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| Impact of hilly slope gradient on phosphorus removal in ecological ditches and optimization strategies |
| Received:May 29, 2025 |
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| KeyWord:non-point source pollution;phosphorus;removal along the way;ecological ditch;hilly area;slope gradient |
| Author Name | Affiliation | E-mail | | WU Chenchen | School of Environmental Science and Engineering, Yangzhou University, Yangzhou 225009, China
Key Laboratory of AgroEnvironment in Downstream of Yangtze Plain of Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China | | | XU Xuan | Key Laboratory of AgroEnvironment in Downstream of Yangtze Plain of Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China | xxu@jaas.ac.cn | | DUAN Jingjing | Key Laboratory of AgroEnvironment in Downstream of Yangtze Plain of Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China | | | CHEN Xiaofeng | School of Environmental Science and Engineering, Yangzhou University, Yangzhou 225009, China | | | XUE Lihong | Key Laboratory of AgroEnvironment in Downstream of Yangtze Plain of Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China | |
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| Abstract: |
| To investigate the impact of hilly slope gradient on phosphorus（P）removal efficiency in ecological ditches, this study evaluated P removal mechanisms and efficiencies under different slope conditions through simulated ditch experiments combined with field validation. In the simulation experiment, two slope gradients（0° and 6°）and two types of ditches（conventional ditches and ecological ditches）were set. The concentrations of different P components in the overlying water（total phosphorus, TP; dissolved total phosphorus, DTP; dissolved inorganic phosphorus, DIP; dissolved organic phosphorus, DOP; and particulate phosphorus, PP）within 24 hours and the changes in the phosphorus forms in the sediment before and after the experiment were monitored. The results showed that the removal rates of TP, DTP, and PP in ecological ditches were significantly higher than those in conventional ditches under both slope gradients. The 6° slope reduced the TP removal rate in ecological ditches by 15.34% compared to 0°, indicating that an increase in slope had a significant inhibitory effect on P removal. The ditch system primarily removed P in water by accumulating labile P fractions（e.g., NaOH-P）in the sediment. The field ditch experiment in Tangshan, Nanjing（approximately 7° slope planted with Acorus gramineus and volcanic rock substrate）verified the actual efficiency of hilly ecological ditches. The 50 m ecological ditch showed an average TP removal rate of 18.06% and a removal load of 29.81 g·d-1. This study confirmed that slope gradient is one of the critical factors influencing P removal performance of hilly ecological ditches. Nevertheless, optimizing ditch structure, substrate materials, and vegetation selection can enhance the application potential of ecological ditches for controlling agricultural non-point source P pollution in hilly areas. |
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