The links below provide an outline of the material for this lesson. Be sure to carefully read through the entire lesson before returning to Canvas to submit your assignments.
Lesson 4 deals particularly with Energy and the Environment. As mentioned before in the unit overview, this lesson is divided into 3 parts. Part A is basically looking at the products that are formed when we burn fossil fuels and the environmental effects of these fossil fuels products. In part B we are going to look at global effects of using fossil fuels and how they are changing the environment. We will also look, some other climate issues like acid rain, ozone layer destruction up above in the stratosphere. Go through part A, part B, and part C; together there will be one quiz for this lesson.
Upon completion of this lesson, you will be able to:
See the Calendar tab in Canvas for due dates/times.
If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!
In the first lesson on the world and the U.S. energy supply, we clearly established that the dependence on fossil fuels is still high (still at about 80 percent of the total energy in 2021).
In this section, we are going to look at what the fossil fuels are and the consequences when these fossil fuels are burnt.
As you may recall from an earlier lesson, these fuels, which we primarily depend on, were formed over millions of years by compression of organic material (plant and animal sources) prevented from decay and buried in the ground. They include:
Fossil fuels are hydrocarbons comprised primarily of the following elements: carbon and hydrogen and some sulfur, nitrogen, oxygen, and mineral matter. Mineral matter turns into ash when burnt.
The composition and the amounts of these elements change for different fossil fuels (coal, petroleum, and natural gas), but the elements are the same. For example, there is more hydrogen in liquid fuels than in coal per unit mass.
Combustion is rapid oxidation of the fossil fuel’s elements resulting in the generation of heat. When these elements oxidize (or combine with oxygen), products of combustion are formed.
Instructions: Click on the purple hot spot shown above the piece of coal below to determine what products are formed from each during combustion.
Some of the fuel (hydrocarbon) may not completely burn during combustion and therefore is released into the atmosphere along with the products. The products that are formed during combustion of fossil fuels are shown in the image below:
We will now look at six products of combustion:
Carbon dioxide is one of the maor products of combustion with fossil fuels since carbon accounts for 60–90 percent of the mass of fuels that we burn.
China has emerged as the largest single emitter of energy-related CO2 emissions, surpassing the U.S. in carbon dioxide emissions back in 2010. Now, China emits more than 10 million metric tons while the U.S. hovers around 5 million metric tons. The chart below shows the trend in carbon dioxide emissions since 1980. For Asia and Oceania, and particularly for China and India, emissions can be seen to have increased significantly in the past two decades.
In 2019, 29 % of CO2 emissions were from transportation, 25 % were from electricity production, 23 % were from industry processes the remaining quarter are from commercial, residential and agricultural applications.
If a carbon-based fuel and its products are not completely oxidized (i.e. not burned completely), carbon monoxide will be formed. Carbon monoxide, or CO, is a colorless, odorless gas. The figure below shows the contribution of various sources to the emissions of CO:
Carbon Monoxide is a component of motor vehicle exhaust, which contributes about 55 percent of all CO emissions nationwide. Other non-road engines and vehicles (such as construction equipment and boats) contribute about 22 percent of all CO emissions nationwide. Higher levels of CO generally occur in areas with heavy traffic congestion. In cities, 85 to 95 percent of all CO emissions may come from motor vehicle exhaust.
Other sources of CO emissions include industrial processes (such as metals processing and chemical manufacturing), residential wood burning, as well as natural sources such as forest fires. Woodstoves, gas stoves, cigarette smoke, and unvented gas and kerosene space heaters are sources of CO indoors.
The highest levels of CO in the outside air typically occur during the colder months of the year, when inversion conditions are more frequent. An inversion is an atmospheric condition that occurs when the air pollutants are trapped near the ground beneath a layer of warm air.
Sulfur dioxide, or SO2, belongs to the family of sulfur oxide gases (SOx). These gases dissolve easily in water. Sulfur is prevalent in all raw materials, including crude oil, coal, and ores that contain common metals, such as aluminum, copper, zinc, lead, and iron.
SOx gases are formed when fuel containing sulfur, such as coal and oil, is burned, and when gasoline is extracted from oil, or metals are extracted from ore. SO2 dissolves in water vapor to form acid and interacts with other gases and particles in the air to form sulfates and other products that can be harmful to people and their environment.
