Variations in methane (CH4) and carbon dioxide (CO2) emissions in municipal sewer driven by pollution sources are complex and multifaceted. It is important to investigate the role of dissolved organic matter (DOM) components and microbiota to better understand what and how those variations occurred. For this purpose, this study provides a systematic assessment based on short-term in-sewer conditioned cultivations, in conjunction with a field survey in four typical sewers in Shanghai Megacity. The results are as follows: (1) Sediment plays a main role in driving the sewer carbon emission behavior owing to its strong associations with the utilized substrates and predominant microbes that significantly promoted the gas fluxes (genera Bacteroidete_vadinHA17, Candidatus_competibacter, and Methanospirillum). (2) Aquatic DOM in overlying water is an indispensable factor in promoting total carbon emissions, yet the dominant microbes present there inversely correlated with gas fluxes (genera Methanothermobacter and Bacteroides). (3) The total fluxes of both CH4 and CO2 enhanced by pavement runoff were limited. Its high COD-CH4/CO2 conversion efficiencies can be ascribed to its dominant anthropogenic humic-like components and the emerged aquatic tyrosine-like components. (4) Domestic sewage can significantly enhance the total fluxes because of its high concentration of bioavailable DOM. However, these substrates, which were more suitable for supporting microbial growth, as well as the substrate competition caused by sulfate reduction and the nitrogen cycle (revealed by the dominant functional microbes genera Acinetobacter, Pseudomonas, Dechloromona, and Candidatus_competibacter and their correlations with indicators), seemed to be responsible for the low COD-CH4/CO2 conversion efficiencies of domestic sewage. (5) A field survey indicated the distinct features of carbon emissions of sewer sewage discharged from different catchments. An extreme hydraulic condition in a sewer in the absence of influent showed unexpectedly high levels of CO2, while a small amount of CH4 emissions.

中文翻译：

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市政下水道中的污染源驱动的CH4和CO2产量和排放量变化：对溶解有机物成分和微生物群的作用的评估。

由污染源驱动的市政下水道中甲烷（CH4）和二氧化碳（CO2）排放的变化是复杂且多方面的。重要的是要研究溶解有机物（DOM）组分和微生物群的作用，以更好地了解这些变化是如何发生的以及如何发生的。为此，本研究结合上海大城市的四个典型下水道的实地调查，提供了基于短期下水道条件下栽培的系统评估。结果如下：（1）沉积物由于与所利用的底物和显着促进气体通量的主要微生物（Bacteroidete_vadinHA17，Candidatus_competibacter和Methanospirillum）密切相关，因此在驱动下水道碳排放行为中起主要作用。（2）上覆水中的水生DOM是促进总碳排放的必不可少的因素，但那里存在的优势微生物与气体通量（甲烷杆菌属和拟杆菌属）成反比。（3）路面径流增加了CH4和CO2的总通量。其高的COD-CH4 / CO2转化效率可归因于其主要的人为腐殖质样成分和新出现的水酪氨酸样成分。（4）生活污水由于其生物可利用的DOM浓度高，可以显着提高总通量。但是，这些底物更适合于支持微生物的生长，以及由硫酸盐还原和氮循环引起的底物竞争（由不动杆菌属，假单胞菌属，脱氯菌属，和Candidatus_competibacter及其与指标的相关性）似乎是造成生活污水COD-CH4 / CO2转化效率低的原因。（5）实地调查表明，从不同流域排放的下水道污水中的碳排放具有明显的特征。在没有进水的情况下，下水道中的极端水力状况显示出出乎意料的高水平的CO2，而少量的CH4排放。