Biogeophysics of Bacterial-Mineral Interactions in Surface and Groundwater Systems

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The objective of the proposed research program is to develop a quantitative understanding of the influence of water flow on the physical and biogeochemical properties and of composite bacterial-mineral aggregates in aqueous systems. Specifically, studies will focus on how hydrodynamic shear densification (i.e., poroelastic deformation) influences microbial activity, bacterial-mineral aggregate structure, size, porosity, permeability, bulk density, and settling behavior. The complex interplay between these various material properties and environmental mass transport also provide scientific context for geophysical investigations using ground penetrating radar and electrical resistivity tomography to detect and image bacterial-mineral interactions in the environment by calibration of geophysical measurements with direct measurements of biogeophysical material properties of bacterial-mineral aggregates. Such insight is of fundamental relevance to addressing the complex interactions between physical, chemical, biological and hydrological processes that regulate nutrient cycling, contaminant transport and water quality, and the exchange of water between subsurface and surface reservoirs. The use of direct measurements of biogeophysical material properties to calibrate indirect geophysical estimates additionally offers numerous potential new applications that range from investigations on the characteristic spatial variability of bacterial-mineral interactions over larger areas, as well as monitoring biogeochemical responses to ongoing natural and anthropogenic environmental change, to exploration of life in extreme environments (e.g., deep subsurface biosphere, other planets).