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

9984715 Imhoff虽然农药、除草剂和其他化学物质和营养物质是用于根区，但它们浸出到地下水或附近的地表水中往往会导致环境污染。据推测，在许多野外土壤中观测到的相对较快的向地下水输送的原因是水通量的空间变异性，或优先流。同样的过程被认为在垃圾填埋场也很重要，它影响着渗滤液的分布、生物降解的总体速度和甲烷气体的产生。虽然优先流动已被认为是影响污染物运输的重要机制，但由于缺乏足够的现场工具来量化这一过程，其表征一直受到阻碍。提出的研究将检查气相示踪剂在实验室和现场实验中的效用。优先水流将通过拟合参数来量化描述非反应性水示踪剂输运的模型。独立于水示踪剂测试，气相示踪剂将用于确定气/水界面面积与体积含水量的比值。据推测，由气体示踪剂确定的这些参数的比率可以与水示踪剂输运模型的拟合参数相关联。如果成功，气体示踪剂可以用来量化优先流动的程度，比目前的方法更快，成本更低，从而提供一个有价值的工具来表征田间土壤和垃圾填埋场渗滤液的优先流动。该项目的教育目标是发展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基于网络的教学模块，这将加强PI的教学风格，并积极影响该系其他教师的教学风格。以学生为中心的学习将被纳入两门本科课程，为期四年。其有效性将通过调查和访谈来确定，这些调查和访谈使用的评估工具是从特拉华大学本科教育转型研究所推荐的评估工具中选择的。这样，环境工程课程中这些教学方法的好处和/或问题的定量数据就可以提供给工程界的其他教员。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来。学生将积极参与上述优先流研究，优先流是影响农药在地下运移的关键过程。＊＊＊

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. ***