Non-aqueous phase Liquids (NAPLS) Flashcards
What common substances can form a NAPL?
Hydrocarbon fuels
dry cleaning solvents
what is the main way that NAPLS are released into the environment?
Spills/leakages from industrial plants/storage facilities
during manufacturing processes
What is MATTE? What factors do the criteria depend on? What are the types of criteria?
- Major Accident to the Environment
- Depends on type of site (eg. Nature reserve/Marine), rareness of site or species present.
- zone affected, % of population affected etc
what are the types of NAPL? give examples for each.
- LNAPL - lighter than water - petrol, diesel, jet fuel, lubrication oils, hexane, benzene
- DNAPLS - denser than water - chlorinated solvents, coal tars, creosote, polychlorinated biphenyls
what is the chemical formula of benzene? What is it used in? What type of NAPL is it? What are the adverse effects? What type of pollutant is it?
- C6H6
- Petrol additive (2.6%), industrial solvent
- LNAPL
- Toxic, carcinogenic, nausea dizziness depression, irritant
- Air pollutant (volatile - 10kPa) - used to be washed onto land to evaporate
What is BTEX composed of?
What does it indicate?
Benzene, toluene, ethylbenzene, xylene
petroleum product contamination in soils and groundwaters
What is the chemical formula for carbon tetrachloride?
What type of NAPL is it?
What is it used for?
Adverse effects?
CCL4
DNAPL
Solvent
Carcinogenic, toxic to brain liver and kidneys
What are polychlorinated biphenyls used in?
Why is it banned under the Stockholm convention?
What type of NAPL is it?
Used in electrical components as an insulating material
Carcinogenic, toxic, developmental toxicant, teratogenic
DNAPL, significant ground contaminant and landfill leachate
What are phases?
What are components?
Phases - different physical states in the subsurface : air, water, solid and NAPL, all can have different densities etc.
Components - individual components that form a NAPL phase
E.g petrol or TCE
What does miscible mean?
Water soluble
What is viscosity?
How does it effect NAPL contamination?
A measure of fluids resistance to flow
Determines how well NAPL moves through the subsurface - low viscosity will move and spread quicker
What is volatility and how does it effect NAPL?
Degree to which the substance vaporises in air
Determines how much NAPL diffuses into the air filled space within an unsaturated zone (above the water table)
Higher vaporisation potential more will evaporate into air filled pores and eventually reach the surface.
What is interfacial tension?
Measure of the surface forces that exist between two immiscible fluids at their physical interface.
They arise from differences between the inward attraction of the molecules in the interior of each phase, and those at the surface of contact
Lower interfacial tension = lower stability of the water:NAPL interface and more immiscible fingering
What is wettability and how does it affect NAPLS?
Tendency of NAPL to spread over a solid surface in the presence of water.
- affects the degree to which NAPL will form globules in pore spaces between grains rather than spreading through grains.
- liquids are described in wettability in terms of the contact angle they make the the surface
- water is the wetting fluid and NAPL is the non wetting fluid
What is sorption and how does it affect NAPL?
What is the difference between absorption and adsorption?
Degree to which NAPL components transfer from the liquid phase into/onto the solid matrix. Dependant on which NAPL and which solid. Sorption effects how much NAPL is locked into the subsurface materials.
Adsorption is adhesion
Absorption is soaking in (absorbing)
