1. why is air pollution a health threat? how is it measured?
2. why is global warming so controversial? what is causing it?
3. what is acid deposition? how is it damaging?

Explanation:

1.  

Air pollution is caused by some degrading elements that enter the atmosphere and degrade the quality of the air that we breath. Air pollution is a health threat because the degraded air contains many harmful and poisonous gases . When these gases enter our body, they cause various diseases such as bronchitis , asthma etc .

These gases not only effect our respiratory system but also eventually effect our circulatory as well as our nervous system.

Air pollution is measured by a parameter known as AQI i.e., Air Quality Index.

Air Quality Index is a parameter used by the government agencies to check the air pollution level .

Air Quality Index increases due to the increase in emission of harmful gasses through vehicular emiiemis, forest fire, or increase in industrial emissions. Sometimes due to anticyclone or low pressure or low wind velocity even the AQI increases.

2.

Global warming is the increase in the amount of heat in the atmosphere from past thousands of years. Our planet earth comprises of a thick blanket of air which is known as the atmosphere. This atmosphere comprises of many gases such as nitrogen, oxygen, carbon dioxide, etc . Apart from these gases there are many other gases which are known to be the major cause of global warming and are known as the Green House Gases .

These gases are water vapor , carbon monoxide, methane, nitrous oxide, carbon dioxide, and CFCs etc

Green House Gases block the infrared radiations to pass through the atmosphere and hence increase the temperature of the earth.

Global warming is caused due to increasing air pollution through industries , vehicles etc

3-

As our earth is surrounded by a layer of air known as the atmosphere, these gases such as nitrogen oxygen carbon dioxide etc during the process of lighting and rain these react with each other and also along with the water . These reactions cause in the formation of acids such as nitric acid, sulfuric acid, carbonic acid etc . Due to the presence of these elements in the atmosphere they react and precipitate in form of rain, hail, fog etc as acid rain, acid snow, acid fog etc.

These acids get precipitated and get deposited on land and are known as acid deposits.

Due to increasing air pollution level we now often find these deposits in the areas which have high level of pollutants in the air due to various emission .

These acidic deposits in form of acid rain , snow, fog not only corrode the buildings, infrastructures etc but also cause soil pollution because of decrease in the pH level of the soil making it more acidic and unfit for plants to grow.

the value of the 4 in the hundreds place is 400 while the value of th e 4 in the tens place is 40

400 is way bigger than 40.