Air (on Final) Flashcards
What Is the first recorded control of air pollution?
13th century when London prohibited the use of coal
What are types of air samples?
- indoor
- Ambient (outdoor)
- air from stacks
- emission exhausts
What are the four types of air quality decisions
1) determination of effects
2) identification of pollutants causing effects
3) source attribution
4) emission control
Explain what determination of effects means as
An air quality decision?
Perceiving a problem exists and is cause by constituents in the atmosphere.
- the air quality affects human respiration, impairs visibility, causes damage to plants and wildlife or is a nuisance
- observations determine the existence of a problem
Explain identification of pollutants causing effects as a air quality decision
Atmospheric constituent must have the chemical and physical properties and be present in sufficient quantities to cause an unacceptable effect.
Classification as a pollutant is based on measurements that establish a cause and effect relationship
Explain source attribution as an air quality decision
Can only reduce exposure to air pollutants by going to their sources
- many sources exists so decisions must be made with respect to contributions from each source.
- based on emissions, meteorological and ambient air measurements
Explain emission control as an air quality decision
Many alternatives exist for reducing emissions. We need measurements of the control efficiency and the assumption that a reduction in emissions will be accompanied by a proportional reduction in ambient concentrations
What categories do air samples taken from the env fall into?
1) ambient
2) indoor
3) emission samples(cars,incinerator stacks)
4) soil atmosphere (landfills,contaminated soil from spills)
What % of air pollutants are organic?
90
What does collection of a
Representative air sample require?
1) knowledge of pollutants present
2) pollutants behaviour
3) pollutants properties
What is used to classify air pollutants
1) chem comp of pollutants (organic or not)
2) chem properties (water solubility, polarity and reactivity)
3) physical properties (density and vapour pressure)
What are the activities for air pollutants
1) vvoc- >15 Kpa
2) voc - >1.010^-2 kpa
3) svoc - 10^-2 to 10^-8
4) nvoc-<1.010^-8
What does vvoc Stand for? What is it’s common physical state? What is it’s vapour pressure?
- very volatile organic compound
- gases
- > 15kpa
What does voc stand for?
What’s is common physical state?
What’s its saturation vapour pressure?
- volatile organic compound
- > 1.0*10^-2
- gas
What’s svoc?
Saturation vapour?
Physical state?
- semi volatile organic chemicals
- 10^-2 to 10^-8
- gasses and aerosols
What’s nvoc?
Saturation pressure?
Physical state?
Non volatile organic chemicals
<1.0 *10^-8
Mostly aerosols
What to consider when selecting a sampling site
- source of contamination
- air flow/direction/velocity
- density of contaminants
- intensity of sunlight
- time of day
- presence of obstructions (trees/buildings)
- traffic
- site access/amenities
Meteorological effect to consider when air sampling
- wind direction/speed
- temp
- atmospheric stability/pressure
- precipitation
What are the 4 collection methods in air sampling?
1) absorption/Adsorption
2) filtration
3) whole air sampling
4) cryogenics
Explain absorption/adsorption as a collection method
- analytes adhered to a physical material
- absorption occurs when the analyte is permanently affixed to a physical substrate
- substrate removed and analyzed
- adsorption is when analyte sticks to substrate and then is stripped for specific analysis
- stripping by chemical of thermal methods
What are sorbet cartridges used for?
What collection method are they apart of?
Used to extract and concentrate both voc’s and scocs from air. Air drawn through cartridge containing solid cartridge. Voc’s retained on surface of cartridge packing
What does a breakthrough mean in regards to sorbet cartridges
Is when the front adsorbent portion is overloaded with the analyte and unretained analyte passes through
How many adsorbent portions do most sorbent cartridges have?
2 to prevent breakthroughs
Why are there two sorbent chambers in a sorbent cartridge?
So the analyst can see if the first chamber has had a break through but seeing if any analyte made it to the second chamber
Explain filtration as a collection method?
High volume air sampler draws air through quartz or glass fibre filters.
T air collected = flow rate * sampling time
Drawback: no break down of samples particle distribution by size
Filter pore size dictates the amount and type of particles collected
Explain whole air sampling as a collection method
Stainless steel canister used to collect samples. Air pumped in preevacuated container and pressurized to a few atmospheres
Analysis done by measuring volume of air and focusing it cryogenically
Explain cryogenics as a collection method
Preferred when dealing with voc’s
Sensitive
Under vacuum and extreme cold sample of air is passed through. Analytes condense upon cooking and can be analyzed
