L4 - Contaminated Land Flashcards
What is contaminated land defined as?
Significant harm has been caused to land or water
What is a brownfield site?
Land that was occupied by a permanent structure
What is the UK target for derelict land?
60% of new housing should be build on brownfield sites
Examples of when contaminated land become a big problem?
Contamination of rivers by oil Air by VOCs Adjacent land with organic waste Smells Unable to reuse
What does the Environmental protection act (1990) say?
Regulatory bodies can request clean up
What is the regolith?
Part between surface and bedrock
What is the regolith subdivided into?
Saturated zone - water fills all pores
Unsaturated or vadose zone
What is soil composed of?
Solid phase - minerals, plant roots, organic matter - provides framework of soil forming pores shared by liquid and gas phase
How can soil conditions vary around the world?
Water and oxygen - 0% to saturated
Temp - -40 to 65
pH - 2.5 to 11
What are the features of soil microbiology
Decrease in number with depth
Bacteria and fungi contribute the greatest to mineralisation activity
Usually oligotrophic
Low nutrient envi means microbial pop must be dormant until more nutrients appear
What are contaminants similar to fuel oil?
BTEX - benzene, toluene, ethylbenzene, xylene
DNAPLs - dense non aqueous phase liquids (usually chlorinated solvents) - don’t float on water
What are examples of major oil spills?
Exxon Valdez - Alaska (1989) - 35000 tonnes
Sea Empress (1996) 65000 t
Deepwater horizon - gulf of mexico (2010) 780000 m3
Answer : 250000
Number of underground tanks at petrol stations estimated to be leaking in the US
What is the problem with terrestrial oil leakage?
Eventually reaches the water table
Features of surface transport of oil?
Travels across surface with out penetrating soil
Common when ground is waterlogged or frozen
Features of subsurface transport of oil?
Sinks through vadose zone to rest on water table
Forms a pancake flowing in direction of ground water
What is photodecomposition of oil?
Result of photoxidation
Addition of hydroxyl groups to aromatics and removal of hydrogen
What is intrinsic remediation?
Oil degraded by naturally occurring microbial population
What happens with plants and hydrocarbons?
Take them up either passively in aqueous phase or by partitioning into organic phase of cell wall
Compounds remain in roots or are translocated to shoots and leaves
Define adsorption
Retention of solutes originally present in solution by surfaces of a solid material
Define absorption
Retention of solute within the mass of a solid rather than on its surfaces
What is volatilisation?
Remove lighter products components of oil
Increases viscosity of oil resulting in decreased infiltration
What are the stages of choosing a remediation strategy?
Desk top study
Preliminary site investigation
Detailed site investigation
What are the features of a desk top study?
Searching of records
Historical maps
Local consultation
Features of a preliminary site investigation?
Limited sampling
Analysing samples (expensive)
Directed by historical info
What pollution does a coking works produce?
Entrained tar
Noxious liquids
What parameters are tested to test the optimal conditions for bioremediation?
Use a 100g flask scale
aeration
seeding with degrading organisms
Different nutrient addition regimes
What are microcosm and mesocosm trials?
Small scale trials controlling system
Measurements made of degredation rates but also see if any become mobile
What is a field scale trial?
To test new treatment technology, funded by authorities
