AIR POLLUTION AND CONTROL METHODS UNIT 1 - Air Pollution PPT

This PPT gives you Brief idea about Air Pollutants, Global Effects of Air Pollution, Types of Air Pollution

1. UNIT 1 AIR POLLUTION By V. Nikhila Bhavani Assistant Professor VJIT, HYD

2. Introduction The earth is the only planet known in the universe capable of supporting life. The life supporting properties are The Atmosphere and Hydrosphere . Environment pollution and efforts for the betterment of living standards are the two sides of the same coin. In the wake of industrialization, consequent urbanization and ever increasing population, the basic amenities of life namely, air, water and land are being polluted continuously.

3. Definition Atmosphere is a thin layer of gas which surrounds the Earth. Three major layers : Troposphere, Stratosphere, Mesosphere. 99% of the volume of clean air is in Troposphere, which extends 17km above MSL (MEAN SEA LEVEL). Nitrogen (78%) and Oxygen (21%) and 1% Argon, CO2 and water vapour.

4. Definition As per the definition of the World Health Organization (WHO), air pollution is a “situation in which the outdoor atmosphere contains materials in concentrations which are harmful to people or their environment”.

5. Scope of Air Pollutants

6. EPISODES OF AIR POLLUTION

7. Episodes of Air Pollution An air pollution episode is the term used for a period of poor air quality, usually lasting up to several days, extending over a large geographical area.

8. Examples 1930 Meuse Valley fog The  1930 Meuse Valley fog  killed 60 people in Belgium owing to a combination of industrial air pollution and climatic conditions in December that year. The River Meuse flows from France through Belgium and the Netherlands before entering the North Sea. The area in the Meuse Valley where the incident occurred is densely populated and has many factories .

9. There were several thousand cases of illness over a period of two or three days and the sixty deaths occurred at the same time. Fifty-six of the deaths were to the east of Engis The main symptom was dyspnea (shortness of breath and the average age of those who died was 62, over a range of ages of 20 to 89 years. Cattle in the area were also affected.

10. Kaj Roholm, Danish scientist and the world's leading authority on fluorine, determined that it was the fluorine gas from the nearby factories that was the killer.  The exact date of this disaster is unknown A statue and plaque commemorating those who died were inaugurated in Engis on 2 nd dec 2000.

11. 1948 Donora smog The  1948 Donora smog  killed 20 people and caused respiratory problems for 6,000 of the 14,000 people living in Donora, Pennsylvania, a mill town on the Monongahela River 24 miles (39 km) southeast of Pittsburgh. The event is commemorated by the Donora Smog Museum.

12. Sixty years later, the incident was described by  The New York Times  as "one of the worst air pollution disasters in the nation's history. Even 10 years after the incident, mortality rates in Donora were significantly higher than those in other communities nearby.

13. MAJOR AIR POLLUTANTS Ammonia (NH 3 ) COx SOx Sulphur dioxide (SO 2 ) NOx Nitric oxide (NO) Nitrogen dioxide (NO 2 ) Ozone (O 3 ) Particulate matter (PM) Volatile organic compounds (VOC) Hydrocarbons Hazardous air pollutants Green house gases

14. Ammonia (NH 3 ) Ammonia is a colourless gas with a pungent odour . Its main source are agricultural processes, particularly in fertilizer production and livestock waste management.  Indoor causes include cigarette smoke and cleaning solutions. Ammonia irritates the eyes, nose, throat, and respiratory tract if inhaled in small amounts due to its corrosive nature and is poisonous in large quantities. It pollutes and contributes to the eutrophication and acidification of terrestrial and aquatic ecosystems. Furthermore, ammonia forms secondary particulate matter (PM 2.5 ) when combined with other pollutants in the atmosphere.

15. Carbon monoxide (CO) Carbon monoxide is a colourless , odourless , and tasteless toxic gas. It is emitted directly from vehicles and combustion engines. Indoors, carbon monoxide is produced by boilers, fireplaces, ovens, cooker hoods, central vacuum systems, tobacco smoke, and propane heaters. Other sources of the gas are power plants, biomass burning, forest fires, and the wood industry. Upon entering the bloodstream, carbon monoxide inhibits the body’s ability to carry oxygen to organs and tissues. As such, extremely high concentrations can cause death. Infants, the elderly, and those with heart and respiratory diseases are particularly susceptible to carbon monoxide poisoning.

16. Nitric oxide (NO) Nitric oxide, also called nitrogen monoxide, is a colourless , toxic gas formed through the combustion processes of coal and petroleum. Main sources include motor vehicles and thermal power plants.  Nitric oxide dissolves in atmospheric water vapour to form acid that damages vegetation, buildings and materials, which contributes to the acidification of terrestrial and aquatic ecosystems. It also combines with VOCs to create ground-level ozone (O 3 ). 

