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| Estimation of nitrogen output load of a river watershed based on net anthropogenic nitrogen input and river inflow coefficient |
| Received:July 07, 2020 |
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| KeyWord:net anthropogenic nitrogen input (NANI);inflow coefficient;watershed;riverine total nitrogen exports |
| Author Name | Affiliation | E-mail | | FAN Xiang | College of Water Conservancy and Civil Engineering, Hunan Agricultural University, Changsha 410128, China
Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | WU Feng-ping | College of Water Conservancy and Civil Engineering, Hunan Agricultural University, Changsha 410128, China | 315228161@qq.com | | MENG Cen | Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | YE Lei | College of Water Conservancy and Civil Engineering, Hunan Agricultural University, Changsha 410128, China
Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | LI Xi | Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | ZHANG Man-yi | Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | LI Yu-yuan | Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | WU Gen-yi | South China Institute of Environmental Science, MEE, Guangzhou 510655, China | | | WU Jin-shui | Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | |
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| Abstract: |
| We constructed a model for calculating total nitrogen(TN)load in a river, based on the net input of man-made nitrogen to the river basin and its inflow coefficient. In order to explore and solve problems such as the spatial heterogeneity of non-point source pollution transmission and the large uncertainty of traditional river inflow coefficient accounting, the simulation results of typical watersheds must be expanded from basic measurement units to a larger scale. As an example, we used the source watershed of a subtropical southern hilly region where the transformation of non-point source pollution is complicated. The riverine TN exports were estimated by establishing a net anthropogenic nitrogen input(NANI)model for the river watershed, and a regression model of the key factors(hydrology, landform, land use, etc.)affecting the river inflow coefficient of TN. At the same time, a relevant model based on a small-scale watershed(Jinjing River) was applied to the downstream large-scale watershed(Laodao River). The results showed that the NANI of 8 catchments(area 2.6~204.1 km2)in the Jinjing River watershed decreased significantly between 2012 and 2017, and varied from(81.7±7.0)kg·hm-2·a-1 to(198.2±32.5)kg·hm-2·a-1, in which nitrogen deposition and net input of chemical fertilizer were the main input sources. A NANI river inflow coefficient regression model, based on runoff coefficient and elevation, was constructed, and riverine TN exports were simulated with the NANI model. The model determination coefficient(R2)and Nash efficiency coefficient(NSE)were 0.729 and 0.714, respectively. The river nitrogen load model based on the Jinjing River watershed was applied to the Laodao River Watershed(2 543 km2). The error between the simulated and measured values of the four sections ranged from 10.3% to 17.2%. This shows that the river TN load model based on NANI and its inflow coefficient is scientific, convenient and applicable to a certain extent, and can be used to estimate the load of agricultural non-point source pollution in the hilly region of South China. |
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