State Key Laboratory of Pollutant Control and Resources Reuse, School of the Environment, Nanjing University, 163 Xianlin Avenue, Nanjing, 210023, People's Republic of China.
Environ Sci Pollut Res Int. 2016 Feb;23(3):2677-83. doi: 10.1007/s11356-015-5485-4. Epub 2015 Oct 6.
Slightly polluted water has become one of the main sources of nitrogen contaminants in recent years, for which constructed wetlands (CW) is a typical and efficient treatment. However, the knowledge about contribution of individual nitrogen removal pathways and nitrogen balance in constructed wetlands is still limited. In this study, a stable-isotope-addition experiment was performed in laboratory-scale constructed wetlands treating slightly polluted water to determine quantitative contribution of different pathways and temporal variation of nitrogen balance using Na(15)NO3 as tracer. Microbial conversion and substrate retention were found to be the dominant pathways in nitrogen removal contributing 24.4-79.9 and 8.9-70.7 %, respectively, while plant contributed only 4.6-11.1 % through direct assimilation but promoted the efficiency of other pathways. In addition, microbial conversion became the major way to remove N whereas nitrogen retained in substrate at first was gradually released to be utilized by microbes and plants over time. The findings indicated that N2 emission representing microbial conversion was not only the major but also permanent nitrogen removal process, thus keeping a high efficiency of microbial conversion is important for stable and efficient nitrogen removal in constructed wetlands.
轻度污染水近年来已成为氮污染物的主要来源之一，而人工湿地（CW）是一种典型且高效的处理方法。然而，关于人工湿地中个体氮去除途径和氮平衡的知识仍然有限。在这项研究中，我们在实验室规模的人工湿地中进行了稳定同位素添加实验，以利用 Na(15)NO3 作为示踪剂来确定不同途径的定量贡献和氮平衡的时间变化。微生物转化和基质保留被发现是氮去除的主要途径，分别贡献了 24.4-79.9%和 8.9-70.7%，而植物仅通过直接同化贡献了 4.6-11.1%，但促进了其他途径的效率。此外，微生物转化成为去除氮的主要方式，而最初保留在基质中的氮随着时间的推移逐渐释放出来被微生物和植物利用。研究结果表明，代表微生物转化的 N2 排放不仅是主要的，而且是永久性的氮去除过程，因此保持微生物转化的高效率对于人工湿地中稳定高效的氮去除非常重要。
