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| Characteristics of spatial and temporal variations of pollutants in typical drainage ditches in the Yellow River Basin，Ningxia Section，and their influencing factors |
| Received:December 02, 2024 |
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| KeyWord:Yellow River basin;drainage ditches;pollutants;spatial and temporal variability;principal component analysis;influencing factors |
| Author Name | Affiliation | E-mail | | ZHANG Weihong | Ningxia Hui Autonomous Region Environmental Monitoring Centre, Yinchuan 750011, China | | | XU Yuzhou | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China | | | LIU Xiaotong | Institute of Agricultural Resources and Environment, Ningxia Academy of Agriculture and Forestry Sciences, Yinchuan 750002, China | | | SUN Yuan | Ningxia Hui Autonomous Region Environmental Monitoring Centre, Yinchuan 750011, China | | | MA Ying | Institute of Agricultural Resources and Environment, Ningxia Academy of Agriculture and Forestry Sciences, Yinchuan 750002, China | | | ZHOU Ruijuan | Ningxia Hui Autonomous Region Environmental Monitoring Centre, Yinchuan 750011, China | | | ZHAO Ying | Institute of Agricultural Resources and Environment, Ningxia Academy of Agriculture and Forestry Sciences, Yinchuan 750002, China | | | LIU Huan | State Key Laboratory of Efficient Utilization of Arid and Semiarid Arable Land in Northern China, Key Laboratory of Non-point Source Pollution Control, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China | | | ZHANG Xuejun | Institute of Agricultural Resources and Environment, Ningxia Academy of Agriculture and Forestry Sciences, Yinchuan 750002, China | zhxjun2002@163.com | | ZHANG Tianpeng | State Key Laboratory of Efficient Utilization of Arid and Semiarid Arable Land in Northern China, Key Laboratory of Non-point Source Pollution Control, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China | | | LEI Qiuliang | State Key Laboratory of Efficient Utilization of Arid and Semiarid Arable Land in Northern China, Key Laboratory of Non-point Source Pollution Control, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China | |
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| Abstract: |
| In order to investigate the spatial and temporal characteristics of pollutants and the factors affecting them in the Yellow River cross sections of the drainage ditches in the Ningxia section of the Yellow River Basin during the“14th Five-Year Plan”comprehensive management period, three typical monitoring cross sections of the drainage ditches in the Yellow River Basin were taken as the objects of the study in the period of 2019—2023 to analyse the spatial and temporal changes in 10 indicators, including total nitrogen（TN）, ammonia nitrogen（NH3-N）and total phosphorus（TP）, and to evaluate the monitoring cross sections based on principal component analysis. Characteristics and correlation of 10 indicators, including TN, NH3-N and TP, were analysed, and the monitoring section was comprehensively evaluated according to principal component analysis. The results showed that: on the time scale, TN and NH3-N varied in the three drainage ditches with the same trend, with low peaks of 0.67 mg·L-1 and 0.02 mg·L-1 during the irrigation period, and high peaks of 9.70 mg·L-1 and 4.71 mg·L-1 during the non-irrigation period; and the peaks of TP, permanganate index（CODMn）, chemical oxygen demand（COD）and biochemical oxygen demand（BOD）appeared during the irrigation period, with the respective values of 0.428, 12.2, 44.3 mg·L-1 and 5.9 mg·L-1. On the spatial scale, TN and NH3-N concentrations decreased by an average of 35.79% and 60.24%, TP concentrations decreased by an average of 53.79%, and COD, BOD, and CODMn concentrations decreased by an average of 35.90%, 31.75% and 31.06% in 2023 compared to 2019 in the three drainage ditches that feed into the Yellow River. In 2023, pollutants in the Zhonggan Ditch decreased by a maximum of 58.78%, the Luojia Ditch decreased by a minimum of 22.87%, while Wupai Ditch decreased by 42.61%. In terms of natural factors, all three drainage ditches into the Yellow River showed a significant negative correlation（P<0.05） between TN and water temperature, and a significant positive correlation（P<0.05）with dissolved oxygen（DO）, i.e., water temperature and DO promoted and inhibited TN removal, respectively. In terms of anthropogenic factors, the water quality of the three drainage ditches into the Yellow River were mainly affected by plantation fertilisers, aquaculture wastewater and domestic sewage. The results of principal component analysis showed that NH3-N and BOD decreased as non-major influencing factors in 2023, i. e., nitrogen and biodegradable organic matter concentrations decreased in the three drainage ditches into the Yellow River. Overall, during the“14th Five-Year Plan” period, the water quality of the three drainage ditches into the Yellow River improved significantly, with the water quality improving from Class Ⅳ or inferior Class Ⅴ in 2019 to Class Ⅱ to Class Ⅲ in 2023. |
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