Research Statement

I study the movement of water and waterborne constituents on and below the earth’s surface. This research relies on laboratory-scale and field-scale experimentation and focuses on complex systems governed by coupled hydrological and geochemical processes. I use data collected from these experiments to test and refine mathematical models that quantify fluid flow, mass transport, and chemical reactions. My overarching goal is to generate new experimental observations and to develop predictive approaches that can be used to inform water-resource management decisions and to guide restoration plans for sites impacted by polluted groundwater or surface water. In the following paragraphs, I summarize my recent and ongoing contributions in three areas of hydrologic research that have bearing on contemporary water-quality and water-supply issues.

• Colloid transport and colloid-facilitated contaminant transport. Colloids play an important role in water quality and contaminant-transport processes. Organic colloids, such as Cryptosporidium and pathogenic bacteria, represent a risk to human health if they are transmitted to groundwater aquifers that serve as a source of drinking water. Inorganic colloids, such as clay particles and mineral precipitates, are capable of adsorbing and accelerating the transport of dissolved contaminants. I seek to identify the physical and chemical factors that govern colloid movement and colloid-contaminant interactions within geologic systems. My most recent work involves the development of mathematical models that describe colloid transport through soils and on testing these models against data collected from laboratory and field experiments. The results of this research have allowed inferences to be drawn regarding the importance of colloids as agents of contaminant migration over a wide range of environmental conditions.
  
  
• Hydrology of the Florida Everglades. Nearly half of the Everglades has been drained over the last 50 years for agriculture and development, and the hydrologic functioning of the remaining marsh has been severely disrupted by the construction of canals and levees. Restoration of this imperiled ecosystem relies on accurate forecasting of the influences of proposed structural and operational modifications on water flow and quality. I have participated in the development of mathematical models capable of predicting surface-water flow within Everglades National Park and groundwater flow within the underlying Biscayne Aquifer. I also am collaborating with scientists from the USGS to build and test models appropriate for describing the transport of sediments and sediment-associated phosphorus through the slow-moving surface waters of the marsh. The knowledge gained from this work should be valuable to water-resource managers who use hydrologic models as decision tools in the Everglades.
  
  
• Migration of redox-sensitive metals and radionuclides. Inorganic chemicals, released inadvertently from liquid and solid waste sources or as a result of mining operations, have polluted groundwaters at sites across North America and Europe. Oxidation-reduction reactions affect the toxicity, bioavailability, and subsurface transport of a broad class of these chemicals. I have worked with scientists at Oak Ridge National Laboratory and at the University of Arizona to determine the effects of geochemical and hydrological processes on the migration of redox-sensitive metals (e.g., cobalt, chromium, iron). Our approach involves the use of laboratory techniques to measure oxidation-reduction rates and the development of computer models to simulate the influences of redox reactions on contaminant speciation and transport. New findings from this research will contribute to the design of strategies for the remediation of groundwater environments polluted by hazardous metals and radionuclides.