NEHA Registered Environmental Health Specialist/Registered Sanitarian (REHS/RS) Practice Exam

Silt is indeed characterized by having the greatest percentage of porosity among the soil types listed. Porosity refers to the volume of pore spaces in a soil that can hold water and air, which is crucial for plant growth and ecosystem sustainability. Silt particles are smaller than sand but larger than clay, allowing for a significant amount of pore space between them, which contributes to higher water retention compared to sand and gravel. This unique particle size results in an ideal balance of drainage and moisture retention, making silt particularly valuable in agricultural contexts where plant health can be significantly influenced by water availability in the soil.

In contrast, uniform sand, gravel, and sandstone have larger particle sizes. While they may provide good drainage due to larger pore spaces, they typically do not retain water very well, thereby exhibiting lower overall porosity compared to silt. Sand, for example, allows water to pass through quickly and doesn’t hold moisture effectively, while gravel, although it can be quite porous, generally has larger voids that do not contribute to moisture retention. Sandstone, being a solid rock formation, also does not match the porosity of silt, as it is not characterized by individual particles that can hold moisture in the same way. Thus, silt