Overview of Air Pollution Sources and Effects

Hey everybody, it's Mr. Smedes. Welcome to Apes Video Notes for topic 7.1, which is an introduction to air pollution, and I have in parentheses here air pollutants, because today we will really focus on the difference between pollution and pollutants. Really critical in apes to try to refer to specific pollutants and not just pollution generally. Our objective today is to identify the sources and effects of different air pollutants. And then the skill that we'll be practicing at the end of today's video will involve explaining how a modification to an experiment will change the results. So we'll start out today talking about some air pollution basics. So as I mentioned in the beginning of today's video, it's really important that in APES, especially on FRQs, we try to write about specific air pollutants. So these are chemicals, compounds, or particles that have specific environmental and human health effects. Pollution in general is just the idea of polluting. In an FRQ setting, it's going to be too vague generally. You want to talk about a specific pollutant anytime you're talking about air or water pollution. We also need to know that the Clean Air Act was passed in 1970, and it gives the EPA the ability to regulate six criteria air pollutants. We'll talk about what those six criteria air pollutants are here shortly. But the other thing we should know is that it allows the EPA to set levels that are acceptable air standard. quality levels for these pollutants, and also the ability to regulate them, meaning that they can punish companies or entities that, you know, exceed the allowed, you know, emissions for these pollutants. So let's talk about the six air pollutants now. The first one is sulfur dioxide or SO2. This comes largely from coal combustion. Coal has a really high sulfur content, so burning it to create electricity releases a lot of sulfur dioxide. We need to know that this is a respiratory irritant to humans. We also need to know that it can form acid rain. Next, we have NOx or nitrogen oxides. And so this refers to both nitric oxide NO and nitrogen dioxide NO2. And so we use that X subscript to denote the two of them together here. This comes from pretty much all fossil fuel combustion, gasoline from cars specifically. That would be the leading anthropogenic source of NOx. Then we need to know that this... helps form tropospheric ozone. We need to know that it contributes to photochemical smog and that it can also be a precursor to acid precipitation, just like SO2. Sometimes we call these NOx and SOx together. And so you may hear people use that language, but it's best to try to refer to these specifically as SO2 or specifically as nitrogen dioxide or nitric oxide. Next, we have carbon monoxide, so CO. And this is going to be produced from the incomplete combustion of just about anything. So fossil fuels, biomass would be two great examples. And we need to know that this is lethal to humans. It can displace oxygen in our bloodstream. And we'll talk about this more when we cover indoor air pollutants later in this unit. Then we have lead. Lead is going to be released when metals are, you know, smelted or melted down. And then also when there's waste incineration. And we need to know that lead is a neurotoxicant. And so lead will damage the nervous systems of individuals, you know, both humans and animals. And so that's a criteria air pollutant that is regulated. And then we have ozone. So specifically tropospheric ozone, which remembers O3. And so when it forms down close to earth in the troposphere, it's going to be really harmful to human health. It is a smog precursor. It's also a respiratory irritant. And so that's one of the six criteria air pollutants. And then finally, we have particulate matter. Particulate matter is a broad... kind of catch-all name for suspended particles. We'll talk more about their specific sizes and why certain sizes of them are more dangerous or less dangerous later on in this unit, but for right now we should know that they come from, you know, combustion, they can come from construction, forest fires, all of these things can contribute particulate matter to the air, and they're going to be very irritating to respiratory tract, so they can worsen asthma, bronchitis, and they also contribute to the formation of smog and kind of the thickening of smog. So notably absent from that list of criteria air pollutants laid out in the original wording of the Clean Air Act in 1970 is carbon dioxide. And so we should clarify here that carbon dioxide is not one of the six criteria air pollutants initially laid out in the Clean Air Act. However, in 2007, the Supreme Court found that the EPA could regulate carbon dioxide and other greenhouse gases because they posed a threat to human health going forward. And that's due to all of the effects of climate change. And so the EPA began regulating carbon dioxide in various ways, primarily in vehicle exhaust emission standards in 2009. Now, this gets a little bit dicey, though, when it comes to AP environmental science. So let's explore further. Carbon dioxide does not directly lower air quality from