17. Nitrogen dioxide (NO 2 ) Nitrogen dioxide is formed through the oxidation of nitric oxide (NO) from combustion processes such as diesel engines and coal, oil, gas, wood, and waste plants. Nitrogen dioxide has an adverse effect on the respiratory systems of both humans and animals, increasing risks of stroke. Just like nitrogen monoxide, it dissolves in water vapour to create acid rain. Nitrogen dioxide contributes to the formation of ground-level ozone (O 3 ), and forms secondary particulate matter (PM 2.5 ) when combined with other atmospheric compounds such as ammonia.

18. Ozone (O 3 ) Ground-level ozone is a pale blue gas with a pungent smell. It is mainly formed through the photochemical reactions of other pollutants such as nitrogen oxides, carbon monoxide, and volatile organic compounds from strong sunlight and UV radiation. Indoor sources stem from electric motors in household appliances including copiers and laser printers. Ozone is suspected to have carcinogenic effects. It leads to reduced lung function and respiratory diseases, with exposure linked to premature mortality.

19. Apart from its impact on the human body, ozone also damages vegetation, contributing to a decrease in crop productivity and forest decline. Ozone accelerates the deterioration of rubbers, dyes, paints, coatings, and various textiles, and is also a major component of smog.

20. Particulate matter (PM) Particulate matter consists of airborne liquid and solid particles. Primary particulate matter is emitted from a direct source, including power plants, vehicle traffic, construction sites, and indoor stoves and heaters. On the other hand, secondary particulate matter is formed as a result of chemical and physical reactions with various compounds, including sulphur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), and ammonia (NH 3 ). Particulate matter has been linked to cardiovascular and respiratory diseases such as asthma, bronchitis, and emphysema. The extent of health damage caused by particulate matter is determined by the size of the particles.

21. Particles with a mass median diameter of less than 10 microns is called PM 10 , while particles with a mass median diameter of less than 2.5 microns is called PM 2.5 . PM2.5 are also called fine particles. Newer classifications can also include PM 0.1 , so-called ultra-fine particles. The smaller the particle, the higher the health risk, due to their ability to penetrate deep into the respiratory and circulatory systems, causing damage to the lungs, heart, and brain.

22. Sulphur dioxide (SO 2 ) Sulphur dioxide is a toxic gas with a pungent smell. It mainly arises from the combustion and refining processes of coal, oil, and metal-containing ores, but also from transport-related emissions such as shipping. Sulphur dioxide is an irritant, and can cause respiratory diseases in humans and animals. It forms acid rain when dissolved in water, which damages vegetation, buildings and materials, and contributes to the acidification of terrestrial and aquatic ecosystems. Sulphur dioxide also forms secondary particulate matter (PM 2.5 ) when combined with other compounds such as ammonia in the atmosphere.

23. Volatile organic compounds (VOC) Volatile organic compounds refer to a large group of carbon-containing substances including hydrocarbons, alcohols, aldehydes , and organic acids. Outdoor sources include emissions from incomplete combustion processes and volatile industry byproducts. VOCs are particularly concentrated indoors due to internal sources from interior products and building materials such as furniture, plastics, carpets, wallpapers, cleaning materials, lacquers, solvents, and tobacco smoke.  As such, the indoor impact of VOCs has greater health implications since people spend time predominantly in buildings.

24. While individual VOC levels tend to be moderate with no expected health effects, concentrations rise to concerning levels after construction works and renovations. Many individual VOCs have been shown to have toxic, carcinogenic, and mutagenic effects on humans. Symptoms include headaches, fatigue, loss of productivity, sleep disorders, and respiratory diseases, which altogether could be summarized as “Sick Building Syndrome”. The more reactive VOCs combine with nitrogen dioxide (NO 2 ) to form ground-level ozone (O 3 ), and contribute to creating secondary particulate matter (PM 2.5 ) as well . 

25. Hydrocarbons (HC)   These pollutants react with nitrogen oxides in the presence of sunlight to form ground level ozone, a primary ingredient in smog. Though beneficial in the upper atmosphere, at the ground level this gas irritates the respiratory system, causing coughing, choking, and reduced lung capacity. Hazardous air pollutants (toxics).  These chemical compounds have been linked to birth defects, cancer, and other serious illnesses. The Environmental Protection Agency estimates that the air toxics emitted from cars and trucks which include Benzene, acetaldehyde, and 1,3-butadiene account for half of all cancers caused by air pollution .

26. CLASSIFICATION OF AIR POLLUTION

27. Natural and Artificial Primary and Secondary Point and non-point Line and Areal sources Stationary and Mobile

28. 1. Natural and Man-made Natural These include volcanic eruptions, deflation of sand and dust, forest or wild fires of natural vegetation, sulphur springs, natural geysers, organic and inorganic decays, vegetative decays, marsh gases, cosmic dust, pollen grains of flowers, photochemical reactions, soil debris etc. Artificial Man-made sources Example: Deforestation, burning of fossil fuel, emission from vehicles, smokes from industries.

