atmospheric pollution dr. manish semwal gmis. concept of atmospheric pollution
TRANSCRIPT
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?
• 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?
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
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