a human health standpoint. And I have the term directly in there because it's not toxic to organisms. So if I breathe in carbon dioxide at reasonable temperatures, as could be found on Earth, even if they're increasing, it's not going to be toxic to me. It's not going to damage my eyes or my lungs. And it's not going to lead to smog. It's not going to decrease visibility. And so a lot of APE students make the mistake of saying that carbon dioxide is an air pollutant. And it's tricky. This is, you know, being litigated in court. And this is something that EPA scientists and other atmospheric scientists are kind of hashing out right now. So it is a greenhouse gas. Clearly, it's going to lead to earth warming. We know that. And because global climate change has environmental threats and human health consequences, consequences, that's the basis for the Supreme Court ruling in 2007. So all of this to say that as of right now, the bottom line from an AP environmental science standpoint, which is, of course, why you're watching this video, is that CO2 has not typically been included on APES FRQ scoring guides when it comes to air pollutants. So I want to be very clear that it is not typical for carbon dioxide to be considered an air pollutant. in AP Environmental Science FRQs. And so it's best to stick to surefire accepted air pollutants that are typically considered air pollutants in AP Environmental Science. So those would be everything else that we're covering in this video. And so again, you know, this is actually a current issue of debate in science and in government and in regulation. But for the time being in AP Environmental Science, we have to consider CO2 to not be an air pollutant. Now we'll talk about coal combustion specifically. So we need to know that coal is going to release more air pollutants per unit of mass that it's burned than any other fossil fuel. And this is important because currently coal represents about 35% of total global electricity generation fuel, and it is the number one source for electricity generation by a long stretch. So we have to understand some of these impacts. So here they are. It's a real laundry list. It's going to release carbon monoxide. CO2, sulfur dioxide, so SO2, and NOx, or nitrogen oxides. It's also going to release a lot of toxic metals, so mercury, arsenic, and lead. And these are going to specifically bind to a lot of the particles or the particulate matter that's released. So these can be borne by the wind to ecosystems far, far away from where the coal is actually combusted or where the electricity is actually generated. So what are some of the more specific impacts of SO2? We're focusing on SO2 here because of course it's one of the six criteria air pollutants, but also it's released in really high amounts in coal. Coal is a really sulfur-rich fuel, and so we want to drill down to a more specific pollutant level here. So it's a respiratory irritant, and that means that it impacts human eyes. It can impact human respiratory tracts, so the bronchioles, the lungs. It can cause inflammation, worsen asthma and bronchitis, and so it can really have a whole host of problems for human health. It's also going to create sulfur aerosols, which are suspended sulfate particles. These can actually reflect the sun and decrease incoming sunlight, so they can decrease photosynthesis in a given area. It's also going to contribute to a specific type of smog, and that's sulfurous or gray smog. And so we have to distinguish that from photochemical smog, which will be coming up in topic 7.2. And then we also need to know that it's a precursor to sulfuric acid, which forms... sulfate particles that are then falling to earth in water droplets, which is acid deposition or acid rain. And so it's a contributor to acidification of bodies of water and soil through this acid precipitation. Now we'll focus more specifically on nitrogen oxides or NOx. So we need to know that these are released by the combustion of basically anything. And that's because the nitrogen in the atmosphere is about 78% of the entire atmosphere. And so Nitrogen is super readily available when there's combustion. So especially though when we combust fossil fuels or biomass. So let's talk a little bit more about the distinction. Remember that NOx refers to both nitrogen oxide, so both nitric oxide and nitrogen dioxide, NO2. And initially we're going to form nitric oxide when nitrogen in the atmosphere, so N2, combines with O2 and especially during a combustion reaction, especially when we're burning something. So we can see here that we have a nitrogen atom N2 or a nitrogen molecule N2, sorry, and we have oxygen molecule and they're going to combine to form two nitric oxide molecules. Nitric oxide can become nitrogen dioxide when this nitric oxide reacts with either ozone or atmospheric oxygen, so O2. And then we also need to know that sunlight is going to convert NO2 back into nitric oxide. And so the reason that we use this NO subscript X or NOX to denote the two is because they readily, you know, exchange back and forth and can kind of convert into one another. And so it's applicable to kind of... used the subscript X here