Root vertical spatial stress: A method for enhancing rhizosphere effect of plants in subsurface flow constructed wetland

Jingying Zhang; Zhiyong Shao; Bin Li; Ge Bai; Lei Yang; Yanbin Chi; Min Wang; Yongxiang Ren

doi:10.1016/j.envres.2023.116083

Root vertical spatial stress: A method for enhancing rhizosphere effect of plants in subsurface flow constructed wetland

Environ Res. 2023 Aug 15;231(Pt 1):116083. doi: 10.1016/j.envres.2023.116083. Epub 2023 May 8.

Authors

Jingying Zhang¹, Zhiyong Shao², Bin Li³, Ge Bai¹, Lei Yang¹, Yanbin Chi⁴, Min Wang⁵, Yongxiang Ren⁶

Affiliations

¹ 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.
² Hefei Municipal Design & Research Institute Co., Ltd., Hefei, 230000, China.
³ Xi'an Botanical Garden of Shaanxi Province, Botanical Institute of Shaanxi Province, Xi'an, 710061, China.
⁴ School of Metallurgical and Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China.
⁵ Shaanxi Environmental Monitoring Technology Advisory Service Center, Xi'an, 710000, China.
⁶ 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. Electronic address: ryx@xauat.edu.cn.

PMID: 37164283
DOI: 10.1016/j.envres.2023.116083

Abstract

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, NH₄⁺-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.

Keywords: Physiological regulation; Pollutant removal in SSF CW; Rhizosphere environment; Root growth spatial stress; Wetland plant.

MeSH terms

Environmental Pollutants*
Nitrogen / analysis
Plants
Rhizosphere
Waste Disposal, Fluid* / methods
Wetlands

Substances

Environmental Pollutants
Nitrogen