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Degradation of microplastics and the plastisphere bacteria in the acidogenic phase of simulated municipal solid waste landfilling
Summary
Researchers simulated conditions inside a municipal solid waste landfill and found that different microplastic types (PE, PS, and PLA) aged and degraded at very different rates during the acidogenic leachate phase, with distinct microbial communities forming on each plastic type. This matters because landfills are both sources and sinks for microplastics, and understanding how plastics degrade there helps predict what eventually leaches into groundwater and surrounding soil.
Landfills serve as major sources and sinks for microplastics. The initial stage of municipal solid waste landfilling will generate substantial amounts of leachate, which carries a significant quantity of microplastics. However the degradation behavior of different microplastics in waste and leachate, along with the plastisphere microbial communities and associated degrading bacteria remains poorly understood. This study investigated the aging of PE, PS, and PLA microplastics with varying particle sizes in simulated landfill reactors during the acidogenic phase under both anaerobic and semi-aerobic landfill conditions. The composition of plastisphere bacterial communities and key degrading bacteria were also determined. Results indicate that microplastics of different particle sizes and polymer types exhibit varying aging degree under different landfill conditions, with most microplastics aging in the order of PLA > PS > PE. Compared with polymer type, the composition of plastisphere microbial community is influenced more by the colonizing environment, with community assembly primarily driven by stochastic processes. Acinetobacter, Chryseobacterium, Sphingobacterium, Flavobacterium, Pseudomonas, and Bacillus were the primary potential degraders of microplastics in the simulated landfill reactor. Additionally, specific microplastic-degrading bacteria were enriched in different plastisphere under different landfill conditions. Correlation analysis revealed that microplastic degradation degree is closely associated with bacterial diversity, Clostridium sensu stricto, and Exiguobacterium abundance. These findings will help to understand the microplastic degradation behavior and degrading bacteria in landfills, providing scientific basis for microplastic pollution prevention and control.