Radioactive contaminants

Hello, I am currently working on my master's project which is: Fate and transport of radioactive contaminants in a lake. Radioactive contaminants into consideration are: Radium-226, Thorium-230 and Uranium-238 and I have their initial concentration in pCi/L (for Radium and Thorium) and mg/l (For uranium) My question is: how do I incorporate these contaminants in the model? Should I consider them under Generic Constituents? Can anyone please help me out in this?