What is the purpose of well purging before sample collection?

• A. To obtain representative groundwater sample by clearing stagnant water, stabilizing temperature, pH, and matrix conditions
• B. To introduce tracers
• C. To accelerate sampling
• D. To increase sample volume

Answer: (A)

Purging before sampling ensures the groundwater sample truly reflects the conditions in the surrounding aquifer by removing water that has been sitting in the well and allowing the water in the well to equilibrate with the formation. This clears stagnant water, reduces water-column residence effects, and stabilizes factors like temperature, pH, and the chemical matrix so the sample isn’t biased by conditions inside the casing. The result is a representative sample of the aquifer, not a snapshot of the water in the well. Introducing tracers, speeding up collection, or increasing volume aren’t the primary goals of purging.