Nitrogen oxides, or NOx, is the generic term for a group of highly reactive gases, all of which contain nitrogen and oxygen in varying amounts. Many of the nitrogen oxides are colorless and odorless.
Nitrogen oxides form when fuel is burned at high temperatures, as in a combustion process. The primary sources of NOx are motor vehicles, electric utilities, and other industrial, commercial, and residential sources that burn fuels as shown in the figure below.
Although many of the nitrogen oxides are colorless and odorless, one common pollutant, nitrogen dioxide (NO2) along with particles in the air can often be seen as a reddish-brown layer over many urban areas.
The major sources of lead emissions have historically been motor vehicles (such as cars and trucks) and industrial sources.
Due to the phase-out of leaded gasoline, metals processing is the major source of lead emissions to the air today. The highest levels of lead in air are generally found near lead smelters (devices that process lead ores). Other stationary sources are waste incinerators, utilities, and lead-acid battery manufacturers.
Lead is used in the manufacturing of many items, including glass, rubber, paint, batteries, insecticides, plumbing, and protective shielding for X-rays.
Particulate matter (PM) is the general term used to describe a mixture of solid particles and liquid droplets found in the air. Some particles are large enough to be seen as dust or dirt. Others are so small they can be detected only with an electron microscope.
Different sizes of Particles include:
Different Sources of Particles include:
The chemical composition of PM depends on location, time of year, and weather. Generally, primary particles make up coarse PM and secondary particles make up most of fine PM.
The pollutants that are emitted directly from a combustion process – or the products of combustion - are called “primary pollutants.” We just described these products earlier in the lesson, now we will look at their impact on the environment and human health.
Carbon dioxide (CO2) is not a pollutant in the sense that would directly harm our health, but it is a proven greenhouse gas. It has an ability to absorb infrared radiation that is escaping from the surface of the earth, causing the atmosphere to warm up. Excessive emission of CO2 along with other greenhouse gases are linked to climate change, which is reaching a critical point.
As we learned earlier, Carbon monoxide, or CO, is a colorless, odorless and tasteless gas that is formed when carbon in fuel is not burned completely.
At much higher levels of exposure not commonly found in ambient air, CO can be poisonous, and even healthy individuals can be affected. Exposure to elevated levels of CO may result in:
The health threat from levels of CO sometimes found in the ambient air is most serious for those who suffer from cardiovascular disease such as angina pectoris.
In the human body, Hemoglobin (an iron compound) in the blood carries the oxygen (O20) from the lungs to various tissues and transports back carbon dioxide (CO2) to the lungs. Hemoglobin has 240 times more affinity toward CO than it does for oxygen. Therefore, when the hemoglobin reacts with CO, it reduces the hemoglobin that is available for the transport of O2. This in turn reduces oxygen supply to the body's organs and tissues.
High concentrations of SO2 can result in the following health problems:
Short-term exposure
- Adults and children with asthma who are active outdoors will experience temporary breathing impairment.
- Individuals with asthma may experience breathing difficulties with moderate activity and may exhibit symptoms such as wheezing, chest tightness, or shortness of breath.
Long-term exposure (along with high levels of PM)
- Aggravation of existing cardiovascular disease
- Respiratory illness
- Alterations in the lungs’ defenses
The subgroups of the population that may be affected under these conditions include individuals with heart or lung disease, as well as the elderly and children.
Instructions: Click on the types of air and observe what happens for each. (Note: The animation has no audio.)
Together, SO2 and NOx (discussed on the next page) are the major precursors to acidic deposition (acid rain), which is associated with the acidification of soils, lakes, and streams and accelerated corrosion of buildings and monuments. We will talk more about this in the next section. SO2 also is a major precursor to PM 2.5, which is a significant health concern, and a main contributor to poor visibility.
Nitric oxide (NO) and nitrogen dioxide (NO2) together are represented by NOx. Most of the emissions from combustion devices (approximately 90%) are in the form of NO.
NOx react in the air to form ground-level ozone and fine particulates, which are associated with adverse health effects.
NOx contributes to a wide range of environmental effects directly and when combined with other precursors in acid rain and ozone.
Acidification of soils causes the loss of essential plant nutrients and increased levels of soluble aluminum that are toxic to plants. Acidification of surface waters creates conditions of low pH and levels of aluminum that are toxic to fish and other aquatic organisms. NOx also contributes to visibility impairment.
