Environmental Studies (SSC202) Lesson 2.pptx

IOBM : Environmental Studies (SSC202) Lesson 2.pptx

1. Environmental Studies (SSC202) Lesson 2: Atmosphere and Air pollution Falak Shad Memon Institute of Business Management ( IoBM )

2. The atmosphere consists of gas molecules, held near the earth’s surface by gravity and extending upward about 500 km. All the weather we see is in just the lowest 10–12 km, in a constantly circulating and swirling layer known as the troposphere. Air is actually a mixture of gases that constitutes our atmosphere surrounding the earth, and extended outward from the earths surface. Air is invisible and tasteless and pure air has no odor. Air in motion is called wind and has capacity to turn wind mills, (energy source) uproot trees and wreck the buildings and homes. The composition of air remains constant. Oxygen, nitrogen and carbon dioxide are continuously being extracted from air. Living organisms breath in air and oxygen, and oxygen is further used in the combustion and slow oxidation process. Atmosphere

3. The atmosphere has four distinct zones of contrasting temperature, which result from differences in absorption of solar energy . Starting from the Earth's surface, these layers are called troposphere, (Sea level to 20 km) stratosphere, (approx 20 to 50 km) mesosphere, (approx 50 to 87 km) thermosphere. (approx 87- >600 km) Gases become less dense, the farther they are from Earth's surface.

4. The layer of air immediately adjacent to the earth’s surface is called the troposphere The troposphere extends to a height of about 20 km above Earth's surface. Most of the gas molecules in the atmosphere are in the troposphere. The troposphere contains most of the water vapor in the atmosphere and is the layer in which most weather occurs. the troposphere contains about 75 percent of the total mass of the atmosphere. The winds that carry weather across Earth are an important factor in the climate of an area. Troposphere

5. The stratosphere extends from the tropopause up to about 50 km (31 mi). This layer is vastly more dilute than the troposphere, but it has similar composition—except that it has almost no water vapor and nearly 1,000 times more ozone (O 3 ). Near the earth’s surface ozone is a pollutant, but in the stratosphere it serves a very important function Ultraviolet radiation is one of many types of electromagnetic waves produced by the sun. without the filtering action of the ozone layer, the sun's UV radiation would destroy much of the life on Earth. Stratospheric UV absorption also protects life on the earth’s surface, because UV radiation damages living tissues, causing skin cancer, genetic mutations, and crop failures Weather disturbances that are common in the troposphere do not occur in the stratosphere. Stratosphere

6. Beyond the stratosphere is the mesosphere , which extends up to 85 km above Earth's surface. The mesosphere is the coldest layer of the atmosphere, with temperatures as low as -100 °C. The thermosphere is the outermost layer of the atmosphere. Unlike the mesosphere, the thermosphere experiences temperatures as high as 2000 °C, though air pressure is less than one ten-thousandth of that at Earth's surface. Gas molecules in one layer of the thermosphere are bombarded with rays from the sun. These rays cause the gas molecules to lose electrons, and they become ions. Because of these ions, this layer of the thermosphere (heat energy is given off) is called the ionosphere . When gas molecules reunite with free electrons, light is given off. This process occurs most often near Earth's poles, resulting in a display of lights called an aurora. Mesosphere and Thermosphere

7. Greenhouse effect Energy balance between incoming and outgoing radiation. The atmosphere absorbs or reflects about half of the solar energy reaching the earth. Most of the energy reemitted from the earth’s surface is long-wave, infrared energy. Most of this infrared energy is absorbed by aerosols and gases in the atmosphere and is re-radiated toward the planet, keeping the surface much warmer than it would otherwise be. This is known as the greenhouse effect. Greenhouse gases is a general term for gases that are especially effective at capturing the long-wavelength energy from the earth’s surface. Water vapor (H 2 O) is the most abundant greenhouse gas, and it is always present in the atmosphere. Carbon dioxide (CO 2 ) is the most abundant human-caused greenhouse gas, followed by methane (CH 4 ), nitrous oxide (N 2 O), and dozens of other gases.