29. 2. Primary and Secondary Pollutants Primary : A primary pollutant is an air pollutant emitted from a source directly into the atmosphere. The source can be either a natural process such as sandstorms and volcanic eruptions or anthropogenic (influenced by humans) such as industrial and vehicle emissions.

30. Examples of primary pollutants are Sulphur dioxide (SO2) Carbon monoxide (CO) Nitrogen oxides (NOX) and Particulate matter (PM).

31. Sulfur dioxide (SO2) Sulfur dioxide is an invisible gas with a strong odor. Its main sources are anthropogenic, resulting from the combustion of fuels and the processing of mineral ores containing sulfur. Humans and animals exposed to sulfur dioxide display severe respiratory problems. Sulfur dioxide can interact with water in the atmosphere to form harmful acid rain.

32. Carbon monoxide (CO) Carbon monoxide is an odorless gas emitted by the incomplete combustion of fuel. The main sources for atmospheric carbon monoxide are gasoline or diesel-powered engines and biomass burning (forest fires and biomass fuels). Carbon monoxide is very toxic and is linked to an increased risk of heart disease. Exposure to high levels of CO may lead to unconsciousness or even death.

33. Nitrogen oxides (NOX) Fossil fuel combustion (gasoline and diesel engines) is the main source for nitrogen oxides in urban areas, while microbial activity in the soil and agricultural practices such as the use of synthetic fertilizers are its main sources in rural areas. Exposure to nitric oxides may cause an inflammation of the respiratory tracts.

34. Particulate matter (PM) Particulate matter is a term referring to solid particles and liquid droplets found in the atmospheric air Primary particles may be natural, originating from soil dust and sea spray. They can be industrial and transportation-related as well when their sources are metallurgical processes or exhausts and tire breaks.

35. Secondary: The pollutants that are formed in the atmosphere by chemical interactions between primary pollutants and atmospheric constituents are known as secondary pollutants.

36. Ground Level Ozone The most important secondary pollutant is the Ground Level Ozone or Tropospheric Ozone.  Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapours , and chemical solvents are some of the major sources of Nox and VOC. Ground Level Ozone forms due to reactions of the NOx, Carbon Monoxide and VOCs in presence of sunlight.

37. Smog Another most important secondary pollutant is the Smog, which has made up of Smoke and Fog. Traditionally, the smog has resulted from large amounts of coal burning in an area caused by a mixture of smoke and sulphur dioxide. Now-a-days, the Vehicle emissions and Industrial emissions that are acted on in the atmosphere by ultraviolet light from the sun to form secondary pollutants that also combine with the primary emissions to form photochemical smog.

38. Fogs:  are formed by a suspension of liquid droplets resulting from the condensation of a vapour, or from a spray. In the atmosphere near the ground, the term fog is used when visibility is reduced to less than 1 kilo- metre . Mists    are made up of smaller droplets or solid particles. They correspond to a lower visibility disorder than fogs, except in exceptional cases of haze in desert or semi-desert regions.

39. Aerosol  is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog or mist, dust, forest exudates, and geyser steam.

40. 3. Point and Non-Point

41. 4. Line and Areal

42. 4. Stationary and Mobile Stationary: This type of pollution has a relatively fixed location Mobile: This type of pollution moves from place to place while emitting pollutants

43. EFFECTS OF AIR POLLUTANTS

44. Effect of air pollution on Man

45. Impact of air pollution on Man Indoor air pollution can be particularly hazardous to health as is released in close proximity to people. It is stated that a pollutant released indoors is many times more likely to reach the lung than that released outdoors. In the developing countries a fairly large portion of the population is dependent on biomass for their energy requirements These include wood, charcoal, agricultural residue, and animal waste. Open fires used for cooking and heating are commonly found in the household both in the rural and the urban areas The stove is often at floor level, adding to the risk of accident and the hygiene factor.

46. In addition, they are often not fitted with a chimney to remove the pollutants. In such house holds the children and women are mostly to be affected, as they are the group that spends more time indoors. The main pollutant in this environment is the SPM. In fact, death due to indoor air pollution, mainly particulate matters, in the rural areas of India are one of the highest in the world Many of the deaths are due to acute respiratory infections in children; others are due to cardiovascular diseases, lung cancer, and chronic respiratory diseases in adults. If emissions are high and ventilation is poor, household use of coal and biomass can severely affect the indoor air quality.

47. Health impact of specific Air Pollutants Tobacco smoke: Tobacco smoke generates a wide range of harmful chemicals and is a major cause of ill health, as it is known to cause cancer. Not only to the smoker but affecting passive smokers too. It is well-known that smoking affects the passive smoker ranging from burning sensation in the eyes or nose, and throat irritation, to cancer, bronchitis, severe asthma, and a decrease in lung function. Biological pollutants: These are mostly allergens that can cause asthma, hay fever, and other allergic diseases.

