Air Pollution ENVS 525 Term 241 PDF

ENVS 525: Environmental Pollution Term 241 Air Pollution BassamTawabini September, 2024 1  Outline ✓ Our Atmosphere ✓ Introduction to Air Pollution ✓ Identify Air pollutants: Their Sources & Health Effects ✓ Understand the d...

ENVS 525: Environmental Pollution Term 241 Air Pollution BassamTawabini September, 2024 1  Outline ✓ Our Atmosphere ✓ Introduction to Air Pollution ✓ Identify Air pollutants: Their Sources & Health Effects ✓ Understand the different types of Outdoor and Indoor pollutants and their toxic effects ✓ Understand the basics of the ambient air modeling ✓ Identify monitoring procedures 2  Importance of Atmosphere 1. Nurtures life on earth with oxygen 2. Forms a thin blanket that protects us from hostile environment (cosmic rays, harmful UV from the sun) 3. Source of CO2 for photosynthesis 4. Source of N2 for nitrogen fixation 5. Basic part of the hydrologic cycle 3  Stratification of Atmosphere The temperature of the atmosphere is a complicated function of altitude. The variation of pressure with altitude is simpler: pressure decreases as altitude increases. 4  Troposphere The closest to the surface of the earth It’s elevation ranges from 0 to 10 km Homogeneous composition of major gases Temp. drop due to air rises and expansion-work Top very cooled layer at top cause water vapor to form ice so it prevents loss of H2 5  Stratosphere It’s elevation ranges from 10 km to around 25 km This layer contains the ozone layer, which protects us from harmful sunlight. Rise of temp. is due to the absorption of UV energy by O3. 6  Mesosphere This layer is above the stratosphere It’s elevation ranges from 30 to 80 km In mesosphere tempe. decreases with increasing height due to decreasing solar heating and increasing cooling by CO2 radiative emission 7  Thermosphere This is the highest layer of the atmosphere It’s height ranges from 100 to 400 km This is where most small meteorites burn up 8  Exosphere It starts at an altitude of about 500 km to about 10,000 km. It is uppermost layer, where the atmosphere thins out and merges with interplanetary space. It gradually fades into the vacuum of space. Satellites Space Shuttle Orbits 9  The Earth’s Gaseous Atmosphere Earth’s atmosphere is affected by temp. and pressure as well as gravity. Lighter molecules and atoms are found at higher altitudes, while heavier ones are found at lower altitudes The troposphere consists mostly of O2 and N2 (99%). Even though other gases are present in low concentrations, their effects on the environment can be profound. 10  Composition of the Atmosphere Major gases (< 0.002%) Traces of gases (< 0.002%) 11  Atmospheric Chemistry Photochemistry is concerned with the absorption, excitation and emission of photons by atoms, atomic/molecular ions, molecules….etc. Photochemical Reaction resulting form the absorption of photons of electromagnetic radiation from the sun. Important aspects of atmospheric chemistry include: Effects of solar radiation leading to photolysis of trace gases Photo-oxidation of oxidizable trace gases in the troposphere 12  Energy of Photons (E) hc E = h =  The higher the frequency of the electromagnetic radiation, the shorter the 13 wavelength and the higher the energy of radiation.  Energy Transfer in the Atmosphere Radiation of energy occurs through electromagnetic radiation which means movement through vacuum. Unlike the energy-transfer mechanisms of conduction and convection, solar energy (radiation) travels through the voids of space. Average earth surface temp. is about 15oC due to the greenhouse effect (CO2 & water) otherwise the temperature should be about -18oC 14  Solar Radiation On The Earth The 'flux' of radiation. The flux of solar radiation incident on a flat horizontal surface when the sun is directly overhead and the sunlight is un-depleted by the atmosphere is 1370 watts per square meter. 