Microplastics are emerging contaminants that are increasingly detected in soil environment, but their impact on soil microbiota and related biogeochemical processes remains poorly understood. In particular, the mechanisms involved (e.g., the role of chemical additives) are still elusive. In this study, we found that plasticizer-containing polyvinyl chloride (PVC) microplastics at 0.5% (w/w) significantly increased soil NH₄⁺-N content and decreased NO₃^--N content by up to 91%, and shaped soil microbiota into a microbial system with more nitrogen-fixing microorganisms (as indicated by nifDHK gene abundance), urea decomposers (ureABC genes and urease activity) and nitrate reducers (nasA, NR, NIT-6 and napAB genes), and less nitrifiers (amoC gene and potential nitrification rate). Exposure to plasticizer alone had a similar effect on soil nitrogen parameters but microplastics of pure PVC polymer (either granule or film) had little effect over 60 days, indicating that phthalate plasticizer released from microplastics was the main driver of effects observed. Furthermore, a direct link between phthalate plasticizer, microbial taxonomic changes and altered nitrogen metabolism was established by the isolation of phthalate-degrading bacteria involved in nitrogen cycling. This study highlights the importance of chemical additives in determining the interplay of microplastics with microbes and nutrient cycling, which needs to be considered in future studies.

微塑料是在土壤环境中越来越多地检测到的新兴污染物，但它们对土壤微生物群和相关生物地球化学过程的影响仍然知之甚少。特别是，所涉及的机制（例如，化学添加剂的作用）仍然难以捉摸。在本研究中，我们发现含增塑剂的聚氯乙烯 (PVC) 微塑料在 0.5% (w/w) 下可显着增加土壤 NH ₄ ⁺ -N 含量，并将 NO ₃ ^- -N 含量降低高达 91%，并塑造土壤微生物群进入具有更多固氮微生物（如nifDHK基因丰度所示）、尿素分解者（ureABC基因和脲酶活性）和硝酸盐还原剂（nasA, NR , NIT-6和napAB基因), 和较少的硝化菌 ( amoC基因和潜在的硝化率）。单独暴露于增塑剂对土壤氮参数有类似的影响，但纯 PVC 聚合物（颗粒或薄膜）的微塑料在 60 天内几乎没有影响，这表明从微塑料中释放的邻苯二甲酸酯增塑剂是观察到影响的主要驱动因素。此外，通过分离参与氮循环的邻苯二甲酸酯降解细菌，建立了邻苯二甲酸酯增塑剂、微生物分类学变化和改变的氮代谢之间的直接联系。这项研究强调了化学添加剂在确定微塑料与微生物和营养循环的相互作用方面的重要性，这需要在未来的研究中加以考虑。