[Dr Youssef Hafez]

We present FERM-1D, a user-friendly and quick computer code for Finite Element Radon Modeling in one dimension (1D). This code accurately calculates the vertical distribution of Radon gas in dry soils, considering various important. It accounts for soil layers with distinct properties such as permeability, porosity, and diffusion coefficient stratification. Different boundary conditions at the ground surface, including convective boundary conditions, are taken into account.
Considering that radon transport is primarily vertically oriented due to depressurization beneath residential buildings, a one-dimensional approach in the vertical direction is both reasonable and practical. This simplification allows us to avoid the complexities associated with two- and three-dimensional considerations. Furthermore, the focus of interest lies in the stable radon profile, making the assumption of a steady state in radon distribution sufficient and appropriate for our purposes. By adopting this approach, we can effectively analyze and understand radon behavior in a simplified yet accurate manner.

FERM-1D incorporates an improved calculation of advective velocity compared to previous studies (Hafez and Awad, 2016; Hafez, 2022). The advective velocity is determined based on the pressure gradient along the soil depth (depressurization), air dynamic viscosity, soil permeability, and porosity. The code also calculates the Radon flux from the soil layer to the ground surface, partitioning it into diffusive and advective fluxes. Additionally, it considers the width of cracks in building foundation slabs or footings when calculating Radon flux.

The modeling and coding details, including input data entry and interpretation of output results, are thoroughly presented. The FERM-1D code, along with the required input files, can be accessed on Google Drive. We provide links to folders containing examples of Radon profiles due to depressurization in multi-layer soils, single layer soils, concrete slabs in building basements, and cracks in concrete floors. Furthermore, we compare FERM-1D results with analytical or exact solutions of the Radon transport differential equation, clearly demonstrating the success and accuracy of FERM-1D.

Accessing FERM-1D is convenient for users with a Gmail account as the code and examples are hosted on Google Drive on the following link:

https://drive.google.com/drive/folde...8Dsbvarr4xsG_I

We encourage researchers and practitioners to utilize FERM-1D for precise and reliable Radon gas distribution modeling in one-dimensional soil systems.

Keywords: Radon gas, soil modeling, finite element method, advective velocity, Radon flux, 1D modeling, Google Drive.