Chapter 8: Air - What Are We Breathing? - PDF

CHAPTER 8 Air: What Are We Breathing? Copyright © 2023 W. W. Norton & Company, Inc. Chapter 8 Outline 8.1 What Makes Up the Air We Breathe and Our Atmosphere? 8.2 What Is Weather and How Does It Change? 8.3 How Does the Atmosphere Circulate? 8.4 How Does the Atmosphere Become Polluted? 8.5 What...

CHAPTER 8 Air: What Are We Breathing? Copyright © 2023 W. W. Norton & Company, Inc. Chapter 8 Outline 8.1 What Makes Up the Air We Breathe and Our Atmosphere? 8.2 What Is Weather and How Does It Change? 8.3 How Does the Atmosphere Circulate? 8.4 How Does the Atmosphere Become Polluted? 8.5 What Is Happening to the Ozone Layer? 8.6 What Is Acid Rain? 8.7 How Are We Responding to Pollution in the Atmosphere? 8.8 What Can I Do? Chapter Objectives: This chapter will help you… name the most prominent gases found in the atmosphere. describe how the four layers of Earth’s atmosphere are distinguished by varying characteristics. explain what an air mass is and how it rises, falls, and circulates with changes in temperature, moisture, and wind conditions. define and provide examples of primary and secondary pollutants. describe how secondary pollutants in the atmosphere react to cause smog, ozone layer depletion, and acid deposition (acid rain). compare and contrast different policies aimed at improving air quality. “Air, I should explain, becomes wind when it is agitated.” —Lucretius, 50 BCE Automobiles are a major source of air pollution. Vehicle engines that are idling add harmful carbon monoxide (CO), particulate matter (PM), and nitrogen oxides (NOx) to the atmosphere, which is the dynamic envelope of gases extending about 62 miles up from Earth’s surface, and that clings to our planet because of its gravitational pull. 8.1 What Makes Up the Air We Breathe and Our Atmosphere? The air around us is actually a mixture of many gases. Earth’s atmosphere is mostly composed of constantly moving gases, and contains 78% nitrogen (N2), 20% oxygen (O2), and smaller amounts of argon, carbon dioxide (C02), water vapor, and other compounds. These atoms and molecules in the form of gases continually bounce around, collide in, and Pressure (1 of 2) Pressure is defined as the force exerted on or acting against something. The pressure in a balloon can be increased by adding more air, compressing the balloon, or increasing the temperature of the air in the balloon, all of which cause internal gas molecules to bump into the walls more frequently. All gases, including air, move from areas of high pressure to low pressure. Pressure (2 of 2) Imagine a cylinder of air extending above Earth’s surface as high as 150 Empire State Buildings. The weight of the air at the top of the cylinder presses down on the lower layers of air, forcing the lower molecules closer together and increasing the atmospheric pressure. As air moves farther away from Earth’s surface, the air pressure becomes thinner or less dense from molecules moving farther apart How Is Earth’s Atmosphere Structured? (1 of 2) The atmosphere is divided into four layers with different pressures, temperatures, and compositions. Most of the atmosphere’s mass is within a 5- to 10- mile-thick layer above Earth known as the troposphere. The next layer, extending 30 miles above the troposphere, is the stratosphere, which contains the ozone layer. How Is Earth’s Atmosphere Structured? (2 of 2) The next layer, the mesosphere, lies above the stratosphere and has the coldest temperatures, which fall as low as –148°F. Above the mesosphere is the thermosphere, which is warmer due to solar and cosmic radiation, and less dense due to low levels of gravity. 8.2 What Is Weather and How Does It Change? Weather refers to short-term variations in conditions such as temperature, moisture, and wind in a specific place. Weather is different from climate, which is the long-term average of weather conditions for a given region. The National Weather Service defines the climate for particular regions of the country using a 30-year average of regional weather conditions. According to Mark Twain, “Climate is what you expect, weather is what you get.” Temperature Temperature is a measure of hotness or coldness of something using a thermometer. Earth is warmed by the Sun due to solar radiation reaching Earth’s surface. It takes about 8 minutes for solar radiation to travel the 93 million miles from the Sun to Earth. Temperature variations across Earth’s surface are mostly due to changes in the amount of radiation received at various latitudes. Land and water features also affect temperature variations. The Unexpected Consequences of Severe Weather Sequoia National Forest lost many trees following the California droughts, but not directly from lack of water. Instead, the trees were stressed by drought and succumbed to insect predators and disease. As droughts become more common, scientists will continue to monitor which trees are most vulnerable to the effects of climate change. Water Vapor Precipitation, humidity, and