Chapter 15: Air Pollution and Stratospheric Ozone Depletion – Flashcards
Unlock all answers in this set
Unlock answersquestion
air pollution
answer
the introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to harm plants, animals, and materials such as buildings, or to alter ecosystems; in general, pollution in the troposphere (the first 16 km [10 miles] of the atmosphere above the surface of the Earth); can occur naturally or anthropogenically and is a human health issue, esp. in developing countries and cities; is a global system (ex: air pollution in Asia has been responsible for acidic rainfall on the American West Coast); examples of inputs include automobiles, airplanes, and tall vegetation; removing factors are vegetation, soil, and atmospheric components (clouds, particles, or gases)
question
ground-level pollution
answer
tropospheric pollution
question
U.S. Clean Air Act (1970)
answer
identifies six pollutants that significantly threaten human well-being, ecosystems, and/or structures: sulfur dioxide, nitrogen oxides, carbon monoxide, particulate matter, tropospheric ozone, and lead
question
criteria pollutants
answer
the six major air pollutants identified by the Clean Air Act
question
other important air pollutants
answer
carbon dioxide, volatile organic compounds (VOCs), and mercury; not officially listed by the Clean Air Act but all considered harmful
question
sulfur dioxide (SO2)
answer
a corrosive gas that comes primarily from combustion of fuels such as coal and oil; it is a respiratory irritant and can adversely affect plant tissue as well; fossil fuels are derived from organic remains that naturally contain sulfur; during combustion, sulfur combines with oxygen to create sulfur dioxide; it is also naturally released by volcanoes and forest fires
question
nitrogen oxides (NOx)
answer
the 'x' indicates that there may be either one or two oxygen atoms per nitrogen: nitrogen oxide (NO), a colorless, odorless gas, and nitrogen dioxide (NO2), a pungent, reddish-brown gas; each easily transforms into the other; the atmosphere is 78% nitrogen gas (N2); all combustion in the atmosphere leads to the formation of some type of NOx; primary anthropogenic sources of NOx include automobiles and stationary sources (i.e. factories), and natural sources are forest fires, lightning, and microbial action in soils; NOx in the atmosphere contributes to the formation of tropospheric ozone and photochemical smog
question
carbon monoxide (CO)
answer
a colorless, odorless gas that is formed during incomplete combustion of most matter, and therefore is a common emission in vehicle exhaust and most other combustion processes; it is a significant component of urban air pollution, and can also be a dangerous indoor air pollutant when exhaust systems on natural gas heaters malfunction and, primarily in developing countries, where there may be poor ventilation when cooking with manure, charcoal, or kerosene
question
carbon dioxide (CO2)
answer
a colorless, odorless gas that is formed during the complete combustion of most matter, including fossil fuels and biomass; absorbed by plants during photosynthesis and released during cellular respiration; in general, the complete combustion of matter that produces CO2 is more desirable than the incomplete combustion that produces CO and other pollutants, but burning fossil fuels has contributed to additional CO2 in the atmosphere and led to its naming as a major pollutant
question
particulate matter (PM), particulates, and particles
answer
solid or liquid particles suspended in the air; comes from the combustion of wood, animal manure and other biofuels, coal, oil, and gasoline; commonly known as a class of pollutants released from the combustion of fuels such as coal and oil; diesel-powered vehicles give off more particulate matter (i.e. black smoke) versus gasoline-powered vehicles; other sources are road dust and rock-crushing operations (anthropogenic), volcanoes, forest fires, and dust storms (natural); scatters and absorbs sunlight, which affects photosynthesis (ex: 1816 explosion of the Java volcano)
question
PM10
answer
particles smaller than 10 micrometers that are considered a threat because they are not filtered out by the nose and throat and can be deposited deep within the respiratory tract
question
PM2.5
answer
are an even greater health concern because they deposit deeply within the respiratory tract and they tend to be composed of more toxic substances than particles in larger size ranges
question
haze
answer
reduced visibility caused primarily when PM from air pollution scatters light
question
oxides
answer
reactive compounds that remove electrons from other substances
question
photochemical oxidants
answer
a class of air pollutants formed as a result of sunlight acting on compounds such as NOx and SO2; they are generally harmful to plant tissue, human respiratory tissue, and construction materials; the most famous photochemical oxidant is ozone (O3)
question
ozone
answer
the most abundant and most frequently measured photochemical oxidant in the troposphere; harmful to both plants and animals and causes respiratory inflammations such as asthma and emphysema; in the presence of NOx and VOCs, O3 reacts to form even more harmful oxidants; in the presence of SO2 and NOx, O3 and its fellows can also enhance the formation of certain PMs, which contributes to light scattering
