brownfield sites

• Brownfield sites are derelict building sites. 
• Contamination of toxic heavy metals, found in groundwater and in plants. 
• Consumption of contaminated materials can lead to bioaccumulation of toxic metals. 
• Remediation of contaminated land:

  • Superficial deposits can be treated in situ or elsewhere. 
• Phytoremediation:

  • Useful bioaccumulation 
  • Heavy metals do not damage plants and are stored in leaves 
  • Removal of vegetation permanently removes heavy metals 
• Solidification and stabilisation:

  • Immobilise toxic waste to prevent leakage 
  • Solidification mixes waste with a binding agent - cement, clay 
  • This forms a solid block when water is added 
• Stabilisation:

  • Mixing wastes with chemicals 
  • Soil can be mixed with water and lime makes the metals insoluble in water 
• Groundwater treatment:

  • Groundwater pumped up to surface 
  • Clays used to remove toxic metals as a result of ion exchange 
  • Can change pH to precipitate minerals - precipitation