48. SPM (suspended particulate matter). Suspended matter consists of dust, fumes, mist and smoke. The main chemical component of SPM that is of major concern is lead, others being nickel, arsenic, and those present in diesel exhaust. These particles when breathed in, lodge in our lung tissues and cause lung damage and respiratory problems. The importance of SPM as a major pollutant needs special emphasis as it affects more people globally than anyother pollutant on a continuing basis; b) there is more monitoring data available on this than any other pollutant; and c) more epidemiological evidence has been collected on the exposure to this than to any other pollutant.

49. Volatile organic compounds: Volatile compounds can cause irritation of the eye, nose and throat. In severe cases there may be headaches, nausea, and loss of coordination. In the longer run, some of them are suspected to cause damage to the liver and other parts of the body. Formaldehyde: Exposure causes irritation to the eyes, nose and may cause allergies in some people. Oxides of Nitrogen: This gas can make children susceptible to respiratory diseases in the winters

50. Impact of air pollution on Material

51. Air pollution effects on materials the acid rain and photochemical smog affect metals and buildings. Acid rain pollutes the soil and water sources. Acidic products of the air pollutant cause disintegration of textile, paper. Many small industrial units and sources of locomotive pollutants have been sifted to save the famous marble structure, Taj Mahal at Agra. Hydrogen sulphide decolorizes silver and lead paints. Ozone oxidizes rubber goods.

52. Sulphur dioxide with water produces sulphurous and sulphuric acids that are extremely corrosive. Different metals, such as iron, aluminum and copper are corroded when exposed to contaminated air. Building and other materials are disfigured by deposition of soot. Increase in carbon dioxide concentration increases the temperature of the earth. Depletion of ozone layer due to fluoro carbon of aerosol causes the exposure of U. V. radiation which is lethal.

53. Environmental Pollution Effects on plants

54. Acid rain can kill trees, destroy the leaves of plants, can infiltrate soil by making it unsuitable for purposes of nutrition and habitation. Ozone holes in the upper atmosphere can allow excessive ultraviolet radiation from the sun to enter the Earth causing damage to trees and plants. Ozone in the lower atmosphere can prevent plant respiration by blocking stomata (openings in leaves)and negatively affecting plants’ photosynthesis rates which will stunt plant growth ozone can also decayplant cells directly by entering stomata

55. Air pollution has serious harmful effects on plants. Sulphur dioxide causes chlorosis . It results in the death of cells and tissues. Forest trees are worst affected by sulphur dioxide pollutants. Excessive sulphur dioxides make the cells inactive and finally are killed. At lower concentrations, brownish red colour of leaf, choruses and necrosis take place Fluorides damage leafy vegetables such as lettuce and spinach.

56. Oxides of nitrogen and fluorides reduce crop yields. Photochemical smog bleaches and blazes foliage of plants, Hydrocarbons cause premature fall of leaves and flower buds, discolouration of sepals and curling of petals. Ozone damages cereals, fruits and cotton crops. It also causes premature yellowing and shedding of leaves Air pollution inhibits growth of lichens on trees. Therefore, lichen can serve as indicator of air pollutions.

57. GLOBAL EFFECTS OF AIR POLLUTION

58. GREEN HOUSE EFFECT

59. Definition Greenhouse effect is the process by which radiations from the sun are absorbed by the greenhouse gases and not reflected back into space. This insulates the surface of the earth and prevents it from freezing .

60. Green house gases Greenhouse gases are the gases that absorb the infrared radiations and create a greenhouse effect. For eg ., carbondioxide and chlorofluorocarbons.

61. The major contributors to the greenhouse gases are Factories, Automobiles,  Deforestation, etc. The increased number of factories and automobiles increases the amount of these gases in the atmosphere. The greenhouse gases never let the radiations escape from the earth and increase the surface temperature of the earth. This then leads to global warming.

62. Causes of Greenhouse Effect Burning of Fossil Fuels Fossil fuels are an important part of our lives. They are widely used in transportation and to produce electricity. Burning of fossil fuels releases carbon dioxide. With the increase in population, the utilization of fossil fuels has increased. This has led to an increase in the release of greenhouse gases in the atmosphere.

63. Deforestation Plants and trees take in carbon dioxide and release oxygen. Due to the cutting of trees, there is a considerable increase in the greenhouse gases which increases the earth’s temperature.

64. Farming Nitrous oxide used in fertilizers is one of the contributors to the greenhouse effect in the atmosphere. Industrial Waste and Landfills The industries and factories produce harmful gases which are released in the atmosphere. Landfills also release carbon dioxide and methane that adds to the greenhouse gases.

65. Effects of Greenhouse Effect Global Warming It is the phenomenon of a gradual increase in the average temperature of the Earth’s atmosphere. The main cause for this environmental issue is the increased volumes of greenhouse gases such as carbon dioxide and methane released by the burning of fossil fuels, emissions from the vehicles, industries and other human activities.

