Environmental Sampling & Data Analysis Flashcards
7 cards from real CES practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Environmental Sampling & Data Analysis flashcards as text
What is the purpose of a control chart (Shewhart chart) in an environmental laboratory's quality control program?
Answer: To monitor analytical process stability and detect shifts or trends over time
Control charts plot QC results (e.g., LCS recoveries) over time to detect out-of-control conditions such as systematic bias, drift, or random error using warning and control limits.
Which field instrument is most appropriate for real-time screening of petroleum hydrocarbon vapors during soil excavation at a brownfield site?
Answer: Photoionization detector (PID)
A photoionization detector (PID) is widely used for real-time, field-screening of VOCs and petroleum hydrocarbons during soil disturbance activities due to its sensitivity and portability.
In the context of EPA's Data Quality Objectives (DQO) process, what does Step 6 ('Specify Tolerable Limits on Decision Errors') establish?
Answer: The acceptable rates of false positive (Type I) and false negative (Type II) errors
DQO Step 6 defines the tolerable probability of incorrectly deciding the site is clean (false negative/Type II) or incorrectly deciding it is contaminated (false positive/Type I).
When collecting a water sample for dissolved metals analysis, which preservation and container combination is correct per EPA protocols?
Answer: Plastic (HDPE) bottle, acidified to pH <2 with HNO₃, refrigerated at 4°C
Dissolved metals samples are filtered in the field, collected in HDPE plastic containers (which don't leach metals), acidified with nitric acid to pH <2, and refrigerated.
A site investigation uses 8 upgradient background wells and 4 downgradient compliance wells. Which statistical approach is recommended by EPA ProUCL for comparing compliance well data to background?
Answer: Prediction limits or tolerance limits based on background data
EPA ProUCL recommends prediction limits or tolerance limits derived from background data as the preferred parametric or non-parametric approach for groundwater monitoring comparisons.
Which term describes the minimum concentration of a substance that can be reliably reported with a defined level of confidence using a specific analytical method, typically set at 5–10× the MDL?
Answer: Practical quantitation limit (PQL)
The practical quantitation limit (PQL) is an operationally defined reporting threshold, typically 5–10 times the MDL, at which reliable quantitation with acceptable precision and accuracy is achievable.
During a RCRA facility investigation, which type of sample is collected to demonstrate that analytical results are not affected by contamination introduced in the laboratory rather than present in the environmental media?
Answer: Method blank
A method blank (reagent blank) consists of all reagents and solvents processed through the full analytical procedure to detect laboratory-introduced contamination absent in field samples.