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| Dynamic changes of chemical oxygen demand in paddy field drainage and reduction of channel storage and storage based on in-situ field monitoring |
| Received:February 26, 2025 |
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| KeyWord:non-point source pollution;chemical oxygen demand;paddy field;drainage ditch;removal rate |
| Author Name | Affiliation | E-mail | | HUANG Xinran | College of Agricultural Science and Engineering, Hohai University, Nanjing 210098, China | | | HUANG Zengjian | College of Agricultural Science and Engineering, Hohai University, Nanjing 210098, China
Shanghai Puhe Engineering Design Co., Ltd., Shanghai 200333, China | | | LI Jiang | College of Agricultural Science and Engineering, Hohai University, Nanjing 210098, China
National State Key Laboratory of Efficient Utilization of Agricultural Water Resources, China Agricultural University, Beijing 100083, China | lijiang@hhu.edu.cn | | JIAO Xiyun | College of Agricultural Science and Engineering, Hohai University, Nanjing 210098, China
State Key Laboratory of Water Disaster Prevention, Nanjing 210098, China | | | GUO Weihua | College of Agricultural Science and Engineering, Hohai University, Nanjing 210098, China
State Key Laboratory of Water Disaster Prevention, Nanjing 210098, China | | | GU Zhe | College of Agricultural Science and Engineering, Hohai University, Nanjing 210098, China
State Key Laboratory of Water Disaster Prevention, Nanjing 210098, China | | | LIU Kaihua | College of Agricultural Science and Engineering, Hohai University, Nanjing 210098, China
State Key Laboratory of Water Disaster Prevention, Nanjing 210098, China | |
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| Abstract: |
| In order to explore the emission characteristics of non-point chemical oxygen demand（COD）from paddy fields in the southern water network area, a two-year field in-situ monitoring experiment was conducted in the Taihu Lake Bay Cultivation and Reading Base, Wujin District, Changzhou City, Jiangsu Province. Based on experimental data, this study analyzes the water depth, COD dynamic changes, and emission characteristics of paddy ditches throughout the entire growth period, and investigates the COD removal efficiency during the drainage and storage process of the ditches. The results showed that the greening and tillering stages of rice are key periods for non-point source pollution emissions. In 2023, the total drainage of paddy fields and gully connected paddy fields were 4 501.0 m3·h m-2 and 6 754.5 m3·h m-2, respectively. At this time, the drainage and COD emissions of paddy fields significantly increased; Fertilization is the main reason for the increase in COD concentration in paddy fields and ditch water bodies. After applying base fertilizer in 2024, the COD concentration reached 46.2 mg·L-1, and the highest COD concentration reached 81.0 mg·L-1 after fertilization during the jointing stage; The alternating effects of rainfall, irrigation, and drainage result in fluctuating COD concentrations throughout the entire growth period; The average concentration of COD in paddy water throughout the entire growth period is greater than or equal to the average concentration of COD in channel water; The drainage from the paddy field was stored in the ditch and digested for a period of time. The COD reduction rates from three storage experiments were 1.0, 0.8, and 2.0 kg · h m-2, respectively. Research has shown that the greening and tillering stages are critical stages for COD emissions in paddy fields, and water quality management during these periods should be given special attention; Fertilization events can significantly increase the COD concentration in water bodies in a short period of time, and the timing and method of fertilization should be reasonably controlled; Channel regulation and storage can effectively reduce COD load by 14.5% to 27.0%, and is an effective means of controlling non-point source pollution in rice fields. |
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