15  Photochemical Reaction Processes A photo-excited species, [X-Y]*, can react via a variety of pathways Wavelengths of light that cause photo-ionization and photo-dissociation are filtered by the atmosphere. Photoionization is the ionization of molecules (and atoms) caused by radiation. It occurs when a molecule absorbs a photon of sufficient energy to remove an electron. Photoionization processes are of great importance high in the atmosphere where pressures are low and short wavelength UV radiation from the sun has a high flux. Photodissociation is the rupture of a chemical bond induced by radiation with sufficient energy to break the required bonds and the molecules must absorb the photons. The excited state species may fragment to a pair of radicals. Reactions of this type, photolysis, are important in gas phase and atmospheric chemistry. 16  Gases Oxides in the Atmosphere ✓ Carbon Monoxide (CO): Cause serious health threat, prevents blood from transporting the oxygen ✓ Carbon Dioxide (CO2) : Most abundant, constantly increases to > 400 ppm, a major player of the global warming ✓ Nitrogen Oxides (NOx) : Enter as NO and converted photochemically to NO2 which can in turn be converted to NO3- or HNO3 >>acid rain ✓ Sulfur Oxides (SOx) : SO2 of burning fuel and coal >> H2SO4>>acid rain 17  Carbon Monoxide CO is produced by incomplete combustion of carbon containing materials e.g. fossil fuels. About 1014 g of CO is produced in the US alone per year (mostly from automobiles). CO binds irreversibly to the Fe in hemoglobin. (CO binds to hemoglobin about 210 times more strongly than oxygen.) 18  Sulfur Compounds ✓ Sulfur dioxide, SO2, is produced by the combustion of oil and coal ✓ The SO2 is oxidized to SO3 e.g. by reaction with O2 or O3 which reacts with water to produce sulfuric acid (H2SO4): ✓ SO3(g) + H2O(l) → H2SO4(aq) ✓ More than 30 million tons per year of SO2 are released into the atmosphere in the USA ✓ It is too expensive to remove sulfur from oil and coal prior to its use. Therefore, the SO2 is removed from fuel upon combustion. 19  Nitrogen Oxides and Smog Industrial Smog Photochemical Smog ◼ SOx + particulates ◼ Secondary pollutants ◼ Industrial, coal, oil ◼ NO, NO2, ozone ◼ Brownish haze, mid-day, summer ◼ Auto exhaust, hydrocarbons, humidity and sunlight ◼ Manifested by particulate matter, oxidants (Ozone) 20  Air Pollution Presence of any substances in the atmosphere in quantities which are or may be harmful or injurious to human health, welfare, animal or plant life, or property or unreasonably interfere with the enjoyment of life or property. Contamination of the air by noxious gases, minute particles of solid and liquid matter (particulates) in concentrations that endanger health 21  Historical Background Humans have been affecting air quality ever since they discovered fire. The burning of fuels and wood, releases elements which can be harmful and are considered as pollutants. Most natural air pollutants are only a nuisance, thus significant air pollution is often a function of industrialisation and urbanisation. 22  Air Pollutants Gaseous Pollutants Particulate Pollutants H2S, SOx, NOx, CO, VOCs, O3 Dust, mist, fume, smoke, and other Oxidants Smog etc. 23  Effects of Air Pollution Health Problems-Respiratory System Damage Global Issues Acid rain Smog Formation Ozone (O3) depletion Global Warming & Climate Change Other Issues 24  Other Effects of Air Pollution Affect the physical and biological environment: Damage to Ecosystems – nitrogen deposition, acid rain Soiling Corrosion of buildings and structures – acid rain Discoloration. 