From Chapter 15. Examine the following ambient air data collected for Pittsburgh
ID: 284270 • Letter: F
Question
From Chapter 15. Examine the following ambient air data collected for Pittsburgh, Pennsylvania, and answer the following questions. (a) Based on the National Ambient Air Quality Standards (NAAQS), the 2008 standard for ozone states that the average ozone levels are NOT to exceed 0.075 ppm (75 ppb) in any 8-hour period (as shown in the Monthly average ozone levels column in the middle). Is Pittsburgh in compliance with this standard? Discuss how this NAAQS may NOT truly reflect the overall air quality focusing on the monthly maximum ozone levels column on the left. (b) Ozone is classified as a secondary pollutant. Identify the primary pollutants necessary for its formation and describe how tropospheric ozone is formed. (c) Identify two relationships between the data presented. Apply these relationships to your answer in (b) to explain the pattern of ozone levels in Pittsburgh. (d) Explain how the same ozone that is harmful in the troposphere is beneficial in the stratosphere.Explanation / Answer
a)
The EPA has set National Ambient Air Quality Standards for Ozone; it states that the average ozone level are not to exceed 75 ppb in any 8 hour period. The monthly average ozone is in compliance with this standard. But the monthly maximum ozone levels are seems to be higher than this standard during summer months.
b)
Ozone is not directly released from any one source. Tropospheric ozone is created by the reaction of sunlight, mainly ultraviolet light, with hydrocarbons and nitrogen oxides, which are emitted from automobiles, gasoline vapors, fossil fuel power plants, refineries, and other industries.
In urban areas in the Northern Hemisphere, high ozone concentrations generally occur during the warm, sunny summer months. Ozone levels reach their peak in mid to late afternoon. A hot, sunny, day is the ideal condition for ozone pollution formation. In early evening, the sunlight's level decreases and the photochemical production process that forms ground level ozone begins to drop.
c)
From the data presented, we can observe that monthly maximum ozone level correlate with the monthly average solar radiation, large value of montly average solar radion is observed during July and highest amount of maximum ozone levels is observed during July. So solar radiation is the main parameter for production of ozone pollution. Also the ozone level decrease with decrease in the solar radiation. Here it is very low during December season and increases during summer season.
d)
Ozone takes place in two layers of the atmosphere. One is in the stratosphere, a layer that extends upward from about 10 to 30 above the earth. This good ozone protects life on earth from the sun's harmful ultraviolet rays.
The other is in the troposphere. The layer adjacent to the earth's surface is the troposphere, it extends from the surface to about 10 miles above the surface. Here, ground-level ozone acts as bad ozone or air pollutant which damages human health, vegetation, and many common materials. It is an important component of urban smog. This is also called tropospheric ozone and good ozone is called stratospheric ozone. Around 80-90% of all ozone in the atmosphere is created in the stratosphere.
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