TROUBLE IN THE AIR

(Air Pollution)a science presentation

Photochemical SmogO 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.

O These are the sources and effects of smog-producing substances:Sources and Effects of Smog-producing

SubstancesSubstance 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

Photochemical Smog

Thermal InversionO 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 pollutionO 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.

Thermal Inversion

Radiation InversionO 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.

Radiation Inversion

Acid DepositionO 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

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

O Dry Deposition- comes from acidic gases and particulates.

Acid Deposition

Ozone DepletionO 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”)

The Hole in the Ozone LayerO 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.

The Hole in the Ozone LayerAntarctic Region

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.

Chlorofluorocarbons (CFCs)

Ozone Depletion

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