just to denote it could be either nitric oxide or nitrogen dioxide. Then we have some environmental and human health impacts we need to be aware of. As is the case with many of these air pollutants, it's a respiratory irritant. I oftentimes tell my students that if you need to pull something out of your back pocket on an FRQ, you're down to the wire and need a human health consequence of air pollution, it's almost always going to be applicable to say it's a respiratory irritant. So that's kind of a go-to human health answer. And then we also need to know that nitrogen oxides are going to contribute to ozone formation. So specifically, nitrogen dioxide is going to be broken down by the sunlight. And then that free oxygen is going to combine with O2 to form ozone. And that will be next video, 7.2, that'll be focused on in depth there. And then finally, we need to know that nitrogen oxides can combine with oxygen and water in the atmosphere. And those can form nitric acid and then nitrate, which... is what forms acid rain. And so just like with sulfur, which forms sulfuric acid and sulfate, we can get acid rain formation due to nitrogen oxides being released in the atmosphere. Now we'll talk about what the EPA has done specifically to target atmospheric lead levels and really bring those down. So before the Clean Air Act or the CEA, it was really common for lead to be an additive in gasoline. This was to prevent engine knock, which is something we don't really experience today. But engines used to rattle a lot due to inefficiencies of the way the gasoline was burning. And so lead was added to kind of stabilize those engines and prevent knock. But as it was found to be a neurotoxicant, and with the addition of catalytic converters in 1975, it became necessary for the EPA to kind of phase out lead from gasoline starting in 1974. And so any vehicle made after 1974 is required to have a device called a catalytic converter. And we'll be focused specifically on catalytic converters later in this unit where we're looking at ways to mitigate air pollutants. But because those catalytic converters are degraded when lead is passed through them, it was really necessary for the EPA to begin this phase out. And then that's along with the fact that it is also a known neurotoxicant. So it is damaging to the nervous systems of humans, especially of infants and babies. So People with developing nervous systems will focus more on this later in the unit as well. But here's a graph that just kind of represents the effectiveness of the EPA's efforts to phase out lead from gasoline and from paint eventually. And we can see here that the concentrations of lead in the atmosphere have just declined dramatically, you know, over the decades since the Clean Air Act targeted lead and since the EPA began its phase out in 1974. Next we'll take a look at primary and secondary air pollutants. So primary air pollutants are air pollutants that come directly from a source. You can think of it as coming straight out of a smokestack or an exhaust pipe or in some cases a natural source. So it could come directly from a vehicle or a power plant or even a natural source such as volcanoes or forest fires. Examples of primary air pollutants would include everything listed here and so most of the pollutants targeted by the Clean Air Act. by those six criteria pollutants would be considered primary. And there's one pollutant though that is not a primary pollutant that is targeted by the EPA in the Clean Air Act, and we'll talk about that shortly. Secondary air pollutants, on the other hand, are going to be primary air pollutants that have undergone some sort of transformation catalyzed by sunlight, water, or oxygen, or some other compound. And so due to this fact that they're often driven by sunlight, they're going to be more prevalent during the daytime. They're going to form in higher concentrations. And the example of the air pollutant that's regulated by the EPA, but that is not a primary pollutant, is ozone. Tropospheric ozone that forms close to Earth's surface, and we'll be talking about that in much more depth coming up in 7.2. But another example would be sulfuric acid and sulfate, and nitric acid and nitrate. So these are going to, of course, come from sulfur dioxide and nitrogen oxide, so NOx, and they're going to be precursors to acid rain. And so by targeting SOX and NOx with legislation, with the Clean Air Act, we can kind of indirectly try to target sulfuric acid and nitric acid and reduce those levels of secondary air pollutants. So in practice FRQ 7.1 here, we're going to take a look at this experiment where EPA scientists are burning coal in chambers at different temperatures. And so they're trying to see the impact that temperature has on NOx production when you're burning coal. And so I want you to explain how the results of the study would be expected to change if the same experiment were repeated with natural gas. And there's a graph over here on the right. This is not raw data. This is not actual experimental results. But it's a graph to help you understand the relationship between temperature change and NOx production when you're combusting coal.

