[Music] hi awesome ap environmental science students this is miss williams of science panda and today we are going to do the unit 8 review of aquatic and terrestrial pollution so let's start off with a little bit of an introduction let's talk about how humans impact the environment so so far in ap environmental science you have probably learned that human activities often are going to have negative consequences on the environment we use a variety of chemicals we release trash we have air pollution being emitted from a variety of sources and all of these can have negative impacts what we often see is the organisms in the environment even sometimes the environment itself does have what we call a range of tolerance so for example a polar bear if you look at the picture in the background is going to have a tolerance level for what is optimal and what is sub-optimal and what is completely not tolerated by that species so take a look at the bell curve notice my polar bear in the middle who's nice and happy he's enjoying you know his normal cool weather he's within his range of tolerance where i've got the dotted lines running vertically just to the left and right of the polar bear in the middle we're starting to go into you know it's not quite so comfortable for that bear anymore he's starting to experience physiological stress uh if it's an organism that might have changes in their growth or reduced reproduction even so he's a little uncomfortable in the middle third of that bell curve now look at our poor polar bears on the far left and far right the far left polar bear is experiencing much hotter temperatures than is natural for him definitely outside of his range of tolerance he's not good with that the polar bear on the right is experiencing very very cold temperatures so something not comfortable for him even though he is a polar bear let's just say it's ridiculously cold so he is not doing so great either the left and the right side of this bell curve are both outside of the range of tolerance and that is where these species that fall on that end or experiencing those changes in the environment will begin to have those symptoms we talked about again physiological stress limited growth possibly even death if it's severe enough other examples other than temperature like with our polar bear could be things like acid rain changing the ph of soil and water bodies species may not tolerate those changes in ph for example amphibians have a very narrow range of tolerance when it comes to ph and they will experience those physiological stress symptoms as a result if the change is more than they can handle so now that we know that human actions can have some major impacts on the environment let's take a look at some specific examples of this that you should be familiar with for the exam let's start with coral you'll hear a lot more about coral and changes in the ocean as you get into unit 9 for climate change but for now just know that things like climate change can cause coral to actually die off increasing ocean temperatures worldwide cause what we call coral bleaching which means that the coral turns white because it's dying oil spills are something that we hear about in the news every once in a while for example deepwater horizon that occurred in 2011 or the exxon valdez accident that occurred in the 80s so oil spills can have a variety of effects first of all oil is hydrophobic it floats on the top of water so because of that it causes it to spread rapidly we also see oil cause problems with bird feathers we also have problems with oil not just staying on the surface though oil can sink and when it sinks it can cover the benthic area of the ocean or the sea floor and kill species there and then oils because of the chemicals in it they are toxic to some extent and it may make it unsafe to fish in that area or not make it safe to consume fish from that area plastics are another huge problem so the problem becomes when plastics get into the environment especially the ocean they begin to photo degrade and i say photo to gray not decomposed because plastics take forever pretty much literally to break down so they might photo degrade into smaller and smaller pieces kind of like break apart but as they do that they become very attractive to small animals in the ocean that may see them as food so what we see is they often are ingested by marine animals and then plastics as they kind of degrade or break apart also release toxins all right and the last thing i wanted to discuss is endocrine disruptors these endocrine disruptors are known to disrupt the hormones in your body meaning they literally either compete with them or alter them or cause some problem that prevents those hormones from doing their job within your cells that means you might have birth defects as a result you may have developmental or reproductive effects or even problems with your immune system let's move on to some specific types of pollution that you need to be familiar with that affect aquatic and terrestrial habitat so first thing is two vocab terms you've got to understand and be able to identify so point source pollution is pollution that is going to be emitted directly from a very identifiable source it often is coming out of a pipe so look at my top picture and my middle picture to the right the top picture is a smoke stack you can literally point at it and say that is that point source of where that pollution is coming from it's easily identifiable or the outflow pipe the picture in the middle where water is coming out at maybe an industrial facility we can again point directly at it and say that's where that pollution is coming from so that's how i like to think of point sources you can literally point at right where it's coming out non-point sources though are much more diffuse or spread out so if you remember runoff from discussing that in past units runoff is where a bunch of water kind of collects stuff as it goes and then runs off to the nearest waterway non-point sources are usually runoff influenced so you may have for example fertilizers on a farm field there's a heavy rain there's a lot of water running off the surface of the earth and to the nearest lake or river it's going to pick up that fertilizer and carry it with it one of the things that we often see result from non-point source pollution is nutrient excess in waterways and nutrients are nitrogen and phosphorus based chemicals these often are from fertilizers directly so when we use inorganic fertilizers plants usually do not take up all of that nutrient and then it