Field-scale study to evaluate the role of bacterial chemotaxis in natural attenuation of groundwater contaminants

0408454福特污染的地下水的补救往往是有限的，因为土壤基质的间隙中捕获的化学污染物是无法进入地下水流动路径。 降解污染物的细菌可以穿透这些传导性较低的区域的一种机制是趋化性，即细菌感知化学浓度梯度并游向更高浓度污染物的能力。趋化性细菌能够从含水层的高传导区域向污染源迁移，这将增加污染物附近的微生物种群，从而提高降解和去除的总体速率。目标和方法：本项目的目的是确定趋化性细菌可在何种程度上促进天然地下水系统中的源区附近的化学污染物的降解。将在美国地质勘探局科德角有毒物质水文研究地点进行一系列实地调查。为了帮助现场规模研究的设计，将在控制良好的二维砂箱系统中进行初步研究。砂箱设计提供了额外的好处，即能够可视化流动模式，并分析污染物和细菌沿着流动路径的空间分布，而无需进行大型现场研究的所有复杂性。尽管许多实验室规模的实验表明细菌的趋化性是细菌在饱和多孔介质中运输的重要机制，其在外地一级的影响尚未得到评价。在现场规模的最终实验将解决的问题，是否在实验室中观察到的长度尺度的厘米趋化反应引起更大规模的影响，是在现场观察到的。广泛的影响：在弗吉尼亚大学和美国地质调查局的研究人员之间的一个新的合作伙伴关系带来了细菌趋化性的专业知识和涉及运动微生物的广泛的现场经验。 研究人员与一个公认的承诺，招募代表性不足的群体在工程将广泛教育一个研究生和两个本科生通过弗吉尼亚大学的跨学科研究计划在污染物水文学。 对当地两所高中的外联活动将向学生及其教师介绍分子生物学技术以及在实验室和实地调查中使用工程生物体。这项研究的结果将用于评估监测自然衰减作为记录有生物降解的污染场地的一种处理办法的可行性

0408454FordThe remediation of polluted groundwater is often limited because chemical contaminants trapped within interstices of the soil matrix are not accessible to groundwater flow paths. One mechanism by which pollutant-degrading bacteria may penetrate these less conductive regions is chemotaxis, the ability of bacteria to sense chemical concentration gradients and swim toward higher concentrations of contaminants. Chemotactic bacteria able to migrate from highly conductive regions of the aquifer toward the contaminant source would increase the microbial population in the vicinity of the contaminant and thereby enhance the overall rate of degradation and removal. Objective and Approach: The objective of this project is to determine the degree to which chemotactic bacteria may enhance the degradation of chemical pollutants near a source zone in natural groundwater systems. A series of field-scale investigations will be conducted at the USGS Cape Cod Toxic-Substances Hydrology Research Site. To aid in the design of the field-scale study, preliminary studies will be conducted in well-controlled two-dimensional sand box systems. The sand box design provides the added benefit of being able to visualize the flow patterns and analyze the spatial distributions of contaminant and bacteria along the flow path without all the complexities of a large field study.Intellectual Merit: Although number of laboratory-scale experiments have implicated bacterial chemotaxis as an important mechanism for transport of bacteria through saturated porous media, its ramifications at the field-scale have not been evaluated. A culminating experiment at the field-scale will address the question of whether chemotactic responses observed over length scales of centimeters in the lab give rise to larger scale effects that are observable in the field.Broad Impact: A new partnership between researchers at the University of Virginia and the US Geological Survey brings together expertise in bacterial chemotaxis and extensive field experience involving motile microorganisms. Investigators with a proven commitment to recruiting underrepresented groups in engineering will broadly educate one graduate and two undergraduate students through the University of Virginia's Program for Interdisciplinary Research in Contaminant Hydrology. Outreach to two local high schools will introduce students and their teachers to molecular biology techniques and the use of engineered organisms in laboratory and field-scale investigations. Results from this study will be used to assess the feasibility of monitored natural attenuation as a treatment option at contaminated sites where biological degradation has been documented