Supported by the Scientific Research Project of State Key Laboratory of Eco-Hydraulics in Northwest Arid Region of China (No. 2016ZZKT-9) and the Research Project of the Department of Education of Shaanxi Province of China (No. 17JS096)
在自然降雨条件下，黄土区坡耕地土壤表层中的养分会随地表径流流失，从而加剧了土壤质量和生产力的下降并造成严重的农业面源污染，使得准确预测黄土区养分随地表径流的流失过程尤为重要。现有的养分流失模型着重于估算长时段的养分流失总量，且未考虑开始产流前入渗水对交换层养分的稀释作用。根据不同降雨时段的养分迁移特性，将整个降雨过程划分为三个阶段：（1）从降雨开始（t0）至交换层土壤完全饱和（tsa），（2）从交换层土壤完全饱和（tsa）至开始产流（tp），（3）从开始产流（tp）至降雨结束。在运动波模型近似解析解的基础上建立了综合雨滴击溅、扩散和入渗作用的养分流失近似解析模型；并进行了降雨试验，以率定模型参数和验证模型的可靠性。结果表明：径流及养分的模拟值可与实测值精确匹配（R2> 0.8，纳什效率系数NSE> 0.347）。养分流失模型中的雨滴诱导水分转移速率er取值在0.006～0.023 cm·min-1之间，交换层深度de取值在0.68～1.32 cm之间；雨滴诱导水分转移速率er可显著影响硝态氮和铵态氮的峰值流失速率，er的增大使得养分流失过程中流失速率减小阶段的衰减速率更快；而交换层深度de可显著影响硝态氮和铵态氮损失率的总体变化范围，即随交换层深度的增大，养分的峰值流失速率和流失总量也随之增大。因此，应采取植被覆盖或深层施肥等措施，减弱雨滴动能、降低交换层养分含量以达到减少养分流失的目的。
[Objective] Under natural rainfall conditions, a large amount of soil nutrients are losing with overland flow or surface runoff on sloping farmlands in the loess area, which exacerbates the decline of soil quality and productivity of the farmlands and causes serious agricultural non-point source pollution to the environment. Therefore, it is particularly important to accurately predict how soil nutrients loing with surface runoff in the loess areas. However, the existing nutrient loss prediction model focuses on estimating the total nutrient loss over a long period of time in an area, but neglects the effect of infiltrating water diluting the nutrients in the exchange layer before runoff starts.[Method] In this study, according to the characteristics of nutrient migration in different time periods of a rainfall event, the entire process of a rainfall event is divided into three phases:(1) from the beginning of rainfall (t0) to the time when the exchange layer is completely saturated (tsa), (2) from the time when the exchange layer is completely saturated (tsa) to the time when runoff occurs (tp), and (3) from first runoff (tp) to the end of the rainfall. Based on the approximate analytical solution of the motion wave model, an approximate analytical model of nutrient loss was established, which integrated the effects of raindrop splashing, diffusion and infiltration;and then a simulated rainfall experiment was conducted to determine parameters of the model and verify reliability of the model.[Result] Results show the values of surface runoff and nutrient loss predicted with the model accurately matched the measured values (R2> 0.8, Nash-Sutcliffe efficiency coefficient> 0.347). In this nutrient loss model, the raindrop-induced water transfer rate er was valued in the range of 0.006~0.023 cm·min-1, and the exchange layer depth de in the range of 0.68~1.32 cm. The former significantly affected peak rate of the nitrate nitrogen and ammonium nitrogen loss, whereas the latter did range of the overall variation of the loss rate and boosted total loss of the nutrients. The model was found to be more sensitive to de than to er.[Conclusion] Some field management measures, such as revegetation, deep fertilization, etc. should be adopted to reduce raindrop kinetic energy and lower the content of nutrients in the exchange layer, so as to realize the purpose of reducing nutrient loss. In general, this approximate semi-analytical model has fully considered the influence of water infiltration in unsaturated soil on nutrient transport in the exchange layer, so it can be used to predict nutrient loss processes on bare slopes in arid and semi-arid regions. However, it should be emphasized that accurate calculation of runoff process is the basis of the nutrient loss simulation, so it is advisable to select an appropriate infiltration formula and solute adsorption coefficients in the light of soil texture, nutrient type, and nutrient concentration in rainwater.
邵凡凡,吴军虎,李玉晨.黄土区裸露坡地径流养分流失模型的建立与验证[J].土壤学报,2021,58(4):900-910. DOI:10.11766/trxb202002240069 SHAO Fanfan, WU Junhu, LI Yuchen. Establishment and Validation of the Model for Prediction of Nutrient Loss with Runoff on Bare Slopes in the Loess Plateau[J]. Acta Pedologica Sinica,2021,58(4):900-910.复制