Aging-Driven Mobilization of Endogenous Phthalate Esters from Microplastics and the Ecotoxicity of PAEs toward Soil Microbiota and Plants.

Abstract

Microplastics are long-term sources of hazardous endogenous additives; however, the release behavior and ecological impacts of phthalate esters (PAEs) during environmental aging remain poorly understood. This study systematically examined the release of dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) from microplastics under mechanical abrasion, accelerated H2O2 oxidation, and prolonged exposure to mildly acidic conditions. We evaluated the concentration-dependent effects of DBP and DEHP on Escherichia coli, a culturable environmental microorganism, pak choi, and soil bacterial communities. Accelerated H2O2 oxidation produced the greatest release, reaching 95.6% for DBP and 31.9% for DEHP, whereas release under mildly acidic exposure remained below 4%. Mechanical abrasion further increased PAE migration during chemical treatments. DBP and DEHP had limited effects on E. coli under the experimental conditions but inhibited culturable water- and soil-derived microorganisms in nutrient-limited media. Higher PAE concentrations significantly inhibited seed germination and plant growth, reducing biomass by up to 91.4%. PAE exposure also increased soil electrical conductivity and altered bacterial community composition, shifting the relative abundances of genera such as Sphingomonas and Bacillus. These findings indicate that endogenous PAE mobilization from microplastics varies with aging conditions and mechanical abrasion. In contrast, biological responses to DBP and DEHP depend on exposure concentration, compound identity, and nutrient availability. This study provides experimental insights into the environmental fate of plastic-associated PAEs and their potential ecological effects under various physicochemical stress conditions.