Cadmium and copper absorption by Eisenia fetida in the presence of different concentrations of microplastics

Abstract

Background: Soil serves as the primary repository for microplastics, yet their impact on soil-dwelling organisms remains insufficiently understood. This study aims to investigate the influence of varying concentrations of microplastics in soil on the absorption of Cd and Cu by Eisenia fetida within an artificial soil matrix. Methods: The artificial soil consisted of kaolinite clay (20% dry weight), quartz sand (70% dry weight), and Sphagnum peat (10% dry weight). Microplastics, derived from worn-out tire rubber, were incorporated into the soil to establish four concentration levels: 5, 25, 50, and 100 grams of tire microplastics per 500 grams of dry soil. Each treatment was inoculated with ten mature earthworms, weighing between 3.0 and 5.0 grams. After 14 days, samples were collected for ICP analysis. Results: : The highest accumulation of both metals was observed in treatments with 25, 50, and 100 grams of tire microplastics. The results demonstrated significant disparities in copper and cadmium accumulation in the tissue samples following the introduction of tire wear particles, indicating an augmenting effect of tire particles on metal uptake by the samples. Statistically notable reductions (p < 0.05) in Cd and Cu concentrations were noted in both the control soil and soil containing microplastics, particularly in the 100-gram microplastic treatment for Cd and the 50-gram microplastic treatment for Cu. Conclusion: Exposure to a combination of microplastics, Cd, and Cu has more pronounced adverse effects on E. fetida, and microplastics enhance the bioavailability of heavy metal ions within the soil environment