So we'll start out today talking about some air pollution basics. So as I mentioned in the beginning of today's video, it's really important that in APES, especially on FRQs, we try to write about specific air pollutants. So these are chemicals, compounds, or particles that have specific environmental and human health effects. Pollution in general is just the idea of polluting.

In an FRQ setting, it's going to be too vague generally. You want to talk about a specific pollutant anytime you're talking about air or water pollution. We also need to know that the Clean Air Act was passed in 1970, and it gives the EPA the ability to regulate six criteria air pollutants. We'll talk about what those six criteria air pollutants are here shortly. But the other thing we should know is that it allows the EPA to set levels that are acceptable air standard.

quality levels for these pollutants, and also the ability to regulate them, meaning that they can punish companies or entities that, you know, exceed the allowed, you know, emissions for these pollutants. So let's talk about the six air pollutants now. The first one is sulfur dioxide or SO2.

This comes largely from coal combustion. Coal has a really high sulfur content, so burning it to create electricity releases a lot of sulfur dioxide. We need to know that this is a respiratory irritant to humans.

We also need to know that it can form acid rain. Next, we have NOx or nitrogen oxides. And so this refers to both nitric oxide NO and nitrogen dioxide NO2.

And so we use that X subscript to denote the two of them together here. This comes from pretty much all fossil fuel combustion, gasoline from cars specifically. That would be the leading anthropogenic source of NOx. Then we need to know that this... helps form tropospheric ozone.

We need to know that it contributes to photochemical smog and that it can also be a precursor to acid precipitation, just like SO2. Sometimes we call these NOx and SOx together. And so you may hear people use that language, but it's best to try to refer to these specifically as SO2 or specifically as nitrogen dioxide or nitric oxide. Next, we have carbon monoxide, so CO. And this is going to be produced from the incomplete combustion of just about anything.

So fossil fuels, biomass would be two great examples. And we need to know that this is lethal to humans. It can displace oxygen in our bloodstream. And we'll talk about this more when we cover indoor air pollutants later in this unit.

Then we have lead. Lead is going to be released when metals are, you know, smelted or melted down. And then also when there's waste incineration.

And we need to know that lead is a neurotoxicant. And so lead will damage the nervous systems of individuals, you know, both humans and animals. And so that's a criteria air pollutant that is regulated.

And then we have ozone. So specifically tropospheric ozone, which remembers O3. And so when it forms down close to earth in the troposphere, it's going to be really harmful to human health. It is a smog precursor.

It's also a respiratory irritant. And so that's one of the six criteria air pollutants. And then finally, we have particulate matter. Particulate matter is a broad... kind of catch-all name for suspended particles.

We'll talk more about their specific sizes and why certain sizes of them are more dangerous or less dangerous later on in this unit, but for right now we should know that they come from, you know, combustion, they can come from construction, forest fires, all of these things can contribute particulate matter to the air, and they're going to be very irritating to respiratory tract, so they can worsen asthma, bronchitis, and they also contribute to the formation of smog and kind of the thickening of smog. So notably absent from that list of criteria air pollutants laid out in the original wording of the Clean Air Act in 1970 is carbon dioxide. And so we should clarify here that carbon dioxide is not one of the six criteria air pollutants initially laid out in the Clean Air Act. However, in 2007, the Supreme Court found that the EPA could regulate carbon dioxide and other greenhouse gases because they posed a threat to human health going forward.

And that's due to all of the effects of climate change. And so the EPA began regulating carbon dioxide in various ways, primarily in vehicle exhaust emission standards in 2009. Now, this gets a little bit dicey, though, when it comes to AP environmental science. So let's explore further. Carbon dioxide does not directly lower air quality from a human health standpoint.

And I have the term directly in there because it's not toxic to organisms. So if I breathe in carbon dioxide at reasonable temperatures, as could be found on Earth, even if they're increasing, it's not going to be toxic to me. It's not going to damage my eyes or my lungs.

