adapted to HTML from lecture notes of Prof. Stephen A. Nelson Tulane
Smoke plus Fog (based on Britain's experience) (Grey smog)
- Photochemical Smog - brown air. (This is what we have in the U.S.)
Results from exhausts from cars, buses and trucks.
- Nitrogen Oxide + Oxgen + Hydrocarbons + Sunlight -- > Ozone
- 6ppm ozone is deadly - We need ozone in stratosphere; at lower
altitudes, however, it can kill.
- Sulfurous Fog- gray air.
- Dominantly from burning coal with a significant pyrite content.
The fogs of London in the past were actually sulfuous fog.
This type of smog is no longer common in London as a result of
environmental regulations on burning coal.
Control of Air Pollution
Catlytic converter converts carbon monoxide, nitrous oxides and
hydrocarbons into carbon dioxide, nitrogen and water.
Recirculating exhaust gas along with a catlytic converter greatly
Coal Main problem is the sulfur dioxide it produces upon burning.
Burn only low sulfur coal.
Wash coal to remove pyrite.
Convert coal to gas (called Gasification)
Fluidized Bed Combustion (or Limestone Injection): Mix coal with
limestone, to form calcium sulfides or sulfates, which are prevent
sulfur from forming sulfur dioxide.
Scrubbing - slurries of lime or limestone.
In valleys or on the lee side of mountains, air inversion may
occur. A warmer air mass moves above cooler air, trapping the cooler,
denser air underneath and increasing the severity of air pollution. Los
Angeles is a good example of this, where warm desert air from the east
comes over the mountains to the east of Los Angeles and lies over the
cooler Pacific Ocean air. The cooler air is trapped because it cannot rise
through the less dense warm air above it, and the pollution in the cold
A similar situation arises in mountain valleys where warm air overlies the
colder air which accumulates in the valleys.
Also, cities tend to form featuers known as heat islands or dust domes,
which tend to collect warm air filled with pollutants, and help spread it
out over nearby suburbs.
- The increase in CO2 is anthropogenic (related to human activities).
It is mostly due to the burning of fossil fuels and deforestation.
| Gases contributing to Anthropogenic Greenhouse Effect
||Rate of Increase
(% per year)