Is there any way I can define pH of soil in GEANT4

Hello, my detector is made up of soil with some chemical composition. I want to specify the pH for my soil layers. How can I do it?

pH is nothing but the potential of hydrogen. It denotes the concentration of hydrogen ions in the soil concentration. I guess we can specify hydrogen concentration in geant4.

Hi. I am not sure of the relevance of pH to nuclear reactions. You can specify a concentration of hydrogen ions [H] (in practice a concentration of hydrogen nuclei). To maintain chemical equilibrium in an aqueous solution, you will need to also specify a concentration of hydronium ions [OH] (again really just nuclei pairs), such that [H][OH] is a constant. However, as pH increases or decreases, [H] and [OH] increase/decrease in direct opposition such that the total number of hydrogen nuclei remains a constant. If you are considering nuclear reactions on the hydrogen nuclei, the nuclear physics processes only care about the number of hydrogen nuclei, not what kind of ions they are in (perhaps with the exception of very low energy neutrons).

If I am missing something, I apologize. Maybe you could elaborate a bit on what you are trying to do.

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 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.

So to find logic for the above point, I went through some research papers with keywords (effects of soil characteristics on radon emanation) I found out that the pH of the soil is proportional to radon emanation in soil. That’s why I want to include it in my detector material.

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.

Geant4 is a particle physics simulation framework. It models how radiation (gamma rays, X-rays, beta particles, and high-energy beams of nucleons or nuclei) interacts with materials. Geant4 does not do diffusion of gases or liquids. Geant4 does not do chemistry.

If you have a model where there is radon that collects at some depth in soil, then you can definitely use Geant4 to answer a question like “how much dose would a person receive at the surface of X feet of soil?” But Geant4 can’t answer the question of “how much radon from depth X will diffuse out into the atmosphere?”

okay. I am still formulating my problem statement for the project. But if you understood my project, please guide me about my 2nd point.

The decay of radon and uranium does not depend on the materials in the soil, rather only on the radon and uranium concentrations. Radon is an inert gas, so its movement through the soil will be governed by diffusion and will depend on physical properties of the soil materials, such as porosity, density, etc. Radon’s daughters are solids and will adhere to materials electrostatically. The sticking will be governed by electrochemical processes. As noted, Geant4 does not model physical processes like diffusion or electrochemical processes. So you really need physical/chemical transport modelling software. The choice of materials really depends on those latter processes.