Impact of microplastic addition on degradation of dibutyl phthalate in offshore sediments

In this work, effects of microplastics (polypropylene and polystyrene) at four concentrations (0.2-10%, w/w) on di-n-butyl phthalate (DBP) degradation in offshore sediments were investigated. DBP degradation percentage was enhanced by 0.2% microplastics (7.3-11.0% increment) but was reduced by 2-10% microplastics (3.7-27.7% decrement). Meanwhile, addition of microplastics with higher sorption ability to DBP led to lower DBP degradation percentage. The initial concentration of bioavailable DBP in sediments decreased with the increase of microplastic sorption ability to DBP and microplastic concentration. Microbial community structure was more significantly influenced by microplastic type than by microplastic concentration. Significant positive correlation was observed between the total relative abundances of dominant DBP-degraders and DBP degradation percentage. The results indicated that the changes in DBP degradation percentage were related to both DBP bioavailability and the total relative abundances of dominant DBP-degraders. Hence, persistence of the pollutant in the coastal environment was microplastic type- and concentration-dependent.