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Updated: Sep 6, 2025
Separation and Identification of Conventional Microplastics from Farmland Soils
Published on: March 21, 2025
Microplastics spatiotemporal distribution and plastic-degrading bacteria identification in the sanitary and
Naying Li1, Zhiyong Han1, Nanfei Guo1
1State Key Laboratory of Geohazard Prevention and Geoenvironment Protection (Chengdu University of Technology), Chengdu 610059, China; State Environmental Protection Key Laboratory of Synergetic Control and Joint Remediation for Soil & Water Pollution (Chengdu University of Technology), Chengdu 610059, China; College of Ecology and Environment, Chengdu University of Technology, Chengdu 610059, China.
Abstract:
The municipal solid waste landfill (MSWL) is an important source of microplastics (MPs) and a huge bioreactor for plastic-degrading microorganisms (PDM). However, the spatiotemporal distribution and degradation mechanisms of MPs in MSWLs are unclear. Therefore, they were studied using the samples drilled in a sanitary landfill (SL) and an non-sanitary landfill (NSL). The results showed that there were a lot of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyurethane (PU), Polyamide (PA), Polyethylene terephthalate (PET) and Polyvinyl chloride (PVC) in the landfill, and their abundance ranged from 0 to 80 items/g. The MPs surface gradually faded, became rough and even yielded cracks and holes with the landfill depth and age increase. The tiny-size MPs (< 100 µm) were the most abundant and their amount significantly increased from 28.14% to 49.13% in SL and from 24.54% to 59.51% in NSL, respectively, while large-size MPs were significantly reduced from the top to the bottom. Lysinibacillus (0.21%~67.87%) and Bacillus (0.10%~67.00%) were the dominate PDMs in SL and Candidatus_Caldatribacterium (5.06%~73.48%) was the dominate in NSL. The PE degradation was closely related to Candidatus_Cloacimonas (r = 0.688*) and Candidatus_Caldatribacterium (r = 0.680*); PS and PA were closely related to Candidatus_Contubernalis (r = 0.595*~0.705*) and PVC was closely related to Candidatus_Caldatribacterium (r = 0.547*). In addition to physical and chemical effects, biological effects can also promote the MPs formation in MSWLs.
Insights
Microplastics (MPs) in landfills degrade over time, with smaller sizes becoming more abundant. Specific plastic-degrading microorganisms (PDMs) are linked to the breakdown of different plastic types, indicating biological effects contribute to MP formation.
Area of Science:
- Environmental Science
- Microbiology
- Polymer Science
Background:
- Municipal solid waste landfills (MSWLs) are significant sources of microplastics (MPs).
- The spatiotemporal distribution and degradation mechanisms of MPs in MSWLs remain unclear.
- Landfills act as bioreactors for plastic-degrading microorganisms (PDMs).
Purpose of the Study:
- To investigate the distribution and degradation of MPs in sanitary (SL) and non-sanitary landfills (NSL).
- To identify dominant PDMs and their correlation with MP degradation.
- To understand the role of biological effects in MP formation within MSWLs.
Main Methods:
- Sampling of MPs and PDMs from SL and NSL at various depths.
- Analysis of MP abundance, size distribution, and surface morphology.
- Identification and quantification of PDMs using microbial techniques.
- Correlation analysis between PDM abundance and MP degradation indicators.
Main Results:
- Common MPs found include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyurethane (PU), polyamide (PA), polyethylene terephthalate (PET), and polyvinyl chloride (PVC), with abundance from 0 to 80 items/g.
- MPs showed surface degradation (fading, roughness, cracks, holes) with increasing landfill depth and age.
- Tiny MPs (< 100 µm) increased significantly with depth (28.14%–49.13% in SL, 24.54%–59.51% in NSL), while large MPs decreased.
- Dominant PDMs identified: Lysinibacillus and Bacillus in SL, Candidatus_Caldatribacterium in NSL.
- PE degradation correlated with Candidatus_Cloacimonas and Candidatus_Caldatribacterium; PS and PA with Candidatus_Contubernalis; PVC with Candidatus_Caldatribacterium.
Conclusions:
- Microplastic degradation in landfills is influenced by both physical/chemical and biological factors.
- Specific PDMs play a crucial role in the degradation of different types of MPs.
- The increasing abundance of smaller MPs suggests fragmentation processes are significant in landfill environments.
- Biological degradation contributes to the overall transformation and potential formation of MPs within MSWLs.
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