Microplastics, considered emerging contaminants, have been accumulating excessively within soil ecosystems, conferring potentially detrimental effects with respect to soil carbon turnover and pools. As a major participant in soil carbon processes, microplastics affecting microorganisms may be one of the main agents affecting soil carbon dynamics. However, the microbial metabolism processes through which microplastics affect soil carbon dynamics remain unclear. Therefore, this study aimed to assess the impact of variously sized (1300, 800, 100, and 0.1 μm) polystyrene microplastics on soil microbial metabolism. Soil microplastics of all sizes invariably and consistently affected microbial metabolism, though nanomicroplastics (0.1 μm) stressed soil microorganisms more than micron-microplastics. Furthermore, microplastics inhibited both microbial carbon use efficiency (CUE) and respiration, the exception being the CUE in the 1300 μm microplastics treatment. As microplastic particle size decreased, the suppressive influence of microplastics on microbial respiration was gradually lost, the inhibitory effect on microbial CUE increased steadily, and the impact on microorganisms shifted from extracellular to intracellular, with intracellular microplastics exhibiting higher toxicity than extracellular microplastics. We used stoichiometric models to provide precise projections of microbial metabolism features associated with microplastic contamination, thereby enhancing the understanding of the effects of microplastic contamination on the carbon cycle and soil ecosystem.

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微生物代谢限制和碳利用效率对土壤中不同尺寸聚苯乙烯微塑料的不同反应

微塑料被认为是新兴污染物，在土壤生态系统中过度积累，对土壤碳周转和碳库产生潜在的有害影响。作为土壤碳过程的主要参与者，影响微生物的微塑料可能是影响土壤碳动态的主要因素之一。然而，微塑料影响土壤碳动态的微生物代谢过程仍不清楚。因此，本研究旨在评估不同尺寸（1300、800、100和0.1μm）聚苯乙烯微塑料对土壤微生物代谢的影响。尽管纳米微塑料（0.1 μm）比微米微塑料对土壤微生物的压力更大，但各种尺寸的土壤微塑料始终持续地影响微生物代谢。此外，微塑料会抑制微生物的碳利用效率（CUE）和呼吸，但 1300 μm 微塑料处理中的 CUE 除外。随着微塑料粒径的减小，微塑料对微生物呼吸的抑制作用逐渐丧失，对微生物CUE的抑制作用稳步增强，对微生物的影响从细胞外转向细胞内，且细胞内微塑料比细胞外微塑料表现出更高的毒性。我们使用化学计量模型来精确预测与微塑料污染相关的微生物代谢特征，从而增强对微塑料污染对碳循环和土壤生态系统影响的理解。