School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China.
School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China.
Sci Total Environ. 2021 Mar 1;758:143594. doi: 10.1016/j.scitotenv.2020.143594. Epub 2020 Nov 17.
Constructed wetlands are efficient in removing nitrogen from water; however, little is known about nitrogen-cycling pathways for nitrogen loss from tidal flow constructed wetlands. This study conducted molecular and stable isotopic analyses to investigate potential dissimilatory nitrate reduction to ammonium (DNRA), denitrification, nitrification, anaerobic ammonium oxidation (anammox), and their contributions to nitrogen removal by two tidal wetland mesocosms, PA (planted with Phragmites australis) and NP (unplanted), designated to treat Yangtze River Estuary water. Our results show the mesocosms removed ~22.6% of TN from nitrate-dominated river water (1.19 mg·L), with better performance obtained in PA than that in NP, which was consistent with the molecular and stable isotopic data. The potential activities of DNRA, anammox, denitrification and nitrification varied between 0.6 and 1.6, 4.6-37.3, 36.4-305.7, and 463.7-945.9 nmol N g dry soil d, respectively, with higher values obtained in PA than NP. Nitrification accounted for 94.3-99.4% of NH oxidation, with the rest through anammox. Denitrification contributed to 77.9-90.3% of NO reduction, compared to 9.2-21.6% and 0.5-1.5% via anammox and DNRA, respectively; 78.4-90.9% of N was produced through denitrification, with the rest via anammox. Pearson correlation analyses suggest NH was the major factor regulating nitrification, while NO played an important role in the competition between denitrification and DNRA, and NO was a key restrictive factor for anammox. Overall, this study reveals the importance of nitrification, denitrification, anammox and DNRA in nitrogen removal, providing new insight into the nitrogen-cycling mechanisms in natural/artificial tidal wetlands.
人工湿地在去除水中氮方面效率很高；然而，对于潮汐流人工湿地中氮损失的氮循环途径知之甚少。本研究通过分子和稳定同位素分析，调查了两种潮汐湿地中潜在的异化硝酸盐还原为铵（DNRA）、反硝化、硝化、厌氧氨氧化（anammox）及其对氮去除的贡献，这两个湿地分别用 PA（种植芦苇）和 NP（未种植）来处理长江口的水。我们的结果表明，湿地从硝酸盐占主导地位的河水（1.19mg·L）中去除了约 22.6%的总氮（TN），PA 的表现优于 NP，这与分子和稳定同位素数据一致。DNRA、anammox、反硝化和硝化的潜在活性在 0.6 到 1.6、4.6 到 37.3、36.4 到 305.7 和 463.7 到 945.9nmol N g 干土 d 之间变化，PA 中的值高于 NP。硝化作用占 NH 氧化的 94.3-99.4%，其余通过 anammox。反硝化作用对 77.9-90.3%的 NO 还原有贡献，而通过 anammox 和 DNRA 的分别为 9.2-21.6%和 0.5-1.5%；78.4-90.9%的 N 通过反硝化作用产生，其余通过 anammox。Pearson 相关分析表明，NH 是调节硝化作用的主要因素，而 NO 在反硝化作用和 DNRA 之间的竞争中起着重要作用，NO 是 anammox 的关键限制因素。总的来说，本研究揭示了硝化作用、反硝化作用、anammox 和 DNRA 在氮去除中的重要性，为自然/人工潮汐湿地氮循环机制提供了新的见解。