25  Air Quality ◼ Air Quality can be affected in many ways by the pollution emitted from these sources. These pollution sources can also emit a wide variety of pollutants. ◼ The EPA has these pollutants classified as the six principal pollutants (or criteria pollutants). Carbon Monoxide (CO) Particulate (PM) Ozone (O3) Sulfur Dioxide (SO2) Nitrogen Oxides (NOx) Lead (Pb) 26  Sources of Air Pollution 1. Stationery or fixed sources (Stacks and Area) 2. Accidental Release 3. Moving Sources 4. Natural sources 27 Types and Sources of Air Pollution 28 Primary and Secondary Air Pollutants 29  Inorganic Pollutant Gases Element Atmospheric Forms Oxygen O3 Carbon CO, CO2 Chlorine Cl , CFCs Nitrogen NH3,N2O,NO,NO2,N2O5 Sulfur H2S,SO2,SO3 30  Oxides Of sulphur (SOx) ◼ Mainly produced by burning of fossil fuels ◼ Even Low concentration of it causes respiratory diseases -2 +4 +6 1. H2S Hydrogen sulfide 1. SO2 Sulfur dioxide 1. H2SO4 Sulfuric acid 2. (CH3)2S Dimethylsulfide (DMS) 2. SO42- Sulfate 3. CS2 Carbon disulfide 4. COS Carbonyl sulfide 31  Sulphur Dioxide (SO2)… Produced through the burning of oils and coal. Of particular significance within Saudi Arabia as many facilities use sulfur-containing heavy fuel oil for firing boilers and furnaces. The presence of Particulate Matter catalyses oxidation of Sulphur dioxide to Sulphur trioxide 2SO2 + O2 2SO3 32  Sulphur Dioxide (SO2)… Sulfur Cycle 33 34  Sulphur Dioxide (SO2)… Health Effects High SO2 can result in temporary breathing impairment. Longer-term exposures to high SO2, with high levels of PM, cause respiratory illness, alterations in the lungs' defences, and aggravation of existing cardiovascular disease Short-term exposures of asthmatic individuals to elevated SO2 levels may result in reduced lung function 35  Other Sulfur Effects : Industrial Smog ◼ Industrial smog typically exists in urban areas where factories burn fossil fuels such as coal, which creates smoke and sulfur dioxide that mix with fog droplets to create a thick blanket of haze close to the ground. ◼ Extreme cases of smog can directly cause people's deaths. The Great Smog of 1952 in London killed an estimated 4,000 people, and some news reports claimed it even asphyxiated cattle. Many more may have died in car accidents as a result of poor visibility 36  Nitrogen Oxides (NOx) Three Oxides of Nitrogen : Nitrous Oxide ( N2O) Nitric Oxide ( NO) Nitrogen dioxide ( NO2) NO and NO2 are designated NOx 37  Nitrous Oxide ( N2O) ◼ Known as laughing gas ◼ Produced by microbiological processes ◼ Uncreative and does not influence important chemical reaction ◼ Decreases rapidly with altitude in the stratosphere N2O + hv N2 + O 38  NOx : NO and NO2 Sources ◼ Natural: Lightening and biological ◼ Anthropogenic: Combustion of fossil fuels (stationary/mobile sources) in internal combustion engines “Thermal NOx” is formed between N2 and O2 and is temperature sensitive “Fuel NOx” from the combustion of fuels containing organic N 39 40 41 NOx Cycle in the Atmosphere 42  Harmful Effects of NOx ◼ Formation of harmful PM ◼ Formation of ground - level ozone ◼ Formation of smog ◼ Acid Rain ◼ Building of Eutrophication 43  NOx: Effects ◼ Human  Toxicity  Inflammation of lung tissue (NO2), etc. ◼ Plants  Mostly from the toxicity of secondary products, PAN  Leaf spotting / breakdown of plant tissue ◼ Textiles  Fading of dyes in inks ◼ O3 layer depletion by supersonic aircraft emissions NO + O3 >>> NO2 + O2 NO2 + O >>> NO + O2 Overall: O + O3 >>> O2 + O2 44  Photochemical Smog ❖ Photochemical smog is a mixture of pollutants that are formed when nitrogen oxides and volatile organic compounds (VOCs) react to sunlight, creating a brown haze above cities. ❖ It contains anthropogenic air pollutants, mainly ozone, nitric acid, and organic compounds, which are trapped near the ground by temperature inversion. ❖ It tends to occur more often in summer, because that is when we have the most sunlight ❖ These pollutants and also some others can affect human health and cause damage to plants 45  Acid Rain ✓ Normal rainwater has a pH of about 5.6 due to the H2CO3 produced from CO2. ✓ Natural waters with a pH below 4 cannot sustain life. ✓ Acid rain has a pH around 4, whereas the pH of natural waters is 6.5 to 8.5. ✓ Acid rain is also corrosive to metals and stone building materials. ✓ Sulfur Oxides contributes to acid rain by forming sulfuric acid ✓ Nitrogen oxides also contribute to acid rain by forming nitric acid. 46 Acid Deposition, Acid Rain  Acid Disposition ◼ Acid deposition, acid rain  The pH < 5  Chemical sources (SOx and NOx)  Formation (photoreactions)  Local versus regional problems (both)  Effects of prevailing winds (direction and speed of wind )  Buffers (alkalinity capacity of the receiving water to neutralize acid)  Where is the worst acid deposition?  