| 摘要 |
[Objectives] To explore the control mode of farmland drainage pollutants and investigate the effects of ecological ditch and wetland on reducing farmland drainage pollutants in Hetao Irrigation District. [Methods] Based on the demonstration construction project of the ecological ditch-constructed wetland system in the Hetao Irrigation District, an experimental study was conducted from July to September 2023 to investigate the interception and purification effects of ecological ditches, constructed wetlands, and the combined ecological ditch-constructed wetland system on farmland drainage pollutants. Key water quality parameters measured included total nitrogen (TN) concentration and total phosphorus (TP) concentration. [Results] Different treatment modes of ecological ditches and constructed wetlands have a certain removal effect on nitrogen and phosphorus pollutants in water bodies. The ecological ditches treated with Astragalus laxmannii, Melilotus officinalis, Medicago sativa, bio-ball substrate, and bio-sheet substrate showed reduction efficiencies for TN and TP of 21.09% and 23.84%, 12.06% and 26.67%, 20.08% and 34.15%, 23.65% and 20.56%, and 19.92% and 25.83%, respectively. The emergent plant area showed reduction efficiencies of 24.28% for TN and 17.89% for TP, while the submerged plant area achieved a reduction efficiency of 10.21% for both TN and TP. Among the different treatment modes, the ecological ditch with M. sativa performed better in TP removal, whereas the bio-ball substrate treatment mode showed higher effectiveness in TN removal. In addition, the emergent plant area exhibited better TP removal performance, while the submerged plant area was more effective in TN removal. The combined system of ecological ditch and constructed wetland achieved removal rates of 37.55% for TN and 11.47% for TP. It effectively facilitates the step-by-step interception and adsorption purification of pollutants, thereby showing significant removal and purification effects on nitrogen and phosphorus contaminants. This contributes to mitigating agricultural non-point source pollution. [Conclusions] The combined ecological ditch-constructed wetland system serves dual functions of agricultural drainage and pollutant interception and purification. It reduces the pollution load of farmland drainage on receiving water bodies to some extent and mitigates agricultural non-point source pollution. Therefore, it is a relatively suitable technology for managing agricultural non-point source pollution in the Hetao Irrigation District. |