Particles smaller than or equal to 10 µm (micro meter or millionth of a meter) in diameter can get into the lungs and can cause numerous health problems. Inhalation of these tiny particles has been linked with illness and death from heart and lung disease. Various health problems have been associated with long-term (e.g., multi-year) exposures to these particles. Shorter-term daily and potentially even shorter term peak (e.g., 1-hour) exposures to these particles can also be associated with health problems.
Particles can aggravate respiratory conditions, such as asthma and bronchitis, and have been associated with cardiac arrhythmias (heartbeat irregularities) and heart attacks. People with heart or lung disease, the elderly, and children are at highest risk from exposure to particles.
Particles of concern can include both fine and coarse-fraction particles, although fine particles have been more clearly linked to the most serious health effects.
In addition to health problems, PM is the major cause of reduced visibility in many parts of the United States by scattering and absorbing some of the light emitted or reflected by the body reducing the contrast. Airborne particles can also impact vegetation and ecosystems, and can cause damage to paints and building materials.
Instructions: See what happens when the name of each size of particulate matter is clicked on. (Note: The animation has no audio.)
Exposure to lead occurs mainly through inhalation of air and ingestion of lead in food, water, soil, or dust. It accumulates in the blood, bones, and soft tissues and can adversely affect the kidneys, liver, nervous system, and other organs.
Instructions: Click the "play" button to see the impact of using unleaded rather than leaded gasoline. (Note: The animation has no audio.)
The pollutants that are emitted directly from a combustion process are called “primary pollutants.” When emitted into the atmosphere, these primary pollutants combine with other reactants and form “secondary” pollutants.
An example of a secondary pollutant would be ozone. When hydrocarbons are emitted, and they react with NOx in presence of sunlight, they form ozone. Health and environmental effects of secondary pollutants are discussed in the next section: Global and Regional Effects of Pollutants.
The Earth is continuously receiving energy from the sun. Energy also leaves the Earth at night (of course in the form of invisible infrared energy!). Otherwise, the Earth would be continuously warming up. This delicate balance between the energy coming in and leaving due to natural greenhouse effect is what keeps the planet warm enough for us to live on.
It is very obvious that if more energy comes in than the energy that leaves, the planet will become warm. Similarly, if the energy that leaves is more than the energy that comes in, the planet will become cool. The atmospheric temperature fluctuates over centuries due to certain natural causes. However, our "recent" (on a geological timescale) use of fuels that have been trapped underground are quickly changing the environment outside of these natural norms.
Go to the next screen to view an animation of the greenhouse effect.
In the first lesson, we saw that energy can be transformed from one form to another, and during this conversion, all the energy that we put into a device comes out. However, all the energy that we put in may not come out in the desired form. Please watch the following presentation:
As can be seen from the Figure below, the amount of CO2 currently in the atmosphere is dramatically higher than previous levels even if we go back 800,000 years!
The onset of this dramatic rise corresponds to the industrial revolution and humanities increased use of CO2 producing fuels.
Our relationships with the greenhouse effect and greenhouse gases are complicated. A little bit is a good thing, and it plays a big role in what keeps us comfortable. However, too many greenhouse gases will heat up our planet and dramatically change climates throughout the world. It's also worth mentioning that CO2 is not the only greenhouse gas being produced by human activity.
The concentration of greenhouse gases in the atmosphere has been changing over the past 150 years. Since pre-industrial times, atmospheric concentrations of the gases have increased:
Scientists have confirmed that this is primarily due to human activities, which include burning coal, oil, and gas, and cutting down forests.
Hold your mouse over the pie chart to see what percentage each gas accounts for in the total greenhouse emissions in the United States, and look at the table below for information about the sources of the gasses.
Greenhouse Gas | Percent of Total Greenhouse Gases |
---|---|
Carbon Dioxide (C02) - Energy Related | 82% |
Carbon Dioxide (C02) - Other | 2% |
Methane (CH4) | 9% |
Nitrous Oxide (N2O) | 5% |
Other Gases (CFC-12, HCFC-22, CF4, SF6) | 2% |
The following list shows the greenhouse gasses and the source of emission:
As you can see, energy related CO2 and CH4 accounts for 90 percent of the total greenhouse gas emissions in the United States. This highlights the impact of energy use on the environment.
Atmospheric lifetime is the period of time during which a gas changes and is either transformed or removed from the atmosphere.
