Units 7+8 Review Book Pt. 2 Flashcards
(31 cards)
The Six Criteria Pollutants
The Environmental Protection Agency (EPA) has determined that there are six pollutants (familiarly referred to as the dirty half dozen) that do the most harm to human health and welfare, and refers to them as criteria pollutants.
carbon monoxide, CO
lead, Pb
ozone, O3
nitrogen dioxide, NO2
sulfur dioxide, SO2
particulates
measurements of gases in the atmosphere
In general, gases in the atmosphere are measured in units of parts per million, or ppm, when they are in relative abundance; when they are present in trace (very small) amounts, they are measured in parts per billion (ppb).
For example, if in a certain geographic area, the carbon dioxide content of the air is 10 ppm, this would mean that there are ten molecules of CO2 per one million molecules of air.
These pollutants are monitored with the National Ambient Air Quality Standards (NAAQS): these standards were established by the EPA to protect human health.
Carbon monoxide (CO)
Carbon monoxide (CO) is an odorless, colorless gas that’s typically released as a by-product of incompletely burned organic material, such as fossil fuels.
CO is hazardous to human health because it binds irreversibly to hemoglobin in the blood—the molecule that is responsible for transporting oxygen around the body from the lungs.
Hemoglobin has a higher affinity for CO than it does for oxygen, which means that in the presence of both CO and O2, CO will bind more readily than O2.
In our normal oxygen-rich environments, this competition is not a problem, but in areas where CO is present in large concentrations, it can be deadly.
More than 60 percent of the CO released into the atmosphere comes from vehicles that burn fossil fuels.
Lead
An air pollutant that, as you now know, has been around since the time of the Roman smelters.
It is generally released into the atmosphere as a particulate (a very small solid particle that can be suspended in the air), but then settles on land and water, where it is incorporated into the food chain and is subject to biomagnification.
If it enters the human body, it can cause numerous nervous system disorders, including cognitive and developmental disabilities in children.
At one time, lead entered the atmosphere primarily as a result of the burning of leaded gasoline.
However, lead gas has been phased out, and now the primary source of lead is industrial smelting.
Incidentally, the “lead” in your pencils is not the element lead; in fact, it’s the mineral graphite.
The graphite in pencils received the name “lead” because of its lead-like color when it’s transferred to paper.
Ozone
Notice that the ozone the EPA calls one of the dirty half dozen is specifically—and only—the ozone that’s formed as a result of human activity. All ozone is O3 and is the same chemically.
However, stratospheric ozone (which absorbs UV light from the sun and therefore protects life on our planet) is functionally very different from tropospheric ozone (a powerful respiratory irritant and precursor to secondary air pollutants).
Up high, ozone helps us; down low, it hurts us.
O3 is a secondary pollutant; it is formed in the troposphere as a result of the interaction of nitrogen oxides, heat, sunlight, and volatile organic compounds (VOCs— more on these later).
Tropospheric ozone is a major component of what we think of as smog (more on this later).
Nitrogen dioxide (NO2)
The next major culprit on the list, nitrogen dioxide (NO2), is one in a family of nitrogen and oxygen gases.
NO2 and the other nitrogen oxides are formed when atmospheric nitrogen and oxygen react as a result of exposure to high temperatures; this type of reaction occurs in combustion engines, for example.
In fact, more than half of the nitrogen oxides in the atmosphere are released as a result of combustion engines.
Other sources of nitrogen oxides are utilities and industrial combustion.
Nitrogen dioxide is also commonly found as a secondary pollutant and is a component of smog and acid precipitation.
Sulfur dioxide (SO2)
A colorless gas with a penetrating and suffocating odor.
It is a powerful respiratory irritant and is typically released into the air through the combustion of coal.
As we mentioned in Chapter 8, the use of scrubbers in coal-burning plants has helped reduce the amount of SO2 released into the atmosphere.
However, there are other sources of sulfur dioxide, including metal smelting, paper pulping, and the burning of fossil fuels, especially diesel.
Sulfur dioxide can also be a component of indoor pollution as a result of gas heaters, improperly vented gas ranges, and tobacco smoke.
In the atmosphere, SO2 reacts with water vapor to form acid precipitation.
Here’s one last note to help you with the test: both nitrogen and sulfur can combine with oxygen to make several different molecules.
Rather than a list of all the possible molecules, you might see the terms NOx and SOx. These terms (Ox) mean that there are several sulfur- and nitrogen- containing compounds mixed together.
Particulate matter
Like lead, it is not a gas, but exists in the form of small particles of solid or liquid material.
These particles are light enough to be carried on air currents, and when humans breathe them in, the particles act as irritants.
Examples include soot (black carbon) and sulfate aerosols.
There have been significant decreases in the atmospheric content of both lead and carbon monoxide since the 1970s, mostly because of the phasing out of lead gasoline and the introduction of car engines that burn more cleanly.
