What Are the Major Pollutants in Air?

Transcription

1 Learning Set 3 What Are Pollutants, and How Do They Get Into Air? Props 2 microphones 2 notebooks empty spray bottle < 0.1% 3.1 Understand the Question What Are the Major Pollutants in Air? carbon dioxide (CO 2 ) carbon monoxide (CO) sulfur dioxide (SO 2 ) nitrogen oxides (NO x ) ozone (O 3 ) mercury (Hg) lead (Pb) soot (C x ) all other substances argon 0.93% oxygen 21% Components of Air nitrogen 78% Pollutants are less than one percent of air, but they can be very dangerous, even deadly. Even though pollutants make up only a tiny amount of the air you breathe, they can be very dangerous, even deadly. Knowing what the pollutants are and how they become part of the air is very important to identifying ways to improve air quality. Explore The Sickening Six To find out what pollutants are commonly found in air, you will be meeting some pollutants in person in a short play. First, listen to the play and pay attention to the pollutants that are mentioned. Then, read the play again, record the information in your Sickening Six page, and answer the Stop and Think questions at the end. Project-Based Inquiry Science AQ 114

2 3.1 Understand the Question Cast of Characters: Susie Lung reporter Billy Wheezer reporter Sammy Soot (PM) Carbon Monoxide Sulfur Dioxide Nitrogen Monoxide Opal Ozone Mercury Setting: In front of the Environmental Protection Agency (EPA) building in Los Angeles. The air pollutants are picketing the EPA. Some carry picket signs with phrases such as: Dirty Air: Let s Keep It That Way! Down with the Clean Air Act, and so on. TV reporters Susie Lung and Billy Wheezer are at center stage, each holding a microphone and a notebook. In turn, each pollutant comes over to be interviewed. Meanwhile, the other pollutants continue to picket in the background. AQ 115 Environmental Protection Agency (EPA): the government agency that protects, restores, and improves the environment to guarantee public health and environmental quality. AIR QUALITY

3 Learning Set 3 What Are Pollutants, and How Do They Get Into Air? Susie: Hi! I m Susie Lung. Clean Air Act: the law that defines the Environmental Protection Agency s responsibilities for protecting and improving the nation s air quality. Billy: And I m Billy Wheezer. We re here in Los Angeles at the Environmental Protection Agency building to cover a late-breaking story. Six of the world s worst air polluters have gathered here to picket the EPA. They re protesting the Clean Air Act. Susie: In tonight s special report, we ll give you the scoop on who these pollutants are, where they come from, and the ways they can harm people, plants, and animals. Billy: Our first interview is with Sammy Soot, also known as Particulate Matter. Sammy Soot (chanting): Dust, soot, and grime. Pollution s not a crime. Soot, grime, and dust. The EPA s unjust! Susie (coughing): So you re a part of the Matter family, Particulate Matter. Sammy Soot: Yeah, that s me. Billy: You re one of those tiny bits of pollution that make air look really dirty? Sammy Soot: Yeah. Most of us get into the air when stuff is burned such as gasoline in cars and trucks, or coal in a power plant, and even wood in a wood-burning stove! And we just love to get into your eyes and make them itch and into your lungs and make you cough, and (turns to look at picketers, who are now sitting down). Hey! Get up and march! (turns to reporters) I gotta get back to the picket line. (Sammy Soot returns to the picket line and scolds the slackers. Meanwhile, Carbon Monoxide sneaks up behind Billy.) Billy: Let s introduce the folks back home to our next pollutant, Carbon Monoxide. Hey! Where did he go? Oh, there you are! Pretty sneaky, Carbon Monoxide. Project-Based Inquiry Science AQ 116

