Global Warming

1. Global Warming

2. Global Warming problems

3. Ozone depletion • Ozone is a pale blue gas made up of oxygen and it has a strong odor. • Ninety percent of all atmospheric ozone is found in the stratosphere, the layer of the atmosphere from 15 to 50 km above the earth. Most of the upper level ozone is concentrated about 25 km from the planets surface in the "ozone layer". • Ozone is extremely important to all forms of life on Earth as it is the only gas that absorbs lethal ultraviolet radiation from the Sun.

4. Ozone depletion • Theozone depletion process begins whenChlorofluorocarbon CFCs and otherozone-depleting substances (ODS) such as halogens, methyl bromide, carbon tetrachloride, and methyl chloroform. leak from equipment (1).

5. Ozone depletion • Winds efficiently mix thetroposphere and evenly distribute the gases. • CFCs are extremely stable, and they do not dissolve in rain. • After a period of several years, ODS molecules reach thestratosphere, about 10 kilometers above the Earth's surface • StrongUV light breaks apart the ODS molecule. • CFCs release chlorine atoms, andhalons release bromine atoms. • These atoms that actually destroy ozone, not the intact ODS molecule. It is estimated that one chlorine atom can destroy over 100,000 ozone atoms before finally being removed from the stratosphere • Ozone is constantly being produced and destroyed in a natural cycle.

6. Ozone depletion • However, the overall amount of ozone is essentially stable.This was the situation until the past several decades. • Large increases in stratospheric chlorine and bromine, however, have upset that balance. • In effect, they have added a siphon downstream, removing ozone faster than natural ozone creation reactions can keep up. Therefore, ozone levels fall. • Since ozone filters out harmfulUVB radiation, less ozone means higher UVB levels at the surface. The more depletion, the larger the increase in incoming UVB • UVB has been linked to skin cancer, cataracts, damage to materials like plastics, and harm to certain crops and marine organisms. Although some UVB reaches the surface even without ozone depletion, its harmful effects will increase as a result of this problem

7. Acid Rain • Acid rain" is referring to a mixture of wet and dry deposition (deposited material) from the atmosphere containing higher than normal amounts of nitric and sulfuric acids. • The acid rain formation result from both natural sources, such as volcanoes and decaying vegetation, and man-made sources, primarily emissions of sulfur dioxide (SO2) and nitrogen oxides (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 result is a mild solution of sulfuric acid and nitric acid.

8. Effects of Acid rains • Acid rain causes acidification of lakes and streams and contributes to the damage of trees at high elevations and many sensitive forest soils. • Acid rain accelerates the decay of building materials and paints, including irreplaceable buildings, statues, and sculptures that are part of our nation's cultural heritage. • Prior to falling to the earth, sulfur dioxide (SO2) and nitrogen oxide (NOx) gases and their particulate matter derivatives—sulfates and nitrates—contribute to visibility degradation and harm public health.

9. Sources of air pollutants • Air pollution comes from a wide variety of sources that are usually classified into three groups: • Mobile • area • point sources. • line sources • Volume sources

10. Sources of air pollutants • Mobile sources (like cars and trucks) are responsible for about 75% of carbon monoxide pollution, and for more nitrogen oxide and volatile organic compound emissions than area or point sources. • Area sources (like small businesses) are responsible for over 50% of particulate matter emissions and for nearly half of all volatile organic compound emissions. • Point sources (like power plants and industrial factories) account for nearly 90% of sulfur dioxide emissions. See Scorecard'snational summary of criteria air pollution emissions.

11. Sources of air pollutants • Volume source is a three-dimensional source of diffuse air pollutant emissions. Essentially, it is an area source with a third (height) dimension (for example, the fugitive gaseous emissions frompipingflanges, valves and other equipment at various heights within industrial facilities such asoil refineries andpetrochemical plants). Another example would be the emissions from an automobile paint shop with multiple roof vents or multiple open windows. • Line sources is one-dimensional source of air pollutant emissions (for example, the emissions from the vehicular traffic on a roadway).

12. Mobile sources • Mobile sources include both on road vehicles (such as cars, trucks and buses) and off road equipment (such as ships, airplanes, agricultural and construction equipment). • Mobile sources contribute significantly to air pollution. Driving a car is probably a person's single most polluting daily activity. Nationwide, mobile sources are responsible for about 75% of carbon monoxide pollution, and more oxides of nitrogen emissions than area or point sources.

13. Mobile sources • In urban areas, the motor vehicle contribution to carbon monoxide pollution can exceed 90 percent. • In a typical urban area, at least half of the hydrocarbon and nitrogen oxide pollutants come from mobile sources. Motor vehicles are also substantial sources of hazardous air pollutants, such as the recognized carcinogens benzene, formaldehyde, acetaldehyde, 1,3-butadiene and diesel particulate matter.

14. Point Sources • Point sources include major industrial facilities like chemical plants, steel mills, oil refineries, power plants, and hazardous waste incinerators. Point sources are defined as those that emit 10 tons per year of any of the criteria pollutants or hazardous air pollutants or 25 tons per year of a mixture of air toxics.

15. Point Sources • Nationwide, point sources like power plants, petroleum refineries, fertilizer manufacturers, industrial paper mills, copper smelters and iron and steel mills contribute the majority of sulfur dioxide emissions, accounting for nearly 90% of this criteria air pollutant. Point sources (predominantly electrical utilities and industrial boilers) are also major emitters of nitrogen oxides (NOx) - accounting for about 40% of total releases. • Point sources are less important sources of VOCs - releasing less than 15% of total volatile organic compounds

16. Area sources • Area sources include small pollution sources like dry cleaners, gas stations, and auto body paint shops. • Area sources are defined as sources that emit less than 10 tons per year of a criteria or hazardous air pollutant or less than 25 tons per year of a combination of pollutants. • The category also includes commercial buildings (heating and cooling units; surface coatings), residential buildings (fire places; surface coatings), fuel combustion in non-road machinery, boats, railroads, and even the family lawnmower or barbecue grill.

17. Area sources • Waste disposal in the form of open burning, landfills and wastewater treatment are significant area sources. • Though emissions from individual area sources are relatively small, collectively their emissions can be of concern - particularly where large numbers of sources are located in heavily populated areas. • Area sources are responsible for over 50% of particulate matter emissions and more than point or mobile sources for volatile organic compound (VOC) emissions, which contribute significantly to the formation of ground-level ozone.