cloud cover reflect the amount of water vapor in the air, as water constantly moves into and out of the atmosphere through evaporation and condensation. Humidity is the amount of water in a given volume of air and can greatly affect rates of evaporation. The relative humidity of air is the amount of water in the air as a percentage of the maximum amount of water that the air can hold at a given temperature. Evaporation from our bodies helps keep us cool and happens more readily in dry heat with its lower relative humidity. Barometric Pressure (1 of 2) During forecasts, meteorologists discuss high and low pressure systems, along with the status of the barometric pressure, which is a measure of the pressure exerted by Earth’s atmosphere at any given point. Temperature and pressure can cause changes in air masses, which are large volumes of air typically several kilometers thick and a thousand or more kilometers wide that have relatively uniform temperature and humidity. Barometric Pressure (2 of 2) High-pressure systems are systems of cooling air that become denser and heavier, causing them to sink and form areas of high pressure that are usually associated with clear, dry conditions. When air masses warm, molecules expand to form a low-pressure system of air where warm, rising air cools as it expands into higher and colder altitudes. This coolness causes the water vapor in the risen air mass to condense into clouds that may eventually produce precipitation. Wind, Fronts, and Storms Wind is air in motion as it flows from high-pressure to low-pressure areas. A cold air mass replacing a warm air mass is called a cold front. A warm air mass replacing a cold air mass it called a warm front. Fronts form at the boundaries between high-pressure systems (cold air masses) and low-pressure systems (warm air masses). In extreme weather situations, low- pressure systems can act like a powerful magnet and pull air from other places, creating hurricanes and typhoons. Lake and Land Effects Continental landmasses also affect weather conditions. Interior regions of a continent receive less precipitation than do coastal areas since they are farther from the ocean. Some large bodies of water, such as the Great Lakes, can produce lake-effect rain and snow when cold winds pick up water vapor while moving across the warmer lake water below, cooling the water vapor into precipitation. Topography can affect weather patterns, especially along mountain ranges where a warm air mass meets mountains and is forced upward, which cools the air mass to release precipitation. 8.3 How Does the Atmosphere Circulate? Regular global patterns of air circulation are driven by Earth’s rotation and differences in temperature between the equator and the poles. These patterns of atmospheric pressure and prevailing winds continue to circulate in the atmosphere, which can pick up particles such as dust, soot, and ash and transport them over Earth. Forest fires send smoke into the atmosphere, causing colorful sunsets miles from the source, as seen in this photo. Patterns of Atmospheric Pressure and Prevailing Winds (1 of 3) At the equator, places like the Amazon jungle near Brazil receive the Sun’s rays most directly, causing water to evaporate, rise into the air, then fall as precipitation more rapidly than at other latitudes. This large body of warm and humid air at the equator is known as the equatorial low- pressure belt and supplies abundant precipitation to tropical rain forests in equatorial zones. As the warm air rises and cools, and then spreads north and south, it descends and creates patterns of increasing atmospheric pressure known as subtropical high-pressure belts. Patterns of Atmospheric Pressure and Prevailing Winds (2 of 3) The subtropical high-pressure belts cause arid conditions at 30 degrees of latitude north and south of the equator, creating the dry interior lowlands of Australia and deserts such as the Sahara Desert. After reaching the equator, the air has warmed again and rises, creating a looping weather pattern that forms circulation systems between the equator and latitudes 30°N and 30°S, which are known as Hadley cells. Ferrel cells also form between latitudes 30°N and 60°N and 30°S and 60°S, with polar cells forming at higher latitudes. Patterns of Atmospheric Pressure and Prevailing Winds (3 of 3) Due to the Coriolis effect, the prevailing winds from the Hadley and Ferrel cells do not move in a straight line but are bent by Earth’s rotation. In subtropical regions of the Northern Hemisphere, Earth’s rotation bends southward-flowing air to the right, and northward-flowing air to the left in the Southern Hemisphere. At midlatitudes, Earth’s rotation bends flowing air to the left (west to east “westerlies”), and at the polar regions, air bends easterly. Prevailing wind patterns called jet streams form at altitudes about 6 miles above Earth’s surface, near the top of the troposphere. Atmospheric Dust Transport Circulation patterns in the atmosphere and oceans carry more than just