Air Pollution: Types & sources of Air Pollution, C , N and S oxide Electronic Control Unit, Slides of Environmental Science

Download Air Pollution: Types & sources of Air Pollution, C , N and S oxide Electronic Control Unit and more Slides Environmental Science in PDF only on Docsity! Air Pollution: The Dirty Truth ©2009teach.com Types and Sources of Air Pollution Air Pollution:- Chemicals added to the atmosphere by natural events or human activities in high enough concentrations to be harmful Two categories:- Primary Air Pollutant • Harmful substance that is emitted directly into the atmosphere Secondary Air Pollutant • Harmful substance formed in the atmosphere when a primary air pollutant reacts with substances normally found in the atmosphere or with other air pollutants Air Pollution The waste in landfills releases methane. Sulfur oxides, carbon monoxide and carbon dioxide, and methane all have a very negative effect on air quality. These pollutants can also contribute to the greenhouse effect. ©2009 abcteach.com Some air pollution is not directly caused by humans: for example, animals emit carbon dioxide when they breathe, and volcanoes release sulfur oxide. However, most air pollution is linked directly or indirectly to human activity. This means that air pollution can be best controlled by modifying human activity to burn a smaller quantity of fossil fuels. Air Pollution ©2009 abcteach.com United States - 2002 NO, Other 2% Electric Utilities 22% Transportation Fuel . 54% Combustion 1? Fo Industrial Sources 5% Sources of Outdoor Air Pollution • Two main sources – Transportation – Industry • Intentional forest fires is also high Major Classes of Air Pollutants o Particulate Material o Nitrogen Oxides o Sulfur Oxides o Carbon Oxides o Hydrocarbons o Ozone Major Air Pollutants Table 20.1 Major Air Pollutants Primary or Pollutant Composition Secondary Characteristics Particulate matter Dust Variable Primary Solid particles Lead Pb Primary Solid particles Sulfuric acid H,SO, Secondary Liquid droplets Nitrogen oxides Nitrogen dioxide NO, Primary Reddish-brown gas Sulfur oxides Sulfur dioxide SO, Primary Colorless gas with strong odor Carbon oxides Carbon monoxide co Primary Colorless, odorless gas Carbon dioxide* CO, Primary Colorless, odorless gas Hydrocarbons Methane CH, Primary Colorless, odorless gas Benzene CoH¢ Primary Liquid with sweet smell Ozone O; Secondary Pale blue gas with acrid odor Air toxics Chlorine Cl, Primary Yellow-green gas * Discussed in Chapter 21. Source: Environmental Protection Agency. Ozone • Tropospheric Ozone – Man- made pollutant in the lower atmosphere – Secondary air pollutant – Component of photochemical smog • Stratospheric Ozone – Essential component that screens out UV radiation in the upper atmosphere – Man- made pollutants (ex: CFCs) can destroy it •1st smog related deaths were in London in 1873; death toll 500 people; can you imagine how much worse the atmosphere is now?! •Limits visibility •Decreases UV radiation •Yellow/black color over cities •Causes respiratory problems and bronchial related deaths al Urban Air Pollution • Photochemical Smog (ex: Los Angeles below) – Brownish-orange haze formed by chemical reactions involving sunlight, nitrogen oxide, and hydrocarbons Case-In-Point Air Pollution in Beijing and Mexico City • Beijing (left) • Mexico City (above) Sources of Smog in Los Angeles Consumer products and homes Effects of Air Pollution • Low level exposure – Irritates eyes – Causes inflammation of respiratory tract • Can develop into chronic respiratory diseases Health Effects of Air Pollution • Sulfur Dioxide and Particulate material – Irritate respiratory tract and impair ability of lungs to exchange gases • Nitrogen Dioxides – Causes airway restriction • Carbon monoxide – Binds with iron in blood hemoglobin – Causes headache, fatigue, drowsiness, death • Ozone – Causes burning eyes, coughing, and chest discomfort Acid Deposition • Sulfur dioxide and nitrogen dioxide emissions react with water vapor in the atmosphere and form acids that return to the surface as either dry or wet deposition • pH scale Acid Deposition and Forest Decline OZONE DEPLETION Ozone Depletion in Stratosphere • Ozone Protects earth from UV radiation – Part of the electromagnetic spectrum with wavelengths just shorter than visible light Effects of Ozone Depletion • Higher levels of UV-radiation hitting the earth – Eye cataracts – Skin cancer (right) – Weakened immunity • May disrupt ecosystems • May damage crops and forests Recovery of Ozone Layer • Montreal Protocol (1987) – Reduction of CFCs – Started using HCFCs (greenhouse gas) • Phase out of all ozone destroying chemicals is underway globally • Satellite pictures in 2000 indicated that ozone layer was recovering • Full recovery will not occur until 2050. Answer the questions in complete sentences. 1. What is air pollution? 2. What causes air pollution? 3. What is an example of air pollution in the text? 4. What is at least one negative outcome of air pollution? 5. How can air pollution be prevented? 6. What is something you could do to reduce air pollution? ©2009 abcteach.com Electronic Control Unit Electronic Control System • The electronic control system consists of various engine sensors, Electronic Control Unit (ECU), fuel injector assemblies, and related wiring. • The ECU determines precisely how much fuel needs to be delivered by the injector by monitoring the engine sensors. • The ECU turns the injectors on for a precise amount of time, referred to as injection pulse width or injection duration, to deliver fuel so that the proper air/fuel ratio is delivered to the engine. Basic System Operation • When the injector is turned on, it opens, spraying atomized fuel at the back side of the intake valve. • As fuel is sprayed into the intake air stream, it mixes with the incoming air and vaporizes due to the low pressures in the intake manifold. The ECU signals the injector to deliver just enough fuel to achieve an ideal air/fuel ratio of 14.7:1, often referred to as stoichiometric ratio. Toyota Computer Control System (TCCS) • Exhaust Gas Recirculation (EGR). The EFI/TCCS system regulates the periods under which EGR can be introduced to the engine. This control is accomplished through the use of an EGR Vacuum Switching Valve. • TCCS Electronic Control Unit (ECU) also controls ignition spark angle. Additionally, TCCS also regulates an Idle Speed Control device, an Exhaust Gas Recirculation (EGR) Vacuum Switching Valve and, depending on application, other engine related systems. Summary The Electronic Fuel Injection system consists of three basic subsystems:- – The electronic control system determines basic injection quantity based upon electrical signals from the air flow meter and engine rpm. – The fuel delivery system maintains a constant fuel pressure on the injector. This allows the ECU to control the fuel injection duration and deliver the appropriate amount of fuel for engine operating conditions. Summary • The EFI system allows for improved engine performance, better fuel economy, and improved emissions control. Although technologically advanced, the EFI system is mechanically simpler than other fuel metering systems and requires very little maintenance or periodic adjustment.