[Music] hey there awesome ap environmental science students this is mrs williams of science panda and i am here to give you your unit 7 review of the air pollution material for the course so today we're going to start off with an intro to air pollution we're going to go over a couple key pollutants their abbreviations and names that you need to know and then also a little bit of background material that is important for scoring well on the test so let's start off with what primary and secondary pollutants are so take a look at the picture of the car over on the right side of your screen that car is directly emitting one pollutant in this case no2 or nitrogen dioxide that makes it a primary pollutant because it is coming directly from a source that no2 though can be converted into ozone or o3 later on through chemical reactions we'll discuss in a few minutes and that o3 is a secondary pollutant because it is not coming directly from a source such as the car but is actually being created in the atmosphere through chemical reactions so let's take a look at the next bullet point down if you'll look at the chemicals we have you do need to know both abbreviations and names so i've given you both here so many of our air pollutants we're going to discuss actually come from burning fossil fuels so you'll see fossil fuels is kind of a running trend through air pollution the sox abbreviation is sometimes referred to as socks it is sulfur oxide chemicals which is where the sox abbreviation comes from so sulfur dioxide for example is a sox chemical and your sulfur chemicals your sulfur oxides are mainly coming from power plant coal burning so when you are creating electricity through coal burning socks are released your next chemical is nox chemicals or nitrogen oxides such as nitrogen dioxide this can come from coal burning power plants as well but also cars you should also be familiar with carbon dioxide which is co2 and if you notice the last three chemicals that i named sulfur dioxide nitrogen dioxide and carbon dioxide they're all dioxides the di means two and so notice there is a two after the o and oxide is referring to oxygen in this case carbon dioxide is a naturally occurring compound and it's going to come from respiration so for example you and other animals breathing out decomposition and also volcanoes are a major source of carbon dioxide as well volcanoes also put out quite a bit of sulfur so carbon dioxide is naturally occurring but because it can also cause climate change issues through warming in the atmosphere because it is a greenhouse gas it can cause some problems now greenhouse gas emissions are a little more of a unit 9 thing so we're not going to spend too much time on that today toxic metals can also be released mainly through combustion of coal those toxic metals include things like lead and mercury which are both toxic to the nervous systems of organisms and particulate matter which is usually abbreviated as pm can come from combustion as well so combustion of coal could be cigarette smoke it could be combustion of wood through fires such as forest fires and other sources the big law that you need to know for this unit is the clean air act and this is a united states federal law the purpose of this law sometimes abbreviated the caa is to help regulate six major air pollutants many of which i just reviewed the other big thing that the clean air act did that you need to know about for the exam is that it helped regulate lead in gasoline all right let's move on to photochemical smog so first we're going to take a look at some information about photochemical smog and then we will look at the formulas next and those formulas are basically the reactions that take place that lead to photochemical smog photochemical smog is also just referred to as smog so for just the ease of not having to say photochemical a million times i am just going to call it smog from here on out so smog forms when nox chemicals often nitrogen dioxide react with sunlight and then again with vocs or volatile organic compounds to end up forming that smog we'll be looking again at that reaction in just a minute so nox tends to be formed early in the day often this is due to car traffic so just imagine rush hour so seven o'clock in the morning everyone's driving to work everyone's on the highway that's a lot of nox compounds again nitrogen dioxide mainly coming out of the tailpipes of vehicles this then tends to react with sunlight and we are now creating ozone through that reaction smog tends to form more in urban areas for the reasons we just discussed a lot of people are on the roads driving to work and so a lot of cars are going to put out a lot of those chemicals that can lead to smog if vocs or those volatile organic compounds are present smog is then going to form so what we have again taking place is nox chemicals are released in the morning mainly from traffic ozone then is created and then when vocs are around we will see the next step which is the creation of photochemical smog and vocs are volatile organic compounds they are chemicals found in a ton of different sources it can be found in gasoline formaldehyde which is a preservative varnishes paint even things like nail polish and perfume even down to natural stuff like tree sap that smell for example when you buy a christmas tree that's so nice that everyone likes that's actually the tree sap releasing its voc scent into the air so vocs easily evaporate into the air room temperature and they often have strong smells as a result the other thing that you need to know before we get into the chemical formula for photochemical smog is that the environment can often affect smog formation and how bad smog is so if you take a look at the picture over on the right you see a city that is basically in a valley notice the mountain range behind it well cities that exist with mountains nearby or valleys smog kind of tends to settle over them a little bit more and they can have worse smog problems okay so now we know a little bit about photochemical