Class Activity on Air Pollution
1. What does it mean by “primary pollutant” and “secondary pollutant”?
2. Please write down 4 examples of primary pollutants
3. Please write down 2 examples of secondary pollutants
4. Why is carbon monoxide so dangerous to human beings?
5. What are the ingredients of photochemical smog?
6. What is “Particular Matter”? What is PM2.5 and PM10?
7. What is the impact of black carbon on glaciers?
8. What is inversion, and how does it affect air quality?
1. What does it mean by “primary pollutant” and “secondary pollutant”? 2. Please write down 4 examples of primary pollutants 3. Please write down 2 examples of secondary pollutants 4. Why is carbon monoxide so dangerous to human beings? 5. What are the ingredients of photochemical smog? 6. What is “Particular Matter”? What is PM2.5 and PM10? 7. What is the impact of black carbon on glaciers? 8. What is inversion, and how does it affect air quality? Two types of Pollutants Gases and particulate matter • Gases: Carbon monoxide, Sulfur Dioxide, Nitric Oxide, Nitrogen Dioxide • Particulates are classified by size PM10, PM2.5—diameter size in microns Pollutants can be classified as: primary pollutants and secondary pollutants. – Primary pollutants are directly emitted; – Secondary pollutants form chemically in the air. Primary Pollutants Carbon Monoxide (CO): is a tasteless, colorless and odorless gas. Sources of CO include: fossil-fuel combustion (Incomplete combustion in autos, trucks and airplanes, some industrial process), biomass burning, and photolysis reactions. Concentrations of CO in urban air are typically 2-10 ppmv. On freeways and in traffic tunnels values rise to more than 100 ppmv. Primary Pollutants Sulfur Dioxide (SO2): is a colorless gas that exhibits a taste at levels of 0.3 ppmv and a strong odor at levels greater than 0.5 ppmv. Sources of SO2 include: coal-fired power plants, automobile tailpipes, and volcanoes. Background concentrations in the troposphere range from 10 pptv to 1 ppbv. In polluted air, 1-30 ppbv. Yellowstone National Park Hawaii Volcano National Park Primary Pollutants Volatile organic compounds (VOCs) represent a class of organic compounds that are mostly hydrocarbons-individual organic compounds composed of hydrogen and carbon. Some VOCs have smell. Methane (naturally occurring) is the most abundant. Others include: benzene, formaldehyde (HCHO) Charcoal Grills Gas Grills When burned, these Franken-coals Gas come from non-renewable fossil can result in 105 times more carbon fuels. dioxide than propane – and they also release volatile organic compounds (VOCs) that may cause cancer and other diseases. However, you can buy true charcoal at some health food and home improvement stores. Known as lump or chunk charcoal, this greener fuel is made from hardwood material and contains no chemical additives. However, gas grills produce far fewer carbon emissions than charcoal when burned. A study by the Oak Ridge National Laboratory for the Department of Energy found that gas grills generate 5.6 pounds of carbon dioxide per hour, while charcoal grills produce 11 pounds per hour. Primary vs Secondary Pollutants Primary pollutants are directly emitted; Secondary pollutants form chemically in the air. Primary pollutant: Nitric Oxide (NO): is a colorless gas and a free radical. Precursor to tropospheric ozone. Sources include: fossil-fuel combustion/autos and planes, and biomass burning. Secondary pollutant: Nitrogen Dioxide (NO2): is a brown gas with a strong odor. Absorbs short wavelengths. Intermediary between NO and O3 production. Secondary Pollutants Ozone is a secondary pollutant in the troposphere. It is NOT directly emitted. Ozone (O3) is a relatively colorless gas. Ozone has a sweet smell (Copy machine, corona wires charging the paper for printing the ink). It exhibits an odor at concentrations of 0.02 ppmv or greater. In 2008, EPA lowered the 8 hr primary standard from 84 ppbv to 75 ppbv. Since October 1, 2015, the new standard is 70 ppbv. 2008 EPA Standards National Ambient Air Quality Standards (NAAQS) • 75 ppb O3 for an 8-hour averaging period • 120 ppb O3 for a 1-hour averaging period 2015 EPA New Ozone Standard EPA Strengthens the Air Quality Standards for Ground-Level Ozone • On October 1, 2015, EPA strengthened the National Ambient Air Quality Standards (NAAQS) for groundlevel ozone to 70 parts per billion (ppb), based on extensive scientific evidence about ozone’s effects on public health and welfare. • The updated standards will improve public health protection, particularly for at-risk groups including children, older adults, people of all ages who have lung diseases such as asthma, and people who are active outdoors, especially outdoor workers. • They also will improve the health of trees, plants and ecosystems. Ozone concentration, 2006 The number of unhealthy days during 2003 Fig. 12-11, p. 338 The days exceeding 1-hr standard in LA Chemistry of Photochemical Smog Ingredients of photochemical smog: – Reactions among NOx and VOCs – Presence of sunlight. Step 1. Emission of NO (later forms NO2) and VOCs Step 2. Sunlight dissociates NO2 into NO and atomic oxygen Step 3. The atomic oxygen then combines with molecular oxygen and they form ozone. NO2 + solar radiation O + O2 + M NO + O O3 + M Photochemical Smog Question: What is the role of VOCs in photochemical smog? VOCs can prevent the newly generated ozone from being destroyed again. Thus the ozone concentration will keep going up. Aerial view of Air Pollution in North India, Agriculture Fires, November 2013 Smog around the world New Delhi Beijing Singapore Chemistry of Photochemical Smog Particulate Matter Particulate Matter (PM) represents a group of solid particles and liquid droplets that are small enough to remain suspended in the air. Collectively known as aerosols, this grouping includes solid particles that may irritate people but are usually not poisonous. These include: soot, dust, smoke, and pollen. Some more dangerous substances include asbestos fibers and arsenic. Particulates are classified by size (PM10, PM2.5—diameter size in microns 2.5 μm) asbestos fiber Black Carbon and Glaciers BC particulates remain in the atmosphere for a few weeks, as opposed to carbon dioxide which remains in the atmosphere for more than one hundred years. When they precipitate onto snow and ice, they reduce its ability to reflect sunlight. Hence, reducing black carbon emissions would be an effective short-term way to slow down glacier loss. Electron microscope image of a particle of Black Carbon soot Inversion layer and sustained pollution • Inversion: when temperature is increasing with height (compared to normally temperature decreases with height) Examples of Inversion • The mixing layer can often be easily seen from an airplane. Examples of Inversion A strong subsidence inversion along the coast of California Ocean upwelling along California coastline If the wind blows parallel to the coast in the northern hemisphere (such as the coast of California, where the wind blows South), then Ekman transport can produce a net movement of surface water 90°to the right. This may result in coastal upwelling. One main reason for the fantastic wineries along the coast! Air Quality Index (AQI) Factors that Affect Air Pollution Video (6 min) https://www.youtube.com/watch?v=Hx_yWFQvJT4