GWP is an index defined as the cumulative radiative forcing (infrared radiation absorption) between the present and some chosen time horizon caused by a unit mass of gas emitted now, expressed relative to a reference gas such as CO2, as is used here. GWP is an attempt to provide a simple measure of the relative radiative effects of different greenhouse gases. In terms of GWP, methane is a much stronger greenhouse gas (~30x more potent) compared to CO2.
As you can see from the graph below, CO2 values have risen dramatically in a very short amount of time. These changes correspond to our increased reliance on fossil fuels which took off in the 1900s.
Instructions: In the graph below, observe how CO2 concentration in the atmosphere has changed over the past 50 years. Based on your observations, answer the questions that follow.
Year | Parts per million (ppm) |
---|---|
1960 | 310 |
1970 | 320 |
1980 | 340 |
1990 | 360 |
2000 | 380 |
2010 | 390 |
2020 | 420 |
Data from the graph above was obtained from ice core samples of trapped air. More specifically, ice in the Polar Regions traps air from that particular time period, and then new ice is deposited over the previously deposited ice, trapping more air from the past. Thus, the analysis of ice core samples provides the composition of past air, which can be used to determine the past temperatures.
The increase in the greenhouse gases between 1950 and 2020 is believed to have caused an increase in the global temperature. The mean increase in the global temperature over the past one century is about 1 degree Celsius. However, this is the global average, which does not distinguish between ocean surface and land surface temperatures. The ocean surface increased by about 0.77 C whereas land temperatures increased by a staggering 1.43 C compared to pre-1900 temperatures. In other words, land areas are heating up about twice as fast!
Instructions: Review the graph below, showing the Annual mean for the Global surface temperature between years 1960 and 2020. The annual mean will show the detailed fluctuations.
Since 1880, about when the industrial age first started, the average increase in global temperature has been 1 degree Celsius.Not only has there been an increase in temperatures with the increase of greenhouse gasses, there has also been an increase in CO2 emissions from fossil fuels – this has been apparent over the last 150 years (since about 1850).
If we overlay the temperature plot with CO2 emissions, you can see a strong correlation between the rise in temperature and increased CO2 production.
So what will happen in the next few decades? Well, it is hard to say because it depends on what we do in the future. Do we continue to replace fossil fuels with renewables, or do we hold onto our existing practices a bit longer? Experts have tried to predict what will happen to global temperatures based on what we currently know about our climate. A key variable is how much additional CO2 we emit over the next few decades.
These assumptions are used within climate models to predict possible temperature changes into the year 2100.
Though a few degrees doesn't seem like much, this is only the average temperature across the whole planet. In practice, many regions on land will have temperature increases far beyond a few degrees. As such, many predict an increase in the frequency and magnitude of heat waves, forest fires and other nature disasters. These factors are pushing societies to weigh the consequences of cheap fuels with their environmental impacts.
Scientists know for certain that human activities are changing the composition of Earth's atmosphere. Increasing levels of greenhouse gases in the atmosphere, like carbon dioxide (CO2), have been well documented since pre-industrial times. There is no doubt this atmospheric buildup of carbon dioxide and other greenhouse gases is largely the result of human activities.
It's well accepted by scientists that greenhouse gases trap heat in the Earth's atmosphere and tend to warm the planet. By increasing the levels of greenhouse gases in the atmosphere, human activities are strengthening Earth's natural greenhouse effect. The key greenhouse gases emitted by human activities remain in the atmosphere for periods ranging from decades to centuries.
A warming trend of about 1oC has been recorded since the late 19th century. Warming has occurred in both the northern and southern hemispheres, and over the oceans. Confirmation of twentieth-century global warming is further substantiated by melting glaciers, decreased snow cover in the Northern Hemisphere, and even warming below ground.
Impact of Global Warming on such things as health, water resources, polar regions, coastal zones, and forests is likely, but it is uncertain to what extent.
The most direct effect of climate change would be the impacts of the hotter temperatures, themselves. Extremely hot temperatures increase the number of people who die on a given day for many reasons:
Changing climate is expected to increase both evaporation and precipitation in most areas of the United States. In those areas where evaporation increases more than precipitation, soil will become drier, lake levels will drop, and rivers will carry less water. Lower river flows and lower lake levels could impair navigation, hydroelectric power generation, and water quality, and reduce the supplies of water available for agricultural, residential, and industrial uses. Some areas may experience increased flooding during winter and spring, as well as lower supplies during summer.
