Atmospheric Pollution

Dr. Manish SemwalGMIS

Concept of Atmospheric Pollution

Atmospheric Pollution

• The quality of the air we breathe is both a personal health and a major economic issue

• Every industrialized country has to grapple with this issue and it appears that some countries with rapidly expanding economies (e.g., China) are making the same pollution mistakes as the United States did earlier

• As you’ll see, air pollution is often an international issue since the air pollution generated in one country can be transported to another by the prevailing winds

Rain and acidity

• Rain, in its theoretically normal, unpolluted state, is slightly acid, with pH 5.6, due to carbonic acid (H2CO3) which is a product of the dissolution of atmospheric carbon dioxide (CO2)

• Acid rain is defined as rain with a pH<5.6

Rain and acidity• The oxides of sulfur and nitrogen (SOx and NOx) are

oxidized in the atmosphere and form sulfuric and nitric acids (H2SO4 and HNO3)

• These acids contribute to rain acidity• Sulfur compounds (and maybe also nitrogen

compounds) can be transported several hundred kilometers per day in the atmosphere

• Chlorine emission may also result in acidity (hydrochloric acid HCl), but usually only close to emission sources

Sources of S and N in atmosphere

• Sulfur oxides are primarily emitted from stationary sources, such as utility and industrial coal-burning boilers

• Nitrogen oxides are emitted from both stationary and mobile sources, especially automobiles

Data from US EPA (1977):• ~56% of NOx was caused from the burning of fossil

fuels by stationary sources• 40% came from transportation-related sources

Sources of S and N in atmosphere

The combustion of fossil fuel in the US results in ~50 million metric tons of SOx and NOx being emitted to the atmosphere per year

Ecological effects of acid rain

• Degradation of water quality• Decrease in fish productivity• Decrease in forest productivity• Accelerated soil leaching

Less concern about effect of acid rain is usually caused by:• data unavailability or only few data are available–about chemical characteristic of precipitation–environmental degradation caused by changes of

precipitation chemistry• emission of SOx and NOx are thought as only causing

less environmental effects

Why Ecological effects of acid rain are recognized

Research Initiative for IA ( If Required)

• Sites to be analyzed?• Sampling methods? Time? • Chemical analysis? Methods and

pollutants/compounds to be analyzed?• Ecological analysis? Type of indicators and

organism to be investigated?• Statistical methods? • Possible interpretation?

Acid Rain and Trees

Dissolution of Limestone and Marble

Dissolution of Marble

• Stratospheric Ozone

Stratosphere – volume of Earth’s atmosphere that extends from ~ 10 – 15 km altitude to an altitude of ~ 50 km; it contains about 90% of the atmosphere’s naturally occurring ozone

How does stratospheric ozone benefit life on Earth?

Where is ozone the “good guy”?

trophosphere

stratosphere

Ground-level Ozone

• Ozone (O3) – a pale blue gas that near the Earth’s surface is a component of photochemical (light induced) smog

• E.G., NOx (nitrogen oxides) gases are released from vehicle exhaust; sunlight energy breaks the bond between the N and O atoms in the NOx compound

• Then O + O2 O3

• Why should we care?

LA smog

Ozone Depletion Over Northern Hemisphere

Source: Data from NASA, Goddard Space Flight Center.

Stratospheric Ozone

• Ramifications of stratospheric ozone reduction?

• 1) Increase in skin cancers• 2) Increase in eye disorders• 3) Decrease in immune response• 4) Decrease in plant productivity• 5) Possible enhancement of Greenhouse

Effect due to less plant productivity• 6) Increase in ground-level ozone

concentrations

The Montreal Protocol has reduced use of CFC’s, but…

• Their long life span means that they will be in the stratosphere for a long time, still destroying ozone.

• However, the rate of increase of ozone depletion has slow, showing we are on the right track

• By the way, ozone “holes” are opening up in places other than Antarctica

Bibliography

http://www.epa.gov/ozone/http://www.beyonddiscovery.org/content/view.article.asp?a=73http://www.ucsusa.org/global_environment/archive/page.cfm?pageID=551http://www.cln.org/themes/ozone.html

Thank You