Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Key Lab of Northwest Water Resource, Environment and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an, 710055, China.
Hefei Municipal Design & Research Institute Co., Ltd., Hefei, 230000, China.
Environ Res. 2023 Aug 15;231(Pt 1):116083. doi: 10.1016/j.envres.2023.116083. Epub 2023 May 8.
The depth of the substrate of subsurface flow (SSF) constructed wetlands (CWs) is closely related to their cost and operation stability. To explore the physiological regulation mechanism of wetland plants and pollutant removal potential of SSF CWs under "vertical spatial stress of roots" (by greatly reducing the depth of the substrate in SSF CWs to limit the vertical growth space of roots, VSSR), the physiological response and wetland purification effect of a 0.1 m Canna indica L. CW under VSSR were studied compared with conventional SSF CWs (0.6 m, 1.2 m). The results demonstrated that VSSR significantly enhanced the dissolved oxygen (DO) concentration (p < 0.05) within the SSF CWs, with the DO in 0.1 m CW remaining stable at over 3 mg/L. Under the same hydraulic retention time (HRT), VSSR significantly improved the removal effect of pollutants (p < 0.05). The removal rates of COD, NH-N, and total phosphorus (TP) remained above 87%, and the mean removal rates of total nitrogen (TN) reached 91.71%. VSSR promoted the morphological adaptation mechanisms of plants, such as significantly increased root-shoot ratio (p < 0.05), changed biomass allocation. Plants could maintain the stability of the photosynthetic mechanism by changing the distribution of light energy. The results of microbial community function prediction demonstrated that aerobic denitrification was the main mechanism of N transformation in the 0.1 m CW under VSSR. VSSR could induce the high root activity of plants, augment the concentration of root exudates, enhance the redox environment of the plant rhizosphere, further foster the enrichment of aerobic denitrifying bacteria, and strengthen the absorption efficiency of wetland plants and substrate, thus achieving an efficient pollutant removal capacity. Studies showed that VSSR was an effective means to enhance the rhizosphere effect of plants and pollutant removal in SSF CWs.
潜流人工湿地（SSF CWs）的基质深度与其成本和运行稳定性密切相关。为了探索湿地植物的生理调节机制和 SSF CWs 在“根系垂直空间胁迫”（通过大大减小 SSF CWs 中的基质深度来限制根系的垂直生长空间，VSSR）下的污染物去除潜力，研究了 0.1 m 美人蕉（Canna indica L.）在 VSSR 下的生理响应和湿地净化效果，并与常规 SSF CWs（0.6 m，1.2 m）进行了比较。结果表明，VSSR 显著提高了 SSF CWs 中的溶解氧（DO）浓度（p<0.05），0.1 m CW 中的 DO 稳定在 3mg/L 以上。在相同水力停留时间（HRT）下，VSSR 显著提高了污染物的去除效果（p<0.05）。COD、NH-N 和总磷（TP）的去除率均保持在 87%以上，总氮（TN）的平均去除率达到 91.71%。VSSR 促进了植物的形态适应机制，如显著增加根冠比（p<0.05），改变生物量分配。植物可以通过改变光能分布来保持光合作用机制的稳定性。微生物群落功能预测结果表明，好氧反硝化是 VSSR 下 0.1 m CW 中氮转化的主要机制。VSSR 可以诱导植物高根活性，增加根分泌物浓度，增强植物根际的氧化还原环境，进一步促进好氧反硝化菌的富集，增强湿地植物和基质的吸收效率，从而实现高效的污染物去除能力。研究表明，VSSR 是增强 SSF CWs 中植物根际效应和污染物去除的有效手段。