8. Good or bad ozone Good Ozone In the stratosphere, t he ozone layer is an essential protector of life on earth as it absorbs harmful UV radiation before it reaches the earth. The total mass of ozone in the atmosphere is about 3 billion metric tons. That may seem like a lot, but it is only 0.00006 percent of the atmosphere The peak concentration of ozone occurs at an altitude of roughly 32 kilometers (20 miles) above the surface of the Earth. At that altitude, ozone concentration can be as high as 15 parts per million (0.0015 percent). Bad Ozone Ground-level, “bad,” ozone forms when nitrogen oxide gases from vehicle the natural concentration of ozone is about 10 parts per billion (0.00001 percent). According to the Environmental Protection Agency, exposure to ozone levels of greater than 80 parts per billion for 8 hours or longer is unhealthy The harmful effects can include throat and lung irritation or aggravation of asthma or emphysema The discovery of stratospheric ozone losses brought about a remarkably quick international response. In 1987 an international meeting in Montreal, Canada, produced the Montreal Protocol, the first of several major international agreements on phasing out most use of CFCs by 2000.

9. Ozone depletion

10. Defining Air Pollution Air Pollution' means presence of any `air pollutant' in the atmosphere. `Air pollutant' means any solid, liquid or gaseous substance (including noise) present in the atmosphere in such concentration as may be or tend to be injurious to human beings or other living creatures or plants or property or environment. Thus, mere presence of so-called polluting substances in the atmosphere does not make it polluted. The substances make it polluted when present in sufficient concentrations, that is, above the `accepted levels'. The air pollution can thus be redefined in more simple terms as the presence of deleterious substances in the atmosphere above accepted levels.

11. Source of Pollution A source of air pollution is a point or place from where pollutants are discharged into the air. Sources of air pollution can be classified as Natural sources (b) Man made sources. (a) Natural sources : The natural sources can be enumerated as follows. i ) Volcanoes: Volcanoes which erupt naturally, emit huge quantities of particulate matter and gases like sulphur dioxide, hydrogen sulphide and methane. Control of such eruption's are not possible. ii) Forest fires: Forest Fires caused by lighting are only natural, but such fires can also be initiated by man for his selfish ends. Forest fires create smoke, incomplete combustion, carbon monoxide, sulphur dioxide and oxides of nitrogen. iii) Oceans: Oceans continuously emits aerosols into the atmosphere in the form of salt particles, which are corrosive to metals and plants. Salt spray damages cement structures near sea shores. iv) Vegetation: Vegetation though very useful to humanity in many ways, is also natural source of air pollution. Decaying plants produce methane. Further, air borne pollens can cause severe respiratory problem in some human beings.

12. v) Radio active materials: Though the natural radioactivity from soils and rocks containing radioactive minerals is small, it is still important as radioactive material is continuously exposed to the atmosphere. vi) Cosmogenous or extraterrestrial sediment: tiny grains, typically small, magnetic spheres and silicate chondrules (bits of asteroids), originating from outer space; extraterrestrial debris. vii) lithogenous sediment : sedimentary. debris produced by the weathering and erosion of rocks on land.

13. We have spent a considerable amount of effort and money to control the major outdoor air pollutants, but we have only recently begun to address indoor air pollutants. The EPA has found that indoor concentrations of toxic air pollutants are often higher than outdoors.. People spend 70% to 80 % of their time indoor Several factors are responsible for the high levels of indoor pollutants. Home products such as plastics, insulation, and cleaning agents - give off harmful fumes. Air circulation in buildings is often poor especially during winter, when buildings are closed up to save energy. The effects of fumes and decreased air circulation are multiplied because most people spend 16 to 18 hours a day indoor. This exposure to pollutants can cause serious health problems. The combination of particulates, gases, and other chemicals contained in cigarette smoke makes it the deadliest of all indoor pollutants. Cigarette smoke is hazardous not only to smokers but to nonsmokers as well. Nonsmokers breathe in secondhand, or side stream, smoke. Secondhand smoke from cigarettes contains higher levels of particulates from burning paper and tobacco than the smoke inhaled by the smoker. Indoor Pollutants

14. Air Pollutants Particulate Matter. In general the term 'particulate' refers to all atmospheric substances that are not gases. They can be suspended droplets or solid particles or mixtures of the two. Particles can be a inert material or extremely reactive materials ranging in size from 100 µm to 0.1 µm and less. The classification of various particulates may be made as follows Dust : It contains the particles of size ranging from 1 to 200 µm. These are formed by natural disintegration of rocks and soil or by mechanical processes of grinding and spraying. Smoke: It is obtained during incomplete combustion of the organic matter such as wood, coal etc. The size can be ranging from 0.01 to 1µm.

