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| Purification efficiency and allocation scale of ecological ditches for pollutants from paddy field runoff in Taihu Lake basin |
| Received:January 16, 2025 |
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| KeyWord:ecological ditches;paddy field runoff;nitrogen;phosphorus;configuration scale |
| Author Name | Affiliation | E-mail | | PAN Wuyi | School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China
Institute of Agricultural Resources and Environmental Sciences, Jiangsu Academy of Agricultural Sciences
Key laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Nanjing 210014, China | | | ZHANG Yingying | Institute of Agricultural Resources and Environmental Sciences, Jiangsu Academy of Agricultural Sciences
Key laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Nanjing 210014, China | fly8006@163.com | | ZHANG Zhiyong | Institute of Agricultural Resources and Environmental Sciences, Jiangsu Academy of Agricultural Sciences
Key laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Nanjing 210014, China | | | GONG Xinyu | Institute of Agricultural Resources and Environmental Sciences, Jiangsu Academy of Agricultural Sciences
Key laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Nanjing 210014, China | | | WEN Xuezheng | Institute of Agricultural Resources and Environmental Sciences, Jiangsu Academy of Agricultural Sciences
Key laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Nanjing 210014, China | | | WANG Yan | Institute of Agricultural Resources and Environmental Sciences, Jiangsu Academy of Agricultural Sciences
Key laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Nanjing 210014, China | | | JIANG Zhihui | Institute of Agricultural Resources and Environmental Sciences, Jiangsu Academy of Agricultural Sciences
Key laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Nanjing 210014, China | | | LIU Haiqin | Institute of Agricultural Resources and Environmental Sciences, Jiangsu Academy of Agricultural Sciences
Key laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Nanjing 210014, China | | | SONG Xuefei | Institute of Agricultural Resources and Environmental Sciences, Jiangsu Academy of Agricultural Sciences
Key laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Nanjing 210014, China | |
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| Abstract: |
| In order to analyze the adaptation scale between ecological ditches and farmland area, based on the field operation test of purifying rice runoff by ecological ditches in Taihu Lake basin, three natural drainage ditches in Wujin rice cultivation area of Changzhou were selected for ecological transformation. A tiered purification system was constructed by introducing aquatic plants and intercepting permeable dams（filled with environmentally friendly substrates）into the ditches. Different treatments were implemented based on ditch length：Ditch 1（ED1, 77 m）was equipped with 2 sets of enhanced purification measures（each comprising a 30-meter vegetation zone and one permeable dam）; Ditch 2（ED2, 186 m）incorporated 5 sets of such measures to form an intensified treatment system; Ditch 3（ED3, 193 m）served as the control group without modifications. Through comparative analysis of pollutant interception efficiencies across treatment levels, this study investigates the relationship between ecological ditch construction scale and purification performance, aiming to identify appropriate configuration scales compatible with farmland areas. The results showed that the ecological ditch with enhanced purification measures was significantly better than the ecological ditch without such measures（P<0.05）. Among them, ED2 with five sets of enhanced purification measures exhibited the optimal purification efficiency. The average reduction rates of total N（TN）, NO-3-N, NH+4-N, total P （TP）, chemical oxygen demand（COD）and suspended solids（SS）by ED2 were 41.54%, 37.32%, 26.72%, 31.19%, 54.67%, 63.56%, respectively. The average reduction of TN and TP pollution flux by ED2 was 652.62 g · d-1 and 28.19 g · d-1, respectively. The growth performance of Iris pseudacorus and Pontederia cordata is better than that of Vallisneria natans, and their contribution to purifying nitrogen and phosphorus in paddy field backwater is more significant. Under the condition of natural rainfall, in order to ensure that TN and TP in the ditch effluent met the standard of surface water, the length of ED2 in the three ditches was the shortest, which was 9.79 m and 11.51 m respectively. The average flow rate of 667 m2 paddy field is about 7.93 m3·d-1, and the average concentrations of TN and TP in farmland backwater are 6.33 mg · L-1 and 0.62 mg · L-1, respectively. The effluent was required to meet the class V standard of surface water. According to the configuration scale of ED2 ditch, 1 m2 ecological ditch can treat about 39 m2 farmland backwater, that is, 1 m3 ecological ditch can treat about 12 m3 farmland backwater. Therefore, subsequent studies should focus on rationally determining the configuration scale of ecological ditches based on regional characteristics, constructing dynamic quantitative models with adaptive parameters, and collaboratively optimizing the scale ratio of the “field-ditch-pond” system. |
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