【作者】 毛萌；

【导师】 石元春； 任理；

【作者基本信息】 中国农业大学 ， 土壤学， 2004， 博士

【摘要】 农药在现代农业中是必不可少的。它们在植物保护方面扮演着十分重要的角色，为提高作物产量、保证粮食安全作出了积极的贡献。但另一方面，农药的使用也引起了环境问题，人们已经认识到农药对人类健康和环境的危害。目前已在地下水、湖泊和沿海流域中发现了多种痕量的农药，而这些痕量农药对水生生态系统及饮用水质量有很大的影响。阿特拉津(Atrazine)是世界范围内最常在地下水中被检测出的农药之一，它广泛应用于我国华北和东北地区的玉米田中，是对我国地下水构成潜在威胁的一种农业化学污染物。随着中国农业的发展，节水农业和生态农业是必由之路。在我国的植物保护政策的制定上，应该制定使用Atrazine的如下重要策略：减少对该农药的依赖、使用；减少该农药向地下水和地表水的迁移。本论文研究了Atrazine在农田土壤中的运移，主要包括三个方面：(1)滴灌施药条件下Atrazine运移的物理模拟与数学仿真；(2)数值模拟入渗—重分布及田间气象条件下Atrazine在农田尺度上淋溶动态的空间分布；(3)构造一种尺度提升算法模拟淹灌条件下大尺度平面非均质土壤中非饱和流动的数值方法，评价有效参数的幂平均技术对农田尺度土壤中Atrazine淋溶模拟的影响。显然，从定量描述Atrazine在土壤中运移的机理方面看，开展滴灌施药条件下Atrazine在土壤中分布规律的数值模拟和农田尺度下Atrazine淋溶风险评价数值预报的研究，在理论和实践上都具有重要的意义。 第一章详细阐述了本论文的研究目的和意义，简要地回顾了有关Atrazine运移和转化方面的研究成果，重点综述了田间尺度土壤中Atrazine运移及滴灌施药条件下农药运移数值模拟方面的研究文献，并在此基础上制定了本文的研究目标、主要研究内容和所遵循的技术路线。 利用滴灌系统将农药直接施加到作物根区已成为近年来一种先进的灌溉、施药方法，所以在本文第二章中开展了室内滴灌施用Atrazine的物理实验和数值模拟的研究。我们在应用批量平衡技术和批培养方法，采用Freundlich吸附等温线和一级动力学方程获得Atrazine在供试土壤中的吸附特性参数和降解速率常数的基础上，运用基于Richards方程和考虑吸附与降解的对流—弥散方程的HYDRUS-2D软件，成功地仿真了物理模拟的实验结果，同时，对Atrazine运移参数、吸附特性和降解特性参数进行了灵敏度分析，表明：对Atrazine运移动态最敏感的参数是吸附等温线参数。最后，就不同初始含水量、不同滴灌流量对土壤水分和Atrazine动态分布的影响进行了数值分析，结果表明：随着初始含水量的增加，土壤水分的湿润范围增大，而Atrazine分布范围基本不变；当初始含水量分别为5％、10％和15％，滴灌施药历时为9 h时，水分在水平方向上的运动距离分别为26.0、27.8和32.3 cm，而在垂向上的运动距离分别为27.0、28.8和33.7 cm，湿润土体占整个土体的比例分别约为21.7％、26.5％和42.0％；Atrazine在水平方向上的运移距离均为20.5cm，而在垂向上的运动距离分别为20.4、20.0cm和20.0 cm；含药土体占整个土体的比例分别约为10.0％、9.7％和9.7％。当滴灌施药历时相同、滴头流量不同时，随着滴头流量的增加，土壤水分和Atrazine的运移范围均增大；对应于由低到高的4个滴头流量(0.5、1.0、1.5和2.0 L／h)，当灌溉施药历时为9h时，水分在土体内的水平运动距离分别为27.8、29.5、30.4和31.0 cm，而在垂直方向上的运动距离分别为：28.8、30.5、31.4和32.3 cm；Atrazine在水平方向上的运移距离分别为：20.5、21.5、22.5和22.9 cm，而在垂直方向上的运移距离分别为：20.0、21.3、21.5和22.0 cm)湿润土体的体积分别约占整个土体体积的26.5％、31.5％、34.5％和37.4％；含药土体约占整个土体的比例分别为:9.7%、11.4%、12.4%和13.2%。 人们己逐渐认识到农田尺度下农药淋溶风险的定量评价，对保护地下水环境是十分重要的。故第三章中以Atrazine为研究对象，通过在北京郊区永乐店试验站一个面积为27 x27澎的田间采集100个土壤样品，分别测定其主要理化特性，由上壤的机械组成和干容重测试数据，采用土壤传递函数生成了van Genuchten型的水力学参数，并进一步间接计算得到溶质运移的弥散度，同时，由实测的土壤有机碳含量估算了Atrazine的吸附参数。在此基础上，根据柱模型假设，运用HYDRUS一ID软件，就所设计的由实际背景概化而来的降雨入渗一重分布算例，对Atrazine在农田尺度非饱和土壤中的淋溶动态进行了数值模拟。模拟表明:对一场雨量为90 mm、雨强为30mm/d的降雨，在连续3天降雨接着重分布20天的情况下，若忽略蒸腾作用对土壤水分和溶质运动的影响，则降雨入渗和重分布过程结束时，通过土壤20 cm耕层的Atrazine的最大累积淋溶量分别占施用量的1 7.87%和75.41%;采样区域内AtraZine淋溶通量的空间分布存在较大差异。所探明的Atrazine易淋溶带，不仅为合理使用该农药，保护土壤环境提供了定量的依据，而且为预防该农药对浅层地下水的污染提供了重要的信息。 由于Atrazin。是我国华北地区夏玉米田常角的除草剂，而夏玉米生育期又是该地区的主要降雨季节。因而在第四章中，以北京市更多还原

