Zhang Wenlong, Shi Meng, Wang Linqiong, Li Yi, Wang Haolan, Niu Lihua, Zhang Huanjun, Wang Longfei
Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, PR China.
College of Oceanography, Hohai University, Nanjing, 210098, PR China.
Environ Res. 2022 Mar;204(Pt D):112371. doi: 10.1016/j.envres.2021.112371. Epub 2021 Nov 10.
The importance of suspended particulate matter (SPM) in nitrogen removal from aquatic environments has been acknowledged in recent years by recognizing the role of attached microbes. However, the succession of attached microbes on suspended particles and their role in nitrogen removal under specific surface microenvironment are still unknown. In this study, the causation among characteristics of SPM, composition and diversity of particle-attached microbial communities, and abundances of nitrogen-related genes in urban rivers was firstly quantitatively established by combing spectroscopy, 16 S rRNA amplicon sequencing, absolute gene quantification and supervised integrated machine learning. SPM in urban rivers, coated with organic layers, was mainly composed of silt and clay (87.59-96.87%) with D50 (medium particle size) of 8.636-30.130 μm. In terms of material composition of SPM, primary mineral was quartz and the four most abundant elements were O, Si, C, Al. The principal functional groups on SPM were hydroxyl and amide. Furthermore, samples with low, medium and high levels of ammoxidation potential were classified into three groups, among which significant differences of microbial communities were found. Samples were also separated into three groups with low, medium and high levels of denitrification potential and significant differences occurred among groups. The particle size, content of functional groups and concentration of SPM were identified as the most significant factors related with microbial communities, playing an important role in succession of particle-attached microbes. In addition, the path model revealed the significantly positive effect of organic matter and particle size on the microbial communities and potential nitrogen removal. The content of hydroxyl and temperature were identified as the most effective predicting factors for ammoxidation potential and denitrification potential respectively by Random Forests Regression models, which had good predictive performances for potential of ammoxidation (R = 0.71) and denitrification (R = 0.61). These results provide a basis for quickly assessing the ability of nitrogen removal in urban rivers.
近年来，通过认识附着微生物的作用，悬浮颗粒物（SPM）在从水生环境中去除氮方面的重要性已得到认可。然而，附着在悬浮颗粒上的微生物的演替及其在特定表面微环境下的脱氮作用仍然未知。在本研究中，通过结合光谱学、16S rRNA扩增子测序、绝对基因定量和监督集成机器学习，首次定量建立了城市河流中SPM特征、颗粒附着微生物群落的组成和多样性以及氮相关基因丰度之间的因果关系。城市河流中的SPM表面覆盖有有机层，主要由淤泥和粘土组成（87.59 - 96.87%），D50（中位粒径）为8.636 - 30.130μm。就SPM的物质组成而言，主要矿物是石英，四种含量最高的元素是O、Si、C、Al。SPM上的主要官能团是羟基和酰胺。此外，将具有低、中、高氨氧化潜力水平的样本分为三组，其中发现微生物群落存在显著差异。样本也被分为具有低、中、高反硝化潜力水平的三组，组间存在显著差异。粒径、官能团含量和SPM浓度被确定为与微生物群落最相关的显著因素，在颗粒附着微生物的演替中起重要作用。此外，路径模型揭示了有机物和粒径对微生物群落和潜在脱氮的显著正效应。通过随机森林回归模型，羟基含量和温度分别被确定为氨氧化潜力和反硝化潜力最有效的预测因素，对氨氧化潜力（R = 0.71）和反硝化潜力（R = 0.61）具有良好的预测性能。这些结果为快速评估城市河流的脱氮能力提供了依据。
