College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao, Shandong Province 266042, PR China.
College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao, Shandong Province 266042, PR China.
J Hazard Mater. 2023 Oct 5;459:132142. doi: 10.1016/j.jhazmat.2023.132142. Epub 2023 Jul 25.
Microplastics (MPs) occur and distribute widely in agroecosystems, posing a potential threat to soil-plant systems. However, little is known about their effects on legumes and N-fixing microbes. Here, we explored the effects of high-density polyethylene (HDPE), polystyrene (PS), and polylactic acid (PLA) on the growth of peanuts and soil N-fixing bacterial communities. All MPs treatments showed no phytotoxic effects on plant biomass, and PS and PLA even increased plant height, especially at the high dose. All MPs changed soil NO-N and NH-N contents and the activities of urease and FDAse. Particularly, high-dose PLA decreased soil NO-N content by 97% and increased soil urease activity by 104%. In most cases, MPs negatively affected plant N content, and high-dose PLA had the most pronounced effects. All MPs especially PLA changed soil N-fixing bacterial community structure. Symbiotic N-fixer Rhizoboales were greatly enriched by high-dose PLA, accompanied by the emergence of root nodulation, which may represent an adaptive strategy for peanuts to overcome N deficiency caused by PLA MPs pollution. Our findings indicate that MPs can change peanut-N fixing bacteria systems in a type- and dose-dependent manner, and biodegradable MPs may have more profound consequences for N biogeochemical cycling than traditional MPs.
微塑料（MPs）广泛存在于农业生态系统中，并分布广泛，对土壤-植物系统构成潜在威胁。然而，关于 MPs 对豆科植物和固氮微生物的影响，我们知之甚少。在这里，我们研究了高密度聚乙烯（HDPE）、聚苯乙烯（PS）和聚乳酸（PLA）对花生产量和土壤固氮细菌群落的影响。所有 MPs 处理对植物生物量均无明显的植物毒性效应，PS 和 PLA 甚至增加了株高，尤其是高剂量处理。所有 MPs 处理均改变了土壤硝态氮（NO-N）和铵态氮（NH-N）含量以及脲酶和 FDA 酶活性。特别是，高剂量 PLA 使土壤硝态氮含量降低了 97%，并使土壤脲酶活性增加了 104%。在大多数情况下， MPs 降低了植物的氮含量，高剂量 PLA 的影响最为显著。所有 MPs 尤其是 PLA 改变了土壤固氮细菌群落结构。高剂量 PLA 使共生固氮根瘤菌大量富集，同时出现根瘤，这可能是花生对 PLA MPs 污染引起的氮素缺乏的一种适应策略。我们的研究结果表明， MPs 可以以类型和剂量依赖的方式改变花生固氮菌系统，生物可降解 MPs 对氮生物地球化学循环的影响可能比传统 MPs 更为深远。
