Chapter 19 Key Terms

Catalytic Converters

Catalytic converters, used immediately following combustion, oxidize most unburned gases. The use of properly functioning catalytic converters to treat auto exhaust reduces carbon monoxide and volatile hydrocarbon emissions by about 85% over the life of the car. Careful handling of petroleum and hydrocarbons, such as gasoline, paint thinner, and lighter fluid, reduces air pollution from spills and evaporation.

Temperature Inversion

During periods of temperature inversion, also called thermal inversion, polluting gases and particulate matter remain trapped in high concentrations close to the ground, where people live and breathe

Ultraviolet Radiation

Ozone (O3) is a form of oxygen that is a human-made pollutant in the troposphere but a naturally produced, essential component in the stratosphere, which encircles our planet some 10 to 45 km (6 to 28 mi) above the surface. The relatively high concentrations of ozone in the stratosphere form a layer that shields the surface from much of the ultraviolet (UV) radiation coming from the sun

Particulate Matter

Particulate matter consists of thousands of different solid and liquid particles suspended in the atmosphere. Solid particulate matter is generally referred to as dust, whereas liquid suspensions are commonly called mists. Particulate matter includes a variety of pollutants, such as soil particles, soot, lead, asbestos, sea salt, and sulfuric acid droplets. Particulate matter reduces visibility by scattering and absorbing sunlight.

Solid Particulate Matter

Solid particulate matter is generally referred to as dust, whereas liquid suspensions are commonly called mists.

Hazardous Air Pollutants

Some of these air pollutants, known as hazardous air pollutants (HAPs), or air toxics, are potentially harmful. To limit the release of more than 180 hazardous air pollutants, the Clean Air Act Amendments of 1990 (discussed later in the chapter) regulate emissions of both large and small businesses, such as bakeries, distilleries, dry cleaners, furniture makers, gasoline service stations, hospitals, auto paint shops, and print shops.

Sulfur Oxides

Sulfur oxides are gases produced by the chemical interactions between sulfur and oxygen. Sulfur dioxide (SO2), a colorless, nonflammable gas with a strong, irritating odor, is a major sulfur oxide emitted as a primary air pollutant.

Circumpolar Vortex

Sunlight returns to the polar region, and the circumpolar vortex develops—a mass of cold air that circulates around the southern polar region and isolates it from the warmer air on the rest of the planet.

Troposphere

troposphere—the layer of atmosphere closest to Earth's surface—is a human-made air pollutant. (Ground-level ozone does not replenish the ozone depleted from the stratosphere because ground-level ozone breaks down to form oxygen long before it drifts up to the stratosphere.) Ozone in the troposphere is a secondary air pollutant that forms when sunlight catalyzes reactions between nitrogen oxides and volatile hydrocarbons.

Carbon Oxides

Carbon oxides are the gases carbon monoxide (CO) and carbon dioxide (CO2). Carbon monoxide, a colorless, odorless, and tasteless gas produced in the largest quantities of any atmospheric pollutant except carbon dioxide, is poisonous and interferes with the blood's ability to transport oxygen.

Air Pollution

Air pollution consists of gases, liquids, or solids present in the atmosphere in high enough levels to harm humans, other organisms, or materials

Smog

Air pollution localized in urban areas, where it reduces visibility, is often called smog. The word smog was coined at the beginning of the 20th century for the smoky fog that was so prevalent in London because of coal combustion

Photochemical Smog

Another important type of smog is photochemical smog. This brownish-orange smog is called photochemical because light—that is, sunlight—initiates several chemical reactions that collectively form its ingredients. First noted in Los Angeles in the 1940s, photochemical smog is generally worst during the summer months. Both nitrogen oxides and hydrocarbons are involved in its formation.

Chlorofluorocarbons

Both chlorine-and bromine-containing substances catalyze ozone destruction. The primary chemicals responsible for release of chlorine in the stratosphere, thus causing ozone depletion, are chlorofluorocarbons (CFCs). Chlorofluorocarbons were used as propellants for aerosol cans, as coolants in air conditioners and refrigerators (for example, Freon), as foam-blowing agents for insulation and packaging, and as solvents.

Vapor Recovery

Gasoline is extremely volatile, and gasoline vapors can be a major source of VOCs. To reduce these emissions, gasoline sellers in most urban (and many rural) parts of the world require some form of vapor recovery. Phase I vapor recovery involves underground storage tanks at gas stations (Figure 19.10). As one hose from a delivery truck fills the underground tank, another returns the vapors in the tank—which otherwise would be vented to the atmosphere—to the truck. The truck then returns to the gasoline depot, where the vapors are either combusted or condensed into gasoline. Phase II vapor recovery involves removing vapor from gas tanks in cars as the gas is pumped in. These vapors are usually returned to the underground tank for removal in the phase I process.

Chronic Bronchitis

Generally speaking, exposure to even low levels of pollutants such as ozone, sulfur oxides, nitrogen oxides, and particulate matter can irritate eyes and inflame the respiratory tract (Table 19.2). Evidence shows that many air pollutants suppress the immune system, increasing susceptibility to infection. In addition, evidence continues to accumulate that exposure to air pollution during respiratory illnesses may result in the development later in life of chronic respiratory diseases, such as emphysema and chronic bronchitis.

