CES Environmental Sampling & Data Analysis 2

Question 1

Which type of blank is used to identify contamination introduced during sample transport and field handling?

Accepted Answer

Trip blank

Answer

A trip blank accompanies samples during transport to detect VOC contamination introduced after collection, not during analysis.

Question 2

What is the purpose of calculating the Relative Percent Difference (RPD) in duplicate sample analysis?

Accepted Answer

To measure precision between two replicate measurements

Answer

RPD measures the variability (precision) between duplicate or replicate samples by expressing the difference as a percentage of the mean.

Question 3

In a soil gas survey, which sampling method is most appropriate for collecting volatile organic compound (VOC) vapor samples?

Accepted Answer

Grab sampling with Summa canisters

Answer

Summa canisters are electropolished stainless steel vessels used to collect instantaneous (grab) VOC vapor samples under evacuated conditions.

Question 4

Under EPA SW-846, what minimum purge volume is typically required before collecting a groundwater sample from a monitoring well?

Accepted Answer

3 well casing volumes

Answer

Standard low-flow or traditional purging protocols require removing at least three well casing volumes to ensure the sample represents formation water.

Question 5

Which statistical test is appropriate to determine whether concentrations at a monitoring well are significantly higher than background concentrations?

Accepted Answer

One-sided Welch's t-test

Answer

A one-sided Welch's t-test (which does not assume equal variances) is used to test whether downgradient concentrations exceed upgradient background concentrations.

(CES) Certified Environmental Scientist Practice Test

(CES) Certified Environmental Scientist Practice Test

CES Environmental Sampling & Data Analysis 2