4 3.1 Understand the Question Carbon Monoxide: Yeah, sneaking up on people is what I do best. I get into the air when cars and trucks burn fuel but you can t see me because I m a gas, AND I don t even have a smell. You might confuse me with oxygen and nitrogen, but it takes only a few of me to make you really sick. Susie (rubbing her temples): Then how can we tell when you re around? Carbon Monoxide (chuckles): Oh, you ll find out when you breathe me in! I can give you a bad headache and make you really tired. Really tired (gives an evil laugh). Billy (yawning): Oh I see what you mean. Thanks for talking with us, Carbon Monoxide. (Billy yawns again.) (Carbon Monoxide returns to the picket line.) Susie (turns to face Sulfur Dioxide): Next we d like you to meet Sulfur Dioxide. I understand you just blew in from the Midwest. Sulfur Dioxide: Hey, I wouldn t miss this for all the pollution in Los Angeles! Billy: I m sure the folks at home would like to know how you get into our air. Sulfur Dioxide: Well, heck, don t they read the newspapers? I ve been making the headlines for years! Most of the time, I just shoot out of the smokestacks of power plants when they burn coal to make electricity. I start as part of the coal and then hook up with my friend, oxygen, and we move through the air as a gas. Very little of me in the air can make really big changes in air quality. Susie: And what kind of nasty things do you do? Sulfur Dioxide: Nasty, that s me (snickers). I hang out with oxygen and nitrogen, but there aren t many of me compared to them. I can be a big problem, though. I think it s cool to make it hard for people to breathe. And I can hurt trees and other plants, too. You think these other pollutants are tough? I can even dissolve rocks. But here s the most rotten thing I do. When I get way up in the atmosphere, I mix with AQ 117 AIR QUALITY

5 Learning Set 3 What Are Pollutants, and How Do They Get Into Air? water in the sky, and presto! I become part of acid rain! (pretends to spray water from a water bottle at the reporters). Billy (brushing at his clothing): Watch that stuff! It will ruin my suit! Acid rain is a big problem. It can kill fish and hurt other animals that live in lakes and rivers. Most scientists think it makes trees sick. Acid rain can even eat away at statues and buildings. Sulfur Dioxide (proudly): That s right. Hey, I can even travel a long way to do my dirty work. If I get pumped out of a smokestack in Ohio, I can ride the wind for hundreds of miles and turn up as acid rain in New York! Susie: It is sure nice saying good-bye to you, Sulfur Dioxide. (Susie coughs.) Billy (to the audience): She s really rotten! Nitrogen Monoxide: You think Sulfur Dioxide is rotten? You haven t met me! Susie: You must be one of the Nitrogen Oxides, aren t you? How do you get into the air? Nitrogen Monoxide: Easy. I get airborne when cars, trucks, and airplanes burn fuel. Right out the old tailpipe. Billy: And what happens once you re in the air? Nitrogen Monoxide: Sulfur Dioxide thinks she s such a big shot. But I can make people s lungs hurt, too especially people who already have asthma. And, like Sulfur Dioxide, I m formed in power plants, mix with water in the air, and form acid rain. But I can do one more trick that Sulfur Dioxide can t. Susie: Oh, please tell us! (She sticks her microphone in Nitrogen Monoxide s face.) Nitrogen Monoxide (taking the microphone): Better than that, I ll introduce her to you. Meet my daughter, Opal Ozone! Billy (astonished): Opal Ozone! Here, in LA? Project-Based Inquiry Science AQ 118

6 3.1 Understand the Question Opal Ozone: Where else? Billy (stammering): B-b-b-b-b-but, I thought all the ozone was way up in the stratosphere and was doing good things for us. Opal Ozone: Oh, you mean my do-gooder twin sister. Yeah, she s all gas, way up in the atmosphere, absorbing ultraviolet rays from the Sun. But I find it more interesting down here at ground level. You know, down and dirty. Susie: So, how do you get made, Opal? ozone: a molecule made up of three oxygen atoms. VOC (volatile organic compound): a pollutant that reacts with nitrogen oxides to make smog. Opal Ozone: It s fun. My mother and her gassy friends, the nitrogen oxides, come over, and we have a smog party. You know, we have a few VOC s, turn up the heat, and the next thing you know, I m there. And when I m there, smog is not far behind. Billy (to audience): I m sure Opal Ozone is a lot of fun, but she s a little shy about her effects on people and other living things. When ozone is on the ground, it is quite dangerous and poisonous. It attacks lung tissue. It also damages crops, trees, and other matter even breaking down rubber compounds. Susie: Well, that about wraps it up, Billy. It will be a happy day when we see the last of the Sickening (counting her fingers) Billy, that s only five. Billy (whispering): Are you sure? (looking around) Mercury (sitting off to the side, talks in a smooth, flowing voice): I m over here. People always forget about me. Which is sort of funny, since I make people forgetful. Susie: Oh, sorry, Mercury, we didn t see you behind all the other pollutants. (Reads notes.) My notes say that you re from the Midwest, like Sulfur Dioxide. Mercury: That s correct, Ms. Lung. I m from the Midwest. I know Sulfur Dioxide, but we don t mix. In fact, I don t mix with any of the other pollutants. You see, I m not a gas like the others, and I m not a molecule. I m much more special than that. I m a liquid element. AQ 119 AIR QUALITY