question
smog (smoke + fog)
answer
created by the mixing of oxidants and PM; partly responsible for hazy views and reduced sunlight observed in many cities
question
photochemical smog, Los Angeles-type smog, and brown smog
answer
a category of smog that is dominated by oxidants such as O3
question
sulfurous smog, London-type smog, and gray smog
answer
the other category of smog that is dominated by SO2 and sulfate compounds
question
atmospheric brown cloud
answer
a relatively new descriptive term that has been given to the combination of PM and O3; derived primarily from the combustion of fossil fuel and burning biomass; has been observed in cities and throughout entire regions (i.e. Asia); characterized by a brownish tint caused by the presence of black or brown light-absorbing particles and/or NO2; causes human health problems, PM and photochemical oxidants, economic harm (ex: poor visibility reduces tourism and inclination to vacation)
question
lead (Pb)
answer
a trace metal that occurs naturally in rocks and soils; present in small concentrations in fuels including oil and coal; Pb compounds were added to gasoline for many years to improve performance, but were then released into the air, traveled with the prevailing winds, and were deposited on the ground by rain or snow, becoming pervasive around the globe, including polar regions far from combustion source; phased out as a gasoline additive between 1975 and 1996, and since then its concentration in the air has dropped considerably; another persistent source of Pb is Pb-based paint in older buildings; toxic to the CNS and can affect learning and intelligence, particularly to young children
question
mercury (Hg)
answer
a trace metal found in coal and oil; toxic to the CNS of biotic organisms; the EPA regulates Hg through its hazardous air pollutants program; mercury concentrations have increased in the atmosphere due to the combustion of fossil fuels like coal; also increased in creatures like fish due to bioaccumulation; recently reduced in factory and emissions waste; because coal is a large source of mercury pollution, coal plants are facing increasingly rigorous standards
question
volatile organic compounds (VOCs)
answer
organic compounds that become vapors at typical atmospheric temperatures; many are hydrocarbons; often give off a strong aroma because their chemicals are easily released into the atmosphere; play an important role in the formation of photochemical oxidants like O3; not necessarily hazardous (i.e. those given off by trees); not currently a criteria air pollutant by watched carefully by scientists because of their potential to form photochemical oxidants
question
hydrocarbons
answer
compounds that contain carbon-hydrogen bonds, such as gasoline, lighter fluid, dry-cleaning fluid, oil-based paints, and perfumes
question
primary pollutants
answer
pollutant compounds that come directly out of the smokestack, exhaust pipe, or natural emission source (i.e. CO, CO2, SO2, NOx, suspended PM, and many VOCs)
question
secondary pollutants
answer
primary pollutants that have undergone transformation in the presence of sunlight, water, oxygen, or other compounds; because solar radiation provides energy for many of these transformations, and because water is usually involved, the conversion to secondary pollutants does not occur as rapidly at night as during the day or in dry environments as in wet environments; an example is O3, which is formed as a result of the emission of primary pollutants such as NOx and VOCs in the presence of sunlight; controlling secondary pollutants means trying to control the primary pollutants that create them
question
transportation
answer
the largest source of CO and NOx
question
human health
answer
the health of the human population and includes the elderly, children, and sensitive populations such as those with asthma
question
welfare
answer
refers to visibility, the status of crops, natural vegetation, animals, ecosystems, and buildings
question
National Ambient Air Quality Standards (NAAQS)
answer
the EPA periodically specifies concentration limits for each pollutant; for each pollutant the NAAQS note a concentration that should not be exceeded over a specific time period; if a locality violates a pollutant standard and does not make an attempt to improve air quality, it is subject to penalties; all criteria pollutant levels have decreased in the last twenty years according to NAAQS, but O3 and PM are on the rise
question
Black Triangle
answer
a large area of Eastern Europe contains a great deal of "brown" coal or lignite, which provides fuel for nearby coal-fired power plants and other industries; emissions from combustion of this high-sulfur-content coal have cause this area to become one of the most polluted areas in the world
question
the formation of smog
answer
the first part of the process takes place during the day in the presence of sunlight; if there is an abundance of NOx but very few VOCs, O3 forms; a few hours later, when sunlight intensity decreases, NO is still present in the atmosphere and the O3 recombines with NO, reforming into O2 + NO2; when petrochemicals or VOCs from human activity are absent or limited, the cycle of O3 formation and destruction generally takes place on a daily basis with relatively small amounts of photochemical smog formations, but when VOCs are present, they combine with NO; this means the NO is not available to break down O3 by recombining with it and a larger amount of O3 accumulates; atmospheric temperatures (usually higher temperatures) and location (most likely urban, but may occur elsewhere) are contributing factors
