Automobiles Catlytic converter
- Converts carbon monoxide, nitrous oxides and hydrocarbons into
carbon dioxide, nitrogen and water.
Recirculating exhaust gas along with a catlytic converter greatly reduces
Main problem is the sulfur dioxide it produces upon burning. Solutions:
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.
Smoke plus Fog (U.K.) (Grey smog). Photochemical Smog - brown air.
Results from exhausts from cars, buses and trucks.
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.
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 air
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.
If there were no greenhouse effect, the average temperature on the earth
would be - 20C with huge fluctuations in a 24 hour period. When visible
light from the sun hits the earth some is absorbed, heating the
earth. The heated earth gives off infrared radiation
characteristic of the 25C temperature. This longer wavelength infrared
radiation is then reradiated back into space. Some of the
infrared radiation, however, is trapped (absorbed) by greenhouse
This is known as The Greenhouse Effect.
There are several gases which cause the greenhouse effect, and whose
concentrations determine the amount of heat retained by the earth. Primary
among these are water vapor, carbon-dioxide and methane. The chart below
shows how the concentration of CO2 in the atmosphere has changed in the
last 40 years:
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)
Global Warming has been studied extensively, and currently, a large
percentage of the scientific community have reached a consensus on various
issues related to global warming. They are listed below:
Scientific Consensus on Global Warming
Added greenhouse gases add heat
Added gases are anthropogenic
Reduction of uncertainty will require a decade
Full recovery will require many centuries
Large stratospheric cooling
Precipitation will increase
Reduction of sea ice
Warming in arctic
Rise in sea level
Local details of global change
Tropical storms increase
Details of next 25 years
Carbon Dioxide (CO2): Roughly 60% of total
Burning Fossil Fuels
Methane (CH4): 15% of total
Subpolar Soil and Wetlands (Methane Hydrate)
Main source of acid rain is sulfur dioxide and nitrogen oxides in the
Power plants are a major source for sulfur dioxide and as well nitrogen
Automobiles, trucks and buses are major contributors of nitrogen oxides in
urban and suburban environments.
Effects of Acid Rain
If the bedrock consists of limestone, effect is not so severe. The
limestone helps to neutralize the acid. If bedrock is granitic, there
is no buffer Results severe.
Acid solutions free nutrients as well as toxic metals from the soil.
As a result, nutrients are lost from the soils and the plants may take
on toxic elements.
In lakes, acidity keeps the nutrients in solution. Nutrient are then
lost with the outflow of water. Algae cannot grow as a result, and so
there is no food for aquatic animals present in the lake.
Fish may be poisoned by heavy metals in solution, and are very
intolerant of high acidity.
High acidity kills trees.
Tree ring studies have shown that concentrations of calcium
(which is an essential nutrient for trees) have been decreasing
steadily in areas of increased acid rain.