air and water. Wind at Earth’s surface can sweep up dust and other small particles and transport them great distances. Dust blown from the Mojave Desert can support the growth of piñon-juniper forests on the Colorado Plateau. Soot from forest fires in North America has traveled to Greenland, where soot-blackened ice absorbs more heat and accelerates melting. Volcanoes can also release particles that attract and collect water droplets to cause rain, thunder, and lightning around the eruption area. 8.4 How Does the Atmosphere Become Polluted? In Chapter 3, we learned how matter is conserved, so when we burn wood or fuel, the matter doesn’t “go away”; instead, it changes form and persists as emissions in the atmosphere. When the addition of materials into the atmosphere adversely affects the health of humans and/or other organisms, we consider this air pollution. The effects of outdoor air pollution are influenced by atmospheric circulation patterns. Primary Pollutants (1 of 3) A primary pollutant is a substance that is harmful in its directly emitted form. A prevalent primary pollutant we are all exposed to is carbon monoxide (CO) in car exhaust from incomplete combustion when a car idles, or when other fuel does not have adequate oxygen. Other examples of pollutants that make their way into the atmosphere include pesticides applied in agricultural areas, benzene released from gasoline production, and asbestos from construction activities. Primary Pollutants (2 of 3) Particulate matter (PM) is a form of air pollution made up of tiny particles and droplets less than 10 micrometers (μm) in size that are suspended in the air we breathe and can cause respiratory ailments. The smallest particulate matter particles can be especially dangerous since they can be absorbed by the lungs and enter the blood stream. Primary Pollutants (3 of 3) Other examples of primary pollutants are toxic metals such as lead, mercury, and arsenic, which can travel in airborne particles. Lead is a neurotoxin that can accumulate in the body and cause delays in mental and physical development, as well as kidney damage. Volatile organic compounds (VOCs) result from fossil fuel burning or using carbon-based compounds like paint or solvents. These VOCs can be found in higher concentrations indoors. Secondary Pollutants (1 of 2) Secondary pollutants are the product of reactions occurring in the atmosphere. Smog is a mixture of secondary pollutants resulting from reactions between sunlight and chemicals in the atmosphere. Smog forms when VOCs and nitrogen oxides (NOx) from fossil fuel combustion interact with sunlight at warm temperatures. Secondary Pollutants (2 of 2) In normal conditions, air is usually warm at the surface and gets cooler at higher altitudes. Thermal inversion happens in some urban areas and involves warm air capping a cooler layer of air below, which prevents air circulation. This results in polluted air becoming trapped over a surface area for an extended period. 8.5 What Is Happening to the Ozone Layer? (1 of 3) Stratospheric ozone protects terrestrial life from ultraviolet (UV) radiation by preventing 99% of it from reaching Earth. The ozone layer sustains itself by splitting oxygen gas (O2) into oxygen atoms (O) in the presence of UV light, which then combines with another oxygen gas molecule to form ozone (O3). What Is Happening to the Ozone Layer? (2 of 3) In the 1970s, a scientist named Lovelock, along with chemists Rowland and Molina, discovered that a category of refrigerants called chlorofluorocarbons (CFCs) was reacting with stratospheric ozone and depleting the ozone layer. It was found that CFCs were accumulating in the stratosphere, where high levels of UV radiation were breaking apart the CFCs and releasing chlorine atoms, which react with ozone and remove ozone at the rate of one chlorine atom to 100,000 ozone molecules. What Is Happening to the Ozone Layer? (3 of 3) Stratospheric ozone showed a steady decline throughout the 1970s and 1980s, with satellite images confirming that the ozone layer was thinning. The highest level of depletion was occurring over Antarctica during the spring season, with discovery of an ozone hole showing 50% reduction. In the area below the ozone hole, the amount of UV radiation can be double the annual average, with increased incidences of skin cancer and cataracts. 8.6 What Is Acid Rain? (1 of 2) Normal rainwater is slightly acidic, with a reported pH of 5.6. In the 1970s, rising sulfur dioxide (SO2) and nitrogen oxide (NOx) levels emitted into the atmosphere from human sources, such as car exhaust, and agricultural and industrial processes, were reacting with water vapor to form sulfuric acid (H2SO4) and nitric acid The (HNO acid 3). created from these air pollutants around the world then precipitates from the sky and is known as acid deposition, also known as “acid rain.” What Is Acid Rain? (2 of 2) Acid deposition has changed the pH of thousands of lakes in eastern Canada and New England, altering the ecology. Freshwater lakes have a natural pH between 6 and 8, and lower pH levels due to acid precipitation are affecting developmental stages and physical development of certain insect and fish species. Acid deposition also affects soil pH and important soil microbes that affect plant growth and mortality. Acid deposition also wears away human structures and artwork, especially ones made of limestone and marble. 