Wetlands play a vital role in regulating the global climate by storing carbon, yet their function may be quietly undermined by emerging pollutants. A study published in Frontiers of Environmental Science & Engineering reveals that nanoplastics—plastic particles smaller than 100 nanometers—can substantially intensify emissions of two powerful greenhouse gases, methane and nitrous oxide, in plant–soil systems. By interfering with plant growth, photosynthesis, and root function, nanoplastics reshape the chemical and biological conditions of wetland soils. These changes stimulate microbial processes that favor greenhouse gas production, potentially transforming wetlands from carbon sinks into significant emission sources. The findings highlight an overlooked pathway through which plastic pollution may accelerate climate change.
Methane and nitrous oxide are among the most potent greenhouse gases, with warming potentials far exceeding that of carbon dioxide. Natural wetlands are major contributors to global methane emissions but can also act as long-term carbon sinks. Meanwhile, nanoplastics are rapidly accumulating in aquatic and terrestrial environments as larger plastics degrade, yet their ecological consequences remain poorly understood. Previous studies have shown that microplastics can alter soil chemistry and microbial activity, but the effects of even smaller nanoplastics on greenhouse gas emissions remain largely unexplored. Based on these challenges, researchers from Tsinghua University and collaborating institutions conducted an in-depth study on how nanoplastics influence biogeochemical processes in wetland ecosystems.
The study, published online on August 10, 2025, with DOI 10.1007/s11783-025-2066-8, used a controlled wetland simulation to examine how polystyrene nanoplastics affect greenhouse gas production. By combining gas flux measurements with microbial and plant analyses, the research provides mechanistic insight into how nanoplastics disrupt plant–soil interactions and alter carbon and nitrogen cycling. Using simulated wetlands planted with reeds, the researchers introduced increasing concentrations of polystyrene nanoplastics to the soil and monitored greenhouse gas emissions over time. They found that nanoplastics increased methane emissions by 20% to nearly 100%, while nitrous oxide emissions approximately doubled under higher concentrations. These effects became more pronounced as plants matured and environmental temperatures rose.
Mechanistic analyses revealed that nanoplastics inhibited plant growth, reduced chlorophyll content, and weakened antioxidant defenses, impairing photosynthesis and stress resistance. Crucially, nanoplastics reduced oxygen release from plant roots, creating more anaerobic conditions in the rhizosphere. This shift favored methane-producing microorganisms and enhanced denitrification processes responsible for nitrous oxide formation. Metagenomic analyses showed increased abundance of genes involved in acetoclastic methanogenesis and denitrification pathways, particularly in rhizosphere soils. At the same time, nanoplastics altered root exudate composition, sharply increasing the release of L-phenylalanine—a compound that can be converted into substrates fueling methane production. Although some methane-oxidizing and nitrous oxide–consuming microbes also increased, their activity was insufficient to offset the elevated greenhouse gas generation.
"This work demonstrates that nanoplastics are not just passive contaminants but active regulators of ecosystem processes," said the corresponding author. "By simultaneously impairing plant physiological functions and reshaping microbial communities in the rhizosphere, nanoplastics create conditions that strongly favor greenhouse gas production. These effects operate through multiple interconnected pathways, which helps explain why even small particles can have outsized impacts on climate-relevant processes in wetlands."
The findings suggest that plastic pollution may contribute to climate change in ways that are not currently accounted for in greenhouse gas models. Wetlands are widely recognized as nature-based solutions for carbon sequestration, yet nanoplastic contamination could undermine their climate-mitigation potential. Incorporating nanoplastics into environmental risk assessments and greenhouse gas inventories may therefore be essential. More broadly, the study underscores the urgency of controlling plastic pollution at its source, as continued accumulation of nanoplastics could amplify greenhouse gas emissions across sensitive ecosystems worldwide.