And it's not going to lead to smog. It's not going to decrease visibility. And so a lot of APE students make the mistake of saying that carbon dioxide is an air pollutant. And it's tricky. This is, you know, being litigated in court.

And this is something that EPA scientists and other atmospheric scientists are kind of hashing out right now. So it is a greenhouse gas. Clearly, it's going to lead to earth warming. We know that.

And because global climate change has environmental threats and human health consequences, consequences, that's the basis for the Supreme Court ruling in 2007. So all of this to say that as of right now, the bottom line from an AP environmental science standpoint, which is, of course, why you're watching this video, is that CO2 has not typically been included on APES FRQ scoring guides when it comes to air pollutants. So I want to be very clear that it is not typical for carbon dioxide to be considered an air pollutant. in AP Environmental Science FRQs. And so it's best to stick to surefire accepted air pollutants that are typically considered air pollutants in AP Environmental Science. So those would be everything else that we're covering in this video.

And so again, you know, this is actually a current issue of debate in science and in government and in regulation. But for the time being in AP Environmental Science, we have to consider CO2 to not be an air pollutant. Now we'll talk about coal combustion specifically. So we need to know that coal is going to release more air pollutants per unit of mass that it's burned than any other fossil fuel. And this is important because currently coal represents about 35% of total global electricity generation fuel, and it is the number one source for electricity generation by a long stretch.

So we have to understand some of these impacts. So here they are. It's a real laundry list. It's going to release carbon monoxide. CO2, sulfur dioxide, so SO2, and NOx, or nitrogen oxides.

It's also going to release a lot of toxic metals, so mercury, arsenic, and lead. And these are going to specifically bind to a lot of the particles or the particulate matter that's released. So these can be borne by the wind to ecosystems far, far away from where the coal is actually combusted or where the electricity is actually generated. So what are some of the more specific impacts of SO2? We're focusing on SO2 here because of course it's one of the six criteria air pollutants, but also it's released in really high amounts in coal.

Coal is a really sulfur-rich fuel, and so we want to drill down to a more specific pollutant level here. So it's a respiratory irritant, and that means that it impacts human eyes. It can impact human respiratory tracts, so the bronchioles, the lungs.

It can cause inflammation, worsen asthma and bronchitis, and so it can really have a whole host of problems for human health. It's also going to create sulfur aerosols, which are suspended sulfate particles. These can actually reflect the sun and decrease incoming sunlight, so they can decrease photosynthesis in a given area. It's also going to contribute to a specific type of smog, and that's sulfurous or gray smog. And so we have to distinguish that from photochemical smog, which will be coming up in topic 7.2.

And then we also need to know that it's a precursor to sulfuric acid, which forms... sulfate particles that are then falling to earth in water droplets, which is acid deposition or acid rain. And so it's a contributor to acidification of bodies of water and soil through this acid precipitation. Now we'll focus more specifically on nitrogen oxides or NOx.

So we need to know that these are released by the combustion of basically anything. And that's because the nitrogen in the atmosphere is about 78% of the entire atmosphere. And so Nitrogen is super readily available when there's combustion. So especially though when we combust fossil fuels or biomass.

So let's talk a little bit more about the distinction. Remember that NOx refers to both nitrogen oxide, so both nitric oxide and nitrogen dioxide, NO2. And initially we're going to form nitric oxide when nitrogen in the atmosphere, so N2, combines with O2 and especially during a combustion reaction, especially when we're burning something. So we can see here that we have a nitrogen atom N2 or a nitrogen molecule N2, sorry, and we have oxygen molecule and they're going to combine to form two nitric oxide molecules.

Nitric oxide can become nitrogen dioxide when this nitric oxide reacts with either ozone or atmospheric oxygen, so O2. And then we also need to know that sunlight is going to convert NO2 back into nitric oxide. And so the reason that we use this NO subscript X or NOX to denote the two is because they readily, you know, exchange back and forth and can kind of convert into one another.

And so it's applicable to kind of... used the subscript X here just to denote it could be either nitric oxide or nitrogen dioxide. Then we have some environmental and human health impacts we need to be aware of.

