Nuclear Engineering Colloquium: Nicole Martinez
Title: "Uptake of select radionuclides in a native South Carolina grass for application in radioactive waste management."
This project is part of a larger effort to understand, and ultimately predict, the influence of coupled chemical, physical, and biological processes on radionuclide transport in the environment. The work described herein seeks to quantify (1) the uptake of Tc, Np, U, and Cs in the grass species Andropogon virginicus in laboratory-scale experiments and (2) the transport of these analytes through soil-columns in order to elucidate mechanisms that may affect this transport when plants are present. Scaling up from previous studies investigating influence of plant exudates on soil sorption as well as hydroponic plant uptake experiments, this work adds to the body of knowledge aimed at providing insight into potential factors contributing to migration of radionuclides in Savannah River Site (SRS; Aiken, South Carolina, United States) soil.
The ability of A. virginicus to alter analyte transport through a soil medium was studied on a macroscale with soil-plant columns. Porewater sampling tubes were used to introduce analytes into the column after plants were established as well as to sample the pore water at the completion of the experiment. Three groups of columns with six replicates each were constructed: (1) columns with plants and radionuclides, (2) columns without plants and with radionuclides, and (3) control columns with plants and without radionuclides. Shoots were harvested four weeks after analyte introduction. The columns were then covered and stored at 5 °C until segmentation. Samples (aqueous, plant digestate, soil digestate) were analyzed with inductively coupled mass spectrometry (ICP-MS) and/or liquid scintillation counting (LSC) as appropriate.
Analysis of effluent and soil digestate samples indicates that plant presence retards downward transport of 99Tc and 237Np through the column with respect to amount of irrigation water (or solution) introduced and contributes to upward migration of these mobile radionuclides. The reasoning for this is multifold; it includes, in part, the evapotranspiration action of the plant, which greatly affects transport of water and mobile ions through the soil column, and it is influenced by plant uptake, particularly for 99Tc as demonstrated from analysis of the plant tissues. Effects on the transport of 133Cs and 238U could not be discerned from aqueous or soil digestate analysis and plant tissue analysis did not reveal significant differences in plant uptake between the group one and control columns as the SRS soil contains native 133Cs and 238U.
Nicole Martinez, Certified Health Physicist, is an Assistant Professor at Clemson University within a unique departmental program designed to address broad environmental issues associated with anthropogenic and natural radioactivity. She received her MS and PhD in Radiological Health Sciences from Colorado State University, specializing in health physics and radioecology, respectively. Prior to attending graduate school, she served in the United States Navy as a nuclear power instructor and radiation health officer. Martinez’s current research interests focus on the behavior and effects of radiological contaminants in the environment, to include radiation transport modelling, improved dosimetric methods, low dose response in microorganisms, and the influence of plants on radionuclide mobility. In addition, Martinez is interested in non-technical issues within radiation protection, such as ethics and diversity. She serves on Committee 4, Application of the Commission’s Recommendations, of the International Commission of Radiological Protection and is the current president of the Women in Radiation Protection section within the Health Physics Society. She is the recipient of the 2018 Bo Lindell Medal from the ICRP and the 2019 Elda Anderson Award from the HPS.
NOTE: This colloquium will be available as a webcast.
Wednesday, January 29, 2020 at 1:30pm to 2:30pm
Nuclear Engineering Building, 302
1412 Circle Drive Knoxville TN 37996