How does water solubility affect contaminant movement?

• A. Highly soluble compounds tend to stay bound to soil and not move.
• B. Highly soluble compounds tend to move with groundwater, while insoluble compounds do not.
• C. Solubility has no effect on movement through groundwater.
• D. Insoluble compounds evaporate and travel with air.

Answer: (B)

Solubility controls how contaminants move through groundwater. If a compound is highly soluble, it dissolves in the pore water and is carried along with the moving groundwater, spreading away from the source. If a compound is insoluble or only slightly soluble, it tends to stick to soil particles (sorption), which slows or prevents its movement, keeping it near the source. Because groundwater transport mainly follows the dissolved phase, solubility is a primary factor in determining how far and how fast a contaminant migrates. Evaporation into air isn’t the main transport mechanism in subsurface conditions, and solubility does affect mobility rather than having no effect.