Polyethylene film incorporation into the horticultural soil of small periurban production units in Argentina

• PE plastic residue was found in horticultural soils (equals to 10% of the area).
• The predominant fragment size was (28 cm2 ± 13 cm2).
• Pesticides can migrate to the inside of the PE film.
• Further bidirectional migrations between soil and plastic film can occur.

Horticulture makes intensive use of soil and extensive use of polyethylene (PE) sheeting and pesticides, producing an environment where the dynamics between soil and plastics can affect pesticide fate. We have determined that the presence of plastic residues in the horticultural soil of small production units equals 10% of the soil area, being meso and macro-sections the predominant fragment sizes. All soil samples were taken from different plots located in Cuartel V, Moreno district, in the suburbs of Buenos Aires city, Argentina. Laboratory experiments were conducted to see the relations among pesticide, soil and PE film. Endosulfan recovery from LDPE films (25 μm and 100 μm) was studied, observing evidence that indicated migration to the inside of the plastic matrix. To further analyze the dynamics of pesticide migration to soil and atmosphere, experiments using chlorpyrifos, procymidone and trifluralin were performed in soil–plastic–atmosphere microenvironments, showing that up to 24 h significant amounts of pesticides moved away from the PE film. To determine whether PE residues could act as potential pesticide collector in soil, column elution experiments were done using chlorpyrifos, procymidone and trifluralin. Results showed an important pesticide accumulation in the mulch film (584 μg–2284 μg pesticide/g plastic) compared to soil (13 μg–32 μg pesticide/g soil). Finally, chemical and photochemical degradation of deltamethrin adsorbed in PE film was studied, finding a protective effect on hydrolysis but no protective effect on photodegradation.We believe that a deeper understanding of the dynamics among soil, plastic and pesticides in horticultural productive systems may contribute to alert for the implications of PE use for plastic sheeting.

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