Distribution characteristics and microbial synergistic degradation potential of polyethylene and polypropylene in freshwater estuarine sediments

The microbial degradation of polyethylene (PE) and polypropylene (PP) resins in rivers and lakes has emerged as a crucial issue in the management of microplastics. This study revealed that as the flow rate decreased longitudinally, ammonia nitrogen (NH4+-N), heavy fraction of organic carbon (HFOC), and small-size microplastics (< 1 mm) gradually accumulated in the deep and downstream estuarine sediments. Based on their surface morphology and carbonyl index, these sediments were identified as the potential hot zone for PE/PP degradation. Within the identified hot zone, concentrations of PE/PP-degrading genes, enzymes, and bacteria were significantly elevated compared to other zones, exhibiting strong intercorrelations. Analysis of niche differences revealed that the accumulation of NH4+-N and HFOC in the hot zone facilitated the synergistic coexistence of key bacteria responsible for PE/PP degradation within biofilms. The findings of this study offer a novel insight and comprehensive understanding of the distribution characteristics and synergistic degradation potential of PP/PE in natural freshwater environments. Microbial degradation of typical microplastics PE and PP in rivers and lakes has always been one of the most important issues in the management of microplastics. However, under different flow rates, the hot zone and potential of PE/PP synergistic degradation in natural freshwater remain elusive. In this study, we identified the distribution characteristics and revealed the synergistic degradation potential of PE/PP in the freshwater estuarine sediments. This study offers novel insights into the synergistic degradation of microplastics in natural freshwater, which is of great significance to the control and management of microplastics