Air Pollution 315/2010

A model provides a fundamental link between emissions and air quality changes by simulating transport, dispersion, transformation, and deposition.

• 1. Emission Assessments
• 2. To discriminate against sources
• 3. To evaluate alternative control strategies
• 4. To compliment ambient monitoring
• 5. To evaluate accidental releases

• Degree of stability must be known if we are to estimate the ability of the atmosphere to be able to disperse pollutants from anthropogenic sources.
• Stable atmospheres do not allow much vertical mixing. As a result, pollutants near the earth’s surface tend to stay there
• Mixing is dependant upon: Mechanical turbulence due to shearing action of wind and; Temperature gradient
• Comparing actual environmental temperature gradient (lapse rate) to adiabatic lapse rate can help determine possibility of thermal mixing

• Stable – does not exhibit much vertical mixing or motion
• Unstable – mechanical structure is enhanced by thermal structure
• Neutral – thermal structure neither enhances nor resists mechanical turbulence

• Rate of decrease in temperature as one ascends through the atmosphere
• ^oK/ Km rise (0^oK = -273^oC)

Rate of temperature decrease of parcel of air as it rises

Temperature gradient of ambient air as changes with altitude.

• Drift dictates the frequency of calibration.
• Zero drift is the change in response to zero pollutant concentration, over 12 and 24 hours of continuous unadjusted operation

the percent change in a response to a pollutant concentration over a 24-hour period of continuous unadjusted operation

Occurring without the addition or loss of heat.

Atmospheric lapse rate cooling faster then adiabatic lapse rate in plume.

Unstable

Neutral

Stable

• From lab/clinical studies, assumes risk at every dose, no safe risk.
• = Risk/Dose (mg/kg/d)^-1

• for contaminant known to cause cancer
• = Risk/Slope Factor (mg/kg/day)
• should be < 1/100,000 for carcinogens

• Tolerable Daily Intake (Rfd - reference dose)
• for non-cancer effects; non-carcinogens
• = NOAEL/(UF1 x UF2 x ... x MF)

• Heterogeneous Population = x10
• Animals to Humans = x10
• Chronic NOAEL from subchronic data = x10
• NOAEL rather than LOAEL = x10
• MF = x10 (general uncertainty)

Estimated Daily Intake through exposure pathways: inhaled, ingested, etc.

• ED = C_a x IR_A x AF_inh/BW
• (mg/kg/day)
• C_a - concentration of contaminant (mg/m³)
• IR_A - inhalation rate (m³/h)
• AF_inh - inh absorption factor = 1.0
• BW - body weight

• EDI < RsD
• minimal risk of cancer from exposure to that contaminant

• EDI < TDI
• exposure to contaminant likely does not pose signif risk to human health

Cancer risk per bite vs. Threshold number of bites resulting in toxic effect.

• Non-carcinogens (air-borne contaminant)
• HQ = Air [ ] (ug/m³) x Fraction of time exposed/Tolerable air [ ] ug/m³
• or
• HQ = ED/TDI (ED - calculated without D's and LE)
• HQ < 1, acceptable risk

• Carcinogens (air-borne) (ug/m³)^-1
• ILCR = Air [ ] ug/m³ x Fraction of time exposed x Cancer Unit Risk (ug/m³)
• ILCR < 1/10⁵ , acceptable risk.

• Lack of studies to back up
• Lack of long term effects evidence
• Difficult to assess risk posed by trace amounts in tissues
• With small doses, dose-response difficult to quantify
• Individual differences
• Lifestyle differences
• Conventional approaches inadequate to measure delayed effects
• Effects only seen in synergism

have built in calibration gases to correct for zero drift and span drift daily i.e. continuous calibration.

SO₂, TRS, NO_x, ppm (TSP, PM_10, PM_2.5, & dustfall), PAHs, PCBs, VOCs, fluoridation rate, meteorological (wind speed/direction, temp, solar radiation)

• Temperature stability of shelter
• Location of sampling probe(s)
• Manifold or sample inlet line system
• Length of probe
• Probe material
• Filters/fittings

• Determine frequency of routine site visits
• Provide training
• Plan approp. level of surveillance
• Plan equipment operations and data checking
• Calibration checks (daily, manual, multi-point)
• Traceability, unique identifiers
• SOPs

Summa Cannister, fills after 24 hours.

• high vol sampler, quartz filter
• Q = 40-60 ft³/min

• high volume sampler, PUF/XAD module
• Q = 7.9 ft³/min

• high vol sampler, quartz filter, selective inlet
• big round top
• Q = 40 ft³/min

• low vol sampler, PTFE filter, size selective filter
• Q = 16.7 L/min

Sydney Tar Ponds Agency - Ambient Air Monitoring Program

Drag Force increases.

decreases with acceleration (eventually reaching 0)

increases with speed.

• F_g
• If the particles are falling in the viscous fluid by their own weight
• due to gravity, then a terminal velocity, also known as the settling velocity, is
• reached when this frictional force combined with the buoyant force exactly balance the gravitational force.
• The result is settling velocity (or terminal velocity) = u_t.

• Settling Chamber: 40-10,000 um
• Cyclone: <10-20 um
• Wet scrubber: 0.1 - 30 um
• Fabric filter: 0.01 - 20 um
• ESP: 0.001 - 10 um

giving particles an electrostatic charge then puts them in an electrostatic field that drives them to a collecting wall.

• Surface filters (coffee filter - form a cake) &
• Depth filters (HEPA - brownian diffusion)

• Rate of collisions are not balanced
• Significant force in the imbalanced direction

• in dirty gas stream with liquid drops (eg. ventruri scrubber)
• Particles collide with droplets, separated in cyclone

• Adsorption
• Absorption
• Condensation
• Combustion

Operations Manual for Air Quality Monitoring in Ontario