【作者】 李成涛； 李振慧； 赵思尧； 崔倩； 吴婉晴；

【Author】 Li Chengtao;Li Zhenhui;Zhao Siyao;Cui Qian;Wu Wanqing;Shaanxi University of Science &Technology, College of Environmental Science and Engineering;

【机构】 陕西科技大学环境科学与工程学院；

【摘要】 和通用塑料相比,可生物降解塑料最大的优势就是使用完之后废弃到土壤等环境中在一定时间内可以自然地被微生物降解至最终消失,而不会对环境带来类似于"白色污染"的环境污染问题。然而,虽然可生物降解塑料最终被转成CO₂和H₂O,但这并不是一瞬间完成的,而是由高分子物质降解成低分子物质、最终被转化成CO₂和H₂O的持续过程。伴随着整个生物降解过程,降解材料自身也呈现有小颗粒的脱落、碎片的产生及再降解等现象,在此过程中,会逐渐有小于5mm以下微塑料的产生。其降解过程及中间降解产物是否会对土壤理化性质、微生物菌群结构及功能、植物生长等产生影响?目前这些问题还没有明确结论且又亟需关注。针对上述问题,本课题组以可生物降解微塑料（PBAT、PLA）为研究对象,对比不可生物降解微塑料（PP、PE）,重点利用高通量测序、宏基因组学、转录组学和代谢组学的方法,较为系统的开展可生物降解微塑料对土壤理化性质、微生物群落结构和代谢功能、植物生态学效应等影响研究。结果表明（1）随着添加量的升高,PBAT的添加使土壤TN含量升高,NO₃^--N、TP含量降低;PLA的添加使TN含量升高,TP先升高后降低;PLA和PBAT微塑料会增加土壤中0.25 mm-0.5 mm的团聚体含量。（2）与PP和PE相比,PBAT和PLA样本的细菌群落丰富度和多样性升高,组成与结构明显不同,出现了特有的Azotobacter、Bradyrhizobium属,相对丰度随添加量升高而升高;PBAT和PLA样本影响氮代谢,PP和PE样本影响细胞脂质膜的稳定性;PBAT和PLA组中glnA、gdhA、nirK、amoCAB等基因丰度显著降低,与氮循环途径相关基因显著降低,但PP和PE样本中基因丰度变化不明显。（3）粒径0.2-1 mm的PBAT会抑制上海青发芽,生长15 d时PBAT会抑制根和茎的生长以及根系活力的活性,高浓度PBAT和PLA使叶片MDA活性显著下降;转录分析中PBAT和PLA对上海青油菜素类固醇生物合成、鞘糖脂生物合成-神经节亚麻酸、亚油酸代谢等通路产生了显著影响;代谢分析中PBAT和PLA微塑料的添加引发了甘油磷脂代谢、卟啉和叶绿素代谢通路的上调,嘧啶代谢、单巴坦生物合成、氨酰t RNA生物合成、亚油酸代谢等通路的下调,PBAT对上海青转录、代谢产生了更强的影响。研究结果说明可生物降解微塑料PBAT和PLA对土壤氮磷相关理化性质,微生物氮循环功能,植物体内激素调节、光合作用及氧化-抗氧化系统等产生显著影响,为评估可生物降解微塑料对土壤生态系统和植物的潜在影响,提供理论依据。更多还原

【Abstract】 Compared with general-purpose plastics, the biggest advantage of biodegradable plastics is that they can be naturally degraded by microorganisms in the environment such as soil after use and eventually disappear within a certain period of time, without causing environmental pollution problems similar to "white pollution". However, although biodegradable plastics are eventually converted into CO₂ and H₂O, this is not done instantaneously, but is a continuous process of degradation from high molecules to low molecules and finally to CO₂ and H₂O. Along with the whole biodegradation process, the degraded material itself also shows the phenomenon of shedding of small particles, generation of fragments and re-degradation, etc. In this process, there will be gradually less than 5 mm microplastics produced. Will the degradation process and intermediate degradation products affect soil physicochemical properties, microbial flora structure and function, plant growth, etc.? These questions are not yet clearly concluded and need urgent attention.In response to the above problems, our group takes biodegradable microplastics（PBAT, PLA） as the research object and compares with non-biodegradable microplastics（PP, PE）, focusing on the effects of biodegradable microplastics on soil physicochemical properties, microbial community structure and metabolic functions, and plant ecological effects using high-throughput sequencing,macrogenomics, transcriptomics and metabolomics methods in a more systematic way.The results showed that（1） the addition of PBAT increased soil TN content and decreased NO₃^--N and TP content with the increase of addition; the addition of PLA increased TN content and decreased TP first and then; PLA and PBAT microplastics increased soil agglomerate content of 0.25 mm-0.5mm.（2） Bacterial community richness and diversity were elevated in PBAT and PLA samples compared to PP and PE, with significantly different composition and structure, and the emergence of endemic Azotobacter and Bradyrhizobium genera, with relative abundance increasing with addition; PBAT and PLA samples affected nitrogen metabolism, and PP and PE samples affected the stability of cellular lipid membranes; The abundance of glnA, gdhA, nirK, and amoCAB genes was significantly reduced in PBAT and PLA samples, and genes related to the nitrogen cycle pathway were significantly reduced, but gene abundance did not change significantly in PP and PE samples.（3） PBAT with a particle size of 0.2-1 mm inhibited Shanghai green germination, and PBAT inhibited root and stem growth as well as root vigor activity at 15 d of growth, and high concentrations of PBAT and PLA significantly decreased leaf MDA activity; PBAT and PLA significantly affected the pathways of Shanghai green oleoresin steroid biosynthesis, sphingolipid biosynthesis-ganglioside, and linoleic acid metabolism in transcriptional analyses. The addition of PBAT and PLA microplastics triggered the up-regulation of glycerophospholipid metabolism,porphyrin and chlorophyll metabolism, and the down-regulation of pyrimidine metabolism,monobactam biosynthesis, aminoacyl t RNA biosynthesis and linoleic acid metabolism in the metabolic analysis, and PBAT had a stronger effect on the transcription and metabolism of Shanghai green. The results indicate that biodegradable microplastics PBAT and PLA significantly affect soil nitrogen and phosphorus related physicochemical properties, microbial nitrogen cycle functions, hormone regulation, photosynthesis and oxidation-antioxidation systems in plants,providing a theoretical basis for assessing the potential effects of biodegradable microplastics on soil ecosystems and plants.更多还原