name two ways pollutants enter the atmosphere.?

Answer 1

Gas leaks and partial burning of wastes or hydrocarbons (like cars), radioactive releases (like Chernobyl) and smog

According to Wikipedia: http://en.wikipedia.org/wiki/Pollution
"air pollution, the release of chemicals and particulates into the atmosphere. Common examples include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFCs), and nitrogen oxides produced by industry and motor vehicles. Ozone and smog are created as nitrogen oxides and hydrocarbons react to sunlight."

The incident in Bhopal India is the most famous gas leak of recent times.
According to Wikipedia: http://en.wikipedia.org/wiki/Bhopal
"The Bhopal disaster: On December 3, 1984, a Union Carbide plant in Bhopal leaked 40 tons of toxic methyl isocyanate gas, which killed more than 3,000 people outright and injured anywhere from 150,000 to 600,000 others. Another 12,000 deaths have officially been ascribed to the disaster's effects, although campaign groups put the figure much higher. (See Bhopal disaster. http://en.wikipedia.org/wiki/Bhopal_disaster)"

The Chernobyl sent cloud of radioactive smoke high into the sky effecting a large part of the Northern Hemishpere.
According to Wikipedia: http://en.wikipedia.org/wiki/Chernobyl_accident
"It is regarded as the worst accident in the history of nuclear power. A plume of radioactive fallout drifted over parts of the western Soviet Union, Eastern and Western Europe, Scandinavia, the UK, Ireland and eastern North America. Large areas of Ukraine, Belarus, and Russia were badly contaminated, resulting in the evacuation and resettlement of over 336,000 people. About 60% of the radioactive fallout landed in Belarus, according to official post-Soviet data."

According to Wikipedia: http://en.wikipedia.org/wiki/Smog
"Smog is a kind of air pollution — the name is a portmanteau of smoke and fog. Classic smog results from large amounts of coal burning in an area and is caused by a mixture of smoke and sulphur dioxide. In the 1950s a new type of smog, known as photochemical smog, was first described. This is a noxious mixture of air pollutants including the following:
- nitrogen oxides, such as nitrogen dioxide
- tropospheric ozone
- volatile organic compounds (VOCs)
- peroxyacyl nitrates (PAN)
- aldehydes (R'O)
All of these chemicals are usually highly reactive and oxidizing. Due to this fact, photochemical smog is considered to be a problem of modern industrialization.

Photochemical smog is a concern in most major urban centres but, because it travels with the wind, it can affect sparsely populated areas as well. Smog is caused by a reaction between sunlight and emissions mainly from human activity. Photochemical smog is the chemical reaction of sunlight, nitrogen oxides (NOx) and volatile organic compounds (VOC's) in the atmosphere, which leaves airborne particles (called particulate matter) and ground-level ozone. Nitrogen oxides are released in the exhaust of fossil fuel-burning engines in cars, trucks, coal power plants, and industrial manufacturing factories. VOC's are vapors released from gasoline, paints, solvents, pesticides, and other chemicals.

It often stays for an extended period of time over densely populated cities, such as London, Los Angeles, Mexico City, Houston, Toronto, Athens, Beijing, Hong Kong or the Ruhr Area and can build up to dangerous levels."

Smog causes acid rain when the sulfuric acid rains down on forests in Germany and Canada.