Which soil property governs how easily water and dissolved contaminants can move through it?

• A. Permeability
• B. Porosity
• C. Sorption
• D. Texture

Answer: (B)

The main idea here is how easily fluids can travel through the pore network in soil. That ease of flow is governed by permeability, which captures how connected and open the pores are for water and dissolved substances to pass through under a gradient. Soils with high permeability—where pore spaces are well connected—allow faster movement of water and contaminants, while low-permeability soils—where connections are limited or pore throats are very small—slow down or restrict flow.

Porosity, by contrast, is about how much void space exists in the soil and thus how much water it can hold, not how fast that water moves. Sorption describes how strongly substances stick to soil particles, affecting retardation and residence time, but not the bulk flow rate. Texture influences the distribution of pore sizes and, indirectly, permeability, but the property that directly controls movement through the soil is permeability.