1.Air pollution Prashant Mehta Assistant Professor, National Law University, Jodhpur

2. Composition: Nitrogen and Oxygen "Minor" Gases (% by volume) Carbon Dioxide 0.036 - Greenhouse Gas Methane 0.00014 - Greenhouse Gas Ozone (variable) - Absorbs UV; eye and respiratory irritant; damages plants Water vapor (variable) - Greenhouse Gas; absorbs long-wave radiation Particulates (variable) - Absorbs long-wave or reflects short-wave radiation; condensation nuclei. 3. Atmosphere temperature and Chemistry is controlled by Trace Gases. Substances in the Lithosphere tend to become more reduced over time. Thus biomass (CH2O) is slowly transformed through multiple steps to substance containing no oxygen atoms and then to compounds with large Carbon to Hydrogen ratio and then finally pure Carbon. Gravity prevents the gas molecules to escape from planet. Point Source (Stationary) Industry Non Point Source (Mobile) Transportation Vehicles 4. The trace atmospheric constituents that are present in unexpectedly high concentration or in concentrations which cause some detrimental effect are called air pollutants. Air Pollution occurs when substances are released into air by human activities in such concentrations as are sufficient to cause detrimental effect on human health, vegetation, animals, and property or interferes with the biosphere impacting the mankind. contamination of the air by noxious gases and minute particles of solid and liquid matter (particulates) in concentrations that endanger health Air pollution only occurs outdoors 5. 1. Man Mad (1) Industrial / Manufacturing. (2) Mining / Metallurgical (3) Transport etc. 2. Natural activities (1) Biodegradation (2) Volcanoes or anthropogenic activities 3. Combustion of gasoline and other hydrocarbon fuels in cars, trucks, and airplanes Burning of fossil fuels (oil, coal, petro chemicals) Insecticides Herbicides Everyday radioactive fallouts Dust from fertilizers Livestock feedlots 6. These occur when: the rate of emission or formation of pollutants is greater than (>)the rate of dispersion. Pollutants are dispersed through chemical destruction or removal by winds or vertical transport via physical processes. London smog/Bhopal disaster are examples of this type of sever air pollution . URBAN AIR POLLUTION Major Cause Massive growth in size of cities, exponential growth in human population, and rapidly growing number of automobiles especially diesel vehicles. 7. 1. PRIMARY POLLUTANTS 2. SECONDARY POLLUTANTS These are directly released /injected in the atmosphere. Sulfur Dioxide Nitrogen Oxides Hydrocarbons Carbon Monoxide Ground Level Ozone Carbon Dioxide, CFCs Volatile Organic Compounds These pollutants are formed in the atmosphere through chemical reactions: Ground Level Ozone Photochemical Smog Organic Compounds 8. 1. Primary Aerosol These are directly released in the air Soil particles Fly ash Smoke 2. Secondary Aerosols These are formed in air via gas to particle conversion Sulfate aerosols Nitrate aerosols Carbonaceous aerosols 9. 1. BIOLOGICAL Seeds, Pollens Spores Hair Fragments of Plants/Animals/Insects Bacteria Fungi Microorganisms Algae Protozoa Viruses etc. 10. 2. GEOCHEMICAL Directly released due to: Mining Volcanic eruptions Crushing Blasting Dispersion of dust through wind/human activities 3. OCEANIC Ocean is big source of marine salt (NaCl) 11. 4.ANTHROPOGENIC Fossil fuel combustion Biomass burning Industrial activities Metallurgical processes Cement manufacture Automobiles, etc 5. OIHER SOURCES Forest fires Meteoritic debris 12. 1. Inorganic Aerosols These are inorganic compounds, Soluble: Salts like sodium chloride, Ammonium sulfate, and Insoluble: Minerals etc. 2. Organic Aerosols Made up of organic compounds, Carbonaceous particles, Polycyclic Organic Compounds and Aromatic Hydrocarbons 13. Creation of heat islands due to waste heat Lower average wind speeds Increase in fog frequency Changes in vertical structure of the lower boundary layer Formation of meso-scale circulation systems Temperature polarization Particulate Increase Less Vegetation 14. It affects urban temperature , moisture content and formation of secondary pollutants. It is unique to urban environment due to dense network of sources. Automobile/Transportation Exhausts Industrial Emissions Power Plant Plumes Domestic Heating/Cooking Air-conditioning Excess heat stored in buildings/other structures Lack of Plant Cover / Rapid Deforestation 15. Carbon Monoxide Due to incomplete combustion