Many of the changes (in the United States, anyway) are due to the Environmental Protection Agency and the Clean Air Act (CAA)
first enacted in 1963: a U.S. federal law designed to control air pollution nationally, amended many times—to set standards for controlling automobile emissions, to address acid rain, ozone depletion, and toxic air pollution, and to make provisions for investigation and enforcement.
VOCs
However, there are other air pollutants that are of growing concern to environmentalists, including volatile organic compounds (VOCs), which are released as a result of various industrial processes including dry cleaning, the use of industrial solvents, and the use of propane.
VOCs can react in the atmosphere with other gases to form O3 and are a major contributor to smog in urban areas.
A couple of examples are formaldehyde and gasoline.
VOCs evaporate or sublimate at room temperature—hence the title “volatile.” Not all of them are human-made pollutants, though: trees also produce some VOCs naturally.
Gray smog
As you might be aware, the setting for many of the Sherlock Holmes mysteries is the foggy, smoggy city of London.
The smog that covered London throughout the 19th century, and well into the middle of the 20th century, was industrial smog—also known as gray smog or gray-air smog.
Tragedy and deaths from industrail smog led to Clean Air Act of 1956 in England.
Industrial smog is formed from pollutants that are typically associated with the burning of oil or coal.
When CO and CO2 are released in the process of combustion, they combine with particulate matter in the atmosphere and produce smog.
The production of smog can also be aided by weather conditions—air inversions, for example, which trap the pollutants; or fog, which holds the pollutants.
As we mentioned above, sulfur dioxide may be another component in gray smog, combining with water vapor to form sulfuric acid that is suspended in the cloud of smog.
Photochemical smog (brown smog)
Also known as brown smog—is a different type of smog, usually formed on hot, sunny days in urban areas, due to the large numbers of vehicles emitting the specific pollutants that cause it.
Many environmental factors, such as topography, amount of sunlight, temperature, humidity, and wind, affect its formation.
Photochemical smog hasn’t caused the acute disasters industrial smog has, but it can harm human health in several ways, including causing respiratory problems and eye irritation.
In photochemical smog, NOx compounds, VOCs, and ozone all combine to form smog with a brownish hue.
It’s also known as summer smog because of its tendency to form on warm, sunny days. Nitrogen oxide is produced early in the day.
The intensity of sunlight on these days also promotes the formation of ozone from the combination of NOx compounds.
Ozone concentrations peak in the afternoon and are higher in the summer because ozone is produced by chemical reactions between oxygen and sunlight.
Los Angeles, California, and Athens, Greece, are two cities that are particularly susceptible to photochemical smog.
Acid precipitation
in the form of acid rain, acid hail, acid snow, etc.
occurs as a result of pollution (from human-made or, occasionally, natural sources) in the atmosphere, primarily SO2 and nitrogen oxides.
These gases combine with water to form acids (typically nitric acid and sulfuric acid) that are deposited on the Earth through precipitation.
Because this acid is highly diluted, acid precipitation isn’t acidic enough to burn skin upon contact, but it does have a significant, measurable effect on humans and the environment.
Acid precipitation is responsible for the following effects:
leaching of some minerals from soil (which alters soil chemistry)
creating a buildup of sulfur and nitrogen ions in soil
increasing the aluminum concentration in soil to levels that are toxic for plants
leaching calcium ions from the needles of conifers
elevating the aluminum concentration in lakes to levels that are toxic to fish
lowering the pH of streams, rivers, ponds, and lakes, which may lead to fish kills
causing human respiratory irritation
damaging all types of rocks, including statues, monuments, and buildings
In certain areas acid precipitation happens more/is a bigger deal
Acid precipitation can be a chronic and significant problem for large urban areas with many vehicles and areas that are downwind of coal-burning plants.
While dry acid particle deposition occurs two to three days after emission into the atmosphere, wet deposition is usually delayed for four to fourteen days after emission; therefore, pollution from wet deposition can travel in air currents to locations that are many miles downwind of the emission source.
Some areas, like those with already acidic soils that were derived from granite, are particularly vulnerable to acid precipitation.
Other areas that are particularly vulnerable to acid precipitation are those where the soil has been leached of its natural calcium content.
This is because calcium acts as a natural buffer and tempers the effects of acid precipitation.
Acid rain is a significant cause of sink holes in Florida due to acid dissolving the limestone rock that much of Florida is made of.
In some areas of the world, progress has been made toward controlling acid precipitation.
The 1990 amendment to the Clean Air Act has led to significant reductions in the amounts of SO2 and NOx that are emitted from industrial plants.
