【作者】 王少丽；

【导师】 王兴奎；

【作者基本信息】 清华大学 ， 水利工程， 2008， 博士

【摘要】 农田排水对水环境的影响正日益受到国内外的关注,大量研究表明,地下排水中硝态氮的损失是地表水和地下水水质恶化的主要污染源,已构成水质环境恶化的一大威胁。由于农业生产活动对水土环境的影响是一个涉及多因素的复杂过程,因此,定量分析模型是目前研究农业水肥管理及氮污染控制预测的有效工具。本文在对现有模型进行综述和分析的基础上,建立了有机或无机肥应用模式的农田土壤中氮转化运移的机理模型。以建立在水动力学基础和水平衡基础上的土壤水热运动模型SWAP及DRAINMOD(DM)中的水热动态输出变量作为氮转化运移模型的驱动因子,构建了基于SWAP和DM水热模型的氮转化运移集成模型,构成农田水肥管理及氮肥对水土环境影响的评价模型,特别是预测农田排水沟(管)排出水中的硝态氮流失量。采用施用无机肥田间试验条件下3年的地下水位、地表和地下排水量、地表和地下硝态氮流失量的动态观测值,通过图形显示和统计参数指标分析方法,对集成DM水热模型的氮转化运移模型进行了性能检验;采用施用有机肥田间试验条件下1年的地下排水量、地下排水硝态氮流失量、土壤硝态氮含量动态观测值,对集成SWAP水热模型的氮转化运移模型进行了性能检验,模拟结果和实测结果吻合较好。采用不同土地利用条件下径流试验小区的地表径流观测值对地表径流子模块SCS法进行了检验,结果表明,SCS法可以较好的模拟地表径流量,其应用误差主要是系统性偏差。为消除系统误差,提出通过建立径流修正系数与降雨量的关系对模拟计算的径流过程进行改进的方法。对影响氮转化运移各过程的主要参数进行了敏感性分析,探讨了主要参数变化对氮动态的影响,对采用本文提出的模型或其它相似模型进行水土环境定量评价时参数的率定提供了判别标准。结合模型的应用预测评价、试验研究数据的对比分析及以往研究成果,对氮肥管理、灌溉管理、地下水位控制、耕作措施、作物系统、排水资源化利用对氮流失量的影响效果进行了分析,提出合理的农田管理措施。更多还原

【Abstract】 The impacts of farmland drainage on water environment have received increasingly great attention from both at home and abroad. A number of studies have shown that nitrate-nitrogen (NO3--N) loss through subsurface drainage is a major source of pollution for surface and groundwater bodies and thus threatens the water environment. The complexity of factors and processes evaluating environmental impacts of agricultural activities makes model development an important tool in the agricultural water-fertilizer management and nitrogen pollution controlling.Based on summarization and analysis of available models, this paper developed a mechanism model of nitrogen transport and transformation in the farmland soil that is suitable for organic and inorganic fertilizer application. Coupled with soil water and heat model SWAP or DRAINMOD (DM), an integrated nitrogen-model that simulates vertical transport of water, nitrogen and heat flow and NO3--N loss was developed.By graphical display and statistical comparison of observed and simulated data, three-year field data receiving inorganic fertilizer application, including water table, daily surface runoff and subsurface drainage flow, and NO3--N losses, were used to test the nitrogen-model coupled with DM. In the same way, one-year field data from four test plots receiving liquid hog manure, including daily subsurface drainage flow and NO3--N losses, soil NO3--N content, were used to test the nitrogen-model coupled with SWAP. Results showed that the simulated and observed values were in good agreement. The event rainfall-runoff data from field runoff plots under different land uses were used to test the surface runoff sub-model SCS in the nitrogen-model. The result showed that SCS method could simulate satisfactorily the surface runoff, and the error of SCS application is mainly systemic bias. To reduce the potentially systemic biases, an improved method for runoff process was proposed, namely, a relationship between runoff correction coefficient and rainfall was used to improve the runoff process.The paper also carried out the sensitivity analysis of main parameters influencing nitrogen transport and transformation, discussed the impacts of main parameters variation on nitrogen transport, and provided the judgment for model calibration. Combined with model evaluation, comparison and analysis of experimental data, and previous researches, the impacts of farmland management measures on nitrogen losses were analyzed, including fertilizer and irrigation management, water-table controlling, tillage measures, crop system and drainage reuse, the reasonable farmland management measures were proposed.更多还原