What is the key concept for this section? Define density, as it relates to the atmosphere, and atmospheric pressure and explain why both are two important atmospheric variables. Define and distinguish...

What is the key concept for this section? Define density, as it relates to the atmosphere, and atmospheric pressure and explain why both are two important atmospheric variables. Define and distinguish among atmosphere, troposphere, stratosphere, and ozone layer. What are greenhouse gases? What is the key concept for this section? What is air pollution? Distinguish between primary pollutants and secondary pollutants and give an example of each. What are atmospheric brown clouds and what have scientists learned about their harmful effects? List the six major outdoor air pollutants and their harmful effects. Describe the effects of lead as a pollutant and how we can reduce our exposure to this harmful chemical. Give examples of a chemical method and a biological method for detecting air pollutants. What is the Air Quality Index?