Effects of PE microplastics on root morphology and soil nutrients with mechanisms of rhizosphere enrichment in Brassica rapa var. chinensis

The extensive accumulation of microplastics in agricultural soils and their effects on the soil environment and plant physiological processes have raised increasing concern. This study seeks to quantify plant root responses to microplastic exposure and to elucidate how plant-microplastic interactions influence soil nutrient dynamics and reshape the spatial distribution of pollutants.

This study systematically investigated the impacts of polyethylene microplastics (PE-MPs), applied at distinct particle sizes (10 μm, 350 μm) and concentrations (0.5%, 1%, 2.0%), on Brassica rapa var. chinensis growth, soil nutrient dynamics, and the plant-mediated influence on MPs spatial distribution through rigorously controlled pot experiments.

Results demonstrated a significant inhibition of root development in Brassica rapa var. chinensis by PE-MPs, with low-concentration, small-particle treatments (10 μm, 0.5%) inducing a 33.5% reduction in root length, and the overall biomass was also suppressed. Meanwhile, the total nitrogen (TN), total phosphorus (TP), and available phosphorus (AP) in the soil, with the extent of reduction being directly proportional to the concentration of microplastics. In contrast, the soil organic matter (OM) content increased significantly with the increase of MP exposure concentration, reaching a maximum increase of 71.1% compared to the control group. Notably, Brassica rapa var. chinensis cabbages could retain MPs around their roots, and compared with 350 μm, 10 μm MPs show significant migration and enrichment in the root zone and surface soil layer. and compared with 350 μm, 10 μm MPs show significant migration and enrichment in the root zone and surface soil layer.

This work provides concurrent quantification of PE-MPs-induced root inhibition alongside their effects on soil nutrient depletion and OM accumulation dynamics, and reveals the key role of root activity in driving the spatial redistribution of MPs particles. These findings establish a vital scientific foundation for evaluating the ecological risks associated with MPs pollution in agroecosystems and for developing targeted soil management and mitigation strategies.