Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Av. Universidad 3000, Del. Coyoacán, 04510 Ciudad de México, Mexico.
Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Av. Universidad 3000, Del. Coyoacán, 04510 Ciudad de México, Mexico.
J Contam Hydrol. 2020 Oct;234:103657. doi: 10.1016/j.jconhyd.2020.103657. Epub 2020 May 21.
Groundwater-N pollution derives from agricultural and urban activities, and compromises water quality in shallow aquifers, putting human and environmental health at risk. Nonetheless, subsurface microbiota can transform dissolved inorganic nitrogen into N. In this study, we surveyed the microbial community of a shallow aquifer by sampling one well, one piezometer and a spring within an agricultural area that receives N-inputs of more than 700 kg/ha per year through irrigation with wastewater. The survey was conducted during a year with a 16S rRNA next-gen approach. In parallel, we quantified the number of gene copies and transcripts related to anaerobic ammonium oxidation (anammox, hzo), nitrite-dependent anaerobic methane oxidation (n-damo, nod and pmoA) and nitrous oxide reduction (last step of denitrification, nosZ), during the dry and rainy seasons. Our results showed that the groundwater samples had 17.7 to 22.5 mg/L of NO-N. The bacterial and archaeal community structure was distinctive at each site, and it remained relatively stable over time. We verified the co-occurrence of N-transforming bacteria, which was correlated with the concentration of NO/NO and ORP/DO values (DO: ~3.0 mg/L). Our analyses suggest that these conditions may allow the presence of nitrifying microorganisms which can couple with anammox, n-damo and denitrifying bacteria in interrelated biogeochemical pathways. Gene density (as the number of gene copies per litre) was lower in the rainy season than in the dry season, possibly due to dilution by rainwater infiltration. Yet, the numbers of hzo gene copies here found were similar to those reported in oceanic oxygen minimum zones and in a carbonate-rock aquifer. The transcript sequences showed that Candidatus Brocadia spp. (anammox), Candidatus Methylomirabilis spp. (n-damo) and autotrophic denitrifying Betaproteobacteria coexist in the groundwater environment, with the potential to attenuate the concentration of dissolved inorganic nitrogen by reducing it to N rather than NO; delivering thus, an important ecosystem service to remove contaminants.
地下水-N 污染源自农业和城市活动，破坏了浅层含水层的水质，危及人类和环境健康。尽管如此，地下微生物群可以将溶解的无机氮转化为 N。在这项研究中，我们通过在一个农业区的一口井、一个测压计和一个泉水取样，调查了浅层含水层的微生物群落，该地区每年通过灌溉废水接受超过 700kg/ha 的 N 输入。该调查是在一个具有 16S rRNA 下一代方法的一年中进行的。同时，我们在旱季和雨季定量测定了与厌氧氨氧化（anammox，hzo）、亚硝酸盐依赖型厌氧甲烷氧化（n-damo，nod 和 pmoA）和氧化亚氮还原（反硝化的最后一步，nosZ）相关的基因拷贝数和转录本数。我们的结果表明，地下水样品的 NO-N 浓度为 17.7 至 22.5mg/L。细菌和古菌群落结构在每个地点都具有独特性，并且随着时间的推移相对稳定。我们验证了 N 转化细菌的共存，这与 NO/NO 和 ORP/DO 值（DO：~3.0mg/L）的浓度相关。我们的分析表明，这些条件可能允许存在硝化微生物，这些微生物可以与 anammox、n-damo 和反硝化细菌在相互关联的生物地球化学途径中耦合。雨季的基因密度（每升基因拷贝数）低于旱季，这可能是由于雨水渗透的稀释作用。然而，这里发现的 hzo 基因拷贝数与海洋缺氧区和碳酸盐岩含水层中报道的相似。转录本序列表明，Candidatus Brocadia spp.（anammox）、Candidatus Methylomirabilis spp.（n-damo）和自养反硝化 Betaproteobacteria 共同存在于地下水环境中，通过将其还原为 N 而不是 NO 来减少溶解无机氮的浓度，从而提供了去除污染物的重要生态系统服务。
