NEET Questions Solved

AIIMS - 2004

Nitrogen oxides produced from the emission of automobiles and power plants, are the source of fine air borne particles which lead to

(a) photochemical smog
(b) dry acid deposition
(c) industrial smog
(d) wet acid deposition

(b) : Sulfur and nitrogen oxides emitted into the atmosphere react to form compounds that are transported long distances and are subsequently deposited to the Earth's surface in wet and dry forms. Although the term "acid rain" is widely recognized, the dry deposition portion ranges from 20 to 60 percent of total pollutant deposition, and represents the particulate and gaseous forms. A more accurate description of the overall process is acid deposition rather than acid rain.

Dry deposition occurs when sulfur dioxide and nitrogen oxides react, but not with water. It settles out of the atmosphere as particle or gases.

The effects of acid deposition include acidification of lakes and streams, nutrient enrichment of coastal waters and large river basins, soil nutrient depletion and decline of sensitive forests, agricultural crop damage, and impacts on ecosystem biodiversity. Toxic pollutants and metals also can be transported and deposited through atmospheric processes. Both local and long-range emission sources contribute to atmospheric deposition.

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