This document summarizes information about air pollution and smog. It discusses photochemical smog, which involves nitrogen oxides, hydrocarbons, and ultraviolet light combining to form substances like nitric acid and aldehydes. Thermal and radiation inversions can trap smog near the ground. Acid deposition from rain and gases damages the environment. The ozone layer is depleted by nitrogen oxides and CFCs, leading to the Antarctic ozone hole. Chlorofluorocarbons react with ozone and each chlorine atom can destroy many ozone molecules.

1. TROUBLE IN THE AIR
(Air Pollution)
a science presentation

2. Photochemical Smog
O Photochemical smog is brown smog, the gray-
brown haze that hovers over many cities.
O It is especially a problem in warm, sunny
regions where lots of cars burn gasoline.
O Photochemical smog involves the blending of
three substances: oxides of nitrogen,
hydrocarbons, and solar energy in the form of
ultraviolet rays (UV).
O Nitric acids, peroxyacyl nitrates (PANs), and
aldehydes are also produced in the
photochemical reaction.

3. O These are the sources and effects of smog-producing
substances:
Sources and Effects of Smog-producing
Substances
Substance Source Effects
Peroxyacetyl nitrates
(PAN)
Formed by the reaction of NO2
with VOCs (can be formed
naturally in some environments)
Eye irritation, high toxicity
to plants, respiratory
irritation, protein damage
Nitrogen oxides Combustion of oil, coal, gas in both
automobiles and industry, bacterial
action in soil, forest fires, volcanic
action, lightning
Heart and lung problems, suppressed
plant growth, decreased resistance to
infection, may encourage the spread of
cancer, decreased visibility due to its
yellowish color
Ozone Formed from the photolysis
of NO2, sometimes results
from stratospheric ozone
intrusions
Bronchial constriction, coughing,
wheezing, respiratory irritation, eye
irritation, decreased crop yields,
retarded plant growth, damage to
plastics, breaking of rubber
Volatile organic
compounds (VOCs)
Evaporation of solvents and fuels,
incomplete combustion of fossil fuels,
naturally occurring compounds like
terpenes from trees
Eye irritation, respiratory irritation,
cancer, decreased visibility due to its
blue-brown haze

4. Photochemical Smog

5. Thermal Inversion
O Thermal inversion creates a situation in which a
layer of warm air (an inversion layer) lies over a
layer of cool air, trapping toxic and harmful
chemicals near the ground.
O It dramatically heightens air pollution
O Poor air circulation due to high-rise buildings
may also prevent the air from circulating or
escaping higher altitudes.
O In this process, smoke or soot are trapped at the
surface of the cool layer of air.

6. Thermal Inversion

7. Radiation Inversion
O Radiation inversion develops at night when the
ground cools and gives off long wave radiation.
O The inversion layer is heightened by the presence of
a large, high pressure system above, which is
usually dry and has only light winds.
O This layer may extend from a few feet to several
hundred feet above the surface, and is usually
dispersed by the next day’s solar beating through
convection.
O Ordinarily, it lasts only through the night. But
occasionally, it can persist for several days.
O The Great London Smog of 1952 took place
because excessive pollution from the coal-burning
furnaces were trapped by the radiation near the
ground.

8. Radiation Inversion

9. Acid Deposition
O Acid deposition is a broad term that describes
how acid can fall back to the earth.
O It damages buildings, monuments, plants, and
animals. It also contributes to fish kills and forest
destruction.
O The two types of acid deposition are:
• Wet Deposition
• Dry Deposition

10. O Wet Deposition- comes from acidic rain, snow,
hail, sleet, and fog.

11. O Dry Deposition- comes from acidic gases and
particulates.

12. Acid Deposition

13. Ozone Depletion
O Tropospheric or ground ozone is a pollutant,
much different from its counterpart in the
stratosphere that protects life from the
damaging effects of ultraviolet radiation.
O The ozone layer is continually damaged as
nitrogen oxides break down and reform in the
atmosphere.
O Ozone formation [also]occurs naturally in the
stratosphere.
O (This topic also includes: “The hole in the
Ozone Layer” and “Chlorofluorocarbons or
CFCs”)

14. The Hole in the Ozone Layer
O Since 1957, the British Antarctic Survey Team has
been monitoring ozone levels over the Antarctic. On
1985, they discovered that there was a hole in the
ozone layer over the Antarctic.
O The reason the hole in the ozone layer appeared
over the Antarctic is that the atmosphere in that
region is different from that of the rest of the world.
O During the Antarctic winter, the sun doesn’t shine
over the continent, which results in the formation of
polar clouds which consists of inactive chlorine
pollutants. One chlorine atom can actually destroy
100 000 ozone molecules.

15. The Hole in the Ozone Layer
Antarctic
Region

16. Chlorofluorocarbons (CFCs)
O A chlorofluorocarbon (CFC) is an organic compound that
contains only carbon, chlorine, and fluorine, produced as
a volatile derivative of methane, ethane, and propane.
O They are also commonly known by the DuPont brand
name Freon.
O Because CFCs contribute to ozone depletion in the
upper atmosphere, the manufacture of such compounds
has been phased out under the Montreal Protocol, and
they are being replaced with other products such as
hydrofluorocarbons (HFCs).
O The most important reaction of the CFCs is the photo-
induced scission of a C-Cl bond:
CCl3F → CCl2F. + Cl.

17. Chlorofluorocarbons (CFCs)

18. Ozone Depletion

19. Thank You for Watching!!!
Prepared By:
 Cherid M. Pariñal
Coordinates (Group 2):
 Joemel Ermoso
 Angelo R-cel Nualla
 Rogene Gay Gayem
 Jillian Nemiada
 Nicole Anne Nulada