Pollution

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An air pollutant can be considered as a substance in the air that, in high enough concentrations, produces a detrimental environmental effect. Air pollutants can be either primary or secondary, depending on how they are formed. Primary pollutants are generated daily and are emitted directly from a source into the air. Examples of primary pollutants include: carbon monoxide, nitrogen dioxide, nitric oxide, sulfur dioxide, particulates and various hydrocarbons, also known as reactive organic compounds. The predominant source of air emissions can be generated by truck diesel emissions. Secondary pollutants are created over time and occur within the atmosphere as chemical and photochemical reactions take place. An example of a secondary pollutant is ozone, which is one of the products formed when reacting with hydrocarbons, in the presence of sunlight. Other secondary pollutants include photochemical aerosols. Secondary pollutants such as oxidants represent major air quality problems. Air pollutant called ozone can affect insects, animals, plants, and people that live in the troposphere. It is the layer where all weather occurs. Ozone occurs naturally at ground-level in low concentrations. The two major sources of natural ground-level ozone are hydrocarbons, which are released by plants and soil, and small amounts of stratospheric ozone, which occasionally migrate down to the earth's surface. Neither of these sources contributes enough ozone to be considered a threat to the health of humans or the environment. But the ozone that is a byproduct of certain human activities does become a problem at ground level and this is what we think of as bad ozone. With increasing populations, more automobiles, and more industry, there's more ozone in the lower atmosphere. Since 1900 the amount of ozone near the earth's surface has more than doubled. Unlike most other air pollutants, ozone is not directly emitted from any one source. Tropospheric ozone is formed by the interaction...
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