Date of Award
12-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Environmental Engineering and Earth Science
Committee Chair/Advisor
Dr. Brian Powell
Committee Member
Dr. Nicole Martinez
Committee Member
Dr. Fanny Coutelot
Committee Member
Dr. Alex Chow
Abstract
Historical uses of radium (Ra)-containing self-luminous paint, such as on gauges and dials in naval ships, have led to the potential for such paint, and thus Ra, to be released into the marine environment. Radium-226 (226Ra) behavior in marine systems is not fully described in the literature, presenting a knowledge gap in the process of evaluating potential ecological impact of Ra in marine systems. This study explores various mechanisms contributing to Ra environmental transport in marine systems on a laboratory scale, including leaching, sorption, and diffusion. 226Ra leaching from watch hand dials containing radioactive luminous paint is evaluated as a notable source of marine system with a maximum value of over 3% 226Ra leached out from radioactive luminous paint to aqueous environment. The 226Ra sorption to pure minerals was then analyzed. 226Ra sorption dominating mechanism differs by different minerals. The ion exchange mechanism is sensitive to the solution condition, thus causing the distribution coefficient (Kd) value of clay minerals (montmorillonite, in range of 542 L kg-1 to 233 L kg-1) and crushed shell (mainly biogenic calcite, in range of 2113 L kg-1 to 203 L kg-1) 226Ra Kd values decreased with increasing seawater concentration. Iron oxides minerals like goethite (in range of 190 L kg-1 to 310 L kg-1) and calcite (in range of 653 L kg-1 to 1013 L kg-1), surface complexation plays a more significant role in Ra sorption, thus seawater concentration has less influence on 226Ra Kd values. 226Ra sorption on marine sediment was studied to better understand the 226Ra sorption process in marine system. The marine sediment from San Diego Bay have decreasing 226Ra Kd values (from 2185 L kg-1 to 65 L kg-1) with increase seawater concentration in solution, suggesting its sorption process is mainly through ion exchange. The following geochemical modeling simulating the 226Ra sorption process reinforces this point and suggests that the cation exchange capacity of sediment and solution competing cations are the main control factors in 226Ra sorption process. 226Ra diffusion process also related to the 226Ra sorption process. The sorbed 226Ra will not contribute to the 226Ra diffusion process. Thus, with the increasing seawater concentration and decreasing 226Ra Kd values, the 226Ra effective diffusion coefficient (from 1.84 × 10-12 to 4.89 × 10-11) and distance increased (from less than 2 cm to over 3.5 cm). The diffusion model also emphasized the importance of effective cation exchange capacity that count the exchangeable sites can involve in the ion exchange mechanism.
Recommended Citation
Wang, Jiusi, "Surface Reaction and Transportation of Radium-226 in Marine Systems" (2025). All Dissertations. 4158.
https://open.clemson.edu/all_dissertations/4158
Comments
This work will aim to reduce the knowledge gap needed for environmental decision making in discrete radioactive material objects from disposal sites. This work primarily focuses on determining the 226Ra leaching percentage from luminous radium paint, then looking at the 226Ra sorption onto pure minerals and marine sediments, as well as the 226Ra transportation through the diffusion mechanisms, following by modeling the 226Ra sorption and diffusion at certain conditions. Figure I.1 conceptually represents the possible 226Ra transport pathways. Thus, improve the understanding of 226Ra behavior in marine systems and contribute to the environmental decision making in discrete radioactive material objects