Application of food waste digestates and digestate-derived biochar for mitigating antibiotic, Pb, and ARGs pollution in soil containing biodegradable microplastics: The key role of exogenous dissolved organic carbon and organic nitrogen

Abstract

The widespread use of biodegradable plastic mulch films and organic manure in agriculture has led to the accumulation of biodegradable microplastics (BMPs), heavy metals, and antibiotics in soil. In this study, three food waste-derived soil amendments, including digestion liquid (DL), digested food waste (DFW), and DFW-derived biochar (DFW-BC), were evaluated for their ability to mitigate co-pollution of Pb, sulfamethazine (SM2), and antibiotic resistance genes (ARGs) in soil containing poly(butylene succinate) microplastics (PBS-MPs). All amendments enhanced SM2 dissipation, and DFW and DFW-BC facilitated the transformation of acid-soluble Pb into less mobile fractions, whereas DL exhibited a more modest effect on Pb immobilization. Regarding ARGs, DL amendment reduced the relative abundances of intl1 and sul1 by 21.6% and 35.0%, respectively. DFW amendment achieved reductions of 77.6% for intl1 and 57.1% for sul2, while DFW-BC amendment reduced them by 17.8% and 28.6%, respectively. Correlation network analysis suggested that Bacillaceae was identified as a potential host of sul1 and intl1, whereas sul2 potential hosts mainly belonged to the phylum Proteobacteria. Mechanistically, these amendments primarily drove changes in the soil bacterial community by increasing soil dissolved organic matter (DOM) and total dissolved nitrogen (TDN) contents, while reducing water-soluble SM2 concentration, thereby suppressing the proliferation of potential ARGs hosts such as Bacillaceae and mitigating soil ARGs contamination. This study demonstrates that food waste-derived amendments, as value-added reutilization resources, offer a promising strategy for the remediation of soils co-contaminated with BMPs and multiple pollutants.