Topic 6.3 Flashcards
What does UNEP estimate about urban air pollution?
- 1 billion people are exposed to outdoor air pollution per year
- Estimated 3 million people will die prematurely due to air pollution in 2020 and up to 9 million premature deaths in 2060 if nothing changes.
- Air pollution has economic costs: 2% of GDP is lost by air pollution in MEDCs, 5% in LEDCs. - there is increased healthcare costs, decrease in productivity of workers and decreased agricultural yields.
- Over 90% of urban air pollution in LEDCs comes from old motor vehicles which are poorly maintained
What are the different types of air pollution?
- Chemicals: most air pollution is caused by burning fossil fuels like coal for industrial uses and gasoline and diesel in motor vehicles.
Particulates: AQI (Air Quality Index) is only a measure of particulate pollution.
Biological materials: Air pollution which comes from living organisms and can affect our health. Include pollen from trees/plants, mold, insects or insect parts, certain fungi, some bacteria and viruses, animal hair/skin scales.
What are the causes of air pollution?
- Primary pollutants: emitted directly from a process
- Secondary pollutants: formed when a primary pollutant undergoes a chemical or photochemical reaction with chemicals already present in the atmosphere. (photochemical reactions occur in the presence of light).
What sort of processes are primary pollutants formed by?
- Burning fossil fuels: motor vehicles, electrical power plants, many industrial processes.
- Forest fires
- Volcano Eruptions
What are the primary pollutants that are produced when burning fossil fuels?
- Carbon monoxide - greenhouse gas, can reduce the amount of oxygen that can be circulated around the blood
- Carbon dioxide - greenhouse gas
- Nitrogen oxides - they react with chemicals in the atmosphere to produce secondary pollutants.
- Sulfur dioxide - from coal with a high sulfur content which also reacts with chemicals in the atmosphere to produce secondary pollutants.
- Soot - particulates which causes lung disease and cancer.
What is tropospheric ozone?
- Tropospheric ozone is a greenhouse gas that increases global warming 2000 times more than CO2.
What percentage of ozone is present in the troposphere?
10%
What does tropospheric ozone damage?
- Plants by being absorbed into leaves and then destroying chlorophyll in the leaves so photosynthesis is less effective.
- Human health affected. Breathing difficulties due to reduction in lung productivity, lower immune system so more susceptible to infections, Eye, Nose, Throat (ENT) irritation.
- Materials and products: Destroys natural rubber, reduces lifetime of car tires, bleaches fabrics.
How is tropospheric ozone produced?
- In hot car engines, nitrogen and oxygen in the atmosphere react to form nitrogen oxides during the combustion process.
- Nitrogen oxide reacts with oxygen to form nitrogen dioxide which is a brown gas that is part of urban haze.
- In sunlight nitrogen dioxide breaks up into nitric acid and oxygen atoms. Oxygen atoms combine with oxygen molecules to form ozone.
How are the particulates in the atmosphere formed?
- Burning fossil fuels incompletely produces small, unburnt particles of soot called particulates.
Why are particulates in the atmosphere dangerous?
- Nose hairs and hairs called cilia in our lungs cannot filter out particulates.
- they settle in our lungs and cause asthma and lung cancer (many particulates are carcinogenic - cancer causing agents)
- in agricultural areas, particulates cover plant leaves and cause photosynthesis to be less effective causing lower crop yields.
How is petrochemical smog formed in urban areas?
- When fossil fuels burned in vehicles and factories especially on warm sunny days photochemical smog is formed complex reactions in the atmosphere create many chemicals secondary pollutants in photochemical smog including VOCs (volatile organic compounds) PANs (peroxyacyl nitrates), carbon monoxide and nitrous oxides.
- highly reactive VOCs oxidise nitrogen oxide into nitrogen dioxide without breaking down any ozone molecules in the process. This leads to a buildup of ozone near the ground level and smog formation.
Why does petrochemical smog look brown?
Because nitrogen oxide is brown in colour
When is petrochemical smog at its highest concentrations and why?
In the afternoon due to the role of the sun in the process of smog formation.
Which areas are most susceptible to the formation of photochemical smog?
Cities in low lying areas or valleys. Surrounding hills and mountains to not allow for pollutants to be blown away from the city.
LA, Mumbai, Beijing for e.g. are cities with the topography that invite a lot of petrochemical smog formation that is not easily dissipated.
