ZnO-loaded PVC microplastics increases soil Zn bioavailability and phytotoxicity

Area of Science:

• Agroecosystem science
• Environmental chemistry
• Soil microbiology

Background:

• Agricultural plastic films are a significant source of microplastic pollution.
• Zinc oxide nanoparticles (ZnO NPs) are common UV protectants in plastics, but their environmental impact is unclear.

Purpose of the Study:

• To investigate the effects of ZnO additives in polyvinyl chloride (PVC) films on soil-plant-microbe interactions.
• To assess how UV aging influences ZnO release and impacts maize growth and soil microbial communities.

Main Methods:

• PVC films with varying ZnO concentrations (0, 1, 5%) were UV aged.
• Fragments were incorporated into maize-growing mesocosms for 9 weeks.
• Soil bioavailable zinc, maize productivity, and microbial communities were analyzed.

Main Results:

• Soil bioavailable zinc increased with ZnO loading and UV aging, with microplastics releasing more zinc than macroplastics.
• Zinc accumulated in maize roots, stems, and leaves.
• Root biomass decreased by 40-50% at 5% ZnO-PVC; microbial diversity showed minor changes, but key nutrient-cycling bacteria declined at high ZnO concentrations.

Conclusions:

• UV weathering of ZnO-containing plastics increases soil bioavailable zinc, especially at high concentrations.
• High ZnO levels in PVC films negatively impact maize development and soil microbial composition.
• Low ZnO concentrations (1%) in PVC films may act as a slow-release zinc fertilizer with minimal adverse effects.