smog let's take a look at the reaction that you need to be familiar with here so if you look at no2 up in the top left no2 is nitrogen dioxide you should know it by name and abbreviation nitrogen dioxide is emitted by cars again usually that's that rush hour traffic we discussed no2 or nitrogen dioxide is going to react with sunlight and we will see it break apart into no and then an oxygen radical that oxygen radical is kind of unstable and so it wants to go kind of find a buddy to hang out with basically so what it's going to do is it's going to go look for oxygen gas so the oxygen radical binds with o2 or oxygen gas in the atmosphere to create ozone or o3 now that is the typical reaction for ozone formation and then once the sun goes down what we'll actually see if you follow my big long arrow here is the o3 that was created the ozone is then going to react with the no in the atmosphere no is also known as nitric oxide so ozone reacts with nitric oxide once the sun goes down to basically degrade and revert back to oxygen gas or o2 and nitrogen dioxide in o2 so that's our normal pattern of ozone formation and then ozone destruction it breaks back down once the sun is down the problem occurs though when vocs are present so follow the kind of squiggly red arrow there when vocs are present that second line that formula there with the green arrow cannot take place and so vocs are actually going to kind of hijack this reaction and stop that second formula from taking place by binding with nitric oxide so no and vocs combine they create something called photochemical oxidants now because that was created an no is no longer available to o3 o3 is just floating around in the atmosphere so what it will do then is once those photochemical oxidants are available that combines with the o3 and now we get smog next up is thermal inversions so i've done this in pictures for you here because i think it's easiest to see visually so normal conditions in the atmosphere are what we see on the left notice that close to the surface of the earth air is warmer and then as we go out towards space generally air gets colder so you can see warm air cool air and then colder air the further you get out of the atmosphere now what happens with a thermal inversion is every once in a while we will get our warm air and our cool air kind of in the middle they flip-flop and so it basically traps cold air close to the earth's surface with warm air above it and that is what we are seeing over on the right side that is known as a thermal inversion the big problem we have with this is when an inversion occurs any pollution in the atmosphere particularly smog or particulates from coal burning they tend to get trapped beneath the warm air so notice my blue arrow is pointing down it's showing that pollution cloud being trapped over the city and so that inversion will settle there with that pollution settled below it trapped with nowhere to go and it can cause some devastating effects one famous example of this is the great smog of london in the middle of the 1900s and that was a couple of days where there was a big inversion and it was in the middle of winter so they had been burning coal and that coal was putting out loads of particulate matter loads of nox and socks chemicals that all got trapped beneath an inversion and it was difficult to see people were struggling with lung health and it's estimated that about 12 000 individuals died because of the effects of that smog directly all right moving on to acid deposition so you may be wondering why i'm not calling it just acid rain so acid deposition can actually be both acid rain or it can even be dry deposition which is basically particulate acid falling out of the atmosphere so when we release the pollutants into the atmosphere that result in acid formation it can actually come out as both wet and dry deposition or rain and particulates this is primarily going to be due to nitrogen oxides and sulfur oxide so our socks and nox chemicals again so when those sox nox chemicals are released into the atmosphere they mix with water vapor the secondary pollutants that they create are nitric acid and sulfuric acid which are then going to contribute to acid deposition so our problem with acid deposition is that once those chemicals get up in the air those acids are created they don't just stay put they can end up being moved to other areas so what we often see is that acid rain may form in one location like let's say near maybe a coal burning power plant but then it's going to end up affecting other areas as well maybe the wind moves it maybe there's a strong storm that helps relocate it out of the way so we often see communities that are downwind or in the direction of the flow of wind from coal burning power plants affected by acid deposition and acid deposition can have some nasty effects on the environment and on people it can be irritating to our skin and our lungs and our eyes for example as human beings it can also cause the acidification or a lowering a decrease in number as far as the ph scale is concerned so the acidification of soils and water bodies so if you take a look at the top picture i've got up there of a forest notice it's kind of bare basically the acid rain in that area has eaten away at the leaves and damaged the trees so that is another big side effect and a very sad one that also occurs is that a lot of our ancient buildings and statuary are made of things like marble marble is going to react with acids and they begin to be kind of almost melted in a way so if you look at the statue on the right if you notice its features look worn away and so what we are seeing is a lot of our ancient structures and buildings so for example the parthenon in greece are actually being damaged by acid deposition mainly by acid rain one of the other big side effects of acid deposition is it can also leach toxic metals from the ground so from soil and from rocks and so that means things like mercury may be actually released into the environment due to these