since the plastics themselves may be changing the risks.
Microplastics (MPs) and nanoplastics (NPs) are rapidly emerging contaminants in both agricultural soils and aquatic systems. Their interactions with pesticides, antibiotics, and mineral colloids fundamentally reshape contaminant behavior, mobility, and environmental risks. This dissertation integrates three research components to investigate how MPs and NPs influence the physicochemical pathways of systemic pesticides and antibiotics across soil and water systems. The first research component examines the sorption behavior of spirotetramat (SP) on pristine and aged PVC microplastics of two representative particle sizes. Aging significantly enhanced sorption affinity due to increased surface polarity, oxygen-containing functional groups, and surface roughness, while particle size controlled accessible sorption area. In soil environments, PVC MPs altered the distribution of SP between soil organic matter and the plastic phase, modifying its mobility and persistence. The second component elucidates structure-driven interactions between fluensulfone (FL) and PVC MPs. FL exhibited fluorine-involved hydrogen bonding and halogen-related interactions with PVC, generating sorption domains distinct from those of SP. Competitive sorption experiments confirmed minimal antagonism between the two pesticides due to differentiated sorption mechanisms. Environmental parameters such as pH, ionic strength, and humic acid further regulated FL–PVC interactions. The third component explores heteroaggregation between nanoplastics and common minerals under varying degrees of background plastic pollution. Nanoplastics promoted or inhibited mineral aggregation depending on ionic strength and plastic loading. These NP–mineral heteroaggregates substantially modified antibiotic adsorption pathways, demonstrating that nanoplastics actively reshape contaminant transport in aquatic systems. Together, these studies provide mechanistic insights into how MPs and NPs modify pesticide and antibiotic behavior at molecular, colloidal, and environmental scales. This work highlights the importance of incorporating plastic pollution into contaminant risk assessments in both agricultural and aquatic environments.