question
thermal inversion
answer
normally, temperature decreases as altitude increases, but sometimes a relatively warm layer of air at mid-altitude covers a layer of cold, dense air below; the warm inversion layer traps emissions that then accumulate beneath it, which causes severe pollution; particularly common in cities, where high concentrations of vehicle exhaust and industrial emissions are easily trapped by the inversion layer (ex: 1998, Tianjin, China)
question
acid deposition
answer
refers to deposition with a pH lower than 5.6; largely the result of human activity, although natural processes, such as volcanoes, may also contribute; formed by the combination of anthropogenically released NOx and SO2 with atmospheric oxygen and water vapor; a series of reactions forms secondary pollutants nitric acid and sulfuric acid; these break down further, producing nitrate, sulfate, and hydrogen ions (H+) that generate the acidity of acid deposition; occurs over a number of days and travels quickly; enters vegetation, soil, and water supply (greatest affect); also affects buildings that are built of limestone and marble
question
fluidized bed combustion
answer
removing SO2 from coal exhaust during combustion, in which granulated coal is burned in close proximity to calcium carbonate, reduces sulfur dioxide emissions; the heated calcium carbonate absorbs SO2 and produces calcium sulfate, which can be used in the production of sheetrock for houses; some of the SO that does escape the combustion processes can be captured by other methods after combustion
question
catalytic converters
answer
reduced the NO and CO emissions from cars; required in the U.S. since 1975; precious metals in catalytic converters (i.e. platinum and palladium) cannot be exposed to Pb, so leaded gasoline was fully eradicated
question
gravitational settling
answer
the simplest method of PM removal; relies on gravity to remove some of the PM as the exhaust travels through the smokestack; ash residue that accumulates must be disposed of in a landfill; depending on the fuel that was burned, the ash may contain sufficiently high concentrations of metals that require special disposal
question
fabric filters (baghouse filters)
answer
a type of filtration device that allows gases to pass through but removes PM; certain filters can remove almost 100% of PM emissions
question
electrostatic precipitators
answer
use an electrical charge to make particles coalesce so they can be removed; polluted air enters the precipitator and the electrically charged particles within are attracted to negative or positive charges on the sides of the precipitator
question
scrubbers
answer
uses a combination of water and air that actually separates and removes particles; particles are removed in the scrubber in a liquid or sludge form and clean gas exits; particles are sometimes ionized before entering the scrubber to increase its efficiency; also used to reduce SO2 emissions
question
smog reduction
answer
smog is particularly challenging to overcome because the main component of photochemical smog, O3, is a secondary pollutant; therefore, control efforts must be directed towards reducing primary pollutants first; most efforts are directed at reducing VOCs in urban areas; with fewer VOCs in the air there are fewer compounds to interact with NOx, and thus more NO will be available to recombine with O3; more recent regional efforts have focused on reducing NO emissions
question
innovative pollution control
answer
ex: reducing the amount of gas spilled at gas stations, restricting the evaporation of dry-cleaning fluids, restricting the use of lighter fluid (a VOC) for starting charcoal BBQs
question
limited automobile usage
answer
ex: Mexico City's every-other rule, China's mass transit expansion during the 2008 Beijing Olympics, carpool lanes
question
amendments of the Clean Air Act
answer
the free-market program (which allows the free market to determine the least expensive ways to reduce emissions of SO2), implemented in two phases (1995 and 2000); also includes the Acid Rain Program, which covers 3,000 factories; the sulfur allowance (ex: a facility that emits 1,000 tons of SO2 must possess at least 1,000 allowances that are usable in that year), which has led to a significant decrease in sulfur emissions
question
stratospheric ozone
answer
absorbs UV rays coming from the Sun and thereby prevents harmful UV radiation from reaching Earth; the Sun's energy occurs at many wavelengths, including harmful high-energy UV waves, medium-energy waves (visible light), and lower-energy infrared heat waves; UV rays are made up of an increasingly energetic spectrum; a protective layer of oxygen and O3 in the stratosphere absorbs over 99% of all incoming UV rays, allowing life to exist on land (historically, organisms only existed in water, as it protected them from these rays); stratospheric O3 and tropospheric O3 may be composed of the same gas, but the former acts as a barrier and the latter is a pollutant!