Acid Deposition Harmful Effects ✓ Human health  Respiratory disorders  Toxins in fish ✓ Leaching of soil nutrients ✓ Lower crop yields ✓ Damage to buildings, statues, and monuments ✓ Loss of crops and trees ✓ Aquatic ecosystems affected  Lowers pH and kills organisms Current and Possible Future Acid Rain Problem Areas  Ground Level Ozone (O3) A secondary pollutant produced principally when the NOx and VOCs react in sunlight. Results in high daytime levels of ozone in areas with high NOx levels. It is a colorless and highly irritating gas that forms just above the earth's surface. 51  Ground Level Ozone (O3) Health Effects Repeated exposures to ozone will cause: Increased susceptibility to respiratory infection Lung inflammation Aggravation of pre-existing respiratory diseases -asthma. Decreases in lung function and increased respiratory symptoms such as chest pain and cough 52 Carbon Monoxide CO A flammable and highly toxic gas, A neutral oxide which burns in air to give carbon dioxide, Quickly enters the blood when inhaled into the lungs. 53  Natural Sources of CO Volcanic activity: CO contents : 0.01% - 2% It also occurs naturally in bushfires. Carbon monoxide is produced by lightning. Some marine algae or kelp will also produce carbon monoxide 54  Industrial Sources of CO ▪ Point sources : Industrial plant exhaust to air (steel plants, oil refining, and chemical manufacturing). ▪ Diffuse sources: combustion of carbon-containing fuels, smoking cigarettes, burning of waste, defective heaters, defective stoves and ovens all cause emission of carbon monoxide to air. ▪ Mobile sources: vehicle exhaust. ▪ Consumer products : tobacco, heaters, ▪ charcoal grills, woodstoves, etc. ▪ 55  Health Effects of CO ▪ CO quickly enters the blood when inhaled into the lungs. CO combines with hemoglobin to form carboxyhemoglobin, reducing the oxygen-carrying ability of the blood. ▪ Harmful levels in poorly ventilated rooms, or in the passenger compartment of vehicles with defective exhaust systems. ▪ At low levels it may cause poor concentration, memory and vision problems, and loss of muscle coordination. 56  Health Effects of CO… ◼ At higher levels (200 ppm for 2-3 hours), it may cause headaches, fatigue and nausea. ◼ At very high levels (400 ppm) the symptoms intensify and will be life-threatening after three hours. ◼ Exposure to levels of 1200 ppm or greater are immediately dangerous to life. 57  Health Effects of CO… ◼ Long-term (chronic) exposure to low levels of carbon monoxide may produce heart disease and damage the nervous system. ◼ Exposure of pregnant women to carbon monoxide may cause low birth-weight, increased mortality and nervous system damage to the offspring. ◼ Carbon monoxide is classified by the as a Category 1 reproductive toxicant (substance known to cause developmental toxicity to humans). 58  Carbon Dioxide (CO2) Excess Formation is due to Burning of Fossil fuel, Decomposition of limestone and cement Manufacture. Deforestation leads to disturbance in balancing the CO2 level Responsible for Global Warming 59  Human Activities Cause Global Warming ◼ 2007 report, Intergovernmental Panel on Climate Change (IPCC,1988) ✓ 1906–2005: Ave. temp increased about 0.74˚C mostly since 1980 ✓ 1970–2009: Annual GHGs emissions from human rose 70% ✓ 2000-2009 : warmest decade since 1881 ✓ Past 50 years: Arctic temp. rising almost twice as fast as the rest of the earth ✓ Melting of glaciers and increased floating sea ice ✓ Last 100 years: sea levels rose 19 cm  Human Activities Cause Global Warming… (Extra) 2010, IPCC updates ✓ projected of climate change effects is 2-3 times higher than in 2007 ✓ The ice melting is much faster than realized ✓ 90–99% likely that lower atmosphere is warming Mostly from