SMALL GRANTS FOR EXPLORATORY RESEARCH (SGER): DEVELOPMENT AND USE OF A VISUALIZATION TECHNIQUE TO BETTER DEFINE MECHANISMS FOR PARTICLE TRANSPORT IN POROUS MEDIA

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0551834 GermaineUnderstanding particle transport in porous media is important to a number ofproblems involving subsurface flow and transport, water and waste-water treatment, andsoil pedology. The migration behavior of particles in porous media is complex. Factorsinfluencing this behavior include the particle density, size and surface chemistry, thewater chemistry, the interstitial velocity, and the characteristics of the porous medium. Inthe case of biological particles, motility, chemotaxis, growth and decay are alsoinfluential.Considerable insight into particle transport in porous media has been gained fromexperimental programs based on batch and column testing. Nonetheless, work of thisnature cannot resolve, in real-time, the processes governing particle transport in theinterior of a porous medium. This limits the scale of understanding that can be gainedfrom such experimental approaches. In order to further understanding of the fundamentalprocesses governing particle fate and transport in porous media, alternative methods thatinvolve visualization studies of particle behavior within a porous medium are needed.In prior work, the Investigators of this proposal developed a visualizationtechnique to study particle behavior in the interior of a porous medium. Use of thistechnique enabled the proposition of new hypotheses regarding particle transportbehavior. The goals of this exploratory research project are to further the newvisualization technique, and to provide further support for the emerging hypotheses onparticle transport behavior. Specifically, the project will:1. Extend the new visualization technique to enable better resolution of particlebehavior, including resolution of individual particle tracks at the micro-scale anddistinction between aqueous and solid phase particles at the macro-scale.2. Prove, irrefutably, that, during non-Brownian particle transport underunfavorable electrostatic conditions, observations of decreasing particle attachment ratewith transport distance are attributable to the early filtration of heavier particles as aresult of gravitational sedimentation, and3. Establish the impact of flow direction on particle transport for micron-sizedparticles whose behavior is, theoretically, dominated by Brownian motion.Broader Impacts The proposed research will provide a visualization tool that canspatially and temporally resolve microscopic and macroscopic particle concentrations inthe interior of a porous medium. The research will also improve understanding ofattachment and detachments mechanisms that impact particle interaction with a medium'ssolid phase. In particular, it will provide an explanation for why irreversible particleattachment rates decrease with transport distance under unfavorable electrostaticconditions. Research training will be provided for one graduate student. Undergraduatestudents will also be engaged in the research through MIT's Undergraduate ResearchOpportunities Program.