Despite National Ambient Air Quality Standards (standards established by the United States Environmental Protection Agency), there is still considerable damage being done to soils and lakes in many areas, and these ecosystems will not be able to continue to tolerate significant lowering of their pH.
vehicles release less air pollution
Today, all new vehicles sold in the United States must meet the EPA standards (in California, they must meet certain standards set by the state).
Due to the Clean Air Act (the CAA) and its amendment (the CAAA), new cars (those produced after the year 1999) emit 75 percent fewer pollutants than cars made before 1970.
Catalytic converter
The most significant device in controlling emissions in cars is the catalytic converter.
This platinum-coated device oxidizes most of the VOCs and some of the CO that would otherwise be emitted in exhaust, converting them to CO2.
Newer models of catalytic converters also reduce nitrogen oxides, but not very successfully.
Vapor recovery nozzle
Another technology that can help reduce the pollution caused by motor vehicles is the vapor recovery nozzle: an air pollution control device used on gasoline pumps that prevents fumes from escaping into the atmosphere when fueling a vehicle.
CAFE (Corporate Average Fuel Economy)
As mentioned in Chapter 8, in the Energy Policy and Conservation Act of 1975, the Department of Transportation was given the authority to set what’s called Corporate Average Fuel Economy (CAFE) for motor vehicles.
CAFE was intended to reduce both fuel consumption and emissions (not surprisingly, because burning less gas creates less air pollution).
Starting in 2011, the CAFE standards were expressed as mathematical functions depending on the vehicle’s “footprint” (a measure of vehicle size determined by multiplying the vehicle’s wheelbase by its average track width).
That complicated 2011 mathematical formula was replaced starting in 2012 with a simpler formula with cut-off values.
In July 2011, President Obama announced an agreement with thirteen large automakers to increase fuel economy to 54.5 miles per gallon for cars and light-duty trucks by model year 2025.
All of these new standards will most likely result in higher purchase prices for vehicles, and they have certainly caused an outcry from auto manufacturers and oil refineries.
However, the new standards are expected to reduce air pollutants by two million tons per year.
Vehicles of the Future
In 1990, the state of California passed a No-Pollution Vehicle Law mandating that, by 2003, 10 percent of the cars sold in the state would be pollution-free.
That law was later rescinded because of problems with the development of the zero pollution electric car, which looked promising at the time the bill was passed.
In the past, electric cars were not widely adopted because they had a limited traveling range, they weighed more than their gasoline-burning counterparts, and they lacked amenities (like air conditioning).
However, a renewed interest as well as new battery technology, which increases energy storage and reduces cost, has motivated car makers to produce a promising generation of fully electric cars.
The Nissan Leaf, Chevrolet Bolt, and Tesla Model 3 are examples of some zero- pollution electric vehicles.
In addition to new electric cars, hybrid vehicles that run on a mixture of gas and electric power have been gaining popularity over the past few years, with the Toyota Prius leading the pack and many auto companies releasing hybrid versions of their standard vehicles.
New hybird cars and government regulations and incentives
Government regulations, incentives, and public acceptance will probably determine how quickly the hybrid car moves into the mainstream vehicle market.
One incentive that’s been offered at a federal level is a full-dollar tax credit.
The amount of the credit varies by car model.
T hat incentive is scheduled to be reduced unless a new energy bill changes it.
Some individual states also provide incentives to residents who purchase hybrid vehicles.
It is highly unlikely that Congress will enact legislation that will provide real incentives for the purchase of hybrid vehicles or other alternatives that would reduce air pollution from vehicles.
This is in part due to the fact that lobbying groups representing the oil companies and vehicle manufactures consistently lobby against these incentives.
However, in the future, grassroots organizations that are backed by the voting public may influence legislation.
Indoor air pollution is at hgher conccentrations
he idea of indoor air pollution and the concept of “sick building syndrome” are still relatively new, but it is now widely recognized that air pollutants are usually at a higher concentration indoors than outside.
This makes sense if you consider that pollutants that exist outside can also move inside as doors and windows are opened.
Once the pollutant is indoors, it remains trapped until air currents move it out the door or windows or through a ventilation system.
Additionally, indoor spaces have certain pollutants that are unique to them.
Indoor air pollution has big impact on health
The World Health Organization (WHO) estimates that indoor air pollution is responsible for 4 million annual deaths worldwide. (That’s one death every 8 seconds!)
According to the Environmental Protection Agency (the EPA), indoor air pollution is one of the five major environmental risks to human health.
One reason that indoor air pollution has such a great impact on health is because humans spend a significant amount of time indoors.
Especially in developed countries, people generally work and live in well-sealed buildings that have little air exchange.
indoor air pollutants in developing countries
one of the worst indoor air pollutants is material that’s used for fuel.
Dung, wood, and crop waste are the primary fuels used by more than half the world’s population to heat homes and cook food, and the particulate matter that results from burning these fuels can exceed acceptable levels by hundreds of times.
