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| Effects of rainfall on nitrogen loads in ponds in citrus orchard catchments |
| Received:July 25, 2024 |
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| KeyWord:rainfall;citrus orchard;ponds;nitrogen loads;Partial Least Squares Structural Equation Modeling（PLS-SEM） |
| Author Name | Affiliation | E-mail | | XIAO Hengbin | Key Laboratory of Arable Land Conservation in Middle and Lower Reaches of Yangtze River, Ministry of Agriculture and Rural Affairs, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China | | | ZHOU Jinyan | Key Laboratory of Arable Land Conservation in Middle and Lower Reaches of Yangtze River, Ministry of Agriculture and Rural Affairs, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China | | | ZHENG Yong | Power China Kunming Engineering Corporation Limited, Kunming 650051, China | | | YUAN Zheng | Key Laboratory of Arable Land Conservation in Middle and Lower Reaches of Yangtze River, Ministry of Agriculture and Rural Affairs, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China | | | ZHAO Yaoyao | Key Laboratory of Arable Land Conservation in Middle and Lower Reaches of Yangtze River, Ministry of Agriculture and Rural Affairs, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China | | | LUO Yue | State Key Laboratory of Soil and Sustainable Agriculture, Changshu National AgroEcosystem Observation and Research Station, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China | | | HU Ronggui | Key Laboratory of Arable Land Conservation in Middle and Lower Reaches of Yangtze River, Ministry of Agriculture and Rural Affairs, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China | | | LIN Shan | Key Laboratory of Arable Land Conservation in Middle and Lower Reaches of Yangtze River, Ministry of Agriculture and Rural Affairs, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China | linshan@mail.hzau.edu.cn |
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| Abstract: |
| In order to study the effects of rainfall on N pollution of pond water and its driving mechanisms, this study selected 8 ponds located in citrus orchard catchments in the Baihewan watershed in the middle reaches of the Yangtze River, were selected as the research objects. The changes in pond water depth, total nitrogen（TN）, nitrate nitrogen（NO3--N）, ammonia nitrogen（NH4+-N）, and particulate nitrogen （PN）concentrations before and after six rainfall events were monitored. Analyze the changes in nitrogen loads in ponds and their response to rainfall and catchment area, slope and changes in pond water volume. The results showed that N concentrations in ponds generally increased after rainfall, especially in PN, with the PN concentration of pond O3 showing the largest increase after rainfall（147%）. The N loads in ponds gradually increased with the increase of rainfall levels and showed significant differences. In the case of moderate rain, heavy rain, rainstorm and heavy rainstorm, the average TN load was 7.06, 10.12, 20.22 kg·hm-2, and 34.62 kg·hm-2, respectively. NO3--N was the main form of N, with the highest proportion（71%）in TN under heavy rain conditions. The proportion of NH4+-N in TN increased from 8% to 19% with increasing rainfall levels. The structural equation model showed that rainfall and slope showed a significant direct positive impact on N loads in ponds, and could also be increased by increasing pond water volume. The catchment area was significantly and negatively correlated with N loads, indicating that smaller catchments transported more N flux to ponds. The whole results showed that N pollution in ponds was generally higher after rainfall, with PN concentrations increasing the most after rainfall. As rainfall levels increased, ponds NH4+-N loads increased most significantly after rainfall. Both rainfall and slope contributed to ponds N loads, while catchment area had a negative effect on N loads. |
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