【Abstract】 Pesticides are indispensable in modern agriculture. They are highly beneficial to corps being grown and play an important role in improving the production and safety of foodstuff. But on the other hand, the use of pesticides has caused environment concerns. The hazards of pesticides with regard to public health and the environment have been recognized for some time. Traces of pesticides are found in groundwater, lakes and coastal waters. These traces may have a strong impact on aquatic ecosystems and/or on the quality of drinking water supplies. Atrazine is one of the most frequently detected herbicide in groundwater throughout the world. In China, it is widely used in summer maize in the north and northeast of China, and is a potential contaminant agrochemical to groundwater. With the development of agriculture in China, water saving agriculture and ecological agriculture must be put into practice. In the Chinese Crop Protection Policy, the following important strategic objectives for the use of atrazine were formulated: reduction of dependency, the use and the transfer of atrazine to groundwater, surface water and air. This thesis reports on a study of atrazine leaching through soils in agricultural areas. The study comprises three aspects: (1) physical simulation and numerical modeling of atrazine transport in soil from trickle irrigation (2) spatial variability of atrazine leaching in soils at field scale under infiltration-redistribution or agricultural meteorology by numerical simulation (3) an upscaling numerical method to simulate unsaturated flow in horizontally heterogeneous soils at large scale under flood irrigation and evaluation of a power averaging technique of effective parameters on simulation of atrazine leached in soils at field scale. Obviously, from the viewpoint to quantitatively describe the transport mechanism of atrazine in soils, it was very important both in theory and in practice to carry out the research on numerical simulation of spatial and temporal distribution of atrazine in soils under trickle irrigation and of risk assessment of atrazine leaching through soils at agricultural field scale.In chapter 1, firstly, the main target and its significance of this paper were addressed in detail, secondly, we briefly reviewed the previous study about atrazine transport and transformation, and the literature with a focus on numerical simulation of pesticide leaching under drip irrigation and of atrazine transport at field scale because much information was available in the literature about atrazine transport through soils, lastly, based on the reviewed literature, the objectives and technical procedure were made for this study.In recent years, the use of chemigation has become a method to apply pesticides directly to the plant root zone through trickle irrigation systems. We, therefore, studied the spatial distribution of atrazine in soil under chemigation in chapter 2. The distribution of atrazine in a sandy loam soil was monitored in a drip chemigation experiment and numerical simulations were conducted. In addition, adsorption and degradation parameters of atrazine on the test soil were obtained by batch equilibrium and batch incubation experiments. HYDRUS-2D software was used to simulate the moisture movement and atrazine transport in the soil. The mathematical model considered unsaturated, non-steady flow in asandy loam and taking into account adsorptive and degradable herbicide. Freundlich equation and first order kinetic equation were used to describe the adsorption and degradation of atrazine respectively. Based on the observed data obtained from a trickle chemigation device to the fan-shaped soil box and result of the sensitivity analysis, the numerical model was validated and it was shown that the numerical simulation of atrazine dynamics in the soil was most sensitive to Freundlich adsorption parameters. Then the mathematical model was used to analyze the effects of different initial water contents and different application rates on the spatial distribution of moi更多还原