lect13+14 air pollution dr. mohammed ajjour university of palestine 2009, 2010

Lect13+14 Air Pollution

Dr. Mohammed Ajjour University Of Palestine 2009,

2010

Atmosphere

University Of Palestine 2009, Dr. Mohammed Ajjour

The atmosphere is a layer of gases surrounding the earth . It protects life on earth by absorbing ultraviolet solar radiation, warming the surface through heat retention, and reducing temperature extremes between day and night. Dry air contains roughly (by volume) 78.08% nitrogen, 20.95% oxygen,0.93% argon, 0.038% carbon dioxide, and trace amounts of other gases. Air also contains a variable amount of water vapor, on average around 1%The atmosphere has a mass of about (5x1018) kg, three quarters of which is within about 11 km of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. At 100 km is regarded as the boundary between atmosphere and outer space.

The troposphere : begins at the surface and extends to between 7 km at the poles and 17 km at the equator, with some variation due to weather. The troposphere is mostly heated by transfer of energy from the surface, so on average the lowest part of the troposphere is warmest and temperature decreases with altitude. The troposphere contains roughly 80% of the mass of the atmosphere. The tropopause is the boundary between the troposphere and stratosphere.


four main layers of Atmosphere

layers of the Atmosphere

Stratosphere The stratosphere extends from the tropopause to about 51 km . Temperature increases with height, which restricts turbulence and mixing. The stratopause, is the boundary between the stratosphere and mesosphere

Mesosphere The mesosphere extends from the stratopause to 80–85 km . It is the layer where most meteors burn up upon entering the atmosphere. Temperature decreases with height in the mesosphere. The mesopause, the temperature minimum that marks the top of the mesosphere, is the coldest place on Earth and has an average temperature around −100 °C . University Of Palestine 2009, Dr. Mohammed Ajjour

Thermosphere Temperature increases with

height in the thermosphere from the mesopause up to the thermopause, then is constant with height. The temperature of this layer can rise to 1,500 °C though the gas molecules are so far apart that temperature in the usual sense is not well defined. The Space Station orbits in this layer, between 320 and 380 km . The top of the thermosphere is the bottom of the exosphere, called the exobase. Its height varies with solar activity and ranges from about 350–800 km . University Of Palestine 2009, Dr. Mohammed Ajjour

Atmosphere

Exosphere :The outermost layer of Earth's atmosphere extends from the exobase upward. Here the particles are so far apart that they can travel hundreds of km without colliding with one another. These free-moving particles may migrate into and out of the magnetosphere or the solar wind. The exosphere is mainly composed of hydrogen and helium.

Environmental main issues in the atmosphere : - Air Pollution - Ozon layer - Green House Effect

- Noise pollution - Radiation Pollution - light pollution


Air Pollution Air pollution is the introduction of chemicals, particulate matter, or

biological materials that cause harm or discomfort to living organisms, or damages the natural environment, into the atmosphere .The damage caused by air pollution is enormous. In money alone it represents a loss of billions of dollars each year. Many crops suffer ill effects from exhaust gases. Trees have been killed . Cattle have been poisoned. Air pollution causes rubber tires on automobiles to crack . Air pollution may cause or contribute to emphysema ( serious Lung disease ) eye and throat irritation .

Air in house and some office buildings can be more polluted than the air outside. Poor ventilation , copying machines, electrical and telephone cables, mold and microbe-harboring air conditioning systems and ducts, cleaning fluids, cigarette smoke, carpet, paint, vinyl molding, and building materials and furniture that emit air pollutants such as formaldehyde.


Classification of air pollution compounds

Pollutants can be classified as either primary pollutants :substances directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide from a motor vehicle. Or Secondary pollutants : are not emitted directly. Rather, they form in the air when primary pollutants react or interact. Example :is ground level ozone .


Primary Air Pollution compounds Sulfur oxides (SOx) - especially sulfur dioxide (SO2 ), is produced by

volcanoes , various industrial processes and coal and petroleum combustion. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources .

