6.3 Photochemical Smog Flashcards
What is photochemical smog?
Are a mixture of pollutants, formed when nitrogen oxides and VOCs react in sunlight, creating a brown haze over cities.
What are some problems associated with photochemical smog?
- 1 billion people are exposed to outdoor air pollution per year
- 1 million premature deaths due to air pollution
- Causes losses in a countries production
- 90% of air pollution in LEDCs comes from old motor vehicles
What are some examples of primary pollutants from the combustion of fossil fuels?
- carbon monoxide
- carbon dioxide
- black carbon or soot
- unburned hydrocarbons
- oxides of nitrogen and oxides of sulfur
Which two carbon oxides are both colour and odourless, and greenhouse gases?
Carbon dioxide and monoxide
What is black carbon (soot)?
These are solid particles suspended in the air, this includes:
- ash
- soot
- dust
- fecal matter
- -> commonly formed from the combustion of fossil fuels and can produce smog
- -> particles can contribute to asthma, heart disease and some cancers
What can black carbon particles contribute towards?
asthma, heart disease and some cancers
How are nitrogen oxides formed?
These are produced when nitrogen and oxygen from the atmosphere come together at high temperatures
–> occurs in hot exhaust gas from vehicles, power plants; or factories
What do nitrogen oxide and dioxide contribute to?
They are greenhouse gases and contribute to acid rain
How is tropospheric ozone formed?
- Nitrogen oxides form as a by product of combustion reactions
- Oxygen and nitrogen (both from the air) react together as a result of the high temperatures.
- Nitrogen dioxide can absorb sunlight and break up to release oxygen atoms that combine with oxygen in the air to form ozone.
Tropospheric ozone is an example of a ________ pollutant
secondary, as it is formed when oxygen molecules react with oxygen atoms that are released from nitrogen dioxide in the presence of sunlight.
What are some impacts of tropospheric ozone?
- Causes plants to close stomata slowing photosynthesis and plant growth.
- If ozone is absorbed into plants through leaves it damages internal cells and degrades chlorophyll, which reduces photosynthesis and therefore productivity
- Interferes with the ability of sensitive plants (e.g. black cherry) to produce and store food.
- Attacks rubber, cellulose and some plastics
- Reduces life of car tires
- Bleaches fabrics
- Increased number of asthma attacks and chance of respiratory diseases
What are VOCs?
volatile organic compounds
–> are organic chemical compounds able to evaporate into gases and take part in photochemical reactions
What are the main sources of VOCs?
drying paints, glues, or inks, and petrol handling and distribution
How is photochemical smog formed?
When VOCs and nitrogen oxides react to sunlight
Where is the frequency and severity of smog the highest?
In places that are:
- sunny
- high traffic density
- where topography limits air circulation
What are thermal inversions?
Thermal inversions occur due to a lack of air movement when a layer of dense, cool air is tapped beneath a layer of less dense, warm air. This causes concentrations of air pollutants to build up near the ground instead of being dissipated by normal air movements
