Lecture 13 - Air Pollution from Fossil Fuels PDF

Lecture 13 (Ch 6) Air Pollution from fossil fuels ENV-474 Energy and Sustainability Energy, Environment, and Climate Copyright © W.W. Norton...

Lecture 13 (Ch 6) Air Pollution from fossil fuels ENV-474 Energy and Sustainability Energy, Environment, and Climate Copyright © W.W. Norton & Company 2012 Air-Pollution from fossil fuels Air pollution hangs over New York City in this photo The Asian “brown cloud”—over eastern from the 1950s. China.  Air Pollutant An air pollutant is defined as a substance that is present in the atmosphere at a concentration that is sufficient to cause harm to humans, animals, vegetation, or materials Primary vs Secondary Air Pollutants Primary pollutants comes from the burning of hydrocarbons in power plants, from industry and traffic and some natural sources (e.g. volcanoes) such as: carbon monoxide (CO); carbon dioxide (CO2); Nitrogen oxides (NOx); sulphur dioxide (SO2); volatile organic compounds (VOC’s) and Particulate Matter (PM10 and PM2.5) Primary vs Secondary Air Pollutants Secondary pollutants which form from the reactions between primary pollutants and atmospheric compounds to form new pollutants such as: Sulphur trioxide (SO3); Nitric acid (HNO3) and Sulphuric acid (H2SO4) – both contribute to acid rain; Ozone (O3); Hydrogen peroxide (H2O2); photochemical smog. Primary vs Secondary Air Pollutants ~90% of air pollutants in US is caused by 5 primary pollutants, CO, SO2, NOx, VOC’s, PM10 &2.5 CO SO2 (VOC’s) VOC’s (PM10&2.5) NOx PM10 & PM2.5 Air Quality Index (AQI) – standards for ambient air quality An air quality index (AQI) is a scale/index used to show how polluted the air is, along with the risks associated with each rating. An AQI is calculated using established standards based on medical AQI research for the acceptable levels of major air (0-500) is based on pollutants. concentrations of typically: https://aqicn.org/map/world/ PM10, NO2, SO2, O3, CO, Pb, serve AQI averaged two over 8hrs or 24hrs purposes: Inform the public about ambient air quality, so that they may take action to protect their health Develop and assess policies for better air quality in UAE National Ambient Air Quality Standards The National Ambient Air Quality Standards for UAE correspond to 100 points in the AQI table, which is the level EAD has set to protect public health.  Each day a human is inhaling ~20 000L air Health effects from ambient air pollution According to WHO – 4-6 million deaths globally are linked to air pollution every year. https://www.youtube.com/watch?v=GVBeY1jSG9Y Physical activity affects the amount of air we breathe:  Particulate Matter (PM) in the atmosphere Suspended particulate matter (PM) from both natural or anthropogenic sources: Consists of: Aerosols particles 10m (e.g. dust, fly-ash) Diameters smaller than H2SO4 (Sulphuric acid) (sandstrone contain CaCO3 that reacts with acid) Values of pH in precipitation falling in the US during the early 21st century. Figure 6.6 Pollution Control in Industry - SO2 removal SO2 emissions mainly from burning coal Flue-gas desulfurization (scrubbing) to remove SO2 from flue gasses: SO2 in flue gases pass through a slurry of water mixed with limestone (CaCO3) or dolomite [CaMg(CO3)2] SO2 + CaCO3 => CaSO3(gypsum) + CO2 Can remove up to 98% of SO2 emissions Expensive to install (15-20% of total cost) Energy cost up to 8% of total production Large amounts of sulphureous waste (gypsum) Carbon Monoxide – mainly from traffic and natural sources The main anthropogenic source of CO is from incomplete combustion of gasoline/diesel in automobile engines Natural sources of emissions of CO (e.g. from volcanoes) 10 times larger than anthropogenic emissions Although CO is one of the most abundant air pollutants, it is not very toxic at the levels usually found in the atmosphere (0.1ppm). Carbon Monoxide – mainly from traffic and natural sources However, in cities – congested with traffic – CO levels can be high In confined spaces CO can cause serious health problems (even death through asphyxiation) CO interferes with the oxygen-carrying capacity of blood. Normally, hemoglobin (Hb) in red blood cells combines with oxygen in the lungs to form oxyhemoglobin (HbO2) CO binds much more strongly to Hb than oxygen CO is colorless and odorless – “silent killer”  Nitrogen Oxides (NOX) Practically all anthropogenic NOx enter the atmosphere from the combustion of fossil fuels by automobiles, aircraft, and power plants N2 reacts with O2 at high temp forming NO that is converted to NO2 after further reaction with O2 NO2, regardless of its source, is ultimately removed from the atmosphere as nitric acid (acid rain) and nitrates in dust and rainfall Acid Rain: 4NO2 + H2O + O2 => 4HNO3 (secondary air pollutant) NO2 can cause irritation of the eyes, inflammation of lung tissue, and emphysema NOx gives the red/brownish color of photochemical smog Volatile Organic Compounds (VOC’s) A great variety of VOC’s, including hydrocarbon’s, enter the atmosphere from both natural and anthropogenic sources The petroleum industry is the main anthropogenic source of HC’s in the atmosphere. VOC’s react with other substances in the atmosphere to form the secondary air pollutants associated with photochemical smog  Photochemical smog – a “chemical soup” Smog develops as a yellow-brown haze in hot sunny weather in many big cities where automobile traffic is congested The reactions that lead to its formation are initiated by sunlight and involve the HC’s and NOx emitted in automobile exhaust. Ozone formation is a secondary air pollutant. https://www.youtube.com/watch?v=xajjmbJrfEM  Pollution Control Traffic – CO, NOx and VOC’s Catalytic converters reduce emissions of CO, NOx and VOC’s from vehicles The metals catalyze the conversion of NOx and CO to nitrogen gas (N2) and CO2 and the conversions of HCs to carbon dioxide and water. https://www.youtube.com/watch?v=DAd_IrXiY CU  Clean air act (US) - regulating air pollution 1970 & following amendments - regulating the 5 primary pollutants (SO2, CO, NOx, VOC, PM) and lead. This led to Pb free gasoline & catalytic cleaning on cars Reduce SO2 emissions by >50% SO2 emission trading in US (older power plants can buy emission rights from newer cleaner plants through cap & trade schemes) China is not part of the Clean air act, and are now biggest emitter of SO2 – increased emissions by 27% between 2000-2006 Clean air act does not regulate CO2 emissions – a greenhouse gas https://www.youtube.com/watch?v=fPtkE2nnLSY  Satellite monitoring of air pollution Dust – mainly from deserts, some from PM Sulphates – from burning of coal Organic black carbon – forrest fires and tps://www.youtube.com/watch?v=e6rglsLy1Ys deforrestion