Enhanced interfacial behaviors of benzo(a)pyrene on the petroleum-based degradable plastics endured long-term bio-aging

Microplastics can harm marine organisms by adsorbing contaminants while aging of microplastics in seawater might induce new risks. This study evaluated the effects of bio-aging on the benzo(a)pyrene adsorption and desorption of petroleum-based degradable PBAT/PBS microplastics in seawater. The surface functional groups of PBAT/PBS microplastics treated with 36 months of bio-aging in seawater (A-PBAT 36M /A-PBS 36M ) significantly increased the O/C ratio (67/61%) and -C=O content compared to virgin PBAT/PBS (V-PBAT/V-PBS). The maximum adsorption capacity of benzo(a)pyrene on V-PBAT/V-PBS in seawater was 213.1/213.6 μg g -1 , whereas significant higher adsorption capacity of 258.0 μg g −1 and 246.3 μg g −1 were observed for A-PBAT 36M and A-PBS 36M , respectively. There was no significant difference in the adsorption of benzo(a)pyrene on PE under different bio-aging times. Bio-aging marginally reduced the potential risk of PBAT due to lower desorption capacity of A-PBAT 36M . Density flooding theory indicated that A-PBAT 36M -benzo(a)pyrene binds were dominated by van der Waals, π-π stacking, and C-H-π/O-H-π interactions, while A-PBS 36M -benzo(a)pyrene binds were dominated by van der Waals and C-H-π/O-H-π interactions. The binding energy of A-PBAT 36M /A-PBS 36M to benzo(a)pyrene decreased to -31.52/-25.87 kcal mol -1 , confirming stronger adsorption than V-PBAT/V-PBS. The results of the study provide new insights into the environmental behavior of petroleum-based degradable plastics in the marine environment, especially the long-term microbial aging process.