66. Depletion of  Ozone Layer Ozone Layer protects the earth from harmful ultraviolet rays from the sun. It is found in the upper regions of the stratosphere. The depletion of the ozone layer results in the entry of the harmful UV rays to the earth’s surface that might lead to skin cancer and can also change the climate drastically. The major cause of this phenomenon is the accumulation of natural greenhouse gases including chlorofluorocarbons, carbon dioxide, methane, etc.

67. Smog and Air Pollution Smog is formed by the combination of smoke and fog. It can be caused both by natural means and man-made activities. In general, smog is generally formed by the accumulation of more greenhouse gases including nitrogen and sulfur oxides. The major contributors to the formation of smog are automobile and industrial emissions, agricultural fires, natural forest fires and the reaction of these chemicals among themselves.

68. Acidification of Water Bodies Increase in the total amount of greenhouse gases in the air has turned most of the world’s water bodies acidic.  The greenhouse gases mix with the rainwater and fall as acid rain. This leads to the acidification of water bodies. Also, the rainwater carries the contaminants along with it and falls into the river, streams and lakes thereby causing their acidification.

69. Runaway Greenhouse Effect This phenomenon occurs when the planet absorbs more radiation than it can radiate back. Thus, the heat lost from the earth’s surface is less and the temperature of the planet keeps rising. Scientists believe that this phenomenon took place on the surface of Venus billions of years ago.

70. This phenomenon is believed to have occurred in the following manner A runaway greenhouse effect arises when the temperature of a planet rises to a level of the boiling point of water. As a result, all the water from the oceans converts into water vapour, which traps more heat coming from the sun and further increases the planet’s temperature. This eventually accelerates the greenhouse effect.

71. HEAT ISLANDS

72. Definition Urbanized area that contains hotter surface and atmospheric temperatures compared to near-by rural areas due to lack of vegetative cooling and increased infrastructure absorption of sun’s heat energy.

73. Causes of Urban heat island

74. Low Albedo Materials According to  Bouyer , Albedo is the ratio of the reflected solar energy to the incident solar energy. It depends on the arrangement of surfaces, materials, pavements, coatings, etc. Albedo has a direct impact on the formation of the microclimate.

75. The albedo of a city varies according to various factors like the surface arrangement, i.e., orientation, heterogeneity, materials for roofs, pavements, etc. If the albedo of the urban surface is low, it will store more solar energy, and the effect will be an increase of urban temperature, i.e., the creation of the urban microclimate.

76. 2. Paved and Impermeable Surfaces Paved over surfaces, such as roads and parking lots, can absorb solar radiation as heat, and these surfaces are typically impermeable, which means that water runoff is redirected to the stormwater system rather than being absorbed by plants or water bodies that help cool the area through evapo -transpiration and evaporation.

77. 3. Thermal Mass Buildings contain a lot of thermal mass, which means they store a lot of heat during the day and are slow to release the heat overnight. 4. Lack of Vegetation Plants and trees provide shade and cool the air through evapo-transpiration. But areas that are dominated by paved surfaces have little room for green space. Forests are wiped out on a massive scale to meet the demand of various urban facilities. Lesser trees mean less cooling efficiency. Trees intercept the solar heat and absorb carbon dioxide for their own photosynthesis to cool the environment. With the destruction of plant life, the efficiency of the cooling system goes radically down, causing the creation of the process.

78. 6. Climate Change The more extreme heat waves in urban areas, mainly in northern regions, are a factor that contributes to urban heat island formation. Urban heat islands also exacerbate the changes in the climate, so the problem feeds on itself.

79. 7. Increased Use of Air Conditioner We use air conditioners massively with a rising trend for comfort. Air conditioners keep a building cool inside but absorb heat from inside, releasing it to the atmosphere. Mechanical air conditioning exhausts heat into the environment around the building, directly adding to the problem. As a result, the outside environment is warmed, leading to increasing atmospheric temperature.

80. 10. Air Pollutants In urban areas, especially in city centers, air pollution is a major issue. Exhaust gases from vehicles, industrial pollutants released in the atmosphere, trap solar radiation, causing an increase in temperature, and the microclimate effect becomes stronger.

81. 11. Human Gathering As human gathering is huge at the city centers owing to the availability of various facilities, the emission of CO2 is also huge in these areas. CO2 stores heat, causing enhanced atmospheric temperature. The ultimate effect is that it assists in the formation of heat island to a great extent.

82. Effects of Urban Heat Island

83. Increased Energy Consumption Increased temperatures during summer in cities amplify energy demand for air conditioning. Studies reveal that electricity demand for air conditioning or cooling increases in the ranges of 1.5 to 2 percent for every 1°F (0.6°C) increase in air temperatures (ranges of 68 to 77°F (20 to 25°C), implying that the community requires about 5 to 10 percent more electricity demand to cater for the urban heat effect.