As is the case with many of these air pollutants, it's a respiratory irritant. I oftentimes tell my students that if you need to pull something out of your back pocket on an FRQ, you're down to the wire and need a human health consequence of air pollution, it's almost always going to be applicable to say it's a respiratory irritant. So that's kind of a go-to human health answer. And then we also need to know that nitrogen oxides are going to contribute to ozone formation.

So specifically, nitrogen dioxide is going to be broken down by the sunlight. And then that free oxygen is going to combine with O2 to form ozone. And that will be next video, 7.2, that'll be focused on in depth there.

And then finally, we need to know that nitrogen oxides can combine with oxygen and water in the atmosphere. And those can form nitric acid and then nitrate, which... is what forms acid rain.

And so just like with sulfur, which forms sulfuric acid and sulfate, we can get acid rain formation due to nitrogen oxides being released in the atmosphere. Now we'll talk about what the EPA has done specifically to target atmospheric lead levels and really bring those down. So before the Clean Air Act or the CEA, it was really common for lead to be an additive in gasoline.

This was to prevent engine knock, which is something we don't really experience today. But engines used to rattle a lot due to inefficiencies of the way the gasoline was burning. And so lead was added to kind of stabilize those engines and prevent knock.

But as it was found to be a neurotoxicant, and with the addition of catalytic converters in 1975, it became necessary for the EPA to kind of phase out lead from gasoline starting in 1974. And so any vehicle made after 1974 is required to have a device called a catalytic converter. And we'll be focused specifically on catalytic converters later in this unit where we're looking at ways to mitigate air pollutants. But because those catalytic converters are degraded when lead is passed through them, it was really necessary for the EPA to begin this phase out.

And then that's along with the fact that it is also a known neurotoxicant. So it is damaging to the nervous systems of humans, especially of infants and babies. So People with developing nervous systems will focus more on this later in the unit as well. But here's a graph that just kind of represents the effectiveness of the EPA's efforts to phase out lead from gasoline and from paint eventually. And we can see here that the concentrations of lead in the atmosphere have just declined dramatically, you know, over the decades since the Clean Air Act targeted lead and since the EPA began its phase out in 1974. Next we'll take a look at primary and secondary air pollutants.

So primary air pollutants are air pollutants that come directly from a source. You can think of it as coming straight out of a smokestack or an exhaust pipe or in some cases a natural source. So it could come directly from a vehicle or a power plant or even a natural source such as volcanoes or forest fires. Examples of primary air pollutants would include everything listed here and so most of the pollutants targeted by the Clean Air Act.

by those six criteria pollutants would be considered primary. And there's one pollutant though that is not a primary pollutant that is targeted by the EPA in the Clean Air Act, and we'll talk about that shortly. Secondary air pollutants, on the other hand, are going to be primary air pollutants that have undergone some sort of transformation catalyzed by sunlight, water, or oxygen, or some other compound. And so due to this fact that they're often driven by sunlight, they're going to be more prevalent during the daytime.

They're going to form in higher concentrations. And the example of the air pollutant that's regulated by the EPA, but that is not a primary pollutant, is ozone. Tropospheric ozone that forms close to Earth's surface, and we'll be talking about that in much more depth coming up in 7.2.

But another example would be sulfuric acid and sulfate, and nitric acid and nitrate. So these are going to, of course, come from sulfur dioxide and nitrogen oxide, so NOx, and they're going to be precursors to acid rain. And so by targeting SOX and NOx with legislation, with the Clean Air Act, we can kind of indirectly try to target sulfuric acid and nitric acid and reduce those levels of secondary air pollutants. So in practice FRQ 7.1 here, we're going to take a look at this experiment where EPA scientists are burning coal in chambers at different temperatures.

And so they're trying to see the impact that temperature has on NOx production when you're burning coal. And so I want you to explain how the results of the study would be expected to change if the same experiment were repeated with natural gas. And there's a graph over here on the right.

This is not raw data. This is not actual experimental results. But it's a graph to help you understand the relationship between temperature change and NOx production when you're combusting coal.

Transcript for:Overview of Air Pollution Sources and Effects

Transcript for:
Overview of Air Pollution Sources and Effects