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Tracking interlinked microbial and geochemical succession over decades in landfilled municipal solid waste
Kimber E Munford1, Daniel S Grégoire2, Laura A Hug1
1Department of Biology, University of Waterloo, Waterloo, Ontario, Canada.
Applied and Environmental Microbiology
|July 16, 2026
Summary
Aging landfills pose risks to groundwater. This study reveals how microbial communities and geochemistry change over 39 years, impacting metal mobility and providing a new model for landfill stabilization.
Area of Science:
- Environmental Science
- Microbiology
- Geochemistry
Background:
- Landfills are engineered ecosystems within freshwater systems, posing risks of groundwater contamination from metal leachates.
- Understanding the long-term evolution of landfill biogeochemistry and microbial communities is crucial for predicting environmental impacts.
- Existing models of landfill aging are limited, particularly beyond 20 years, and often lack microbial insights.
Purpose of the Study:
- To investigate the interconnected changes in landfill biogeochemistry, microbial community composition, and metal cycling over a 39-year period.
- To develop a conceptual model of landfill characteristics across their lifespan, integrating geochemical and microbial data.
- To understand the processes occurring during the stabilization phase of landfills and their implications for environmental stability.
Main Methods:
- Analysis of 1,647 metagenome-assembled genomes from landfill samples spanning 39 years of waste decomposition.
- Comparison of geochemical data and microbial community composition between Newer (3-20 years) and Older (31-39 years) waste cells.
- Integration of historical geochemical data, current microbial membership data, and physical processes like leachate recirculation.
Main Results:
- Newer landfill cells showed higher labile carbon, redox activity, and mobile metal concentrations compared to Older cells.
- Microbial communities shifted from chemoorganoheterotrophs in Newer cells to chemolithoautotrophs and more versatile organisms in Older cells.
- Metal resistance and cycling genes were significantly more abundant in Older landfill cells.
Conclusions:
- Landfill biogeochemistry and microbial communities undergo substantial changes during the stabilization phase (30+ years).
- Leachate recirculation is a key process influencing geochemical parameters and metal fate within landfills.
- The developed conceptual model provides an empirically data-based understanding of landfill aging, including microbial dynamics and long-term metal mobility.
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