Synergistic Immobilization and Degradation of Microplastics in Sandy Calcareous Soils Using Fe-Biochar Compost Amendment

Abstract

Microplastic accumulation in calcareous soils irrigated with treated wastewater is an emerging concern, particularly in arid agroecosystems where conventional remediation is often ineffective. We investigated whether a Fe-modified biochar–compost amendment could enhance the retention and degradation of microplastics. Laboratory tests and on-field experiments, aided by machine learning cut leaching by sixty to eighty-five percent. Polyethylene and polypropylene showed the retention of microplastic. The composite amendment improved soil structure by two and a half times. Helped microplastic break down. Thirty to forty percent of microplastic mass loss came from iron-mediated reactions. Unlike amendments the composite amendment kept soil pH and salinity within acceptable limits and caused no obvious harm. Field observations confirmed that the results were consistent across space. Machine-learning models predicted retention with eighty-nine percent accuracy. Overall the composite amendment offers a scalable solution, for reducing microplastic mobility while improving soil structure in farms that use treated wastewater.