Faculty Field Experiences

 

 

Dr.  Matthew Becker          mwbecker@geology.buffalo.edu

EFFECT OF CELL MORPHOLOGY ON BACTERIA TRANSPORT BY GROUND WATER:  FIELD-SCALE TRACER EXPERIMENTS IN FRACTURED CRYSTALLINE BEDROCK

Matthew Becker¹, David Metge², Allen Shapiro³, and Samantha Collins¹, Ronald Harvey²

¹Department of Geology, University at Buffalo, Buffalo, New York, USA

²U.S. Geological Survey, 3215 Marine St, Boulder, CO, USA

³U.S. Geological Survey, 431 National Center, Reston, Virginia, USA

    The mobility of bacteria in saturated fractured bedrock is of interest to environmental health scientists who want to reduce the transport of pathogenic bacteria, ground-water remediators who want to increase the transport of bacteria capable of metabolizing contaminants, and contaminant hydrogeologists who want to predict the co-transport  of toxic substances.  Although transport experiments have been performed in a number of unconsolidated aquifers, field-scale bacterial transport experiments in fractured bedrock are very rare.  In May of 2000, a forced-gradient microbial tracer test was conducted in the fractured crystalline bedrock of the Mirror Lake Fractured Rock Research Site.  Deuterated water, negatively charged polystyrene microspheres (carboxylate-modified surface), positively charged polystyrene microspheres (amidine-modified surface), and cultured indigenous aerobic bacteria were injected in two tracer experiments.  The cultured indigenous aerobic bacteria were of varying morphology.  Non-motile coccoid, non-motile gram-negative rod, motile gram-negative rod, and a non-motile gram-positive rod bacteria were injected simultaneously.  Postively and negatively charged microspheres were injected separately to avoid aggregation.  Field experiments are supported by bench-top experiments in two columns: one packed with iron (III) oxyhydroxide coated glass beads, and another packed with clean glass beads.  Based upon the ground-water chemistry at the Mirror Lake Site,  it is suspected that the in-situ fractures have some oxyhydroxide coating.  Field breakthrough results are still under analysis, but it is apparent that the coccoidal bacteria arrived well ahead of the other bacterial, colloidal, and deuterated water tracers.  All bacteria were extensively filtered during transport, with the gram positive rods being the most efficiently captured.  Motile rods appeared to be filtered to a greater extent than non-motile rods.  All breakthrough curves of bacteria exhibited extensive tailing, suggesting that filtration was somewhat reversible.  Selective filtration of positively charged microspheres suggests that if iron (III) oxyhydroxide coatings are present in the subsurface, they did not dominate filtration in these experiments.

Photos from Mirror Lake, May 2000 microbe field tests.  Pictured below are Matt Becker (green hat), David Metge (pink hat), Samantha Collins (no hat).

 Dr.  Michael F. Sheridan          mfs@eng.buffalo.edu

    Michael Sheridan is currently completing a 3-year project on volcanic risk assessment at Pico de Orizaba Mexico with funding from NASA.  Bernard Hubbard just finished his Ph.D. on this project.  Work in this area continues with a new M.A. student, Fernanda Scuderi, who will work on understanding the source of a giant debris avalanche and flow that originated from Las Cumbres volcano, located about 30 km north of Pico. He will continue working with civil protection authorities in Veracruz State to coordinate volcanic hazard mapping with public safety policy.  A new project on the volcanic hazards of Las Tuxlas volcanoes south of Veracruz will probably begin next year. Dr. Sheridan is associated with risk assessment groups elsewhere in Mexico, including Popocatepetl and Volcan Colima, both of which are currently active.  The focus in these projects is to develop better models for emplacement of volcanic debris flows.  A project on the back burner is the development of a volcanic hazard map for El Chichon volcano in the state of Chiapas.  Ricardo Molinero, a Ph.D. student is working on the Chichinautzin Volcanic Field that extends from Mexico City southward. This project will look into the relationship of volcanism and tectonism in this area, relating the sequence and volume of volcanic products to volcanic risk in Mexico City. Adam Stinton has begun his research project on a comparison of sector collapse of young Cascade Volcanoes.  He will use GIS to determine likely areas of edifice collapse on Mt. Rainier and possibly other volcanoes. John Donarummo is finishing his Ph.D. dissertation on an interpretation of dust/ash in the Greenland ice core. Potential new projects for the next 2 or 3 years include additional volcanic hazard work in Latin America.  He and Morgan Salisbury, a M.A. student, will begin work on Sabancaya Volcano in Peru to investigate the pyroclastic history of the volcano as it pertains to risk assessment. This study will focus on the pyroclastic history of the volcano and the large volcanic debris avalanche that slid from the volcano Hualca Hualca into the Colca valley.  He will submit a proposal to study the pyroclastic flow deposits of Villarrica Volcano in Chile and develop a hazard map for that volcano as well.   A study of lahars at Galeras Volcano, Colombia is a strong potential, also.

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