does quickly get washed off into waterways with the next large rainfall that we have what this can lead to is eutrophication again another idea you've probably heard of in the past units but let's go ahead and go through the steps of it so that you are familiar with it for this time around so the steps of eutrophication involve runoff carrying nutrients into a waterway what we will see is an algae in the waterway is going to increase dramatically the problem with algae multiplying in water though is they will block sunlight they can end up keeping plants deeper in the water from photosynthesizing and then when you have that many algae an algae or a small organism they don't live very long and so we will see them die in large quantities when they die and decompose they begin to use oxygen up out of the water so the dissolved oxygen is literally used up in that decomposition reaction and as the oxygen levels lower and potentially become what we call hypoxic or lacking in oxygen we end up seeing fish and plant die-offs as a result when eutrophication is particularly bad one of the things that can happen is dead zones uh there is a famous dead zone that forms in the gulf of mexico pretty much most summers as a result of nutrients being washed from the mississippi river watershed toward the gulf right around louisiana so dead zones are hypoxic areas which means oxygen lacking that basically have had so many nitrogen and phosphorous chemicals dumped into them that algae has grown and it is decomposed and it has used up all the oxygen in the water what happens though in the summer though is that the water in the gulf so the gulf of mexico stratifies meaning it separates into hot and cold layers and it prevents mixing of water that does have oxygen with water that has become hypoxic so what that means is that the deeper bottom waters don't have any oxygen in them the hot water sitting on top of it may still have some oxygen but they don't mix and so we end up with this deeper water just totally dead zone there's just no oxygen in it whatsoever so we've been discussing how oxygen affects water quality meaning how it affects the organisms that live there one of the ways we can actually chart and measure this is by doing an oxygen sag curve or by looking at an oxygen sag curve to see where oxygen has become depleted and where oxygen returns to a body of water so what we call the oxygen use in a water is biological oxygen demand it's basically the amount of oxygen that's used up per quantity of water by the organisms that live there if you have water that has a very low body it means that the water itself is still pretty full of oxygen and it's not being used up rapidly by organisms a higher biological oxygen demand or bod means though that the water is probably polluted and that organisms there are using up the oxygen rapidly so what we can do is look at a particular point source of pollution and we can take a look at how moving away from that point source changes the oxygen within the water so on our graph the blue line is showing us the biological oxygen demand so notice that near our point source over to the left there is a lot of oxygen demand it means that there's a lot of pollution we have a lot of microorganisms probably using up the oxygen in the water notice as we move further down the river though that biological oxygen demand does decline so that's why you have before that demand is high a live fish and after that demand drops off live fish notice the red line though at the very beginning right where that point source is we see that our dissolved oxygen is actually high but as the biological oxygen demand remains high it chews up that oxygen so you can see it drop off this is the oxygen sag and then you can see that as the bod drops off here we have our dissolved oxygen increasing again and that's where live fish are able to return so the sag curve basically shows us distance downstream away from a pollution source and how the oxygen and the biological oxygen demand have changed over time one of the other effects that we see from pollution is bioaccumulation and biomagnification of certain substances for example mercury so when we burn coal mercury is often released into the atmosphere mercury though has a bit of an issue it tends to get into the atmosphere and then settle back out into waterways and when it does that it's often converted into a toxic form known as methylmercury well methyl mercury has a huge habit of bioaccumulating in the tissues of organisms what this means is the compound gets into usually fats in the organism and then stays there so over time as you're exposed to mercury again you get more in your system and as you're exposed again it just continues to build up in the organism's body on top of that we can also have biomagnification take place in a food chain so if you look at my picture on the right notice our krill have the methyl mercury entering them and then krill are eaten by small fish which are eaten by medium fish which are eaten by big fish well biomagnification would tell us that the mercury gets passed up that food chain as the other animals are consumed and we will often see top level predators with very very high levels of mercury as a result next up is thermal pollution and thermal pollution is kind of an odd one because thermal pollution is caused by hot water that's it okay it's not toxic it's not full of a chemical but hot water can affect the well-being of species in the water body that it's being dumped into so thermal pollution is going to be a problem when the water body has one temperature of water usually cooler and then much hotter water is dumped into it so if you remember studying coal-fired and nuclear power plants the way they work is they basically boil water to help spin a turbine to create electricity well that water is going to have to be condensed back into liquid and cooled down but these plants don't always have enough time to cool it back down to the outside temperature especially if it's winter so the water that's released it is higher in temperature and so when we release that into the water now we may have fish avoiding that location and one of the other big problems is that warmer water just does not hold as much oxygen as cooler water so we will see fish having physiological stress due to the change in temperature we may also see a lack of oxygen in the water as well now that we've gone over some types of aquatic pollution let's move on to terrestrial pollution one of our biggest problems on land is dealing with solid waste usually solid