Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing 210096, China.
Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing 210096, China.
Sci Total Environ. 2019 Jun 1;667:522-531. doi: 10.1016/j.scitotenv.2019.02.396. Epub 2019 Feb 26.
The wide application of consumer products containing silver nanoparticles (AgNPs) inevitably results in their release into sewer systems and wastewater treatment plants, where they would encounter (and cause potential negative impacts) constructed wetlands (CWs), a complex biological system containing plants, substrate and microorganisms. Herein, the long-term effects of environmental AgNPs concentrations on nitrogen removal, key enzymatic activities and nitrogen-related microbes in constructed wetlands (CWs) were investigated. The short-term exposure (40 d) to AgNPs significantly inhibited TN and NH-N removal, and the inhibition degree had a positive relationship with AgNPs levels. After about 450 d exposure, 200 μg/L AgNPs could slightly increase average TN removal efficiency, while presence of 50 μg/L AgNPs showed no difference, compared to control. The NH-N removal in all CWs had no difference. The present study indicated that short-term AgNPs loading evidently reduced nitrogen removal, whereas long-term exposure to AgNPs showed no adverse impacts on NH-N removal and slightly stimulated TN removal, which was related to the increase of corresponding enzymatic activities. After exposing AgNPs for 450 d, the abundance of relative functional genes and the composition of key community structure were determined by qPCR and high-throughput sequencing, respectively. The results showed that the abundance of amoA and nxrA dramatically higher than control, whereas the abundance of nirK, nirS, nosZ and anammox 16S rRNA was slightly higher than control, but had no statistical difference, which accorded with the TN removal performance. The microbial community analysis showed that different AgNPs concentrations could affect the microbial diversity and structure. The changes of the relative abundance of nitrogen-related genera were associated with the impacts of AgNPs on the nitrogen removal performance. Overall, the AgNPs loading had impacts on the key enzymatic activities, the abundance of nitrogen-related genes and microbial community, thus finally affected the treatment performance of CWs.
纳米银（AgNPs）广泛应用于各类消费品，这不可避免地导致其释放到污水系统和废水处理厂中，在这些地方，AgNPs 会遇到（并可能造成潜在的负面影响）人工湿地（CWs），这是一种包含植物、基质和微生物的复杂生物系统。本研究调查了环境中 AgNPs 浓度对人工湿地（CWs）中氮去除、关键酶活性和氮相关微生物的长期影响。AgNPs 的短期暴露（40d）显著抑制了 TN 和 NH4-N 的去除，其抑制程度与 AgNPs 水平呈正相关。经过约 450d 的暴露，与对照组相比，200μg/L 的 AgNPs 略微提高了平均 TN 去除效率，而 50μg/L 的 AgNPs 则没有差异。所有 CWs 中的 NH4-N 去除没有差异。本研究表明，AgNPs 的短期负荷明显降低了氮的去除，而长期暴露于 AgNPs 对 NH4-N 去除没有不良影响，反而略微刺激了 TN 的去除，这与相应酶活性的增加有关。经过 450d 的 AgNPs 暴露后，通过 qPCR 和高通量测序分别确定相对功能基因的丰度和关键群落结构的组成。结果表明，amoA 和 nxrA 的丰度明显高于对照组，而 nirK、nirS、nosZ 和 anammox 16S rRNA 的丰度略高于对照组，但无统计学差异，这与 TN 去除性能相符。微生物群落分析表明，不同浓度的 AgNPs 会影响微生物的多样性和结构。与 AgNPs 对氮去除性能的影响相关的是氮相关属的相对丰度的变化。总的来说，AgNPs 负荷会影响关键酶活性、氮相关基因和微生物群落的丰度，从而最终影响 CWs 的处理性能。
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