Nitrate (NO-N) is ubiquitously present in groundwater, constituting a growing threat to human health. In this study, iron-scrap and pyrite-based constructed wetlands (CWs) were constructed to investigate the treatment performance and removal mechanisms in purifying nitrate-contaminated groundwater. Results showed that the NO-N removal efficiency of iron-scrap-based CWs (87.1%) was higher than that of pyrite-based CWs (59.5%), and the higher NO emission (28.46 μg/(m•h)) was also obtained in CW with iron-scrap. Nevertheless, total nitrogen removal did not exhibit a significant difference between two CWs due to the accumulation of ammonium nitrogen (NH-N) in iron-scrap-based CWs. Additionally, sulfate was produced in CW with pyrite, as a by-product, and caused oxidative stress damage to plants. Metagenomic analysis showed that the addition of iron-scrap could increase microbial diversity and enrich autotrophs denitrifies (), which explained the higher NO-N removal reasonably. Additionally, the abundance of dissimilatory nitrate reduction bacterium was enhanced in iron-scrap-based CW, explaining the NH₄⁺-N accumulation. Further metabolic analysis confirmed the occurrence of Fe cycle in CW with iron-scrap, and functional genes related to NO-N removal and TCA cycle were up-regulated, offering a rationale for the improved NO-N removal in CW with iron-scrap. This study offers comprehensive insights into the NO-N removal and its mechanism through iron mediated CWs in controlling groundwater pollution.

中文翻译：

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人工湿地中铁屑和黄铁矿介导的自养反硝化增强硝酸盐污染地下水修复：性能和机制

硝酸盐（NO-N）普遍存在于地下水中，对人类健康构成越来越大的威胁。在本研究中，构建了以废铁和黄铁矿为基础的人工湿地（CW），以研究净化硝酸盐污染地下水的处理性能和去除机制。结果表明，废铁基水煤浆的NO-N去除效率（87.1%）高于黄铁矿水煤浆（59.5%），且NO排放量较高（28.46 μg/(m•h)）。也可以用废铁在 CW 中获得。然而，由于废铁基化武中铵态氮（NH3-N）的积累，两种化武之间的总氮去除率没有表现出显着差异。此外，CW 中还与黄铁矿一起产生硫酸盐作为副产品，并对植物造成氧化应激损害。宏基因组分析表明，添加铁屑可以增加微生物多样性并丰富自养反硝化菌（），这合理地解释了较高的NO-N去除率。此外，铁屑化学水中异化硝酸盐还原菌的丰度增加，解释了NH₄⁺-N的积累。进一步的代谢分析证实了铁屑CW中Fe循环的发生，并且与NO-N去除和TCA循环相关的功能基因上调，为铁屑CW中改善NO-N去除提供了理论依据。这项研究提供了对通过铁介导的化学水来控制地下水污染的 NO-N 去除及其机制的全面见解。