84. This means the increased demands for cooling or air-conditioning during summer contribute to higher energy bills. Also, during exacerbated periods of urban heat islands, the resulting demand for air conditioning can overload systems, which can lead to power outages and blackouts

85. 2. Elevated Greenhouse Gas Emissions and Air Pollution As explained earlier, urban heat island (UHI) raises electricity demand during summer. As a result, power plants have to supply the needed extra energy, and since they rely on fossil fuel for energy production, there is an increase in greenhouse gas emissions and air pollutants. The main greenhouse gases and pollutants include carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter and Mercury (Hg).

86. Increased greenhouse gases cause global warming and climate change, while the pollutants negatively impact human health as well as the decline of air quality. Sometimes the UHI can also lead to the formation of ground-level ozone and acid rain. Research shows that high UHI correlates with increased levels and accumulation of air pollutants at night, affecting the next day’s air quality.

87. 3. Poses Danger to Aquatic Systems High temperatures within the urban areas mean elevated temperatures for pavements and rooftops. Accordingly, these surface temperatures can heat storm water runoff. Trials have demonstrated that pavements with temperatures of 100°F (38°C) can increase initial rainwater temperately from about 70°F (21°C) to over 95°F (35°C).

88. This heated storm water is the runoff that flows into storm drainage systems and raises water temperatures as it is discharged into ponds, streams, rivers, lakes and oceans, resulting in thermal pollution. As a result, the increased water temperature affects the aquatic system, especially the reproduction and metabolism of aquatic species and can be even fatal to aquatic life.

89. 4. Discomfort and Danger to Human Health Higher air pollution reduced nighttime cooling, and increased temperatures as outcomes of urban heat island can adversely affect human health. Human health is negatively impacted because of increased general discomfort, exhaustion, heat-related mortality, respiratory problems, headaches, heat stroke and heat cramps.

90. Because urban heat islands can also worsen the impacts of heat waves, abnormal weather periods can arise, which can seriously affect the health of sensitive and vulnerable populations such as older adults, children, and those with weather-responsive health conditions.

91. Exacerbated heat events or sudden temperature increases can result in higher mortality rates. Research by the Center for Disease Control and Prevention indicates that between 1997 and 2003, more than 8,000 premature deaths were registered in the United States owing to excessive exposure to heat.

92. 5. Secondary Impacts on Weather and Climate Besides the high-temperature increases, urban heat island (UHIs) can bring forth secondary effects on the local weather and climate. This includes changes in local wind patterns, the formation of fog and clouds, precipitation rates and humidity. The unusual heat caused by UHI contributes to a more intense upward wind movement that can stimulate thunderstorm and precipitation activity.

93. Furthermore, urban heat island (UHI) creates a local low-pressure area where cool air from its adjacent areas converges that induces the formation of clouds and rain. This increases the total rainfall rates within cities. These changes may impact growing seasons within cities, especially by prolonging the growth of plants and crops.

94. 6. Impacts on Animals Most species need optimum temperatures to colonize, utilize and thrive in their ecosystems. When there is the existence of high temperatures due to urban heat island (UHI), harsh and cruel ecological surrounding is created which limits the essential activities of the organisms such as metabolism, breeding and reproduction.

95. Adverse heat can also significantly reduce the availability of food, shelter, and water. The temperature changes may also make the cities more suitable for survival compared to the wilderness, which may attract wild animals into the cities. An example is the Grey-headed flying foxes in Melbourne Australia, which colonized urban habitats following an increase in temperatures there.

96. Besides, the urban heat island (UHI) can equally alter the natural selection process, causing a counterbalance of a new set of selective forces. For instance, the number of insects may be more in urban areas than the rural areas since most of them depend on environmental temperatures to control their body temperatures. Hence, moving to the city is just right for their survival.

97. Solutions to Urban Heat Island

98. Use of Light-colored Concrete and White Roofs The use of light-colored concrete and white roofs has been found to be effective in reflecting up to 50% more light and in cutting down the ambient temperature. These strategies have been shown to offer great solutions in reducing the urban health island effect. Black and dull colors absorb copious amounts of solar heat, resulting in warmer surfaces. The use of light-colored concrete and white roofs can as well reduce the overall air conditioning demands.

99. 2. Green Roofs and Vegetation Cover Green roofs present a great method of lessening the impacts of urban heat islands. Green roofing is the practice of planting vegetation on a roof, just like they are planted in a garden. Plants on the roof are excellent insulators during summer and decrease the overall urban heat island effect. Plants also cool the surrounding environments, thereby reducing air conditioning demands.

100. Furthermore, air quality is improved as the plants absorb carbon dioxide and produce fresh air. Other practices that can be used include open space planting, street trees and curbside planting. All these practices produce a cooling effect within the urban areas and lower the costs of temperature reduction.

101. 3. Planting Trees in Cities The practice of tree planting within and around cities is an incredible way of reflecting solar radiation while at the same time decreasing the urban heat island effect.  Trees provide shade, absorb carbon dioxide, release oxygen and fresh air, and provide a cooling effect.  Deciduous trees are the best for urban areas because they provide a cooling effect in summer, and they don’t block warmth during winter.

