Amount of and amounts of.

[hoangkha]

Hi, teachers!
I have just seen this paragraph.
Scientists often divide resources into two groups: renewable and non– renewable. When a resource is used, it takes some time to replace it. If the resource can be replaced quickly and easily, it is called renewable. If it can not be replaced quickly and easily, it is non-renewable. All fossil fuels are non-renewable resources. Solar energy, air, and water are usually called renewable because there is an unlimited supply.
However, this definition may change if people are not careful with these resources. The amount of solar energy that reaches the earth depends on the atmosphere. If the atmosphere is polluted, the solar energy that reaches the earth may be dangerous. If life is going to continue, the air must contain the correct amount of nitrogen (N), oxygen (O), carbon dioxide (CO2), and other gases. If humans continue to pollute the air, it will not contain the correct amounts of these gases.
Many resources are limited and non- renewable, and many are in danger of pollution. As a consequence, resources must be conserved and the environment protected. Conservation must become an important part of everyone’s life.

I am wondering what is the difference between AMOUNT in the first bold and AMOUNTS in the second bold. Could you please explain it?

[probus]

Amount is used with non-countable nouns, and number with countable. This is the simple explanation for your first example.

The reason for using the plural amounts in your second example is that each of the atmospheric gases has its own "correct" amount. There is a correct amount for oxygen, another correct amount for nitrogen, and so on.