6 - Air pollution Flashcards
What is a primary pollutant?
Pollutants emitted into the environment in a form that can be directly harmful, or that can react to form harmful substances
What is a secondary pollutant
Harmful substances formed when primary pollutants react with constituents of the environment (often atmosphere)
Example of a primary pollutant and some of its secondary pollutants
Primary = nitrogen dioxide
Can react with water to form nitric acid (acid rain)
Reacts with molecular oxygen to form ozone
Reacts with atomic oxygen and hydrocarbons to form aldehydes
Sequence of layers of the atmosphere from innermost to outermost
Troposphere, stratosphere, mesosphere, thermosphere, exosphere
Two types of air pollutant sources
Point sources: emanates from a discrete location (buildings, factories, mines)
Non-point sources: emanates from diffuse points, many sources (e.g. cars, planes)
What is CEPA? Goals?
Canadian Environmental Protection Act
Created in 1999 implemented in 2000 to regulate the production and use of toxic substances
Goals:
- reduce pollution
- protect the environment
- protect human health
What does CEPA cover for air pollutants?
- criteria air contaminants (pollutants for which maximum allowable concentrations have been established)
- persistent organic pollutants (POPs)
- heavy metals (highly dense metals, toxic in low conc)
- toxic air pollutants (all others, e.g. asbestos, CFCs)
Name the criteria air contaminants
- sulfur dioxide (SO2)
- nitrogen dioxide (NO2)
- particulate matter (PM)
- volatile organic compounds (VOCs)
- carbon monoxide (CO)
- ammonia (NH3)
- tropospheric ozone (O3)
What is sulfur dioxide? How is it produced?
Smelly colorless gas
Produced primarily from fossil fuel combustion
What is nitrogen dioxide? How is it produced?
Smelly red-brown gas. Contributes to smog and acid precipitation (reacts w H2O)
Combustion engines
What is particulate matter? Forms? How is it produced
Tiny solid or liquid particles
PM10 = particles <10 um
PM2.5 = particles <2.5 um
Produced through combustion, dust
What are volatile organic compounds? How are they produced
Carbon compounds that are volatile (evaporate), have low water solubility. Wide range
Household chemicals, engine combustion, solvents, industrial processes
Examples of building materials, home and personal care products and activities that have/produce VOCs
Paint, varnishes, carpet
Air fresheners, cleaning products, gasoline, cosmetics
Smoking, cooking, burning wood
What is carbon monoxide? What can it cause? How is it produced?
Colorless, odorless gas
Exposure to high concentrations leads to red blood cell dysfunction and death by asphyxiation
Combustion of fuel. Mostly vehicles, also industry, waste combustion, and wood combustion
What is ammonia? How is it produced
Colorless gas that smells awful (like urine)
Livestock waste, fertilizer production. Can combine with sulfates and nitrates to create PM2.5
What is tropospheric ozone? How is it produced
Colorless gas, smells slightly sweet
Secondary pollutant created from the interaction between sunlight, heat, nitrogen oxides and carbon compounds
When is O3 a pollutant
When it is in the troposphere
Occurs naturally in the stratosphere
Was are POPs? Sources?
Persistent organic pollutants
Volatile organic compounds that are resistant to degradation/decomposition via biological, chemical and photolytic processes
Primarily come from anthropogenic sources (most are pesticides)
Pesticides that are POPs? Industrial chemicals?
Aldrin, chlordane, DDT
Chemical/by product: hexachlorobenzene
Human exposure to POPs is mostly via… Except for…?
Food
Chlordane is a pesticide used from the 50s to the 80s in houses to repel pests. Banned in 1988, but still found in soil and the blood of most people. Can affect the nervous system (short term exposure = convulsions, long term = affects coordination, cognitive processes)
What are heavy metals? The ones of concern?
Dense and heavy metals
Mercury and lead
Problems with heavy metals?
- Associated with particulate matter, easily transported in the atmosphere
- Toxic, even in low concentrations
- Can bioaccumulate
Characteristics of mercury? Sources?
Volatile, toxic, common, lipophilic (accumulates in fat)
Burning coal, found in fluorescent light bulbs
Characteristics of lead? Sources?
Particulate, was common but now less common
Lead smelting still exists, but anthropogenic sources less common
Used to be added to gasoline to prevent small detonations in the engine when air would mix with fuel, but lead gas was banned in 1993 in Canada
What are toxic air pollutants? Examples and what their used for
Other stuff that doesn’t fit into the categories of criteria air contaminants, POPs or heavy metals
- Asbestos: used to insulate houses as fire retardant
- Chlorofluorocarbons (CFCs): used as refrigerant, in solvents. Can deplete ozone
- Methyl bromide: used in pesticide, shipping material on boats. Can also deplete ozone
What is smog?
Mixture of air pollutants that form primarily over urban areas
Two types of smog
Industrial smog: produced from the incomplete combustion of coal or oil
Photochemical smog: produced from light-driven reactions between pollutants and atmospheric components
What does industrial smog contain
Carbon monoxide, carbon dioxide
Sulfur dioxide, sulfur trioxide, sulfuric acid, ammonium sulfate
Slide 37
What does photochemical smog contain
Nitric oxide, nitrogen dioxide
NO reacts with light to produce ozone and with water to produce nitric acid (HNO3)
NO2 + hydrocarbons = peroxyacyl nitrates (PANs)
Slide 38
What is air quality health index
Metric of air quality developed by the government of Canada. Calculated based on relative risks of common pollutants:
- tropospheric ozone
- particulate matter
- nitrogen dioxide (NO2)
Health affects of outdoor air pollution on humans
- Respiratory and cardiac issues
- Can affect blood vessels of the heart / distribution of oxygen throughout the body
- Small particulate matter (PM2.5) can easily travel into the lungs
- POPs and heavy metals associated with birth defects
Global air circulation (different cells)
Hadley cells move air from equator to 30 degrees latitude north and south
Ferrel cells move air 30 to 60 degrees latitude
Polar cells move air 60 degrees to pole
Hot air rises
Slide 45, 46
Read
Slide 46** important
Why did pollution get so bad in beijing in 2013?
Thermal inversion
Layer of warmer air on top of cold air. Slow moving, high pressure air above the city trapped pollutants beneath
How does pollution affect clouds?
Non polluted cloud will be darker (less light reflected, more passes through) with larger water droplets
Polluted cloud has smaller droplets (water accumulates on volatile particulate matter instead of on the cloud) and reflects more light
How does pollution affect rainfall
25% more rainfall after urbanization because of pollution
With urbanization, there is less water at night and more water in the afternoon
Rainfall is more concentrated = floods
Soil less able to absorb water
