Summary of Studies and Current Work for

Molly Costanza-Robinson, Fiessinger Scholarship Winner 2000  

(Dr. Costanza successfully completed her Ph.D. program in May 2001 and is now working as a postdoctoral Research Specialist at Northern Arizona University.)

(Final report - summer 2001) 

The past several months have been an exciting time of transition.  In May 2001, I graduated from The University of Arizona (Tucson, AZ) with a doctorate in Soil, Water and Environmental Science and a Ph.D. minor in Analytical Chemistry.  My research focused on the gas-phase transport and retention of organic contaminants in unsaturated soil (i.e., simulated vadose zone systems).  Laboratory and intermediate-scale experiments revealed that contaminant accumulation at the interface between soil-water and soil-gas can dramatically influence the magnitude of retention of some organic compounds in unsaturated soils.  In fact, up to 87% of the retention of trichloroethene (TCE), an industrial solvent and among the most prevalent environmental contaminants, was attributed to accumulation at this “air-water interface”.  Depending on the environmental conditions, neglect of this process could result in significant error in contaminant transport predictions and risk assessment. 

Since May, I have been getting settled into my new position as a postdoctoral researcher and lecturer at Northern Arizona University (Flagstaff, AZ) (NAU) in the Department of Chemistry.  Currently, I am teaching second-semester general chemistry, and the fast pace of summer school is keeping me quite busy!  In the future, I expect to teach other lecture and lab courses in the Chemistry Department and the Center for Environmental Sciences and Education.  My research centers on the fate and transport of arsenic in freshwater systems.  Much to my liking, this research allows me to get out into the field.  The study area is Montezuma Well, a steep-walled, collapsed travertine spring basin located in Montezuma National Monument (north-central Arizona).  Its nearly isothermal water, unusually high dissolved carbon dioxide concentrations and alkalinity, and high natural arsenic levels combine to form a unique freshwater environment.  My preliminary work on this project has involved analysis of arsenic speciation in plant, soil, and invertebrate samples from the Well using X-ray Adsorption Near Edge Spectroscopy (XANES) at Stanford University’s Synchrotron Radiation Laboratory.  This innovative analysis technique is increasingly being applied to environmental questions, because of the ease of obtaining information regarding oxidation state.  This is an important advantage, since arsenic toxicity is largely controlled by redox chemistry. 

Eventually my research may include investigating such questions as:  Is arsenic bioaccumulated in a freshwater foodchain?   How does the Well serve as a source of arsenic to surrounding surface waters?  Did the high arsenic levels affect Native American populations that used the Well water for irrigation hundreds of years ago?  Such investigations will certainly benefit from collaboration with other scientists, such as biologists, hydrogeologists, and archaeologists. 

I am excited to see where these investigations lead!  Naturally, I will also be contributing to other research projects in our group, such as in the study of arsenic in geothermal waters in Yellowstone National Park and the water chemistry of springs in the Grand Canyon. 

Publication List for Molly S.C.-Robinson
(Work Completed During or Relevant to Fiessinger Scholarship)

M.S. Costanza-Robinson, M.L. Brusseau.  “Elucidation of Retention Processes Governing Trichloroethene Fate and Transport in Unsaturated Soils”.  In Preparation for Environmental Science and Technology, 2001.

M.S. Costanza-Robinson, M.L. Brusseau.  “Evaluation of a Water-Partitioning Tracer Method for in situ Measurement of Soil-Water Content”.  In Preparation for Journal of Contaminant Hydrology, 2001.

M.S. Costanza-Robinson, M.L. Brusseau.  “Gas-Phase Advection and Dispersion in Unsaturated Porous Media”.  Submitted to Water Resources Research, August 2001. 

M.S. Costanza-Robinson, M.L. Brusseau.  “Air-Water Interfacial Areas in Unsaturated Soils:  Evaluation of Interfacial Domains”.  Submitted to Water Resources Research, June 2001.

M.S. Costanza, M.L. Brusseau.  “Contaminant Vapor Adsorption at the Gas-Water Interface of Soils”.  Environmental Science and Technology, 34(1): 1-11, 2000.