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

[4084554]地下水污染的修复通常是有限的，因为被困在土壤基质间隙中的化学污染物无法进入地下水流动路径。降解污染物的细菌能够穿透这些不太导电的区域的一种机制是趋化性，即细菌感知化学浓度梯度并向高浓度污染物游去的能力。趋化细菌能够从含水层的高导电性区域向污染源迁移，从而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度。目的和方法：该项目的目的是确定趋化细菌可能在多大程度上促进天然地下水系统中源区附近化学污染物的降解。一系列的实地调查将在美国地质勘探局科德角有毒物质水文研究站进行。为了帮助设计现场规模的研究，将在控制良好的二维砂箱系统中进行初步研究。沙盒设计的另一个好处是能够可视化流动模式，并分析沿流动路径的污染物和细菌的空间分布，而无需进行大型现场研究的所有复杂性。智力优势：尽管许多实验室规模的实验表明细菌趋化性是细菌通过饱和多孔介质运输的重要机制，但其在现场规模上的影响尚未得到评估。在现场尺度上的最终实验将解决在实验室中观察到的厘米长度尺度上的趋化反应是否会引起在现场可观察到的更大规模效应的问题。广泛影响：弗吉尼亚大学和美国地质调查局的研究人员建立了新的合作伙伴关系，汇集了细菌趋化性方面的专业知识和涉及活动微生物的广泛现场经验。通过弗吉尼亚大学的污染物水文学跨学科研究项目，致力于招募工程领域代表性不足群体的研究人员将广泛教育一名研究生和两名本科生。与两所当地高中的接触将向学生和他们的老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在有生物降解记录的污染地点监测自然衰减作为一种治疗选择的可行性

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