102. 4. Green Parking Lots Green parking spaces utilize green infrastructure strategies to limit the impacts of urban heat island effect. In precise, it cushions against the elevation of pavement temperatures which can considerably prevent thermal pollution resulting from storm water runoff. With this in place, the danger posed to aquatic systems is reduced.

103. 5. Implementation and Sensitization of Heat Reduction Policies and Rules The state implementation of environmental policies such as the Clean Air Act, Low carbon fuel standards, uses of renewable energy, and clean car rule standards can impressively regulate the anthropogenic inducers of urban heat island effect.

104. With fewer emissions, the level of greenhouse gases in the atmosphere can be reduced, thus decreasing the effects of climate change and global warming. Education and outreach can also be done to ensure communities are aware of the economic and social benefits of planting trees and eco-roofing.

105. ACID RAINS

106. Definition Acid rain, or acid deposition, is a broad term that includes any form of precipitation that contains acidic components, such as sulfuric acid or nitric acid. The precipitation is not necessarily wet or liquid; the definition includes dust, gases, rain, snow, fog and hail. The type of acid rain that contains water is called wet deposition. Acid rain formed with dust or gases is called dry deposition.

107. CAUSES OF ACID RAIN

108. Man-made or Anthropogenic Causes of Acid Rain

109. Human activities leading to chemical gas emissions such as sulfur and nitrogen are the primary contributors to acid rain. Factories, power generations facilities, and automobiles are the chief emitters of sulfur and nitrogen gases. Use of coal for electrical power generation is the biggest contributor to gaseous emissions leading to acid rain.

110. Automobiles and factories also release high scores of gaseous emissions on a daily basis into the air, especially in highly industrialized areas and urban regions with large numbers of car traffic. As a result, these areas experience exceedingly high amounts of acid rain. Let’s look at the details.

111. Combustion of coal and oil As stated earlier, the principal emissions accountable for acidic depositions in the atmosphere are oxides of nitrogen (NOx) and sulfur dioxide (SO2). Combusting coal and oil emit loads of these gases into the atmosphere. Once in the atmosphere, these compounds react with atmospheric water molecules in the presence of sunlight to form mild sulfuric and nitric acids.

112. Coal and oil are burned to produce energy to power machinery and are also used for heating, cooking, and lighting. The bottom line is, combustion of these substances releases the core gases responsible for the formation of acid rain.

113. 2. Power plants and manufacturing industries Contemporary power plants use fuel to generate energy. In the process of energy generation and combustions, sulfur dioxide and nitrogen oxide gases are released into the atmosphere. Manufacturing industries that manufacture cement, refine petroleum, process plastics, produce chemical products and pharmaceuticals or those that produce metals such as steel and aluminum release scores of NOx and SO2 gases into the atmosphere.

114. A much as these industries use technologies to reduce the emission of NOx and SO2 gases, the pollutants are released in small amounts but continuously for prolonged time periods eventually leading to the formation of acid rain.

115. 3. Automobiles and other vehicles Another main source of NOx and SO2 emissions are the fuel combustion of trucks, cars, airplanes, and buses. These automobiles release high levels of sulfur and nitrogen gaseous emissions on a daily basis into the atmosphere, mainly in highly industrialized areas and urban areas with large numbers of car traffic. Accordingly, these areas usually experience substantial amounts of acid rains.

116. The sulfur and nitrogen emissions can also be blown to other regions leading to acid rain formation in other areas away from the emission sources. For instance, it is believed the acid rain in Sweden is influenced by air pollution in Britain.

117. Natural causes of Acid Rain

118. Natural causes of acid rain are relatively small compared to those from anthropogenic sources as discussed above. The following are the most common natural causes of acid rain. Volcanic eruptions:   The main natural causal agent for acid rain is volcanic emissions. Volcanoes emit acid-producing gases, mainly sulfur, to create higher than normal amounts of acid rain or any other form of precipitation such as fog or snow to an extent of affecting vegetation cover and health of residents within the surrounding.

119. Decaying vegetation, wildfires, and biological processes:  Decaying vegetation, wildfires, and biological processes within the environment also generate the acid rain forming gases. Dimethyl sulfide is a typical example of a major biological contributor to sulfur-containing elements into the atmosphere.

120. Lightning:  Lightning strikes naturally produce nitric oxides that react with water molecules via electrical activity to produce nitric acid, thereby forming acid rain. Lightning is the major natural source of NOx.

121. OZONE HOLES

122. Definition The ozone layer is a region in the earth’s stratosphere that contains high concentrations of ozone and protects the earth from the harmful ultraviolet radiations of the sun

123. What is an Ozone Layer ?

124. The ozone layer is mainly found in the lower portion of the earth’s atmosphere. It has the potential to absorb around 97-99% of the harmful ultraviolet radiations coming from the sun that can damage life on earth. If the ozone layer was absent, millions of people would develop skin diseases and may have weakened immune systems.

