Soil and Groundwater Contamination and Remediation
What this domain tests
The risk-based logic of 土壤污染防治法, the difference between screening values and cleanup targets, and matching a contaminant and a geological setting to a remediation technology.
Regulatory framework
- 土壤污染防治法 (2019-01-01) is risk-based: prevent first, then investigate, assess risk, and apply risk control or remediation. Farmland is split into priority protection, safe utilisation and strict control; construction land passes through suspected-site listing, investigation, risk assessment, control or remediation, and post-remediation assessment.
- GB 36600-2018 gives screening values and control values separately for Category 1 land (residential, schools, medical, social welfare) and Category 2 land (industrial, commercial). Category 1 is stricter.
- GB 15618-2018 covers agricultural land, banded by pH.
- The HJ 25 series sets the sequence: investigation (25.1), monitoring (25.2), risk assessment (25.3), remediation plan (25.4), post-remediation assessment (25.5).
Remediation technologies
- Soil: solidification and stabilisation for metals; soil vapour extraction for volatile organics in the vadose zone; thermal desorption; in-situ chemical oxidation with persulfate, permanganate or Fenton reagents; chemical reduction with zero-valent iron; bioremediation and biopiles; soil washing; phytoremediation; soil replacement.
- Groundwater: pump-and-treat for plume containment; permeable reactive barriers for dissolved plumes; in-situ chemical oxidation; air sparging; monitored natural attenuation where the plume is stable.
- Core concept: source, pathway, receptor. Break any one leg to remove the risk, and note that institutional controls can be a legitimate risk-control measure instead of excavation.
Worked example
A site planned for housing shows benzo[a]pyrene at 0.8 mg/kg. Category 1 screening value is 0.55 mg/kg and the control value is 5.5 mg/kg.
- 0.8 exceeds the screening value but stays below the control value.
- That combination triggers risk assessment, not automatic excavation. The assessment determines whether risk is acceptable for the planned residential use.
- If risk is unacceptable, the remediation target is derived from the risk assessment and may not exceed the control value.
- Had the result been above 5.5 mg/kg, remediation or a change of land use would be mandatory before residential use.
Traps
- Treating the screening value as the cleanup target.
- Mixing the two land categories; schools and hospitals are Category 1, not Category 2.
- Siting a monitoring well upgradient of the source and concluding the site is clean.
- Calling a single post-remediation sampling round an adequate effectiveness assessment.
- Forgetting that a change of land use can be a valid alternative to remediation.