waste is going to go to sanitary landfills or just landfills and these are pits that we dig out and then often line with plastic or other type of barrier called a liner to prevent leaking within a landfill though there's a lot more engineering involved there's often a leachate collection system this is all the fluid that accumulates due to rainwater runoff in the landfill or due to the decomposition process and that needs to be collected to make sure that we don't have leaks in our landfill in addition to that methane often needs to be collected methane is caused by the decomposition process of the trash but methane is flammable and potentially explosive so one of the interesting things that we can do is collect it and then if the landfill is set up for it it could even be burned for electrical production once a landfill is finalized and done being used a cap is applied and that landfill may even be able to be reverted back to green space by planting grass on top for example another way of disposing of solid waste is through incineration which is burning at very high temperatures this is a good method for reducing the volume of trash but may not be the method of traps disposal for the future for example because it does release a large amount of air pollution our final method of dealing with solid waste is recycling now unfortunately not everything can be recycled and recycling is extremely energy intensive and very expensive but it is a way of reusing some materials for example some plastics are recyclable but not all communities are set up to recycle humans also create a lot of sewage that needs to be dealt with before it can be released back to the environment so think of every time you wash your hands every time you flush the toilet every time you run the shower that water has to be treated before it can just go back into a lake or river otherwise it could cause toxicity or eutrophication issues due to the chemicals that we use within our water every day for example adding laundry detergent when you wash your clothes so with sewage treatment we go through three levels of processing in addition to disinfection so primary treatment is also known as physical treatment this is where we remove large objects from the water so let's say the storm water runoff that went to that water treatment plant collected some leaves or trash from roadways we need to take that out usually grates and screens are used to kind of separate those or filter them out of the rest of the water secondary treatment is biological treatment we use bacteria to break down waste such as human feces food waste soaps and detergents and then we may also even aerate the tanks so that that bacteria does this job faster our final form of treatment is going to be chemical treatment or tertiary treatment and this is where we make sure that nutrients are removed water may also be disinfected before it's released back to the environment using a variety of chemicals so we may use chlorine to sterilize it or remove bacteria ozone gas can be bubbled through it to help kill bacteria or we may even use uv light unit 8 also involves a little bit of information about human health and there's one key idea that you guys should know about which is the ld50 or lethal dose 50. we'll get to that in just a second but there's two basic facts that you should be familiar with regarding human health and environmental science one of the things we are experiencing as we see climate change is that diseases that would normally affect only very very warm areas are beginning to expand their range for their north and further south this usually has to do with the vector or whatever it is that carries and transmits the disease is able to be in areas that it did not exist in before due to warming temperatures so for example we might see things like west nile virus or zika or malaria which are all transmitted by mosquitoes spread further north and south than they might normally as temperatures warm pathogens also have a habit of spreading when there is poverty lack of sanitation especially dirty water in an area and lack of clean drinking water so if communities do not have water treatment they do not have proper solid waste sanitation pathogens also tend to be a real problem and we usually see this in developing countries all right back to our lethal dose 50 or ld50 this is your graph that you're seeing on the right which might look familiar from class ld50 is the dose of a chemical that's required to kill 50 of a population if we're trying to determine what dosing is safe and what dosing is no longer safe so take a look at our graph on the right what we see along the bottom is the dosage of a particular drug or medication on the left or the y-axis we see percent mortality ranging from zero to a hundred right at 50 is where we see the dosage that 50 of the population will be killed at or the lethal dose 50 or ld50 so to read this what we would do is follow across from 50 percent to our what we call a dose response curve and then follow down to determine the dosage so notice on this graph the dosage of 100 milligrams per kilogram is deadly to 50 percent of the population our final part of the unit that we need to review is a few laws that show up throughout this unit that are important to know for the exam they include the clean water act which makes it unlawful to discharge pollutants from a point source into navigable waters our second law is the safe drinking water act this law makes sure that underground sources of drinking water or aquifers are protected from contamination we have rcra sometimes known as rekra or the resource conservation and recovery act the whole point of this act is to make sure that hazardous waste is monitored from the time it's created to the time it's disposed of you should be familiar with the phrase cradle to the grave management which sounds kind of funny but basically just means cradle is creation of the hazardous waste and grave is destruction or disposal of the hazard we also have circla or superfund the main point of circla is to make sure that companies are responsible for cleaning up hazardous waste if they create it and then our final part that you need to know is kind of a part of a law it's not a law on its own it's the delaney clause this clause bans food additives that are known to cause cancer whether it be in humans or in animals thank you for choosing science panda to review for the ap environmental science exam we hope this video was helpful don't forget to like and subscribe and check out our other unit reviews on our channel