question
UV-A
answer
passes through the atmosphere without being absorbed and contributes to, and possibly irritates, skin cancer
question
UV-B and UV-C
answer
have enough energy to cause potentially significant damage to the tissues and DNA of living organisms
question
stratospheric ozone cycling
answer
1.) O2 + UV-C --> 2O 2.) O2 + O --> O3 3.) O3 + UV-B (or UV-C) --> O2 + O
question
chlorofluorocarbons (CFCs)
answer
the major source of Cl in the stratosphere is a class of anthropogenic compounds; this family of organic compounds have properties ideal for use in refrigeration and air conditioning, as propellants in aerosol cans to deliver ingredients (i.e. deodorant and insect repellant), and as "blowing agents" to inject air into foam products like Styrofoam cups and foam insulation; historically, CFCs were released into the atmosphere or escaped from leaky or broken appliances; features of CFCs are that they are extremely stable, inert, nontoxic, and nonflammable, which are the same features that allow them to harm the stratosphere; CFC bonds do not break down except in the presence of UV rays
question
breakdown of CFCs in the stratosphere
answer
1.) O3 + Cl --> ClO + O3 2.) ClO + O --> Cl + O2 3.) O3 + O --> 2O2
question
other harmful compounds
answer
NOx, bromines, and carbon tetrachloride are all anthropogenic compounds that can contribute to the destruction of stratospheric O3
question
ozone layer depletion
answer
in the mid-1980s, atmospheric researchers noticed that stratospheric O3 in Antarctica had been decreasing each year, beginning in about 1979, since the late 1970s, global O3 concentrations had decreased by more than 10%; depletion was greatest at the poles but occurred worldwide; researchers also determined that Antarctic O3 depletion was seasonal
question
ozone hole
answer
areas of severely caused ozone concentrations over most of Antarctica; its formation is highly complex; appears that extremely cold weather conditions during the polar winter cause a buildup of ice crystals mixed with NO; provides the perfect surface for the formation of the stable molecule Cl2, which accumulates as atmospheric Cl interacts with ice crystals; when the Sun reappears in the spring, UV radiation breaks down this molecule into Cl again, which in turn catalyzes more O3 destruction; because almost no O3 formed during the polar winter, a large hole occurs; the hole diminishes when the air warms and the Cl gets diluted; decreased stratospheric O3 has also increased incoming UV-B radiation, mostly at the poles (but it's still harmful, i.e. skin cancer, cataracts, suppressed immune system and photosynthesis)
question
Montreal Protocol on Substances That Deplete the Ozone Layer (1987)
answer
a promise by 24 nations to commit to concrete steps toward a solution of the ozone hole problem and to resolve to reduce CFC production 50% by 2000; a series of increasingly stringent amendments were also signed by more than 180 countries requiring the elimination of CFC usage by 1996; the Protocol addressed 96 CFC compounds
question
asbestos
answer
a long, thin, fibrous silicate mineral with insulating properties; for many years it was used as an insulator on steam and hot-water pipes and in the shingles for the siding of buildings; the greatest health risk from asbestos has been respiratory diseases such as asbestosis and lung cancer found in very high rates among those who have mined asbestos; asbestos becomes harmful and unstable as it ages or its fibers are damaged or disrupted (the fibers become airborne); asbestos has been banned as an insulator in the U.S. but can still be found in older buildings; asbestos removal is extremely difficult
question
Radon-222
answer
a radioactive gas that occurs naturally from the decay of uranium; exists in granitic and some other rocks and soils in many parts of the world; humans can receive significant exposure if it seeps into a home through cracks in the foundation or soil, or from drinking the water from underlying rock, soil, or groundwater; it decays within four days to a radioactive daughter product; radon and polonium can attach to dust and other particles in the air and then be inhaled, which causes a great risk of lung cancer, especially in smokers
question
Polonium-210
answer
the radioactive daughter product of Radon-222
question
sick building syndrome
answer
in newer buildings in developed countries, efforts are taken to create a more comfortable existence (i.e. more effective heating and cooling systems); this reduces energy use but may have the unintended side effect of allowing the buildup of toxic compounds and pollutants in an airtight space; these buildings may contain products made with synthetic materials and glues that create off-gassing if they're not fully dried, etc.; therefore, indoor levels of VOCs, hydrocarbons, etc. can be quite high
question
EPA's reasons for sick building syndrome
answer
1.) inadequate or faulty ventilation 2.) chemical contamination from indoor sources (ex: glues, carpeting) 3.) chemical contamination from outdoor sources (ex: vehicle exhaust) 4.) biological contamination (ex: mold, pollen)
