Before coming to Randolph College, I studied the synthesis and spectroscopy of luminescent transition metal complexes. These are remarkable molecules that absorb ultraviolet light and re-emit visible light, producing brightly colored glow-in-the-dark solutions. In addition to the obvious and simple aesthetic enjoyment that these molecules bring, they also have many useful chemical properties. The color, intensity, and time profile of the emitted light can all be strongly affected by changes in the molecule’s environment, and for this reason, luminescent species have been widely used as probes to detect and measure changes in temperature, solvent polarity, solution pH, and the concentration of innumerable soluble analytes.
I have enjoyed continuing this research at Randolph College. In the summer of 2003, I worked with sophomore student Chi Pham to use luminescent ruthenium compounds measure the concentration of oxygen in solution during the enzyme-catalyzed oxidation of glucose. The graph here shows the luminescent intensity of the probe species during the course of several reactions witvaryingng amounts of glucose and the enzyme, glucose oxidase.
The measured intensity of the luminescent probe and its known response to dissolved oxygen allowed for a calculation of the oxygen concentration at each second during the progress of the reaction (as shown on the right), and this allowed for an improved determination of the kinetic parameters for this reaction. This was a novel application of this technology, and Chi’s work on this project was recently published in the Journal of Chemical Education.
Recently, my work in environmental chemistry has led me to focus on other areas of research, but I continue to look for interesting projects and interested students to continue work in this fascinating field.
Phytoremediation of Lead in Soil:
Lynchburg is a beautiful city with many historic and stately homes. With these beautiful houses, however, there is also a hidden hazard of lead-based paint. The hazards associated with flaking lead paint inside homes has long been recognized, and abatement projects to remove old interior paint have been undertaken for many years. Exterior lead-based paint, however, is also a concern. As paint ages and flakes off, it ends up in the soil near the perimeter of the house, and as the paint further crumbles and degrades, the pigments decompose, releasing lead into the soil. In 2003, the students in my Environmental Chemistry class found many local soil samples with lead concentrations in excess of 1000 parts per million (ppm). The highest of these was nearly 5000 ppm, more than ten times the limit recommended by the EPA. These contaminated soils are a serious health concern – especially for children.
Phytoremediation is a new approach to lead abatement in soil which may be appropriate for residential sites in and around Lynchburg. The process of phytoremediation is based on the ability of plants to absorb metal ions and other nutrients from soil. Lead is often absorbed form soil along with essential elements, and plants grown in lead-contaminated soil are often found to have high levels of lead in their tissues. In addition, there are many plant species which are known to “hyperaccumulate” lead. In these hyperaccumulating species, the concentration of lead may be as high as 2 or 3% of the dry weight of the plant.
Since 2005, my students and I, in collaboration with Professor Kristy Bliss in the Biology Department, have been studying both soil analysis and phytoremediation. We have been working for the last two years with the Lynchburg Neighborhood Development Foundation and Lynchburg College to perform soil analyses near low-income housing units. This project has included more than fifty residential sites, with some houses built in the last ten years and others dating back to the late eighteen hundreds. As we complete the sampling phase of our study, we are now in the process of analyzing the soil samples and collating the data to look for trends in soil contamination levels throughout the city. The photo here shows Jen Mullins and Shirae Leslie at one of our sampling locations.
Shirae Leslie (left) has been working in my lab since 2006, and is currently working on the development of a new analytical procedure. This new extraction process will improve upon existing techniques for not only quantifying the amount of lead in the soil but also providing information about its probable toxicity. Shirae presented her work at a regional undergraduate research conference in 2007 and in the Randolph College Student Symposium in 2008. Shirae is posing proudly with our new microwave-assisted digestion equipment.
Aliyah Barrett began working in my lab as a Summer Research student in 2007, and is completing a project begun a few years ago by Mamata Thapa, Jessica Ericksen, Amanda Leto, and Rebecca Chapman. She is developing an undergraduate laboratory project in phytoremediation for use in Environmental Chemistry teaching labs. Her work is also helping to define protocols for our continuing greenhouse study of hyperaccumulating corn plants.
Research students from my group have routinely presented their work at regional and national research conferences. Some of these are listed here.
Shirae Leslie, "Improvements to Existing Methods of Sequential Selective Extraction of Lead from Contaminated Soil"; MARCUS Conference; Amherst, VA; October, 2007.
Aliyah Barrett, "Development of an Undergraduate Laboratory Activity Demonstarting Phytoremediation" , MARCUS Conference; Amherst, VA; October, 2007.
Jessica Shahan, "Biodeisel Generation: A College-Community Partnership" , National Confernce of Association for Advancement of Sustainability in Higher Education; Albequerque, NM; October, 2006. (with Professor Karin Warren, Department of Environmental Studies)
Rebecca Chapman, "Translocation of Lead in English Ivy: with Application in Phytoremediation" , MARCUS Conference; Amherst, VA; October, 2006. (with Professor Kristy Bliss, Department of Biology)
Mamata Thapa, " Analysis of Lead-Contaminated Soil Using Sequential Selective Extractions: Implications for Pytoextraction" , Undergraduate Research Symposium in the Chemical and Biological Sciences; Baltimore, MD; October, 2005.
Chi V. Pham, "An Improved Method fro Studying the Enzyme-Catalyzed Oxidation of Glucose Using Luminescent Probes" , MARCUS Conference; Amherst, VA; October, 2003.
Rebecca Chapman , 2006 Summer Reseach student, Currently employed at electrochemical lab in San Francisco
Mamata Thapa , 2005 Summer Research student, Currently in Ph.D. Program at Universtity of Marlyland-Baltimore County
Chi V. Pham, 2003 Summer Research student, Currently in Ph.D. program at University of Southern California