8.7 How Are We Responding to Pollution in the Atmosphere? (1 of 3) Policy strategies addressing air pollution in the United States have been successful, as can be seen in the reduction of many pollutants, even as the country experienced increased population growth. The Clean Air Act of 1970 is a law in the United States that established two important policy strategies: air quality standards and regulations of the source of pollutants. 8.7 How Are We Responding to Pollution in the Atmosphere? (2 of 3) In 1975, the Energy Policy and Conservation Act empowered the Department of Transportation to set minimum miles per gallon (mpg) standards for cars and vehicles considered light trucks. These standards are now known as corporate average fuel economy (CAFE) standards. The greater the mpg performance of a vehicle, the more the fuel efficiency. 8.7 How Are We Responding to Pollution in the Atmosphere? (3 of 3) In 1990, amendments to the Clean Air Act of 1970 added a new policy strategy, the tradeable emission allowance policy where the EPA sets the total allowable annual emissions for a pollutant from utilities, then divides this total into tradeable units called allowances, which are bought and sold. This is an example of the US cap-and-trade policy strategies, which are market-driven strategies. Air Pollution: How Will the Chinese Government Respond? Read the article on page 235 discussing the air pollution issues in China. In 2015, the Chinese government issued its first “red alert” for hazardous air pollution in Beijing, which had become a regular occurrence. The World Health Organization study found 1 million people die each year from polluted air in China due to China’s rapid industrial development and economic growth. As a communist country, how did China’s interest in avoiding social unrest affect their progress in minimizing their air pollution issues? 8.8 What Can I Do? Choose your transportation with pollution in mind, cut down on vehicle idling, and keep your car running properly. Look for ways to limit pollution at home and on campus by raising your thermostat in the summer and lowering it in the winter, as well as using ENERGY STAR appliances and battery-powered motors. Explore the impacts of new technology, such as what CityTree has done by using mosses in cities to remove particulate matter and capture greenhouse gases. Learn more about power generation in your community in order to influence local policy. Question 1 What gas composes the largest portion of Earth's atmosphere? A. oxygen B. nitrogen C. sulfur D. hydrogen Question 1 Answer What gas composes the largest portion of Earth's atmosphere? A. oxygen B. nitrogen (Correct) C. sulfur D. hydrogen Question 2 Ozone in the __________________ is important for absorbing and scattering much of the UV radiation coming into Earth's atmosphere from the sun. A. troposphere B. mesosphere C. thermosphere D. stratosphere Question 2 Answer Ozone in the __________________ is important for absorbing and scattering much of the UV radiation coming into Earth's atmosphere from the sun. A. troposphere B. mesosphere C. thermosphere D. stratosphere (Correct) Question 3 Typical patterns of atmospheric conditions in a specific location over years, decades, and longer time periods are described by _________________. A. climate B. sunspots C. the moon D. weather Question 3 Answer Typical patterns of atmospheric conditions in a specific location over years, decades, and longer time periods are described by _________________. A. climate (Correct) B. sunspots C. the moon D. weather Question 4 Morning commutes in urban areas can result in which type of secondary air pollution? A. ozone depletion B. acid rain C. smog D. carbon monoxide Question 4 Answer Morning commutes in urban areas can result in which type of secondary air pollution? A. ozone depletion B. acid rain C. smog (Correct) D. carbon monoxide Question 5 Which of the following is a successful market-driven mechanism for addressing air pollution in the United States? A. international treaties from global conferences B. carbon taxes C. carbon neutrality D. cap-and-trade Question 5 Answer Which of the following is a successful market-driven mechanism for addressing air pollution in the United States? A. international treaties from global conferences B. carbon taxes C. carbon neutrality D. cap-and-trade (Correct) Credits This concludes the Lecture PowerPoint presentation for Environmental Science and Sustainability, Chapter 8, by David Montgomery and Daniel Sherman For more resources, please visit https://digital.wwnorton.com /environsci2 Copyright © 2023 W. W. Norton & Compan y, Inc.