Hydrocarbons

Hydrocarbons are a diverse group of organic compounds that contain only hydrogen and carbon; the simplest hydrocarbon is methane (CH4). Small hydrocarbon molecules are gaseous at room temperature.

Stratospheric ozone thinning

In 1985, however, stratospheric ozone thinning was first observed to be greater than could be explained by natural causes. This increased thinning, which occurs each September, is commonly referred to as the "ozone hole"

Montreal Protocol

In 1987 representatives from many countries met in Montreal to sign the Montreal Protocol, an agreement that originally stipulated a 50% reduction of CFC production by 1998. Despite this effort, the environmental news about CFCs continually worsened in the early 1990s. After scientists reported that decreases in stratospheric ozone occurred over the heavily populated midlatitudes of the Northern Hemisphere in all seasons, the Montreal Protocol was modified to include stricter measures to limit CFC production.

Emphysema

In addition, evidence continues to accumulate that exposure to air pollution during respiratory illnesses may result in the development later in life of chronic respiratory diseases, such as emphysema

Stratosphere

In the stratosphere, which extends from 12 to 50 km (7.5 to 30 mi) above Earth's surface, oxygen reacts with UV radiation coming from the sun to form ozone. Stratospheric ozone prevents much of the solar UV radiation from penetrating to Earth's surface. Unfortunately, certain human-made pollutants (chlorofluorocarbons, or CFCs) react with stratospheric ozone, breaking it down into molecular oxygen, O2.

Ozone

Ozone (O3) is a form of oxygen considered a pollutant in one part of the atmosphere but an essential component in another

Corporate average fuel economy

the corporate average fuel economy, or CAFE, standard required that the average fuel economy of all covered vehicles sold by a single company be 27.5 miles per gallon (mpg). One strategy to improve mileage is to shift to low carbon fuels

Lead

Lead, a soft metal that is used in industrial and chemical processes, has a variety of health impacts. Acute lead poisoning rarely results from outdoor exposure, but chronic effects can include permanently reduced cognitive ability, behavioral problems, slowed growth, hearing problems, and headaches

Stationary Sources

Main human source of primary air pollutants are industries..

Malignant Melanoma

Malignant melanoma, the most dangerous type of skin cancer, is increasing faster than any other type of cancer (Figure 19.14). Some forms of malignant melanoma spread rapidly through the body and may cause death a few months after diagnosis

Air Toxics

Most of the hundreds of other air pollutants—such as chlorine, lead, hydrochloric acid, formaldehyde, radioactive substances, and fluorides—are present in low concentrations, although it is possible to have high local concentrations of specific pollutants

Nitrogen Oxides

Nitrogen oxides are gases produced by the chemical interactions between atmospheric nitrogen and oxygen when a source of energy, such as combustion of fuels, produces high temperatures.

Green house gas

Nitrous oxide is associated with global warming (nitrous oxide traps heat in the atmosphere and is therefore a greenhouse gas) and depletes ozone in the stratosphere. Nitrogen oxides cause metals to corrode and textiles to fade and deteriorate.

Pollutants

Other gases and particles, including those we call pollutants, occur in much smaller concentrations. The two atmospheric gases most important to humans and other organisms are carbon dioxide and oxygen.

Atmosphere

The atmosphere is a gaseous envelope surrounding Earth

Ecosystem Services

The atmosphere performs additional ecosystem services, namely, blocking Earth's surface from much of the ultraviolet (UV) radiation coming from the sun, moderating the climate, and redistributing water in the hydrologic cycle.

Sherwood Rowland, Mario Molina, Paul Crutzen

The evidence linking CFCs and other human-made compounds to stratospheric ozone destruction includes laboratory measurements, atmospheric observations, and calculations by computer models. In 1995 the Nobel Prize in chemistry was awarded to Sherwood Rowland, Mario Molina, and Paul Crutzen, the scientists who first explained the connection between the thinning ozone layer and chemicals such as CFCs. This Nobel Prize was the first one ever given for work in environmental science.

Carbon Intensity

The goal of the LCFS is to reduce the carbon intensity, or amount of carbon produced per unit of energy, of fuel used in passenger vehicles by 10% or more by 2020. This means that alternative fuels—including biomass, hydrogen, and electricity—would represent a larger share of the fuel supply. Natural gas, a fossil fuel, could also play a role, since it has a lower carbon intensity than does gasoline.

Mobile Sources

The two main human sources of primary air pollutants are transportation (mobile sources) and industries (stationary sources)

Ulf Merbold

a German space shuttle astronaut, felt differently about the atmosphere after viewing it in space

Primary Air Pollutants

are harmful chemicals that enter directly into the atmosphere. The major ones are carbon oxides, nitrogen oxides, sulfur dioxide, particulate matter, and hydrocarbons

Industrial Smog

Today there are several different types of smog. Traditional London-type smog—that is, smoke pollution—is sometimes called industrial smog. The principal pollutants in industrial smog are sulfur oxides and particulate matter.

Secondary Air Pollutants

are harmful chemicals that form from other substances released into the atmosphere. Ozone and sulfur trioxide are secondary air pollutants because both are formed by chemical reactions that take place in the atmosphere.