[SOUND] [NOISE] All right. So let's start talking about acid rain. This was a really big topic through the 70s. People were noticing that forests were starting to decompose. That rivers, or particularly lakes, were starting to have fish die off. Incidences of asthma-like symptoms, or even if you look statistically, higher causes of mortality from lung problems, would occur in regions that were very rich with coal power plants. And maps, that would map out what is the pH of the rain? Were developed and done throughout the world, particularly in the United States. Before you actually try to understand the topic of course, we need to understand what an acid is. So when we're talking about acids, we need to have some numbers. And the scale we use is called pH. It's actually the concentration of hydronium ion. It's a log concentration. So 7.0 is neutral. Anything lower, like 6.0, is ten times more acidic. 5.0 would be a hundred times more acidic. And this keeps going, these numbers could keep going down. These are all acids. Higher numbers are bases. These are things that each larger digit is again, a factor of ten or a factor of 100 or a factor of 1000. These are bases. So this is the scale. So perfect distilled neutral water, 7.0. Now you might think okay, so I guess clean pure rain is 7.0. But it isn't. Take a look at this graph. This is a graph of a chart, that shows the pH level of the rain across the country in 1980. If you look out on the California coast, where the only thing the prevailing winds which go west to east are going to bring us is, clean air that's been over the Pacific Ocean. And you look at those pH levels and they're 5.6. And you wonder why is this? Why is pure, clean, pure rainwater have a pH of 5.6? Why is it somewhat acidic? Well, you should not despair. 5.6 is normal. That is the pH of the rain. More or less very close to that number, has been the pH of the rain. That is what we actually would consider wonderful water to drink, to use, to consume. That's rain water. The reason it's slightly acidic is that, when the water drips through the air, it hits some carbon dioxide molecules. We're not talking about global warming and the CO2 going up, this has always had some level of CO2 in our atmosphere. And when the rain goes through it, it picks up a little of this and turns to a carbonic acid. A rain level of 5.6 is normal. That's what life has evolved having. If you go lower than that. If you go to those regions on the map that have four, 4.2, these are below the levels where things go well. The effect of having this type of acidity can be very bad. If this happens to be in certain types of vegetation, it will kill the vegetation. If you breathe this in. Right. If somehow this type of acid level water vapor gets into your lung tissue, it can damage it over time. Or certainly give you more distress If it falls into the lakes and the whole acidity level of the lake goes down, it'd kill the vegetation and marine life in that lake. Buildings can fall into disrepair. Marble in particular, is an extremely soft type of mineral. A demonstration with a piece of chalk and vinegar, not all that strong of an acid, demonstrates what happens quickly to a marble building in just acid rain, over many decades. Features of ancient sculptures have actually disappeared. As the acid rain from the air has slowly over time, ruined these works of antiquity. So acid rain is something that was recognized as being a culprit. Recognized as being something that we should prevent. Well the first question was, how is it caused? Let's look for a moment at this graph of the sulfur dioxide being made in power plants or factories, across the United States in 1980. Notice any similarity to the Ph map? In fact maybe just shifted a little up wind. Those darkest colored states, were ones where the most sulfur-rich coal was being burned. And just like coal is designed to have carbon turn into carbon dioxide, sulfur will turn into sulfur dioxide by being burned. Now sulfur dioxide itself is relatively stable. But if I take some ash, some dust. Coal power plants are really good at producing a lot of fine dust. Plus SO2 and plus a little more oxygen from the air. I can get sulfites, SO3. And these are on the dust surface. This SO3 containing dust is called dry acid precipitate. So this SO3 that's on the dust surface. What happens to it? Well let's say you're standing around and there's a slight amount of this in the dust, because you're somewhere down wind of a coal power plant. And you breathe. [SOUND] Some of that dry acid precipitate has now gone into your lungs. What does it encounter there? [LAUGH] SO3 + water, the surface of your lung tissue goes to H2SO4, this is sulfuric acid. You have just created sulfuric acid on your lung tissue. A little bit of an accelerated demo that shows, what happens if you take some type of nice hydrocarbon type material, paper which is sort of like what your body is