7 Learning Set 3 What Are Pollutants, and How Do They Get Into Air? Billy: Well, Mercury, how do you get into the air, then? In some special way? Mercury (dramatically): Trapped in coal at an early age, I m purified by fire and released into the air through the smokestacks of power plants. Though I m a heavy element, I can travel hundred of miles before landing gently in forests and fields, and in rivers and streams. Susie: And how do you do your damage? Mercury (with a sinister look): Slowly. Quietly. I react slowly to form mercury molecules that get into the food chain. I get into the bodies of small animals such as fish. Then, as predators eat prey, I move up the food chain. My effects are seen in the nervous system, especially of young, fast-growing animals including children! Good day. You re boring me. Billy: That Mercury guy makes me nervous. Susie: Definitely creepy. (to audience) And that wraps it up for tonight. The bottom line? These pollutants are a pretty tough bunch but people create them, and people can reduce the amounts that are in our air. Billy: Thank you and good night. Stop and Think 1. Which of the six pollutants are gases? The other pollutants are which state of matter? 2. Which of the pollutants are caused by combustion? 3. Which of the pollutants are elements? Which of the pollutants are compounds? 4. How does the concentration of the pollutants in air compare to the concentration of nitrogen and oxygen? 5. Which of the six pollutants would you expect to find in the air of a big city? Describe why you think each would be in a big city. Project-Based Inquiry Science AQ 120

8 3.1 Understand the Question 6. Which of the six pollutants would you expect to find in your community? Describe why you think each would be in your community. 7. What else do you need to know about pollutants and how they form to understand how they get into the air and cause harm? Communicate Compare and discuss your answers to the Stop and Think questions with the rest of the class. Add what you think you know about pollutants to the What do we think we know? column of the Project Board. Add the questions you generated to the What do we need to investigate? column of the Project Board. How Do Scientists Measure the Amounts of Pollutants? In the play, The Sickening Six, you explored six dangerous pollutants. None of these pollutants are present in air at even 0.1 percent. The concentration of each of these pollutants in air is very, very small, and yet each can cause serious health effects. Recall from Learning Set 2 that concentration describes the amount of a solute in a solvent. The concentration of nitrogen in air, for example, is about 78 percent. The concentrations of the pollutants in The Sickening Six, however, are much too small to describe in percentages. To describe the concentration of some pollutants in air, scientists use parts per million (ppm). For example, the amount of carbon dioxide in the air is about 385 ppm. This means that every one million (the m in ppm) particles of air include 385 molecules of carbon dioxide. This is the same as saying that percent of the air is carbon dioxide, but it is easier for most people to think about the concentration as 385 ppm. When the concentration of some gas in the air is smaller than 1 ppm, scientists use smaller units to describe concentration parts per billion (ppb). A concentration of 1 ppb is 1000 times less than a concentration of 1 ppm. If a gas has a concentration of 37 ppb in air, then every billion particles of air (the b in ppb) contain 37 particles of the gas. part per million (ppm): the number of particles of one substance in one million particles of a mixture. One out of a million. part per billion (ppb): the number of particles of one substance in one billion particles of a mixture. One out of a billion. AQ 121 AIR QUALITY