of fuel. Correct air to fuel ratio is 14:6 If the mixture is rich(more fuel), there is insufficient oxygen to completely oxidize hydrocarbons to carbon dioxide. It causes oxygen deficiency by combining with hemoglobin to form carboxy- hemoglobin, which is formed 250 times more than the oxy- hemoglobin. Un-burnt Hydrocarbons Released by Exhaust Emissions, Evaporative Losses from Fuel Tank. These major sources of Toxic and Carcinogenic, Polycyclic hydrocarbons and Volatile Organic Compounds 16. Odor Due to partial oxidation of hydrocarbons into aldehydes. Smoke / Soot In diesel vehicles the emission of soot/smoke is most visible. It is formed due to incomplete oxidation of carbon. The soot particles are polymeric substances having carbon chains Due to free valence the soot particles have sticking property. Nitrogen oxides High temperature of the combustion engine leads to the formation of Nox 17. Petrol Engines release large amounts of CO Diesel engines release large amounts of NOx, Smoke, Particulate, and Odor. Control Measures Proper Maintenance of the Engine Petrol Tank must be full to control evaporative losses. Catalytic converter / Fuel Injection system must be used. Blending fuels with bio-fuels 18. The Earths Atmosphere is Basically Oxidizing in Nature. The Major Oxidant is Oxygen(21%) and Mostly Oxygen- Based Compounds and Oxy Radicals Other Oxidants are Cl2 - CO is removed by Atmospheric Oxygen Reactions are very slow at ambient conditions All reactions in atmospheric chemistry are photochemistry based as sun provide major source of energy. All reactions are cyclic in nature that is they repeat indefinitely. 19. These are: Ozone Hydrogen Peroxide OH radical HO2 Radical NO3 Radical SO4 - Radical Organic Peroxy Radicals 20. The hydroxyl radical (OH) dominates the daytime oxidation chemistry in the troposphere, controlling the atmospheric lifetime of the majority of trace species that are emitted natural or via man's activities. OH is primarily produced by the photolysis of ozone to form O(1D) followed by reaction with H2O. It is the primary daytime oxidising species responsible for the removal of CO, CH4 (and higher hydrocarbons), H2, NO2, H2S, (CH3)2S, NH3, the hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). The concentration of OH defines the oxidising capacity of the atmosphere and hence the ability to control levels of species that contribute to global warming, acid rain or photochemical smog. Intermediate peroxy radicals, of which HO2 is the simplest, are generated during the oxidation of trace gases and a fast photochemical cycle links these radicals with OH. 21. 1. Is the gas water soluble or fully oxidised (If Yes) Gas Eventually returns to earth surface. If No 1. Does the Gas photo-decompose in sunlight (If Yes) Free Radicals are produced. If No 1. Does Gas molecule have multiple bonds to with OH* can add to (If Yes) Free Radicals are produced. If No 1. Does gas molecules have an H that OH* can abstract in exothermic reaction (If Yes) Free Radical is produced 22. First step in photochemical reaction: XY + h XY* absorption Then: XY* X + Y decomposition or XY* + other reactants (can be toxic) products formed can be toxic E.g. NO2 +h NO + O (generate ozone) 23. Homolysis (Breakdown) of covalent bonds lead to the production of free radicals: Cl:Cl 2Cl* Radicals normally take part in so-called chain reactions and the following steps are involved: 1. Initiation, 2. Termination, 3. Propagation 24. Most molecules in the atmosphere contain pairs of valence electrons. A few stable molecules have an odd number, eg. NO has 11 Electron dot structure: The most important free radical in atmospheric chemistry is OH, N=O 25. Initiation: 26. Formation: OHOHO OOhO MOMOO ONOhNO es gs 2.4 .3 .2 .1 2 * ** 23 32 2 27. Quenching: O* + M O + M + kinetic energy Concentrations of OH are difficult to measure due to high reactivity Important reactions: OH + CO H + CO2 70% OH + CH4 CH3 + H2O 30% Above reactions in unpolluted atmosphere. They React further to form peroxy radicals: H + O2 + M HOO + M (Important oxidants) 28. If other gases are available, the hydroxyl radical can undergo two additional types of reactions: Hydrogen abstraction OH + HCHO HC=O + H2O Addition across a double bond: OH + H2C=CH2 H2C-CH2OH In Summary: A great variety of organic species is present in the environment Biogenic or anthropogenic origin Many reactions initiated by hydroxyl or other radicals 29. Photo-dissociation of NO2 NO2 + h (