Environmental Monitoring & Instrumentation Flashcards
6 cards from real ETC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Environmental Monitoring & Instrumentation flashcards as text
When recording field measurements for groundwater depth using an electronic water level meter (e-tape), measurements are typically reported as:
Answer: Depth to water from the top of the well casing to the nearest 0.01 foot
Water level measurements are recorded as depth-to-water from a fixed reference point (usually the top of the well casing) measured to the nearest 0.01 ft or 0.001 m using a calibrated e-tape.
What is a 'field blank' in environmental sampling, and what contamination source is it designed to detect?
Answer: Reagent-grade water processed through all sampling equipment at the site; detects equipment or reagent contamination
A field blank is prepared by pouring reagent-grade (VOC-free) water through all sampling equipment at the field site to determine whether any contamination is being introduced by the sampling equipment, containers, or preservatives.
In air monitoring, what does a direct-reading flame ionization detector (FID) measure, and how does it differ from a PID?
Answer: FID uses a hydrogen flame to ionize compounds and detects a wider range of hydrocarbons including methane; PID uses UV light and cannot ionize methane
FIDs burn sample gas in a hydrogen flame to ionize organic compounds, detecting a broader range including methane and saturated hydrocarbons, while PIDs use UV light and cannot ionize methane or compounds with ionization potentials above the lamp energy.
A technician observes that a monitoring well has silt and turbidity that does not clear after extended purging. What remedial action is most appropriate before sample collection?
Answer: Redevelop the well to improve formation connectivity and reduce fine particle intrusion
Persistent turbidity despite purging indicates the well needs redevelopment (surging and bailing or air jetting) to improve the hydraulic connection to the formation and clear fines from the filter pack.
What is the significance of the 'holding time' requirement for environmental samples, and which analyte class has one of the shortest holding times at 14 days?
Answer: Holding time limits sample age before analysis to prevent degradation; volatile organic compounds (VOCs) have a 14-day holding time
Holding times define the maximum time between sample collection and laboratory analysis to prevent analyte degradation; aqueous VOC samples preserved with HCl and stored at 4°C have a 14-day holding time under EPA SW-846 methods.
During a soil sampling event, a technician collects a duplicate sample from every 10th location. What type of quality control sample does this represent, and what does it assess?
Answer: Field duplicate (co-located duplicate); assesses sampling variability and reproducibility
Field duplicates are independently collected samples from the same location using identical procedures; comparing their results assesses sampling variability, sample heterogeneity, and the reproducibility of the field collection method.