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Urban Air Pollution & Monitoring 5.7.1-5.7.3 & 5.2.1 What is Air Pollution? Air pollution is the introduction of many kinds of gases, chemicals, particulate matter or biological materials into the atmosphere by humans •Reduces the “Air quality”. Look at that Beautiful Skyline! Can you spot the pollution? 5.7.2 Outline the formation of photochemical smog. • Photochemical Smog is a mixture of about 100 primary and secondary pollutants formed under the influence of sunlight. • Tropospheric Ozone is the main pollutant! Formation of Tropospheric Ozone Tropospheric Ozone = “Bad Ozone” 1. Burning of fossil fuels emitted by automobiles, gasoline vapors, and power plants creates NO (nitric oxide), Volatile Organic Compounds (VOC), and other hydrocarbons. 2. VOCs and NO reacts with Oxygen to form NO2 (nitrogen dioxide) a brown gas that contributes to urban haze. 3. NO2 gets hit with a UV ray, breaking of a free oxygen atom. This combines with an oxygen molecule (O2) to form Tropospheric Ozone (O3). 4. When will ozone levels reach their peak in an urban environment? 5. Is Ozone a primary or secondary pollutant? http://airnow.gov Sources of Tropospheric Ozone EPA Graphic Tropospheric Ozone Effects 1. Respiratory irritation - bronchial constriction - asthma - coughing, wheezing 2. Eye irritation 3. Decreases crop yields - slows plant growth 4. Damages plastics, rubber and nylon 5. Has a harsh odor Photochemical Smog Thermal Inversions A. Under normal conditions air rises and disperses pollutants B. A thermal inversion, occurs where a layer of warm air sits over a layer of cooler air, which prevents the dispersal of the pollutants. C. The dense, cooler air becomes stagnant and accumulates more and more pollutants. D. Occurs in cities located in valleys surrounded by mountains, with light winds and lots of people driving cars! - Ex. Los Angeles, Mexico City, Beijing. E. What will get rid of the pollutants? Thermal Inversion LOS ANGELES, SANTIAGO, MEXICO CITY, RIO DE JANEIRO, BEIJING, AND EVEN DENVER, CO London’s Great Smog of ’52 Los Angeles Overtime A is from 1940’s B is from 1960’s C is from 1990’s Places like Bejjing are so smoggy it can be really hazardous to ones health to breathe! Beijing, China air on a day after rain (left) and a sunny but smoggy day (right) August 2005. Photo taken by Bobak Ha'Eri CNN Report Sunday 11/8/15 5.2.1 – Direct method of monitoring air pollution 1. Schoenbein Paper = ozone - using a mixture of starch, potassium iodide, and water spread on filter paper - The paper will vary in color depending on the amount of the oxidation. - Those that have a lavender appearance were exposed to more ozone and, finally, those that look dark purple had high ozone exposures. - This is a qualitative test for comparison purposes - Relative humidity can affect results Evaluate this method: 5.7.3 – Describe and evaluate the pollution management strategies for urban air pollution • Replace – • Regulate – – The U.S. Congress passed Clean Air Acts in 1970, 1977, and 1990. Brought on by smog deaths in PA • National Ambient Air Quality Standards (NAAQS) were established for six outdoor “criteria” (main) pollutants. • Two limits were established: a primary standard is set to protect human health and a secondary standard is set to prevent environmental, property and crop damage. • Restore -