What are the sources of air pollution?

Air pollution can be in the form of either a gas or an aerosol, and it can either be anthropogenic (man-made) or natural. Man-made sources of pollution include factories, cars, motorcycles, ships, incinerators, wood and coal burning, oil refining, chemicals, consumer product emissions like aerosol sprays and fumes from paint, methane from garbage in landfills, and pollution from nuclear and biological weapons production and testing.

How much pollution is generated by airplanes?

At any given moment in time, there are about 5,000 non-military aircraft plying the skies over the United States. It takes a tremendous amount of fuel to keep all these transports aloft, and the burned fuel results in exhaust similar to that coming from car engines: nitrogen oxides, sulfur dioxide, carbon monoxide, and soot. In addition, water vapors are released, which form ice crystals at high elevations commonly called contrails. Meteorologists believe that these contrails increase the formation of cirrus clouds, which may contribute to global warming.

Large tracts of land in the Amazon rain forest are regularly deforested to make way for farms, but, ironically, the soil is not very fertile.

Large tracts of land in the Amazon rain forest are regularly deforested to make way for farms, but, ironically, the soil is not very fertile.

Does air pollution reach as far as the North Pole?

Yes. Winds can carry air pollutants far beyond the Arctic Circle, resulting in a condition called "Arctic haze." The pollution tends to be worse during winter and spring, when prevailing winds from northern Europe to Siberia blow emissions northward from industrial areas. Recent shifts from coal burning to natural gas (primarily from Russia) has created cleaner air conditions, fortunately.

What are some natural sources of air pollution?

Natural sources of pollution may include dust, methane from human and animal waste or flatus, radon gas, smoke from wildfires, and volcanic activity.

Are there any circumstances where air pollution could be beneficial?

Yes. In fact, dust storms and volcanic ash can be a means for nature to distribute soils across the surface of the planet to regions that might not otherwise get certain nutrients. For instance, the Amazon rain forest may be famous for its verdant plant life, but in actuality the soil beneath the dense canopies is of very poor quality. Dust blown across the ocean from Africa to South America may help fertilize the rain forests. Not only that, but such storms bring nutrients to plankton in the ocean, which form the basis for aquatic food chains.

Can weather actually make pollution worse?

Yes, and it can alleviate it, as well. Rain, for instance, can wash away haze over cities, and wind can blow it away. Stagnant air masses, humid air, or temperature inver-

Did air pollution originate with the Industrial Age of the eighteenth century and beyond?

No. Since before recorded history, when humans first discovered fire, people have been generating pollution. As people learned to burn coal, they were also subjected to sulfur dioxide poisoning. Indeed, even Native Americans such as the Hopi used coal as a source of fire and heat.

sions, on the other hand, will allow pollution to build up. During the night, "nocturnal inversions" cause carbon monoxide to build up around freeways and other high-traffic areas. On the other hand, "mixed layer" conditions help to disperse pollutants when temperatures decrease over several thousand feet at a rate of about 4.5°F (2.5°C) for every thousand feet (about 300 meters) or so.

How much does air pollution damage crops in the United States?

It is estimated that the United States loses millions of dollars in crops every year because of air pollution. In the East, crop reductions cost about three billion dollars in losses annually, and farmland near such cities as Los Angeles and Chicago is far less productive than land far from such cities.

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