Soil Contamination and Site Assessment
Domain scope
This domain tests conceptual site models, sampling design, contaminant mass estimation, background evaluation, and the source–pathway–receptor logic used in site assessment.
Core rules and concepts
- A complete exposure pathway requires a source, a transport pathway, and a receptor. Removing any link breaks the pathway.
- Phase I assessment uses records, interviews, and site inspection; Phase II uses intrusive sampling and analysis.
- Sampling designs include judgmental, systematic grid, and stratified random. Heterogeneity means one boring rarely represents a site.
- Contaminant mass in soil = volume × bulk density × concentration, with consistent units.
- NAPL, soil gas, and groundwater data help distinguish residual source from dissolved plume.
Worked example
A 10 m × 10 m × 2 m source zone has bulk density 1.6 t/m3 and average concentration 50 mg/kg. Volume = 200 m3. Soil mass = 200 × 1.6 = 320 t = 320,000 kg. Contaminant mass = 320,000 kg × 50 mg/kg = 16,000,000 mg = 16 kg.
Traps that cost marks
Forgetting bulk density when converting volume to mass; mixing mg/kg with µg/L; treating a single boring as representative; and ignoring background or off-site sources.