125. However, scientists have discovered a hole in the ozone layer over Antarctica. This has focussed their concern on various environmental issues and steps to control them. The main reasons for the ozone hole are chlorofluorocarbons, carbon tetrachloride, methyl bromide and hydrochloro fluorocarbons.

126. Ozone Layer Depletion Ozone layer depletion is the gradual thinning of the earth’s ozone layer in the upper atmosphere caused due to the release of  chemical compounds containing gaseous bromine or chlorine from industries or other human activities

127. What is Ozone Layer Depletion?

128. Ozone layer depletion is the thinning of the ozone layer present in the upper atmosphere. This happens when the chlorine and bromine atoms in the atmosphere come in contact with ozone and destroy the ozone molecules. One chlorine can destroy 100,000 molecules of ozone. It is destroyed more quickly than it is created. Some compounds release chlorine and bromine on exposure to high ultraviolet light, which then contributes to ozone layer depletion. Such compounds are known as Ozone Depleting Substances (ODS).

129. The ozone-depleting substances that contain chlorine include chlorofluorocarbon, carbon tetrachloride, hydrochlorofluorocarbons , and methyl chloroform. Whereas, the ozone-depleting substances that contain bromine are halons , methyl bromide, and hydro bromofluorocarbons . Chlorofluorocarbons are the most abundant ozone-depleting substance. It is only when the chlorine atom reacts with some other molecule, it does not react with ozone. Montreal Protocol was proposed in 1987 to stop the use, production and import of ozone-depleting substances and minimise their concentration in the atmosphere to protect the ozone layer of the earth.

130. Causes of Ozone Layer Depletion

131. Ozone layer depletion is a major concern and is associated with a number of factors. The main causes responsible for the depletion of the ozone layer are listed below: Chlorofluorocarbons Chlorofluorocarbons or CFCs are the main cause of ozone layer depletion. These are released by solvents, spray aerosols, refrigerators, air-conditioners, etc. The molecules of chlorofluorocarbons in the stratosphere are broken down by ultraviolet radiations and release chlorine atoms. These atoms react with ozone and destroy it.

132. Unregulated Rocket Launches Researches say that the unregulated launching of rockets results in much more depletion of the ozone layer than the CFCs do. If not controlled, this might result in a huge loss of the ozone layer by the year 2050.

133. Nitrogenous Compounds The nitrogenous compounds such as NO 2 , NO, N 2 O are highly responsible for the depletion of the ozone layer.

134. Natural Causes The ozone layer has been found to be depleted by certain natural processes such as Sun-spots and stratospheric winds. But it does not cause more than 1-2% of the ozone layer depletion. The volcanic eruptions are also responsible for the depletion of the ozone layer.

135. Ozone Depleting Substances (ODS) Ozone-depleting substances are the substances such as chlorofluorocarbons, halons , carbon tetrachloride, hydrofluorocarbons , etc. that are responsible for the depletion of the ozone layer.

136. Following is the list of some main ozone-depleting substances and the sources from where they are released:

137. Effects Of Ozone Layer Depletion

138. The depletion of the ozone layer has harmful effects on the environment. Let us see the major effects of ozone layer depletion on man and environment. Effects on Human Health Humans will be directly exposed to the harmful ultraviolet radiation of the sun due to the depletion of the ozone layer. This might result in serious health issues among humans, such as skin diseases, cancer, sunburns, cataract, quick ageing and weak immune system. Effects on Animals Direct exposure to ultraviolet radiations leads to skin and eye cancer in animals.

139. Effects on the Environment Strong ultraviolet rays may lead to minimal growth, flowering and photosynthesis in plants. The forests also have to bear the harmful effects of the ultraviolet rays. Effects on Marine Life Planktons are greatly affected by the exposure to harmful ultraviolet rays. These are higher in the aquatic food chain. If the planktons are destroyed, the organisms present in the food chain are also affected.

140. Solutions to Ozone Layer Depletion

141. The depletion of the ozone layer is a serious issue and various programmes have been launched by the government of various countries to prevent it. However, steps should be taken at the individual level as well to prevent the depletion of the ozone la Following are some points that would help in preventing this problem at a global level Avoid Using ODS Reduce the use of ozone depleting substances. E.g. avoid the use of CFCs in refrigerators and air conditioners, replacing the halon based fire extinguishers, etc.

142. Minimize the Use of Vehicles The vehicles emit a large amount of greenhouse gases that lead to global warming as well as ozone depletion. Therefore, the use of vehicles should be minimized as much as possible. Use Eco-friendly Cleaning Products Most of the cleaning products have chlorine and bromine releasing chemicals that find a way into the atmosphere and affect the ozone layer. These should be substituted with natural products to protect the environment.

143. Use of Nitrous Oxide should be Prohibited The government should take actions and prohibit the use of harmful nitrous oxide that is adversely affecting the ozone layer. People should be made aware of the harmful effects of nitrous oxide and the products emitting the gas so that its use is minimized at the individual level as well.