Microplastics in Soils with Contrasting Organic Carbon Content and Clay Fraction Mineralogy: Effects on Copper and Phosphorus Adsorption

Contamination with microplastics (MP) can interfere with the dynamics of Cu and P in soils. Two soils with contrasting organic matter content and clay fraction mineralogy were selected: Haplic Inceptsol (HaI) and Humic Inceptsol (HuI). Two MP standards were used (5% m/m): MP mulching collected directly from soils under strawberry cultivation (FMP) and unused MP mulching (UMP). The soil samples were saturated with Cu and P and subjected to sequential and selective extractions (outer-sphere and inner-sphere forms). The addition of MP interfered positively in the total adsorption of H2PO4− in the HaI. No significant differences were observed between the adsorption of Cu2+ and H2PO4− with MP degradation degree (FMP × UMP). The presence of MP also increased the environmental availability of Cu2+ (increase in outer-sphere and reduction in inner-sphere forms). Contamination of soils with high organic matter contents with MP can cause negative synergistic effects in terms of increased mobility of Cu and P (increased leaching and water contamination potentials). This situation can be particularly important in areas with high discharge of MP and Cu and P-based contaminants. These environmental negative interferences in the dynamics of Cu and P are independent of the degree of MP degradation.