made out of, some carbon, hydrogen, oxygen compound, and we take some concentrated sulfuric acid. And by the way, nitrous oxide is produced in power plants as well. You might say whoa, you mean there's some nitrogen in the coal? Well yes, there is some nitrogen in the coal. But that's not our main culprit. When we burn coal, the air is 80% nitrogen. Some of that will actually burn, well combine chemically into nitrous oxide compounds. They're called NO with an X. You might say what is X? Well X is a number. X could equal one half, one, two or three. In other words, I could make N2O that's the one half, NO, NO2, or NO3. Those nitrous oxide compounds also will do this same type of reaction. And instead of turning into sulfuric acid, it turns into nitric acid. Now I have water vapor, that will have sulfuric acid in it and a nitric acid in it. Or dry acid precipitate that has nitrates and sulfites on the material, that will turn into those acids when it reaches my lung tissue. This demonstration illustrates what happens, when I take some nitric and sulfuric acid and drip it onto simulated long tissue, or simulated plant matter. Actually there's nothing simulated about it, paper is plant matter. And we'll watch here a little bit over time, what acid can do to these type of substances. So lets get back to your lungs. 30% of the sulfur dioxide that goes up the smoke stack, comes back to the earth in this dry acid precipitate, which will turn into acid as soon as it hits water. 70% is washed out of the atmosphere by the rain. Which meant it hit water up there and came down as slightly acidic rain, acid rain. You and I, sitting here today, can overlay the acid pH level map with the, here is where the sulfur dioxide is produced map, and say clear one to one correspondence. Because after all, this is the reaction that's going on. Even in the face of scientific fact, often a community is skeptical. Hey, I'm not really convinced that this acid rain thing is true because, look that lake over there that's down-wind the my coal power plant. The fish in it are fine, the fishing tournaments go on, no one's ever been better, nobody's complaining. Why do think, you're saying I am making acid rain here in my factory? Well, you're absolutely right. Some lakes were not affected, because they were made of limestone! All right? Limestone is a natural buffer. We've talked about pollution controls, and when you want to actually get the sulfur dioxide out of a system, you can buffer it. You can combine it with calcium carbonate, limestone. So if you have a lot of limestone in your lake, the pH level is going to stay just fine, at the level that that lake evolved with. If your lake is not so lucky, you get a dead lake. There was more evidence too. And I like this because of course, I'm a nuclear scientist. And along came a diagnostic that was able to distinguish very small traces, nuclear reaction analysis. And you could determine parts per billion levels of material. Certainly parts per million, levels of rare earth elements. Things that are called on the periodic table rare earths, in part because they're really rare in the Earth. It turns out that many power plants, coal power plants, had long-term contracts with a given coal mine. They would always get their coal from that nearby coal mine. And that makes a lot of sense. Transportation cost is high. Why should I buy my coal from someone really far away, probably the cheapest solution is to buy it from the nearby mine. And this means over a long time span, that coal power plant is burning that type of coal. With nuclear reaction analysis, you can go to the coal and analyze it for these rare earths. Two part per billion of europium, five parts per billion of some other rare earth elements, 70 parts per billion of this rare earth. It's a chemical footprint, a signature of that particular coal that's unique to that particular coal. Then you can go to the dead lake, a hundred miles upwind of the power plant. And you can pull up the muck at the bottom of the lake, that's been settling there and accumulating over being downwind of this power plant, for the last 50 years while it's been burning that coal. And you can look at the same rare earths and see them in the same magnitude, the same signature. That coal, the unburned parts of that coal, were ending up in that Lake. Evidence like that, the overwhelming evidence of just looking at the maps, the understanding of the chemistry, led the country to say yes burning sulfur, turning sulfur into sulfur dioxide, turning nitrogen into nitrous oxides, produces acid rain. We better do something about it. And the Clean Air Act was passed. And it set a limit coming up by a certain date, of 2.4 pounds of sulfur dioxide produced for every million British thermal units of energy produced. A lot of British i.e. American, units there. But it's a limit of the amount of sulfur dioxide per amount of energy, heat made. [MUSIC]
