Adsorption behaviors and bioavailability of tetrabromobisphenol A in the presence of polystyrene microplastic in soil: Effect of microplastics aging*

Microplastics, a kind of emerging pollutant, have become a global environmental research hotspot in recent years due to its wide distribution in soil and its impact on soil ecosystems. However, little information is available on the interactions between microplastics and organic contaminants in soil, especially after microplastic aging. The impact of polystyrene (PS) microplastic aging on the sorption of tetrabromobisphenol A (TBBPA) in soil and the desorption characteristics of TBBPA-loaded microplastics in different environments were studied. The results showed a significant increase of 76.3% in adsorption capacity of TBBPA onto PS microplastics after aging for 96 h. Based on the results of characterization analysis and density functional theory (DFT) calculation, the mechanisms of TBBPA adsorption changed mainly from hydrophobic and 7C-7C interactions on pristine PS microplastics to hydrogen bond and 7C-7C interactions on aged PS microplastics. The presence of PS microplastics increased the TBBPA sorption capacity onto soil-PS microplastics system and significantly altered the distribution of TBBPA on soil particles and PS microplastics. The high TBBPA desorption over 50% from aged PS microplastics in simulated earthworm gut environment suggested that TBBPA contamination combined with PS microplastics might pose a higher risk to macroinvertebrates in soil. Overall, these findings contribute to the understanding of impact of PS microplastic aging in soil on the environmental behaviors of TBBPA, and provide valuable reference for evaluating the potential risk posed by the co-existence of microplastics with organic contaminants in soil ecosystems.