Journal of Ecology and Rural Environment ›› 2024, Vol. 40 ›› Issue (1): 107-118.doi: 10.19741/j.issn.1673-4831.2022.1189

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The Removal of N and P by Terrestrial Vegetable Floating Beds in Eutrophic Waters and the Microbiological Analysis of Water and Root System

ZHOU Jia-lin1,2, DUAN Jing-jing2, WANG Ning2, LI Ming1, CHEN Xiao-feng1, XUE Li-hong2   

  1. 1. College of Environmental Science and Engineering, Yangzhou University, Yangzhou 225009, China;
    2. Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory of Food Quality and Safety (State Key Laboratory Cultivation Base of Ministry of Science and Technology), Nanjing 210014, China
  • Received:2022-11-11 Online:2024-01-25 Published:2024-01-23

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Abstract: In order to explore the nitrogen (N) and phosphorus (P) removal efficiencies of terrestrial vegetable floating beds in eutrophic waters and their influence on microbial communities and denitrification, 16S rDNA high-throughput sequencing and quantitative PCR (qPCR) techniques were used on water samples to analyze the dynamics of N and P concentrations, microbial communities, and functional genes. The results show high removal efficiencies for total phosphorus (TP) and ammonium (NH4+) by terrestrial vegetable floating beds, with the average TP removal efficiency of treatments groups of Oenanthe javanica, Lactuca sativa and Brassica rapa (57.13%, 46.91%, and 40.86%, respectively) superior to that of the control group (25.46%), and the average NH4+ removal efficiency of treatments groups of Oenanthe javanica and Lactuca sativa (51.30% and 48.16%, respectively) higher than that of the control group (27.23%). Analysis of the dominant bacterial species by 16S rDNA high-throughput sequencing indicated that the root surfaces of different vegetable floating beds were all enriched with Rhodobacter for denitrification, and the root surfaces of Oenanthe javanica and Lactuca sativa were enriched with high amounts of Hydrogenophaga to enhance hydrogen autotrophic denitrification. Higher amounts of Gemmatimonas were found in waters surrounding Brassica rapa and the root surfaces of Oenanthe javanica and Lactuca sativa, which would convert N2O into N2 to achieve complete denitrification. Limnohabitans and Flavobacterium exhibited higher abundance in waters of the control group, which would promote ammonia oxidation and denitrification, respectively. The abundance of denitrification functional genes (nirK, nirS, norB and nosZ) in waters increased during the later period of the experiment, with relatively large copy numbers of waters surrounding the roots of Brassica rapa and the root surfaces of Oenanthe javanica and Lactuca sativa. It indicates that, during the latter period of the experiment, the root surfaces of the vegetable floating beds or the surrounding water accumulated a significant number of denitrification functional genes, leading to an enhanced denitrification process. Our study shows that terrestrial vegetable floating beds have good purifying effects on N and P in waters, and can promote denitrification by adjusting dominant bacterial species on the root surfaces or in the surrounding water.

Key words: terrestrial vegetable floating bed, 16S rDNA, functional gene, denitrification

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