【作者】 丁森；

【导师】 杨大文；

【作者基本信息】 清华大学 ， 水利工程， 2010， 硕士

【摘要】 随着农业生产中化肥使用量的增加,化肥流失所造成的水环境污染也越来越严重。为了研究农业活动对地下水体带来的面源污染状况,本论文以铵态氮与硝态氮为研究对象,结合山东位山引黄灌区的田间水文气象及地下水水质等观测数据,建立了基于LEACHM与MODFLOW数值模拟软件的灌区非饱和带与饱和带水氮联合运移模拟模型,对农田生态系统中氮素的运移转化和地下水污染进行了模拟研究,可为指导农业生产、控制水环境污染提供参考。位山灌区是黄河下游最大的引黄灌区,其气候条件、作物种植和农业管理等各方面都具有典型华北农业特色和良好的代表性。研究中采用田间试验与数值模拟相结合的方法。田间试验包括水文气象数据的测量、土壤不同深度含水率与养分含量的测量以及地下水水位和水质的观测。数值模拟中,通过对灌区模拟范围进行合理的划分,并用非饱和带与饱和带之间的水分和氮素的淋溶量,将描述非饱和带水分与氮素运移的LEACHM模型与地下水模拟模型MODFLOW相结合,建立了灌区水分与氮素在非饱和带与饱和带运移的联合模拟模型,实现水分与氮素在非饱和带和饱和带运动的联合模拟。论文中模拟期为2006年6月至2009年12月,采用2007年至2009年实测数据,对模型进行率定和验证,模拟结果的平均相关系数和Nash效率系数分别达到0.95与0.75,证明该联合模型可用于当地的水分与氮素联合运移模拟。为了分析农业生产对地下水水质的长期影响,选取具有代表性的20年长降雨系列,设置不同的农业施肥灌溉措施,利用率定验证后的模型,对灌区地下水中的氮素长期运移累积规律进行研究。结果表明,长期农田施肥和灌溉将导致灌区浅层地下水面临着严峻的氮素污染。通过情景模拟还发现,灌溉量是控制氮素淋溶的重要因子。在实际生产生活中,灌区应当发挥自身优势,严格控制灌溉水量。论文还对较深层潜水进行了定性模拟,发现水分与氮素垂向运移较为缓慢,在短时期内整个潜水层水质不会发生剧烈的恶化,但是随着地下水抽水量增大,其污染状况依然不容乐观。更多还原

【Abstract】 The increasing of fertilizer utilization and leaching in farmland have led to serious problem of groundwater pollution in China. In order to investigate the non-point source pollution of groundwater caused by agricultural activities, the leaching of ammonium nitrogen and nitrate nitrogen and groundwater pollution caused by them are studied in this master thesis. Based on the field experiment and hydrological and meteorological observation in the Weishan Irrigated District of Shandong province, with the LEACHM model and MODFLOW model an integrated model of water and nitrogen transportation in unsaturated and saturated zone is established. This integrated model is applied to the whole study area to analyze the groundwater pollution caused by nitrogen leaching. The result can be used for decision supporting of the groundwater pollution control and guide agricultural production.The Weishan Irrigated District, which is the largest irrigated area in the downstream of Yellow River basin, is typical for its features of climate condition, crop type and agricultural management in the North China Plain. Field experiments include observation of hydrological data, observation of soil moisture and nutrient content in different depth and observation of groundwater table elevation and qualities. In the numerical simulation, divide the whole district to different sub-district reasonably and the movements of water and nitrogen in unsaturated zone and saturated zone are linked by the leaching of water and nitrogen. Based on LEACHM model and MODFLOW model, an integrated simulation model of water and nitrogen in unsaturated and saturated zone is established. This model can simulate water and nutrient transportation in both unsaturated and saturated zone.According to the observation of water content and nitrogen concentration in soil and groundwater during 2007-2009, the integrated model is calibrated and validated, with correlation coefficient and Nash efficiency coefficient are 0.95 and 0.75 respectively. It means that this model can simulate the transportation of water and nutrient in unsaturated and saturated zone without much difference. Based on this model, we choose typical long series of rainfall data and carry out scenario study to understanding the potential nitrogen accumulation in the groundwater under present agricultural management. Results show that irrigation and fertilization would result in nitrogen pollution in shallow groundwater. It is also known that irrigation is an important factor of nitrogen leaching in farmland, which suggests irrigation can used as a method to reducing nitrogen pollution. For the slow movement in the vertical direction, deeper shallow groundwater could maintain good quality in a longer time. However, if a large quantity of groundwater is pumped to meet the rapid increasing of water consumption in the future, it would accelerate the groundwater deteriorations and threaten drinking water safety.更多还原