Climate models indicate that global warming will be felt most acutely at high latitudes, especially in the Arctic, where reductions in sea ice and snow cover are expected to lead to the greatest relative temperature increases. Ice and snow cool the climate by reflecting solar energy back to space, so a reduction in their extent would lead to greater warming in the region.
Sea level is rising more rapidly along the U.S. coast than worldwide. Studies by EPA and others have estimated that along the Gulf and Atlantic coasts, a one-foot (30 cm) rise in sea level is likely by 2050.
In the next century, a two-foot rise is most likely, but a four-foot rise is possible. Rising sea level inundates wetlands and other low-lying lands, erodes beaches, intensifies flooding, and increases the salinity of rivers, bays, and groundwater tables. Low-lying countries like the Maldives located in the Indian Ocean and Bangladesh may be severely affected. The world may see global warming refugees from these impacts.
The projected 2°C (3.6°F) warming could shift the ideal range for many North American forest species by about 300 km (200 mi.) to the north.
Scientists have identified that our health, agriculture, water resources, forests, wildlife, and coastal areas are vulnerable to the changes that global warming may bring. But projecting what the exact impacts will be over the twenty-first century remains very difficult. This is especially true when one asks how a local region will be affected.
Scientists are more confident about their projections for large-scale areas (e.g., global temperature and precipitation change, average sea level rise) and less confident about the ones for small-scale areas (e.g., local temperature and precipitation changes, altered weather patterns, soil moisture changes). This is largely because the computer models used to forecast global climate change are still ill-equipped to simulate how things may change at smaller scales.
Some of the largest uncertainties are associated with events that pose the greatest risk to human societies. IPCC cautions, "Complex systems, such as the climate system, can respond in non-linear ways and produce surprises." There is the possibility that a warmer world could lead to more frequent and intense storms, including hurricanes. Preliminary evidence suggests that, once hurricanes do form, they will be stronger if the oceans are warmer due to global warming. Stil, the net result appears to be a more complex environment that is less hospitable compared to what we are accustomed.
Today, there is no single action that will reverse the course of climate change. The main question is whether we want to wait and adapt to a new environment, or whether we want to start to do something now?
There is certainty that human activities are rapidly adding greenhouse gases to the atmosphere, and that these gases warm our planet. This is the basis for concern about global warming.
The fundamental scientific uncertainties are these: How much more warming will occur? How fast will this warming occur? And what are the potential adverse effects? These uncertainties will be with us for some time, but many suspect that point of no return is well past us. If we don't change our habits soon, we will be stuck with a warmer world until we find a way to reduce the concentration of greenhouse gases in our atmosphere.
Global warming poses real risks, and those risks increase as we continue to change the composition of the atmosphere. Ultimately, this is why we have to use our best judgment—guided by the current state of science—to determine what the most appropriate response to global warming should be.
When faced with this question, individuals should recognize that, collectively, they can make a difference. In some cases, it only takes a little change in lifestyle and behavior to make some big changes in greenhouse gas reductions. For other types of actions, the changes are more significant.
When that action is multiplied by the 300 million people in the U.S. or the 7 billion people worldwide, the savings are significant. The actions include being energy efficient in the house, in the yard, in the car, and in the store.
Everyone's contribution counts, so why not do your share?
Energy Efficiency Means Doing the Same (or More) with less Energy. When individual action is multiplied by the 300 million people in the U.S., or the 6 billion people worldwide, the savings can be significant.
Instructions: You can help save the environment by making changes from the top to the bottom of your home. Click on the hot spots below to see how you can make a difference:
To review, these are the things you can do in your home – from top to bottom - to protect from the environment:
When you remodel, build, or buy a new home, incorporate all of these energy efficiency measures—and others.
Each of us, in the U.S., contributes about 22 tons of carbon dioxide emissions per year, whereas the world average per capita is about 6 tons.
The good news is that there are many ways you and your family can help reduce carbon dioxide pollution and improve the environment for you and your children.
Acid rain is a serious environmental problem around the world, particularly affecting Asia, Europe, and large parts of the U.S. and Canada. The acidic pollutants such as SO2 and NOx are emitted into the environment by combustion of fossil fuels.
Most of the sulfur in any fuel combines with oxygen and forms SO2 in the combustion chamber. This SO2 when emitted into the atmosphere slowly oxidizes to SO3. SO3 is readily soluble in water in the clouds and forms H2SO4 (sulfuric acid).
