Document Type
Article
Publication Date
2023
Abstract
Plastic is a pervasive and persistent environmental pollutant. Widespread use of plastics, such as polyethylene terephthalate (PET), exacerbate this issue. PET plastics can degrade in the environment and generate microplastics, which can then interact with other substances, including adsorption of metal ions. Copper is a metal that is often applied as a fungicide to agricultural fields, and repeated application leads to its accumulation in soil to a level that inhibits plant growth. I investigated the growth of soybean (Glycine max) in the presence of PET microplastics and copper (CuSO4). I predicted that increased copper in soil has phytotoxic effects, which would be offset by the presence of soil microplastics. Soybeans grown in pots of soil were treated with 250 mg/kg copper and/or 10 g/kg microplastics (w:w dry soil). Bioavailable soil copper; leaf and root copper concentration; and leaf, stem, and total biomass did not vary among treatments. This was unexpected but is explainable as only ~1.2 % of total copper in the control soil was bioavailable. The low copper bioavailability was attributed to the high concentration of soil organic matter (~40 %) to which copper ions were likely bound. Regardless, there was evidence that microplastics interact with copper: Fv/Fm in the combined treatment was reduced by ~2.0 % relative to the control, and soybean root biomass in the combined treatment was ~35 % greater relative to the control and copper treatments. These effects could be related to the influence of microplastics on soil physiochemical properties.