15. Fumes: They are obtained by sublimation, condensation or cracking at high temperature, size is 0.1 to 1µm. Mist: It is formed by condensation in the atmosphere or released from industrial operations. It is made up of liquid droplets generally smaller than 10 µm. Fog: It is a mist in which the liquid is water and formed by temperature inversion. (stream of cold air blowing over warmer surfaces) Smog: It is a combination of natural fog and man made smoke. Aerosols: Aerosols refers to particles smaller than 1 microns. The smaller size of particles keep them suspended in air even at very low wind velocities.

16. Classification of Air Pollutants Air pollutants are divided into two major categories i ) Primary pollutants ii) Secondary pollutants. i ) Primary Pollutants The primary pollutants are those that are emitted directly from the sources. For example : carbon monoxide (CO), sulphur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), lead ( Pb ), and particulate matters (PM), ii) Secondary Pollutants The secondary pollutants are those that are formed in the atmosphere by chemical interactions among primary pollutants and normal atmosphere. For example : Sulphur trioxide, nitrogen dioxide, PAN ( Peroxyacetyl nitrate). Acid rain (weak Sulphuric acid, weak nitric acid). Carbonic acid etc. are in this category.

17. Primary/Secondary Air Pollutant Sources Secondary air pollutants derive from reactions that occur between primary pollutants and other atmospheric chemicals Ozone PANs ( peroxyacetyl nitrates) Acids: sulfuric and nitric

18. Sulphur dioxide (SO 2 ) It is a colourless , poisonous gas, highly soluble in water. It has a pungent and suffocating odour . Sources: Burning of fossil fuels Thermal power plants Fertilizer plants Textile industry Steel plants Sulphuric acid plants Petroleum industry Oil refining Smelting of sulphid ores

19. Excess SO 2 levels in air can lead to some consequences like: acid rain - which is the result of SO 2 is converted into sulphite in presence of atmospheric oxygen. SO 3 ( sulphite ) can mix with rain water to bring mild sulphuric acid to earth's surface during its movement. SO 2 + atmospheric humidity (H 2 O) can result into fine particles of sulphites and H 2 SO 4. They are often attached to dust or fine carbon particles released out of vehicular pollution. When inhaled they have capacity to damage delicate tissue linings to eyes, nose, respiratory tract, On an average, about 25 million tons of sulphur dioxide is emitted into the atmosphere annually.

20. Temperature inversions trap pollutants Inversions occur when a stable layer of warmer air lies above cooler air. The normal conditions, where temperatures decline with increasing height, are inverted, and these stable conditions prevent convection currents from dispersing pollutants. Often these conditions occur when cold air settles in a valley that is surrounded by hills or mountains. When a cold front slides under an adjacent warmer air mass, or when cool air subsides down a mountain slope to displace warmer air in the valley below, the cold air becomes trapped, as in a bowl. Inversions might last from a few hours to a few days.

21. Effects of Air pollution Polluted air damages lungs The World Health Organization estimates that some 5 to 6 million people die prematurely every year from illnesses related to air pollution. Heart attacks, respiratory diseases, and lung cancer all are significantly higher in people who breathe dirty air, compared to matching groups in cleaner environments We once thought that particles smaller than 10 micrometers (10 millionths of a meter) were too small to be trapped in the lungs. Now we know that fine PM2.5 particles (less than 2.5 micrometers in diameter) pose even greater risks than coarse particles. They have been linked with heart attacks, asthma, bronchitis, lung cancer, immune suppression, and abnormal fetal development, among other health problems. Fine particulates have many sources. Until recently power plants were the largest source, but clean air rules will require power plants to install filters and precipitators to remove at least 70 percent of their particulate emissions. Acid deposition has many negative effects, like ocean acidification that can disrupt the food chain by killing aquatic plants, insects, and invertebrates on which fish depend for food Forest Damage Buildings and Monuments Smog and haze reduce visibility

22. Acid Deposition

23. Prolonged exposure to sulphate causes damage to buildings and marble monuments, as the carbonates like lime stone and CaCO 3 react with H 2 SO 4 to produce gypsum (CaSO 4 ), which is washed away leaving behind the eroded surface. It is now believed that there is a severe acid rain threat on the Taj Mahal .

24. Air Pollution Control “Dilution is the solution to pollution” was one of the early approaches to air pollution control. air pollution in the developed world is associated with transportation and energy production, the most effective strategy would be conservation: Reducing electricity consumption, insulating homes and offices, and developing better public transportation could all greatly reduce air pollution. Alternative energy sources, such as wind and solar power, produce energy with little or no pollution, and these and other technologies are becoming economically competitive. An electrostatic precipitator traps particulate material on electrically charged plates as effluent makes its way to the smokestack.