Presentation on photochemical smog (1) final.pptx

Photo chemical smog, causes and effects

1. Photochemical smog Acid rain its Theory and Adverse Effects Chlorofluorocarbons and its Effects Represented To: Mam Saima Shehzadi Represented By: Rabia Batool (Roll No: 14) Sundas Shehzadi ( Roll No:17)

2. What is Photochemical Smog? Photochemical smog : is a type of smog produced when ultraviolet light from the sun reacts with nitrogen oxides in the atmosphere. It is visible as a brown haze, and is most prominent during the morning and afternoon. Photochemical Smog can also be defined as a mixture of various gases with dust particules .

3. How is Photochemical S mog F ormed? 1) Nitrogen dioxide (NO₂) can be broken down by sunlight to form nitric oxide (NO) and an oxygenradical (O): NO2 + sunlight → NO + ( O ) 2) Oxygen radicals can then react with atmospheric oxygen (O₂) to form ozone (O3). ( O) + O2 → O3 3) O zone is consumed by nitric oxide to produce nitrogen dioxide and oxygen . O3 + NO → No2 + O2 4) Harmful products, such as PAN, are produced by reactions of nitrogen dioxide with various hydrocarbons (R), which are compounds made from carbon, hydrogen and other substances: NO₂ + R → products ( such as PAN )

4. 5) The main source of these hydrocarbons is the VOCs. Similarly, oxygenated organic and inorganic compounds (RO) react with nitric oxide to produce more nitrogen oxides

5. Types of pollutants Causing Photo-chemical Smog Primary pollutants : The two major primary pollutants, nitrogen oxides and VOCs, combine to change in sunlight in a series of chemical reactions, to create what are known as secondary pollutants. Secondary pollutants: The secondary pollutant that causes the most concern is t h e ozone that forms at ground level. While ozone is produced naturally in the upper atmosphere, it is a dangerous substance when found at ground level. Many other hazardous substances are also formed, such as peroxyacetyl Nitrate (PAN).

6. Sources of photochemical Smog 1)Biogenic Sources: I n nature, bushfires, lightning and the microbial processes that occur in soil generate nitrogen oxides. VOCs are produced from the evaporation of naturally occurring compounds, such as terpenes, which are the hydrocarbons in oils that make them burn. Eucalypts have also been found to release significant amounts of these compounds. 2) Anthropogenic S ources : Nitrogen oxides are produced mainly from the combustion of fossil fuels, particularly in powerstations and motor vehicles. VOCs are formed from the incomplete combustion of fossil fuels, from the evaporation of solvents and fuels, and from burning plant matte r such as backyard burning and wood b urning stoves. In Adelaide in 2000, an estimated 66% of nitrogen oxides (NO and NO₂) came from motor vehicles, and a further 20% from fuel combustion. Motor vehicles contributed 44% of VOC emissions .

7. Effects of photochemical smog: Effects on Environment: Photochemical smog has devastating effects on the environment. The collection of chemicals found in photochemical smog causes problems for plants and animal life.

8. 2.Effect on plants Deposition of particulate matter containing toxic metals affects the growth of plants. The particulate matter after deposition in plants leaves block stomata opening of plants and reduce growth. De crease the pH of the soil which makes the soil infertile. Can lead to extensive damage to crops, trees.and vegetation. Some plants such as tobacco, tomato and spinach are highly responsive to ozone, so photochemical smog can decimate these sensitive crops, trees and other vegetation.

9. Brown Necrotic leaves Brown Necrotic leaves: Ozone causes necrotic (dead) patterns on the upper surfaces of the leaves of trees. Ground-level ozone also can interfere with the growth and productivity of trees.

10. It can cause anything from minor pain to deadly diseases such as lung cancer ,wheezing. High levels of smog also trigger asthma attacks because the smog causes increased sensitivity to allergens, which are triggers for asthma. 3.Effects On Human Health

11. Precautions To Reduce photochemical Smog Take precautionary steps to safeguard against the ill effects of photochemical smog. Keep your motor vehicle regularly serviced .Reduce your daily pollutant emissions by driving less, making use of carpools . Other small actions, such as tightly sealing the lids of chemical products like garden chemicals, solvents, and household cleaners. Use energy efficient appliances and Look for the Energy Star logo when buying an electricical Appliances. I f renovating or building s use energy-efficient designs and materials. Turn off unnecessary electrical appliances. Limit your wood fires at home.

