ASBOG ASBOG - Association of State Boards of Geology Environmental Site Assessment and Remediation Questions and Answers 2 — Questions and Answers
Question 1: Monitored Natural Attenuation (MNA) as a remediation strategy relies on:
- Physically excavating and disposing of contaminated soil off-site
- Adding chemical oxidants to destroy contaminants in-situ
- Natural biological, chemical, and physical processes to reduce contaminant concentrations over time (Correct answer)
- Installing a permeable reactive barrier to intercept the plume
Correct answer: Natural biological, chemical, and physical processes to reduce contaminant concentrations over time
MNA relies on naturally occurring processes including biodegradation, dispersion, dilution, sorption, and volatilization to reduce contaminant concentrations to acceptable levels without active intervention.
Question 2: A permeable reactive barrier (PRB) treats contaminated groundwater by:
- Physically blocking and containing the plume within a steel sheet pile wall
- Allowing the plume to flow passively through reactive media (commonly zero-valent iron) that degrades contaminants (Correct answer)
- Pumping groundwater from the plume to an above-ground treatment system
- Injecting steam to volatilize and extract contaminants
Correct answer: Allowing the plume to flow passively through reactive media (commonly zero-valent iron) that degrades contaminants
A PRB is installed perpendicular to groundwater flow; as the plume passes through the reactive medium, contaminants are immobilized or degraded without ongoing energy input.
Question 3: Electrokinetic remediation is particularly suited for treating contaminated soils that are:
- Coarse-grained sands with high hydraulic conductivity
- Fine-grained, low-permeability soils where hydraulic methods are ineffective (Correct answer)
- Fractured bedrock with open fractures
- Shallow vadose zone soils with volatile contaminants
Correct answer: Fine-grained, low-permeability soils where hydraulic methods are ineffective
Electrokinetic remediation drives contaminant movement via electromigration and electroosmosis under an applied electric field, making it effective where low permeability prevents fluid injection or extraction.
Question 4: The Risk-Based Corrective Action (RBCA) framework determines site cleanup goals based on:
- Technology-based limits achievable by best available treatment
- The most stringent federal standard regardless of site-specific conditions
- Site-specific risk to identified human health and ecological receptors (Correct answer)
- Restoration to pre-industrial background concentrations
Correct answer: Site-specific risk to identified human health and ecological receptors
RBCA establishes cleanup levels that are protective of actual receptors at a specific site given the realistic exposure pathways and land use, allowing more flexible and cost-effective remediation objectives.
Question 5: Soil Vapor Extraction (SVE) is most effective for removing which type of contaminants?
- Non-volatile heavy metals in fine-grained soils
- Radioactive isotopes bound to soil particles
- Volatile organic compounds (VOCs) in the unsaturated vadose zone (Correct answer)
- Dense non-volatile petroleum residues below the water table
Correct answer: Volatile organic compounds (VOCs) in the unsaturated vadose zone
SVE applies a vacuum to extraction wells in the vadose zone, inducing airflow that volatilizes and transports VOCs to the surface for treatment, making it most effective for volatile contaminants above the water table.
Question 6: Bioremediation treats organic contaminants by:
- Using high-temperature thermal processes to destroy contaminants
- Physically separating contaminants from soil using water washing
- Using microorganisms to metabolically degrade contaminants into less harmful end products (Correct answer)
- Chemically oxidizing contaminants using permanganate or persulfate
Correct answer: Using microorganisms to metabolically degrade contaminants into less harmful end products
Bioremediation harnesses indigenous or introduced microorganisms that use organic contaminants as carbon or energy sources, transforming them into COâ‚‚, water, and biomass through metabolic pathways.
ASBOG ASBOG - Association of State Boards of Geology Environmental Site Assessment and Remediation Questions and Answers 2
Monitored Natural Attenuation (MNA) as a remediation strategy relies on: