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Biodegradable and non-biodegradable microplastics affect greenhouse gas emissions through chemical diversity and microbial biodiversity
Summary
Researchers investigated how biodegradable polylactic acid (PLA) and non-biodegradable polystyrene (PS) microplastics affect greenhouse gas emissions in soil, finding that both types elevated CO2 and N2O emissions while shifting microbial community composition at both phylum and genus levels. Structural equation modeling revealed that GHG emissions were more strongly correlated with chemical diversity driven by the microplastics than with microbial diversity, with PLA increasing soil organic carbon content.
While the environmental risks of soil microplastics (MPs) are well-established, their roles as exogenous carbon sources in driving greenhouse gas (GHG) emissions remain poorly understood. Particularly, the mechanisms by which biodegradable and non-biodegradable microplastics influence GHG emissions through microbial community shifts and soil organic carbon (SOC) chemical composition are unclear. To address this, this study investigated the impacts of two microplastics - biodegradable polylactic acid (PLA) and non-biodegradable polystyrene (PS), applied at 0.1 % or 1 % (w/w), on soil properties, carbon-related enzyme activities, GHG emissions, and microbial/chemical diversity. PLA addition significantly increased SOC and dissolved organic matter (DOM) content. Both microplastics stimulated lignin peroxidase and cellulase activities and shifted microbial composition: at the phylum level, Proteobacteria, Acidobacteriota, and Actinobacteria abundances changed; at the genus level, Vicinamibacterales, Vicinamibacteraceae, and Sphingomonas were altered. High-molecular-weight aromatic compounds increased under 1 % PLA and PS treatments. Microplastics elevated CO₂ and N₂O emissions but did not affect CH₄. Piecewise structural equation modeling revealed that GHG emissions correlated with chemical diversity (R²=0.45) and microbial diversity (R²=0.15). Our findings elucidate mechanistic links between microplastics-induced carbon transformation, microbial activity, and GHG emissions, highlighting distinct impacts of biodegradable versus conventional microplastics on soil-climate feedbacks.
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