What type of soil is best for the removal of viruses?

The optimal soil type for the removal of viruses is fine loamy sand and coarse sand and gravel. This combination of soil properties provides a balance between porosity and filtration capability. Fine loamy sand ensures that there is sufficient surface area and particle size to trap and retain viruses while allowing for adequate water flow through the soil. Additionally, coarse sand and gravel help facilitate drainage, which prevents standing water conditions that could lead to increased virus persistence.

The filtration effect of these soils is critical because smaller particles can capture pathogens, including viruses, effectively during the process of percolation through the soil matrix. The combination of particle sizes allows for both effective pathogen retention and the promotion of microbial communities that can further degrade or inactivate viruses.

In contrast, other soil types listed may not provide the ideal conditions for virus removal. For instance, clay soil can retain moisture but may not have optimal drainage and could potentially lead to anaerobic conditions, which aren’t favorable for pathogen removal. Heavy silt retains moisture well but can also create standing water conditions, leading to virus survival rather than removal. Rocky gravel, while allowing good drainage, lacks fine particles that are necessary for capturing viruses effectively due to poor surface area.