acids one of the ways we can hope to offset that is if limestone is present in soils limestone is on the alkaline or basic end of the ph scale and if there is limestone present in soils it will often help neutralize the acid that is falling from the atmosphere next up is indoor air pollutants so indoor air pollutants often come from both natural and man-made sources but they can also come from combustion so for example burning wood in a fireplace so i've given you a list here of various things that are considered indoor air pollutants things from natural sources can include radon which is a radioactive material we'll actually take a look at that in just a minute things like mold and dust particulates might be asbestos which is a construction material that has tiny fibers that can actually cause lung damage and lung diseases dust and smoke can also be considered particulates man-made air pollutants might include insulation volatile organic chemicals from things like furniture paneling carpets formaldehyde and even lead and paint from old homes those vocs seem to be in just about everything if you have ever smelled like the smell after brand new carpet has been installed or after you've painted your bedroom or even if you've sat in a brand new car that lovely new car smell everyone loves these are all actually vocs and they can cause lung and eye irritation combustion of materials such as wood in your fireplace can also release chemicals into the air that are considered pollutants as well so carbon monoxide co the nox and sox chemicals again primarily nitrogen dioxide and sulfur dioxide some particulate matter and then even the combustion of tobacco and cigarettes as well carbon monoxide you should also keep in mind is an asphyxiant i mentioned radon on our last slide radon is a radioactive material it actually comes from uranium decaying so uranium is naturally occurring in the ground we probably don't usually think of it that way because we normally think of it in terms of nuclear power production or even atomic bombs but uranium does occur naturally because it's radioactive it does decay and that means it becomes other elements so when it decays it becomes radon 222 which is actually a gas now not all homes have this problem but when they do radon can often leak into the foundation of the home through cracks and it often will start in basements because basements are partially or all the way underground so radon will move up through the soil into the home again it's a gas and then enter the home and if the home is not very well ventilated this can lead to quite a bit of radiation exposure and as a result radon is actually known to damage the lungs and it is the second leading cause of cancers in the lungs in the united states our last form of pollution that we need to discuss is noise pollution so noise pollution is kind of an odd one because you think well how can noise you know be a pollutant but noise in high enough levels can actually cause as we know hearing loss in addition to physiological stress for both humans and other animals so the sources of noise pollution tend to often be man-made so urban transportation construction domestic activity for example loud stereos industrial activity all of these things are noisy they can be at a high decibel level the higher the decibel the more damaging it can potentially be so the effects on humans include things like anxiety poor concentration loss of sleep and stress and general just effect on physical health whereas on the environment animals are often impacted so animals might alter their behavior they may not be able to communicate with others of the same species they may have difficulty finding a mate if they have to actually make sound and that sound is kind of cut off by the noise around them so they end up not being able to communicate animals that communicate by echolocation which is literally communicating by sound would struggle as well animals in the ocean can also be affected and they are often affected by like boat motor noise it might be sonar it might be from drilling for example offshore drilling from oil extraction our final topic for unit 7 is just a few methods for reduction of air pollutants so there's a few specific ones that you need to know for the exam so let's take a look at those first one of them is catalytic converters this is a component of a car and other types of vehicles that burn fossil fuels that are designed to help take the nox chemicals and the carbon monoxide that are emitted from the tailpipes the emissions and turn them into less harmful chemicals we also have things like vapor recovery nozzles these nozzles are found on gasoline pumps and their job is to capture fumes before they're released into the atmosphere we also have equipment for more of an industrial use such as scrubbers and electrostatic precipitators scrubbers are used to remove particulates through water so it helps remove particulates at for example a coal-fired power plant before they're released to the atmosphere and then also electrostatic precipitators which instead of using water like scrubbers they actually use a type of static created to help remove particulates and these are often used in the smokestacks at power plants that are burning coal for electricity generation so the other big thing that we can do is we can just reduce fossil fuel use in general so i told you at the beginning of this video that fossil fuels often are a large source of our air pollutants so general reduction or conservation practices for not using fossil fuels would help and then one of our final ways is just through regulatory methods and we already discussed the clean air act in the usa which is in place for helping regulate some of the six major air pollutants such as the sox and nox chemicals carbon dioxide particulates and vocs to help keep them out of the atmosphere thank you for choosing science panda to help you review for the ap environmental science exam be sure to check out our youtube channel sciencepanda for other unit reviews