9 Learning Set 3 What Are Pollutants, and How Do They Get Into Air? Scientists use another unit to describe the concentrations of solids and liquids micrograms per cubic meter (μg/m 3 ). One microgram is g. To understand just how small that is, consider that a penny has a mass of about 3 g, and a pen cap has a mass of about 1 g. One microgram is one millionth of one gram. One cubic meter is the space that is one meter by one meter by one meter. Look at the table. It lists the allowable concentration of each pollutant in the air and the dangerous concentration of that pollutant. The allowable concentration is the permissible concentration at which the pollutant can exist in air, based on human health standards. The dangerous concentration is the concentration at which the pollutant begins to cause serious harm to living things. Allowable and Dangerous Levels of Some Air Pollutants Pollutant Allowable Level Dangerous Level carbon monoxide 35 ppm 50 ppm nitrogen oxides ppm 2 ppm ozone 0.08 ppm 0.4 ppm small particulate matter (PM) 65 mg/m 3 * 1000 mg/m 3 large particulate matter (PM) 150 mg/m mg/m 3 sulfur dioxide 0.14 ppm 1 ppm mercury none 0.12 mg/m 3 lead none 1.5 mg/m 3 volatile organic compounds (VOC) none mg/m 3 * Some pollutants are not measured in ppm. Instead, they are measured in micrograms/cubic meter (mg/m 3 ) Project-Based Inquiry Science AQ 122

10 3.1 Understand the Question Understanding Concentration A million or a billion particles is a lot of particles. There are so many that it can be difficult to imagine what the number of particles means. It may also be hard for you to imagine how little of air is actually made up of pollutants. This investigation will help you imagine this concept. In this investigation, you will observe a solution as the concentration of particles gets smaller and smaller. In other words, the solution becomes more dilute. Because gas is hard to see, and gas particles are hard to imagine, you will model concentrations of pollutants using water and food coloring. The food coloring will represent a pollutant, and the water will represent air. You will pay attention to how the color of the water changes as the concentration of food coloring (pollutant) changes. Procedure 1. With a marker, label each cup with a letter: A, B, C, or D. 2. Use a pipette to place 1.0 ml of food coloring into Cup A. 3. Carefully measure 99 ml of water in the graduated cylinder. Add the water to the food coloring and stir with a spoon until you have a homogeneous mixture. Recall that in a homogenous mixture, the particles of solute are spread evenly throughout the solvent. 4. Record the color of the solution on your Understanding Concentration page. 5. Compare the color of the solution in Cup A with the dilution strip to determine its concentration. Materials 4 clear plastic cups, 275 ml marker blue food coloring 4 plastic pipettes, graduated to 1.0 ml 100-mL graduated cylinder spoon water pen Understanding Concentration page AQ 123 AIR QUALITY

11 Learning Set 3 What Are Pollutants, and How Do They Get Into Air? Analyze Your Data 1. On your Understanding Concentration page, record your comparison of the solution in Cup A with the dilution strip. Adding 1.0 ml of food coloring to 99 ml of water makes this a 1 percent solution. The concentration is 10,000 parts of food coloring to 990,000 parts of water (10,000 ppm). 2. What do you think will happen if part of the solution in Cup A were mixed with more water? How will the concentration change? Dilute the 1 Percent Concentration To dilute means to decrease the concentration of some substance in a solution. Cup A is a 1 percent (10,000 ppm) solution of food coloring in water. You will decrease the concentration of food coloring in the water by adding some of the 1 percent solution to more water. Follow the instructions below. Procedure 1. Use a clean pipette to measure 1.0 ml of the solution in Cup A. Add it to Cup B. 2. Measure 99 ml of water in the graduated cylinder. Add the water to Cup B and stir with a spoon. 3. Record the color of the solution on your Understanding Concentration page. 4. Compare the color of the solution in Cup B with the dilution strip to determine its concentration. Analyze Your Data 1. On your Understanding Concentration page, record your comparison of the solution in Cup B with the dilution strip. The concentration of food coloring in the water in Cup B is 100 times less than the concentration of food coloring in Cup A. This is because you added 99 ml of water to 1.0 ml of the solution in Cup A. The concentration of food coloring in Cup A is 1 percent, or 10,000 ppm. The concentration of food coloring in Cup B is 100 ppm. 2. Compare the color of the solution in Cup A with the color in Cup B. Describe the difference. Project-Based Inquiry Science AQ 124

