Atrazine sorption on biodegradable microplastics: Significance of microbial aging

The study of the environmental sorption behavior of typical biodegradable microplastics (BMPs) during biodegradation is essential given the different characteristics of BMPs and conventional microplastics (MPs) and the knowledge gap on the sorption capacity of BMPs for pollutants during degradation. In this study, polylactic acid (PLA) and poly (butylene-adipate-co-terephthalate) (PBAT) were chosen as research objects, and the effects of soil microbial aging on their surface properties and atrazine (ATZ) sorption were investigated. The structural composition of the bacterial community was essentially similar between B-PLA and B-PBAT. Microbial aging action created new pores and cavities in PLA, forming microbial films that led to the agglomeration of PLA particles. The microbial aging action destroyed the amorphous regions of PLA and PBAT, resulting in higher crystallinity, and the ester groups broke to form carboxyl groups. The equilibrium sorption (Qe) of B-PLA increased by 11.12 % compared with PLA, while the Qe of B-PBAT decreased by 4.95 % compared to PBAT. These results show that soil microbes change the surface properties of PLA and PBAT, thus affecting the sorption mechanism of ATZ, and provide a theoretical premise for the behavior and ecological risk assessment of ATZ in the presence of BMPs.