CPG Specimen Collection & Handling 3

Question 1

During low-flow (minimal drawdown) groundwater purging, when is the well generally considered ready to sample?

Accepted Answer

When field parameters such as pH, conductivity, temperature, DO, and ORP stabilize within set criteria

Answer

Low-flow protocols rely on stabilization of indicator parameters over consecutive readings, not a fixed purge volume.

Question 2

An equipment rinsate blank is collected mainly to evaluate which of the following?

Accepted Answer

How well non-dedicated sampling equipment was decontaminated

Answer

Analyte-free water poured over or through decontaminated equipment shows whether cross-contamination could come from reused gear.

Question 3

A geologist collects a field duplicate. What does comparing the duplicate with its parent sample mainly assess?

Accepted Answer

Precision of the combined sampling and analytical process

Answer

Field duplicates are evaluated by relative percent difference to measure overall precision, including sampling variability.

Question 4

When logging a split-spoon sample, the blow counts for the second and third 6-inch increments are added together to report what?

Accepted Answer

Standard Penetration Test N-value

Answer

Under ASTM D1586, the N-value is the sum of blows for the last two 6-inch increments of an 18-inch drive.

Question 5

Why are samples for VOC analysis in water collected in 40-mL vials with no headspace?

Accepted Answer

To prevent volatile compounds from partitioning into trapped air and escaping

Answer

Any air bubble lets VOCs partition out of the water, so vials are filled to a convex meniscus and checked for bubbles.

CPG - Certified Professional Geologist Practice Test