human-caused increases in greenhouse gases ✓ Significant climate disruption is inevitable in this century ✓ Ecological, economic, and social disruptions IPCC: Panel from 130 countries, 2500 scientists  Global Warming Effects ❖ Climate Change ❖ Ice Melting ❖ Sea-Level Rise ❖ Desertification ❖ Diseases Spreading ❖ Other effects Alaska’s Muir Glacier in the Glacier Bay National Park melted between 1948 and 2004  Projected Climate Disruption >>>Severe Consequences Tipping point and irreversible climate change- Worst-case scenarios ▪ Ecosystems collapsing ▪ Low-lying cities flooded ▪ Prolonged droughts and wildfires in forests ▪ More destructive storms ▪ Glaciers shrinking; rivers drying up ▪ Extinction of up to half the world’s species ▪ Spread of tropical infectious diseases ▪ Declining stream flows, dry lakes, lower water tables ▪ Other effects of prolonged lack of water  Volatile Organic Compounds (VOC’s) ◼ From incomplete burning of fossil fuels - gases and vapors such as gasoline fumes and solvents. ◼ Carcinogenic such as VOCs: BTEX, PAHs, TPHs, PCBs, Phenols…etc ◼ Some Toxic and Carcinogenic to Humans ◼ Harms plants by causing ageing, breakdown of tissues shedding of leaves etc. 64  (VOCs) include: ❖ Biogenic Organic compounds : methane, terpenes, esters ❖ Hydrocarbon: alkanes, alkenes, alkynes, PAHs, BTEX….etc ❖ Carbonyl Compounds: formaldehydes, acetaldehyde ❖ Oxygen-Containing Compounds: alcohols, phenols, ethers, solvents ❖ Organonitrogen compounds: Amines, Nitriles ❖ Organohalide compounds: THMs, PCE, TCE, CFCs, Dioxin ❖ Organosulfur compounds : Dimethyle sulfide, methanethiol ❖ Organic particulate matter 65  Methane (CH4) ◼ Atmospheric Methane (CH4) is most abundant hydrocarbon in the atmosphere ◼ Generated from natural gas and fermentation of organic material ◼ Methane level in the atmosphere has doubled for the last 250 years due to fossil fuel burning and agriculture activities and fermentation of organic material by anaerobic microorganisms ◼ Least reactive in the atmosphere, but it plays major role in the atmospheric chemical processes such as global warming. More effective than CO2 per molecule ◼ Affects both troposphere and stratosphere chemistry 66 67  Heavy Metals o Heavy metal is a general collective term which applies to the group of metals and metalloids with an atomic density greater than 4 g/cm³. o They are elements which occur naturally in the Earth’s crust: cadmium, chromium, copper, mercury, lead, zinc, arsenic, boron, platinum, palladium, rhodium, ruthenium, osmium, and iridium. o Found naturally in soils and rocks with a subsequent range of natural background concentrations in soils, sediments, waters and organisms. o They are emitted to the environment from a variety of anthropogenic sources o Combustion processes are the most important sources of heavy metals, particularly, power generation, smelting, incineration and the internal combustion engine. o Hg and Pb are most common HM in the atmosphere 68  Temperature (Thermal) Inversion ◼ At Certain atmospheric conditions can result in opposite conditions (increasing temp. with increasing altitude) >> high atmospheric stability leads to stagnation and the trapping of air pollutants in localized areas. ◼ A reversal of the normal behavior of temperature in the troposphere in which a layer of cool air at the surface is overlain by a layer of warmer air. ◼ Diffusion of dust, smoke, and other air pollutants is limited. ◼ Inversions play an important role in determining cloud forms, precipitation, and visibility. Dr. B. Tawabini 69  Thermal inversion and smog Smoke rising in Scotland is stopped Winter smoke in Shanghai with a clear by an overlying layer of cooler air. border-layer for the vertical air-spread. Particulate Matter (PM) 71  Minute solid particles or Liquid droplets in air Particulate Maters (PM) Smoke Dust Mist Fumes 72  Particulates (PM) ◼ Sources: smoke, dust, ash, coal, diesel, lead additive to gasoline ◼ Size matters Large, > 10 µm: pollens, dust; filtered by nose Fine, PM10