12. What is Acid Rain? Introduction To A cid Ra in : Normal rain water is always slightly acidic because CO₂ present in atmosphere and get dissolved in it form carbonic acid. H₂O (1) + CO₂ (g) ⇒ H₂ CO3 (aq) Carbonic acid then can ionize in water forming low concentrations of carbonate and hydronium ions . H₂O (1) + H₂CO3 (aq) ⇒ HCO3 (aq) + H30+ (aq) Unpolluted rain can also contain other chemicals which affect its pH (acidity level) . The pH of rain is further lowered to as this type of Precipitation is called as ACID RAIN. Acid rain is the combination of H₂SO4, HNO3 and HCI

13. Types of Acid Rain 1)Wet Deposition 2) Dry Deposition 1) Wet Deposition : This type of deposition occurs when any form of condensation removes acids from the environment, leading to acidic deposition on the earth's surface. 2) Dry Deposition : This type of deposition occurs when polluted particles and gases begin to stick to the surface of the earth through smoke and dust in the absence of precipitation.Wet deposition is more dangerous than dry deposition, as it washes all the pollutants, and carries it to the lakes and rivers.

14. Causes Of Acid Rain NATURAL CAUSES : Volcanic E missions Biological processes Lightning Anthropogenic Causes : Factories (industrialization) Motor vehicles, A utomobile Ex haust Coal based power plants Domestic fires Smelters

15. Theory of Acid Rain ROBERT ANGUS SMITH : The phrase acid rain was first used in 1852 by Scottish chemist Robert Angus Smith during his investigation of rainwater chemistry near industrial ci ty Manchester in England and Scotland. The phenomenon became an important part of his book Air and Rain T he Beginnings of a Chemical Climatology . ROBERT ANGUS SMITH was first to show relation between acid rain & atmosphere pollution . Term acid rain was generated by SMITH in 1 8 72. Father of acid rain. The earliest report about acid rain in the United States came from chemical evidence gathered from Hubbard Brook Valley public awareness of acid rain in the US increased in the 1970s.

16. Sundas shahzadi Roll number 17 Effects of Acid Rain

17. Effects on trees The needles and leaves of the trees turn brown and fall off. Trees can also suffer from stunted growth; and have damaged bark and leaves, which makes them vulnerable to weather. Direct contact between trees and acid rain but it also happens when trees absorb soil water that has come into contact with acid rain. The soil poisons the tree with toxic substances that the rain has deposited into it.

18. Effects on plants Causing brown necrosis of plants and trees causing the yellowing of Leaf tissue (chlorosis) Direct effect on plants growth due to toxifIcation of soil. It takes away soil nutrients causing stunted growth. Block stomatal pores of leaves. Biochemical reactions dominated by pH are effected. Degradation of chlorophyll in plants.

19. Effects on vegetation Leaches nutrients from soil, slowing plant growth. increase acidity in soil. Leach out toxins from the soil , poisoning plants. impeding photosynthesis allows organisms to infect through broken leaves.

20. In the US many Coal burning power plants use flue gas desulfurization to remove sulphur containing gases from their stack gas.An example of FGD is wet scrubber.Wet scrubber is basically a reaction tower equipped with a fan that extract hot smoke stack gases from a power plant into the tower. Limestone is also injected into the tower to mix with stack gases and combine with the Sulphur Dioxide present, the calcium carbonate of the limestone produces pH neutral calcium sulphate that is physically removed from the scrubber, that is how the scrubber turns sulphur pollution into industrial sulphates. PREVENTION METHODS TECHNICAL SOLUTION

21. CHLOROFHLOROCARBONS AND THEIR EFFECTS Introduction: A chlorofluorocarbon (CFC) is an organic compound that contains only carbon, chlorine, and fluorine, produced as a volatile derivative of methane, ethane, and propane. The Chlorofluorocarbons (CFCs) are man-made chemicals that exist as gases or liquids. Thy are non-toxic & non-flammable in nature.

22. SOURCES OF CHLOROFHLOROCARBONS They do not occur naturally, they are always manufactured. The most common source of CFCs are refrigerants but fire suppression system for aircrafts and aerosol also emit CFC into the atmosphere. Aerosol cans are also a source of CFC, as CFC are used as propellants in these cans. Halons that are used in protection system, are also a source of CFC.

23. EFFECTS OF CHLOROFHLOROCARBONS Chlorofluorocarbons have these major effects on atmosphere. 1. Greenhouse effect : CFCs are greenhouse gases Absorb heat in the atmosphere, sending some of the absorbed heat back to the surface of the earth Contribute to global warming and climate change 2. Ozone-depletion effect : UV radiation in stratosphere causes CFC molecules to dissociate into free radicals that contains one or more unpaired electrons. Thus contributing to the thinning of the protective ozone layer.