Most of the NOx that is emitted is in the form of NO. This NO is oxidized in the atmosphere to NO2. NO2 is soluble in water and forms HNO3 (nitric acid).
Sunlight increases the rate of most of the SO2 and NO reactions. The result is a mild solution of sulfuric acid and nitric acid. "Acid rain" is a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is acid deposition, which has two parts: wet and dry.
Prevailing winds blow the compounds that cause both wet and dry acid deposition across state and national borders, and sometimes over hundreds of miles. Please watch the 1:22 presentation below to learn more about the process of acid deposition.
Acid rain is measured using a pH scale.
pH is a measure of hydrogen ion concentration, which is measured as a negative logarithm. In other words, acids produce hydrogen ions and alkalis produce hydroxyl ions, so pH is the power of a solution to yield hydrogen ions [H+].
The pH scale ranges from 0 to 14 and indicates how acidic or basic a substance is.
The lower a substance's pH, the more acidic it is. Each whole pH value below 7 (the neutral point) is ten times more acidic than the next higher value.
The higher a substance’s pH, the more basic or alkaline it is.
Pure water has a pH of 7.0. Normal rain is slightly acidic because carbon dioxide dissolves into it, so it has a pH of about 5.5. As of the year 2000, the most acidic rain falling in the US has a pH of about 4.3.
Below is a video demonstration that replicates the effect of acid rain on plant life. In this video, beans are placed in: a) water, b) slightly acidic water and c) acidic water, and their growth is observed over a period of three days. Please watch the following 5:35 video:
Acid rain results in many negative consequences. Place your mouse over the image below to see the effects of acid deposition.
Acid rain does not usually kill trees directly. Instead, it is more likely to weaken trees by:
Quite often, injury or death of trees is a result of these effects of acid rain in combination with one or more additional threats. Click on the hot spots in the image below to see the effects of acid rain on the forest:
Acid rain causes acidification of lakes and streams and contributes to damage of trees at high elevations (for example, red spruce trees above 2,000 feet) and many sensitive forest soils. Several regions in the U.S. were identified as containing many of the surface waters sensitive to acidification. They include the:
Some types of plants and animals can handle acidic waters. Others, however, are acid-sensitive and will be lost as the pH declines. View the image of the fish, shellfish, and insects below to see what pH levels they can tolerate:
Acid rain and the dry deposition of acidic particles contribute to the corrosion of metals (such as bronze) and the deterioration of paint and stone (such as marble and limestone). These effects seriously reduce the value to society of buildings, bridges, cultural objects (such as statues, monuments, and tombstones), and cars.
Sulfates and nitrates that form in the atmosphere from sulfur dioxide (SO2) and nitrogen oxides (NOx) emissions contribute to visibility impairment, meaning we can't see as far or as clearly through the air.
Sulfate particles account for 50 to 70 percent of the visibility reduction in the eastern part of the United States, affecting our enjoyment of national parks, such as the Shenandoah and the Great Smoky Mountains.
Through the Acid Rain Program, SO2 reductions will be completed to improve visual range at national parks located in the eastern United States. Based on a study of the value national park visitors place on visibility, these reductions are expected to be worth over a billion dollars annually by the year 2010.
In the western part of the United States, nitrates and carbon also play roles, but sulfates have been implicated as an important source of visibility impairment in many of the Colorado River Plateau national parks, including the Grand Canyon, Canyonlands, and Bryce Canyon.
Acid rain looks, feels, and tastes just like clean rain. The harm to people from acid rain is not direct. Walking in acid rain, or even swimming in an acid lake, is no more dangerous than walking or swimming in clean water. However, the pollutants that cause acid rain also damage human health.
You can do the following to protect the environment:
Ozone (O3) is a triatomic oxygen molecule gas that occurs both in the Earth’s upper atmosphere and at ground level. Ozone can be good or bad, depending on where it is found: It is a bluish gas that is harmful to breathe. Therefore, it is bad at the ground level.
The presentation below shows the process of ozone depletion. Ozone depletion is caused by chlorofluorocarbons (CFCs) and other ozone-depleting substances. Please watch the following 1:16 video.
