Work

Aged polyethylene microplastics reduce CO2 emissions by altering carbon degradation genes rather than soil chemical properties at different aggregate scales

Year: 2025

Type: article

Abstract: The accumulation of microplastics (MPs) in agricultural soil can affect soil CO 2 emissions by changing microbial functions. However, little is known about how aged MPs affect CO 2 emissions and its mechanism at soil aggregate scale. Therefore, large macroaggregates (>2 mm), small macroaggregates (0.25–2 mm), microaggregates (0.053–0.25 mm), and silt and clay (<0.053 mm) were separated in a pot experiment involving polyethylene microplastics (PE) treated at different application times and a reference (CK), while CO 2 emissions, carbon (C) degradation function genes, and soil chemical properties were evaluated at the end of the mineralization incubation. Results showed PE aging for 2 months (SPE) stimulated CO 2 emissions by 12.8–31.7 %, while PE aging for 2 years (LPE) decreased CO 2 emissions by 0.5–24.9 % among all aggregation sizes. Meanwhile, CO 2 emissions and impact hotspots occurred in smaller soil aggregates, with the degree of impact depending on MP aging. Specifically, LPE significantly decreased soil aggregates pH by 0.1–0.2 units ( p < 0.05), while SPE increased soil aggregates pH by 0.02–0.13 units. Although the presence of MPs did not significantly affect soil nutrient and mineral content, SPE significantly increased the labile C degradation genes related to starch, hemicellulose and cellulose, whereas LPE effectively reduced these genes. Furthermore, partial least squares path model revealed labile C degradation genes have more contribution on soil aggregate CO 2 emissions than soil chemical properties, which were the main drivers of CO 2 emissions. This study provides new insights for evaluating MP aging on soil mineralization in cultivated soil under different aggregation sizes. • Effects of pristine and microplastic (MP) on CO 2 emissions in aggregation sizes were evaluated. • Both MP aging and aggregation sizes significantly affected soil CO 2 emissions. • Soil CO 2 emissions were positive correlated with C degradation genes and soil pH. • MP aging affected CO 2 emissions by altering soil microbes rather than chemical properties.

Source: Applied Soil Ecology

DOI: 10.1016/j.apsoil.2025.106641