Nitrogen oxides (NOx) - especially nitrogen dioxide NO2 and N2O , are Natural component of the Earth's atmosphere. They are emitted from high temperature combustion of fuel and burning of biomass . NO2 is one of the most prominent air pollutants especially in the formation of both acid precipitation and photochemical smog (ozone), and causes nitrogen loading. It has a role in reducing stratospheric ozone.

Univ Dr. Mohammed Ajjour

Primary Air Pollution compounds

Carbon dioxide (CO2) - is a natural gas in the atmosphere but also is one of the major pollutants . Major sources of CO2 are fossil fuels burning and deforestation

Carbon monoxide - is a colorless , odorless, but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.


Primary Air Pollution compounds . Industrial countries account for 65% of CO2 emissions with the

United States and Soviet Union responsible for 50%. Less developed countries (LDCs), with 80% of the world's people, are responsible for 35% of CO2 emissions . "Carbon dioxide emissions are increasing by 4% a year". .

CO2 is a good transmitter of sunlight, but partially restricts infrared radiation going back from the earth into space. This produces the so-called greenhouse effect that prevents a drastic cooling of the Earth during the night. Increasing the amount of CO2 in the atmosphere reinforces this effect and is expected to result in a warming of the Earth's surface.


Primary Air Pollution compounds Volatile organic compounds - VOCs are important outdoor pollutant. They

are often divided into the categories of methane (CH4) and non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas . Other hydrocarbon VOCs are also significant greenhouse gases via their role in creating ozone and in prolonging the life of methane in the atmosphere. Within the NMVOCs, the aromatic compounds benzene, toluene and xylene are suspected carcinogens and may lead to leukemia through prolonged exposure.

Particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas. Some particulates occur naturally, originating from volcanoes, dust storms, and forest fires. Human activities, such as the burning of fossil fuels and various industrial processes also generate significant amounts of aerosols.


Cont. Primary Air Pollution compounds Increased levels of fine particles in the air are linked to health

hazards such as heart disease, altered lung function and lung cancer Toxic metals, such as lead, cadmium and copper. Chlorofluorocarbons (CFCs) - are lowering the average concentration

of ozone in the stratosphere. Aerosols are still the largest use, Spray cans, leaking refrigeration and air conditioning equipment, and the burning plastic foam products release the CFCs into the atmosphere. CFCs stay in the atmosphere from 22 to 111 years. Under high energy ultra violet (UV) radiation, they break down and release chlorine atoms, which speed up the breakdown of ozone (O3) into oxygen gas (O2). CFCs, also known as Freons, are greenhouse gases that contribute to global warming. University Of Palestine 2009, Dr.

Mohammed Ajjour

Cont.Primary Air Pollution compounds Ammonia (NH3) - emitted from agricultural processes.

Odors — such as from garbage, sewage, and industrial processes Radioactive pollutants - produced by nuclear explosions, war

explosives, and natural processes such as the radioactive decay of radon.


Secondary pollutants : smog include : photochemical smog .classic Smog

results from large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. Modern smog does not usually come from coal but from vehicular and industrial emissions that are acted on in the atmosphere by sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog. smog has become predominant in many cities, which are located in sunny, warm, and dry climates with many motor vehicles.


Secondary pollutants: ground level Ozone

Ground level ozone (O3) formed from the effect of UV light on Oxygen in presence of NOx and VOCs in polluted Cities :

O2 + UV = O+O

O + O2 = O3 (Ozone)

NO2 +UV = NO+O

O+ O2 = O3 (Ozone)

Photochemical and chemical reactions involving it drive many chemical processes that occur in the atmosphere . At abnormally high concentrations brought about by human activities (combustion of fossil fuel), it is a pollutant, and a constituent of smog .In high concentrations it causes damage to crops ,Buildings, car rubber, paints and irritation to eyes and skin. University Of Palestine 2009, Dr. Mohammed Ajjour

Cont.Secondary pollutants : Acid Rain is a broad term referring to a mixture of

depositions from the atmosphere containing higher than normal amounts of nitric and sulfuric acids which result from both natural sources, such as volcanoes ; and man-made sources, primarily emissions of (SO2) and (NOx) resulting from fossil fuel combustion. Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. the acids can fall to the ground in the form of rain, snow, 0r fog, causing damage to a variety of plants and animals.