12 3.1 Understand the Question 3. If you had a very powerful tool and could see the particles of water and food coloring, how would the solution in Cup B look different from the solution in Cup A? 4. Next you will make another solution in Cup C by taking 1.0 ml of Cup B and diluting it with another 99 ml of water. What do you expect will be the color of the water in Cup C? Why will this happen? Dilute the Solution in Cup B Procedure 1. Use a clean pipette to measure 1.0 ml of the solution in Cup B. Add it to Cup C. 2. Measure 99 ml of water in the graduated cylinder. Add the water to Cup C and stir with a spoon. 3. Record the color of the solution on your Understanding Concentration page. 4. Compare the color of the solution in Cup C with the dilution strip to determine its concentration. Analyze Your Data 1. On your Understanding Concentration page, record your comparison of the solution in Cup C with the dilution strip. The concentration of food coloring in the water in Cup C is 100 times less than the concentration of food coloring in Cup B. This is because you added 99 ml of water to 1.0 ml of the solution in Cup B. The concentration of food coloring in Cup B is 100 ppm. The concentration of food coloring in Cup C is 1 ppm. 2. Compare the color of the solution in Cup B with the color in Cup C. Describe the difference. 3. If you had a very powerful tool and could see the particles of water and food coloring, how would the solution in Cup C look different from the solution in Cup B? 4. Next you will make another solution in Cup D by taking 1.0 ml of Cup C and diluting it with another 99 ml of water. What do you expect will be the color of the water in Cup D? Why will this happen? AQ 125 AIR QUALITY

13 Learning Set 3 What Are Pollutants, and How Do They Get Into Air? Dilution to a Concentration of Parts per Billion (ppb) Procedure 1. Use a clean pipette to measure 1.0 ml of the solution in Cup C. Add it to Cup D. 2. Measure 99 ml of water in the graduated cylinder. Add the water to Cup D and stir with a spoon. 3. Record the color of the solution on your Understanding Concentration page. 4. Compare the color of the solution in Cup D with the dilution strip to determine its concentration. Analyze Your Data 1. On your Understanding Concentration page, record your comparison of the solution in Cup D with the dilution strip. The concentration of food coloring in the water in Cup D is 100 times less than the concentration of food coloring in Cup C. This is because you added 99 ml of water to 1.0 ml of the solution in Cup C. The concentration of food coloring in Cup C is 1 ppm (1000 ppb). The concentration of food coloring in Cup D is 10 ppb. 2. Compare the color of the solution in Cup C with the color in Cup D. Describe the difference. 3. If you had a very powerful tool and could see the particles of water and food coloring, how would the solution in Cup D look different from the solution in Cup C? Reflect 1. At which concentration could you no longer see any color? How much food coloring was still in the water? 2. Even though you may not be able to see the food coloring in Cups C and D, how do you know it is still there? 3. Imagine that the food coloring is a dangerous pollutant. How could you decide if the solution in Cup C or Cup D is safe to drink? Justify your answer with evidence. Project-Based Inquiry Science AQ 126

14 3.1 Understand the Question 4. Imagine that the water is air. How does this investigation help you understand the danger of even small amounts of pollution in air? 5. What else do you still need to know to determine how good or bad the quality of the air is in your community? Update the Project Board In the What do we think we know? column of the Project Board, record what you think you know about the major pollutants in your community. You may have some ideas about what you need to investigate to identify the pollutants in your community. Record these ideas in the second column, What do we need to investigate? What s the Point? Six major types of pollutants affect air quality. Five of these pollutants can be produced by combustion in engines and power plants. These are soot (particulate matter, PM), carbon monoxide, the nitrogen oxides, mercury, and sulfur dioxide. Particulate matter is inhaled and affects the breathing of people and animals, particularly infants, older people, and people who already have asthma. Carbon monoxide is a poison that interferes with the uptake of oxygen in the lungs. In extreme cases, it can even kill living things. The nitrogen oxides also cause impaired breathing. When nitrogen oxides react with volatile organic compounds (VOC s), the sixth pollutant, ozone, is formed. Ozone is extremely reactive. The nitrogen oxides, sulfur dioxide, and mercury get into the air through the burning of coal in power plants. Acid rain forms when nitrogen oxides and sulfur dioxide mix with water vapor. Acid rain can return to the land many hundreds of miles away from the power plants that put the pollutants into the air. All of the pollutants are gases, except for particulate matter and mercury. Particulate matter is small enough to be carried long distances by the wind. Mercury is a heavy element, but it can be changed into a gas in power plants and carried long distances by the wind. Air pollutants are present in very small amounts. Scientists need to measure these amounts. For the pollutants that are gases, they use calculations of parts per million (ppm) and parts per billion (ppb). AQ 127 AIR QUALITY