CAREER: Characterizing Preferential Water Flow in Laboratory and Field Soils with Gas Tracers

9984715虽然杀虫剂、除草剂和其他化学物质和营养物质是用于根区的，但淋溶到地下水或附近的地表水往往会导致环境污染。有人假设，在许多田间土壤中观察到的地下水相对快速运移的原因是水通量的空间变异性，即优先流。这一同样的过程被认为在垃圾填埋场也很重要，因为它影响到渗滤液的分布以及生物降解和甲烷气体产生的总体速度。虽然优先流已被认为是影响污染物迁移的一个重要机制，但由于缺乏足够的现场工具来量化这一过程，其特征一直受到阻碍。拟议的研究将检查气相示踪剂在实验室和现场实验中的用途。优先流量将通过将参数与描述非反应水示踪剂传输的模型进行拟合来量化。与水示踪剂测试无关，将使用气相示踪剂来确定气/水界面面积与体积水含量的比率。假设从气体示踪剂确定的这些参数的比率可以与水示踪剂传输模型的拟合参数相关联。如果成功，气体示踪剂可以比目前的方法更快且成本更低地用于量化优先流的程度，从而为表征田间土壤中的优先流和垃圾填埋场的渗滤液提供了一个有价值的工具。该项目的教育目标是开发主动学习或以学生为中心的教学方法，包括基于问题的学习、本科生导师、本科生和研究生研究以及一个基于网络的教学模块，该模块将加强PI的教学风格，并对系内其他教师的教学风格产生积极影响。以学生为中心的学习将在四年内纳入两门本科课程。其有效性将通过调查和访谈来确定，评估工具选自特拉华大学本科教育转型研究所推荐的评估工具。通过这种方式，环境工程课程中这些教学方法的好处和/或问题的定量数据可以提供给工程界的其他教师。教育计划的一个方面是让本科生和研究生参与到通过科学研究发现的过程中。学生将积极参与上述优先流的研究，优先流是影响农用化学品在地下运输的关键过程。***

9984715 Imhoff While pesticides, herbicides and other chemicals and nutrients are intended for the root zone, leaching to groundwater or nearby surface water often leads to environmental contamination. It has been hypothesied that spatial variability in water fluxes, or preferential flow, is the cause of the relatively fast transport to the groundwater observed in many field soils. This same process is thought to be significant in landfills as well where it affects the distribution of leachate and overall rates of biological degradation and methane gas production. While preferential flow has been recognized as an important mechanism influencing contaminant transport, its characterization has been hampered by a lack of adequate field tools for quantifying this process. The research proposed will examine the utility of gas phase tracers in the laboratory and in field experiments. Preferential water flow will be quantified by fitting parameters to a model describing the transport of a nonreactive water tracer. Independent of the water tracer test, gas phase tracers will be used to determine the ratio of the gas/water interfacial area to the volumetric water content. It is hypothesied that the ratio of these parameters determined from the gas tracers can be correlated with fitted parameters to the model for transport of the water tracer. If successful, gas tracers may be used to quantify the degree of preferential flow faster and at less cost than current methods, thereby providing a valuable tool for characterizing preferential flow in field soils and of leachate in landfills.The educational objectives of this project are to develop active-learning or student-centered teaching methods involving problem-based learning, undergraduate tutors, undergaduate and graduate student research and a web-based teaching module that will strengthen the PI's pedagogical style and positively influence the teaching styles of other faculty in the department. Student-centered learning will be incorporated in two undergraduate courses over a four-year period. Their effectiveness will be determined through surveys and interviews using assessment tools selected from those recommended by the University of Delaware Institute for Tranforming Undergraduate Education. In this way, quantitative data on the benefits and/or problems with these teaching methods in an environmental engineering curriculum can be made available to other faculty within the engineering community. One aspect of the educational plan is to involve undergraduate and graduate students in the process of discovery through scientific research. Students will actively participate in the above research on preferential flow, a critical process that affects the transport of agricultural chemicals in the subsurface. ***