Ozone is constantly produced and destroyed in a natural cycle, as shown in the figure below. However, the overall amount of ozone is essentially stable. This balance can be thought of as a stream's depth at a particular location. Although individual water molecules are moving past the observer, the total depth remains constant. Similarly, while ozone production and destruction are balanced, ozone levels remain stable. This was the situation until the past several decades. Please watch the following 1:32 video about ozone destruction.
Large increases in stratospheric chlorine and bromine, however, have upset the balance of the Ozone. In effect, they have added a siphon downstream, removing ozone faster than natural ozone creation reactions can keep up. Therefore, ozone levels fall.
Since ozone filters out harmful UVB radiation, less ozone means higher UVB levels at the surface. The more the ozone is depleted, the larger will be the increase in incoming UVB radiation. UVB has been linked to:
Although some UVB reaches the surface even without ozone depletion, its harmful effects will increase as a result of this problem.
Ozone-Depleting Substance(s) (ODS) are:
Recent studies by NASA and others have indicated that about 40 percent of the ozone in the Antarctica has been destroyed and that about 7 percent of ozone is destroyed from the Arctic Circle. The destruction of ozone is also called “Ozone Hole."
Ozone hole does not mean that there is no ozone in the region. The ozone hole is defined as the area having less than 220 dobson units (DU) of ozone (concentration) in the overhead column (i.e., between the ground and space).
The image below shows the reduction in ozone concentration over Antarctica. This hole in the Antarctica is unfortunately allowing more Australians to be exposed to UV radiation. However, if this kind of ozone destruction ever takes place in the Arctic zone, more humans (in the Northern Hemisphere) would be exposed to higher levels of UVB radiation.
A Dobson Unit is the measure of the amount or thickness of ozone in the atmosphere. It is based on a measurement taken directly above a specific point on the Earth's surface. One Dobson unit refers to a layer of ozone that would be 0.001 cm thick under conditions of standard temperature (0 degree C) and pressure (the average pressure at the surface of the Earth). The Dobson unit was named after G.M.B. Dobson, who was a researcher at Oxford University in the 1920s. He built the first instrument (now called the Dobson meter) to measure total ozone from the ground.
The size of the Southern Hemisphere ozone hole as a function of the year is shown in the figure below. The graph compares the size of the hole over a twenty-year period, from 1980 to 2010. It can be seen that the size increased each year. Each year, in the spring, the ozone hole is at its largest.
Effects of ozone depletion can result in 1) increased cases of skin cancer, 2) skin damage, 3) cataracts and other eye damage, and 4) immune suppression.
The incidence of skin cancer in the United States has reached epidemic proportions. One in five Americans will develop skin cancer in their lifetime, and one American dies every hour from this devastating disease.
Medical research is helping us understand the causes and effects of skin cancer. Many health and education groups are working to reduce the incidence of this disease, of which 1.3 million cases have been predicted for 2000 alone, according to The American Cancer Society. The figure below shows the sources of ozone depleting substances.
Melanoma, the most serious form of skin cancer, is also one of the fastest growing types of cancer in the United States. Many dermatologists believe there may be a link between childhood sunburns and melanoma later in life. Melanoma cases in this country have more than doubled in the past 2 decades, and the rise is expected to continue.
Nonmelanoma skin cancers are less deadly than melanomas. Nevertheless, left untreated, they can spread, causing disfigurement and more serious health problems. More than 1.2 million Americans will develop nonmelanoma skin cancer in 2000 while more than 1,900 will die from the disease. There are two primary types of nonmelanoma skin cancers.
These two cancers have a cure rate as high as 95 percent if detected and treated early. The key is to watch for signs and seek medical treatment.
Other UV-related skin disorders include actinic keratoses and premature aging of the skin.
Protect yourself against sunburn. Minimize sun exposure during midday hours (10 am to 4 pm). Wear sunglasses, a hat with a wide brim, and protective clothing with a tight weave. Use a broad spectrum sunscreen with a sun protection factor (SPF) of at least 15. To be safer, 30 is better.
Cataracts are a form of eye damage in which a loss of transparency in the lens of the eye clouds vision. If left untreated, cataracts can lead to blindness. Research has shown that UV radiation increases the likelihood of certain cataracts. Although curable with modern eye surgery, cataracts diminish the eyesight of millions of Americans and cost billions of dollars in medical care each year.
Instructions: Place your mouse over the image below to see the effect cataracts can have on vision. (Note: This video has no audio.)
