Which soil condition is most favorable for the removal of viruses?

The condition described as fine loamy sand over coarse sand and gravel presents a unique combination of soil properties that enhances the removal of viruses from contaminated water. This layered structure allows for effective filtration due to the different particle sizes and porosities.

Fine loamy sand has a moderate amount of water-holding capacity and surface area, which helps in trapping and adsorbing viruses. Its texture allows for adequate water drainage, preventing pool formation that could otherwise facilitate viral survival. Beneath this layer, the coarse sand and gravel provide excellent drainage and prevent clogging, which maintains a flow of water and encourages the movement of microbes, including viruses, through the soil profile.

This combination thus optimizes both the physical and biological processes involved in virus removal. The fine layer aids in adsorption, while the underlying coarse layer supports effective filtration and prevents saturation that can hinder the removal of pathogens. Such a system embodies the ideal conditions for viral attenuation through natural soil processes.