A study published in Frontiers of Environmental Science & Engineering reveals that nanoplastics—plastic particles smaller than 100 nanometers—can substantially intensify emissions of methane and nitrous oxide in wetland plant–soil systems. The research, conducted by scientists from Tsinghua University and collaborating institutions, provides mechanistic insight into how these emerging pollutants disrupt plant–soil interactions and alter carbon and nitrogen cycling.
Wetlands play a vital role in regulating the global climate by storing carbon, yet their function may be quietly undermined by emerging pollutants. 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.
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."
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. 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.
The full study is available at https://doi.org/10.1007/s11783-025-2066-8.