Other kinds of eye damage include pterygium (i.e., tissue growth that can block vision), skin cancer around the eyes, and degeneration of the macula (i.e., the part of the retina where visual perception is most acute). All of these problems can be lessened with proper eye protection from UV radiation.
Scientists have found that overexposure to UV radiation may suppress proper functioning of the body's immune system and the skin's natural defenses. All people, regardless of skin color, might be vulnerable to effects including impaired response to immunizations, increased sensitivity to sunlight, and reactions to certain medications.
Your “Power” in Protecting the Environment from Ozone Depletion
In 1987, the Montreal Protocol, an international environmental agreement, established requirements that began the worldwide phase out of ozone-depleting CFCs (chlorofluorocarbons). These requirements were later modified, leading to the phase out in 1996 of CFC production in all developed nations.
Ozone is a secondary pollutant that forms from the primary pollutants such as Volatile Organic Compounds (Hydrocarbons) and nitrogen oxides (NOx) in the presence of sunlight. Its formation is mainly from the automobile emissions.
Below is a demonstration on how ozone forms at the ground level (note ground level ozone is also known as “bad” ozone). Please watch the following 5:29 video:
As previously mentioned, the formation of ozone is mainly from automobile emission. A typical profile of pollutants in the air of major cities is well repeatable and is shown in the figure below. Note how the formation changes over the course of a day:
Ozone, by itself, is damaging to health and also to the environment. Ozone triggers a variety of health problems even at very low levels and may cause permanent lung damage after long-term exposure. Ozone also leads to the formation of smog or haze, causing additional problems such as a decrease in visibility as well as damage to plants and ecosystems.
As we have learned, volatile Organic Compounds (Hydrocarbons) combine with nitrogen oxides (NOx) in the presence of sunlight to form ozone.
In turn, sunlight and hot weather cause ground-level ozone to form in harmful concentrations in the air. As a result, it is known as a summertime air pollutant.
Many urban areas tend to have high levels of "bad" ozone, but even rural areas are also subject to increased ozone levels because wind carries ozone and pollutants that form it hundreds of miles away from their original sources.
View the graph below to compare the major sources of NOx and VOC that help to form ozone.
Several groups of people are particularly sensitive to ozone—especially when they are active outdoors—because physical activity causes people to breathe faster and more deeply. In general, as concentrations of ground-level ozone increase, more and more people experience health effects, the effects become more serious, and more people are admitted to the hospital for respiratory problems. When ozone levels are very high, everyone should be concerned about ozone exposure.
Click on the hotspots in the image below to find out what you can do to protect the environment.
The questions below are your chance to test and practice your understanding of the content covered in this lesson. In other words, you should be able to answer the following questions if you know the material that was just covered! If you have problems with any of the items, feel free to post your question on the unit message board so your classmates, and/or your instructor, can help you out!
You must complete a short quiz that covers the reading material in lesson 4. The Lesson 4 Quiz, can be found in the Lesson 4: Energy and the Environment module in Canvas. Please refer to the Calendar in Canvas for specific time frames and due dates.
Links
[1] http://www.flickr.com/photos/pelegrino/3222848999/lightbox/#/
[2] http://www.flickr.com/photos/pelegrino/
[3] http://creativecommons.org/licenses/by-nc-sa/2.0/
[4] http://www.flickr.com/photos/ex_magician/3620349271/lightbox/#/
[5] http://www.flickr.com/photos/ex_magician/
[6] http://creativecommons.org/licenses/by-nc-nd/2.0/
[7] http://www.giss.nasa.gov/research/observe/surftemp/2002fig1.gif
[8] https://www.nature.com/articles/d41586-020-01125-x
[9] http://www.flickr.com/photos/mafleen/292293822/lightbox/
[10] http://www.flickr.com/photos/mafleen/
[11] http://www.flickr.com/photos/goldyohio/5110977636/lightbox/
[12] http://www.flickr.com/photos/goldyohio/
[13] http://www.flickr.com/photos/39544517@N08/4677323288/lightbox/
[14] http://www.flickr.com/photos/39544517@N08/
[15] http://creativecommons.org/licenses/by-nc/2.0/
[16] http://www.epa.gov/ozone/science/process.html
[17] http://ozonewatch.gsfc.nasa.gov/
[18] http://www.nasa.gov/
[19] https://cfpub.epa.gov/airnow/index.cfm?action=ozone_health.index