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Synchronous regulation of MPs release and H2S accumulation by SRB in landfill environments
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Landfills naturally release both microplastics and smelly hydrogen sulfide gas, and this study found these two processes are connected: certain sulfur-processing bacteria in landfills actually help break down plastic waste into smaller microplastic fragments as a side effect of their normal activity. This matters because it shows landfills may be releasing more microplastics into the environment (and eventually water, soil, and food chains) than previously understood, especially in wet conditions—information that could help engineers design better landfills to reduce this pollution.
The formation of microplastics (MPs) and the release of HS in landfill environments show a synchronous pattern, yet lack clear scientific explanation. In this study, simulated landfill systems were constructed under varying moisture and temperature conditions to explore the direct coupling mechanism between these two processes from the perspectives of key functional genes and enzymatic activities. The results revealed that the release of MPs exhibited distinct stage-specific characteristics and was highly coupled with the sulfate reduction process, which became particularly pronounced under high-moisture conditions. The sulfate reduction process not only drove the early rapid release of MPs but also determined the subsequent variations in release intensity. The dominant genus Thiobacillus contributed most to the key genes involved in sulfur metabolism, yet its dominance gradually declined with increasing temperature. SRB not only promote the aging of MPs through metabolic products, but specific groups (such as Desulfovibrio) may also directly participate in degradation, with plastic degradation genes being genus-specific and environmentally regulated. Fourteen SRB genera were found to harbor multiple plastic-degrading genes, the abundances of which were influenced by moisture and temperature. A degradation enzyme system centered on CAZymes and PDZymes gradually formed within the landfill environment, suggesting that SRB may regulate plastic degradation and release of MPs by modulating related enzyme activities. In conclusion, this study further unveils the coupling mechanism between MPs release and sulfate reduction in landfill systems at the genetic and enzymatic activity levels, clarifying the multiple ecological functions of SRB in the MPs release process, and providing new theoretical insights for landfill management and pollution control.
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Microplastic, a possible trigger of landfill sulfate reduction process
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Researchers investigated microplastic occurrence in landfill environments through field sampling and found abundances reaching over 11,000 particles per gram in deeper soil layers. The study revealed a significant correlation between microplastic abundance and sulfate reduction metabolites, suggesting that microplastics may trigger the sulfate reduction process that contributes to landfill odor emissions.
Effect of microplastics on sulfate reduction in landfill leachate-saturated zone
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Researchers investigated how different types of microplastics affect sulfate reduction in landfill leachate-saturated zones at varying temperatures. They found that polylactic acid microplastics dramatically increased hydrogen sulfide release compared to polystyrene, polyethylene, and PVC, with cumulative release at 55 degrees Celsius being 33 times higher than at 25 degrees. The study suggests that biodegradable plastics in landfills may paradoxically worsen certain pollution processes by enriching sulfate-reducing microbial communities.
Differential effects of sulfide-induced transformation of biodegradable and conventional microplastics on sedimentary CO2 and CH4 emissions: Underlying microbiome-mediated mechanisms
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Microplastics buried in sediments don't just sit inert — they interact with soil microbes in ways that affect how much methane and CO2 the sediment releases into the atmosphere. This incubation study found that fresh biodegradable plastic (PLA) dramatically increased greenhouse gas emissions, but once the plastic had aged through a chemical process called sulfidation, it actually suppressed them — while conventionally aged polyethylene had the opposite effect, boosting methane by stimulating methane-producing microbes. The findings complicate the assumption that biodegradable plastics are automatically better for the environment, and suggest that how plastics age underground matters as much as what they are made of.
Microplastic release and sulfate reduction response in the early stage of a simulated landfill
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An experiment simulating a landfill found that microplastics rapidly leach into landfill liquid (leachate) during the early stages of waste decomposition, with circulating leachate carrying 1.45 times more microplastics than non-circulating systems. Larger plastic fragments broke down into smaller particles during the process, and a positive correlation was found between microplastic release and sulfate-reducing activity. Landfills represent an underappreciated but significant pathway for microplastics to enter groundwater and surrounding environments.
Effects of microplastics on denitrification and associated N2O emission in estuarine and coastal sediments: insights from interactions between sulfate reducers and denitrifiers
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This study investigated how microplastics affect nitrogen cycling and greenhouse gas emissions in estuary sediments by altering the interactions between two key types of bacteria. Microplastics disrupted the balance between sulfate-reducing and nitrogen-removing bacteria, with different effects depending on location in the estuary. These changes could worsen water quality in coastal zones where microplastic pollution is severe, potentially affecting fisheries and water resources that communities depend on.
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