Acid Rain Acid rain causes acidification of lakes

and streams and contributes to the damage of trees at high elevations and many sensitive forest soils. In addition, acid rain accelerates the decay of building materials and paints, including irreplaceable buildings, statues, and sculptures . Prior to falling to the earth, sulfur dioxide and nitrogen oxide gases and their particulate matter derivatives—sulfates and nitrates—contribute to visibility degradation and harm public health.”


Competing Air pollution Regulations to reduce the production and the releasing of

pollutants. Educations of peoples on the importance of these measures You can help to reduce global air pollution and climate change

by : Driving car that consumes less fuel, walking, bicycling, and using mass transit when possible. Replace light bulbs with fluorescent bulbs, make your home more energy efficient, and buy only energy efficient appliances. Recycle newspapers, and other materials. Plant trees and avoid purchasing products such as Styrofoam that contain CFCs.


Ozone layer Ozone :About 90% of the ozone in our

atmosphere is contained in the stratosphere. Although the concentration is very small (2-8 ppm ), it is vitally important to life because it absorbs biologically harmful ultraviolet (UV) radiation coming from the Sun.


Ozon formation Ozone in the stratosphere is created by

UV light striking (O2) molecule , splitting them into individual 2 oxygen atoms; the atomic oxygen then combines with unbroken O2 to create ozone, O3. The ozone molecule is also unstable and when ultraviolet light hits ozone it splits into a molecule of O2 and an atom of atomic oxygen, a continuing process called the ozone-oxygen cycle, thus creating an ozone layer in the region from about 10 to 50 km above Earth's surface.


ozon depletion The ozone layer can be depleted by free radical catalysts, like : nitric

oxide (NO), nitrous oxide (N2O), hydroxyl (OH), atomic chlorine(Cl), and atomic bromine(Br). While there are natural sources for all of these species, the concentrations of chlorine and bromine have increased markedly in recent years due to the release of large quantities of chlorofluorocarbons (CFCs) .These highly stable compounds are capable of surviving the rise to the stratosphere, where Cl and Br radicals are liberated by the action of ultraviolet light. Each radical is then free to initiate and catalyze a chain reaction capable of breaking down over 100,000 ozone molecules. The breakdown of ozone in the stratosphere results in the ozone molecules being unable to absorb ultraviolet radiation. Consequently, unabsorbed and dangerous ultraviolet-B radiation is able to reach the Earth’s surface.University Of Palestine 2009, Dr. Mohammed Ajjour

Green House effect It is the heating of the surface of a planet due

to the presence of an atmosphere containing gases that absorb and emit infrared radiation.Thus, greenhouse gases trap heat within the surface-troposphere system. In the absence of the greenhouse effect and an atmosphere, the Earth‘s average surface temp. of 14 °C could be as low as −18 °C. Global warming is believed to be the result of an "enhanced greenhouse effect" mostly due to human-produced increases in greenhouse gases. This human induced part is referred to as anthropogenic global warming (AGW).


Basic mechanism of GHE Earth receives sun energy mostly in the form of

visible light . About 50% of the sun's energy is absorbed at the surface. Like all bodies with a temp. above zero , the Earth's surface radiates energy in the infrared range. Greenhouse gases in the atmosphere absorb most of the infrared radiation emitted by the surface and pass the absorbed heat to other atmospheric gases through molecular collisions. Radiation is emitted both upward, with part escaping to space, and downward toward Earth's surface. The surface and lower atmosphere are warmed by the part of the energy that is radiated downward, making our life on earth possible.


Greenhouse gases In order, Earth's most abundant greenhouse gases are: water vapor contribute to 36–70% carbon dioxide contribute to 9–26% methane contribute to 4–9% ozone contribute to 3–7% CFCs nitrous oxide


Global warming


lect13+14 air pollution dr. mohammed ajjour university of palestine 2009, 2010

Documents

atmosphere stratosphere

atmosphere exosphereexosphere

thermosphere temperature

average temperature

temperature decreases

mohammed ajjour slide

temperature extremes

temperature minimum