Pollution
History of Earth
Hank Green
(Source: http://open.163.com)
Pollution
Hank Green
(Source: http://open.163.com)
（Chinese and English subtitles：张铮）
Pollution is a kind of catch-all term for any substance that’s in the wrong place or in the wrong concentrations in the environment.Trash in the environment,that’s pollution,but chemicals,bothnaturally-occuring and synthetic,those are the real killers.Now ,we tend to think of pollution in terms of werid synthetic.chemicals made in big chemical processing plants.and they are certainly a problem.But as we’ll see in a bit,you gotta understand that natural compounds in the wrong concertrations can do just as much damage as whatever petro-insecticides we’re making.One of the main ways we’re altering concentrations of natural compounds is by messing with the biogeochemical cycle. This paper describes the main kinds of pollution on the earth from the following aspects.
1) Natural compounds
Carbon cycle keeps going on ,but we’re overloading it by digging up all that carbon-rich coal,oil and gas.There’s more carbon getting releasted than the reservoirs can handle.The carbon can’t just go back into the rock ,so it hangs around in the atmosphere as agreenhouse gas insulating our planet and change the climate.
We’ve also been tampering with the nitrogen and phosphorus cycles to similar effect.nitrogen and phosphorous are nutrients,which we and other organism need,like, really need,in order to grow and respire and,exist.But when we go and make like,ludicrous amounts of these nutrients available,escosystems get very confused.
Phosphates and nitrates are basically the main ingredients in fertilizers,and phosphates are also found in somedetergents.So when waste water from our houses runoff from farms washes those compounds into rivers and stream,it can cause huge algal blooms that chokes out the rest of the plants and animals in the stream and it’s totally gross looking.When all the phosphorus and nitrogen are used up ,the algae die.Then bacteria get started on decomposing that dead algae.But of course the decomposers need oxygen ,which they take out of the water ,and then oxygen levels in the water plummet killing all the fish and just about everything else that needs oxygen.
Food like almonds,spinach and lima beans contain cyanide.Cyanide is useful to plants because it’s a primitive insecticide,causing a lot of molecular asphyxiation,preventing a bug’s cells from being also to use oxygen.Mining operations use cyanide in large quantities in order to sparate gold,silver and other precious metals from the ore. But the toxin is never totally eliminated.
Mercury is another important pollutant.it’s a super-toxic,naturally-occurring metal found in coal.among other place.When that coal is burned to make electricity,the mercury is released into the air.And then the mercury falls on the land ,where it makes its way into groundwater and eventually into the food chain.
E) Sulfur dioxide and nitrogen dioxide
We release millions of tones of sulfur dioxide and nitrogen dioxide into the environment every year by burning fossil fuels like coal.And when these compounds react with water vapor in atemposphere .they turn into sulfuric acid and nitric acid and then return to the surface as acid rain.
2) Synthetic compounds
There’s a whole class of chemicals endocrine disruptors,which we put in pharmaceuticals,pesticides and plastics, but some of them are also just by products of industry and agriculture.
