Effects of soil characteristics on uranium decay OR radon particles

I will explain my project in detail.

We are a team of computer scientists, geologists, and physicists. Our goal is to understand how radon propagates through the soil. But this is a high level. I will go into detail.

Radon is a gas that transports from soil to air and harms humans. It is a byproduct of uranium decay. I am using geant4 to understand if I have x number of uranium/radon particles at the bottom of my soil layers and how many radon particles (radon flux) will I get on the surface. So either I need to use radon particles in the particle gun or perform uranium decay and analyze radon through it(this I will decide).

The main thing for the project is detector material. Since my detector is nothing but 4-5 soil layers of earth. It is made of 4-5 concentric spheres with different radii. Now each sphere is nothing but a soil layer. I need to find the chemical composition of these layers. Now there are two ways I can put chemical composition:

  1. random approximation of different materials (Al, Mg, Si, C, O) found in organic soil.
  2. some logic to select chemical elements from the periodic table so that the elements selected affect most radon/radon decay/uranium decay. ( I am not able to find any logic)

I need to tell geologists which elements concentration from the soil I need to add to my simulation. They will give me value.

I am going by the second way. There should be something in the geant4 source code/ or some equation or some property of radon/uranium which can help me to understand which chemical elements affect the radioactive decay/radon traversal.

HELP::: Any input for my 2nd point will be a great help. The answer can be in terms of geant4 source code perspective or chemistry perspective.

This question is already being dealt with here: Is there any way I can define pH of soil in GEANT4