Chapter 18: Air Pollution

## 18.1 What Is the Nature of the Atmosphere?

### The Atmosphere Consists of Several Layers

* Density varies→ Decreases with altitude
* Atmospheric pressure→ Decreases with altitude

### Air Movements in the Troposphere Play a Key Role in Earth’s Weather and Climate

* Troposphere
* 75–80% of the earth’s air mass
* Closest to the earth's surface
* Chemical composition of air
* Rising and falling air currents
* weather and climate
* Involved in chemical cycling

### The Stratosphere Is Our Global Sunscreen

* **Stratosphere**: Similar composition to the troposphere, with 2 exceptions
* Much less water
* O3, ozone layer
* **Ozone layer**: Filters 95% of harmful UV radiation and allows us and other life to exist on land

## 18.2 What Are the Major Outdoor Pollution Problems?

### What is Air Pollution?

* **Air pollution**: Concentrations high enough to harm human health or alter the climate
* Natural sources
* Dust blew by the wind
* Pollutants from wildfires and volcanoes
* Volatile organics released by plants
* Pollutants mix in the air to form industrial smog
* Primarily as a result of burning coal and photochemical smog
* Caused by emissions from motor vehicles, industrial facilities, and power plants

### Air Pollution Comes from Natural and Human Sources

* Human sources: mostly in industrialized and/or urban areas
* Stationary sources: power plants and industrial facilities
* Mobile sources: motor vehicles

### Some Pollutants in the Atmosphere Combine to Form Other Pollutants

* **Primary pollutants**: Emitted directly into the air
* **Secondary pollutants**: From reactions of primary pollutants
* Air quality improving in developed countries
* Less-developed countries face big problems
* **Indoor pollution**: a big threat to the poor

### Human Impact on the Atmosphere

* Burning Fossil Fuels
* Adds CO2 and O3 to troposphere
* Global Warming
* Altering Climates
* Produces Acid Rain
* Using Nitrogen fertilizers and burning fossil fuels
* Releases NO, NO2, N2O, and NH3 into troposphere
* Produces acid rain
* Refining petroleum and burning fossil fuels
* Releases SO2 into troposphere
* Manufacturing
* Releases toxic heavy metals (Pb, Cd, and As) into the troposphere

### Criteria Air Pollutants

* EPA uses six "criteria pollutants" as indicators of air quality


1. **Nitrogen Dioxide**: NO2
2. **Ozone**: ground level O3
3. **Carbon monoxide**: CO
4. **Lead**: Pb
5. **Particulate Matter**: PM10 (PM 2.5)
6. **Sulfur Dioxide**: SO2


1. **Volatile Organic Compounds**: (VOCs)

* EPA established for each concentration above which adverse effects on health may occur

### Carbon Monoxide (CO)

* **Properties** **of carbon monoxide**: colorless, odorless, heavier than air, 0.0036% of the atmosphere
* **Effects** **of carbon monoxide**: binds tighter to Hb than O2, mental functions, and visual acuity, even at low levels
* **Sources** **of carbon monoxide**: incomplete combustion of fossil fuels 60 - 95% from auto exhaust
* **Class** **of carbon monoxide**: carbon oxides (CO2, CO)
* **EPA Standard** **of carbon monoxide**: 9 ppm
* 5.5 billion tons enter the atmosphere/per year

### Nitrogen Dioxide (NO2)

* **Properties of nitrogen dioxide**: reddish brown gas, formed as fuel burnt in the car, potent oxidizing agent, include Nitric acid in the air
* **Effects of nitrogen dioxide**: acid rain, lung and heart problems, decreased visibility (yellow haze), suppresses plant growth
* **Sources of nitrogen dioxide**: fossil fuels combustion @ higher temperatures, power plants, forest fires, volcanoes, bacteria in soil
* **Class of nitrogen dioxide**: Nitrogen oxides (NOx)
* **EPA Standard of nitrogen dioxide**: 0.053 ppm

### Sulfur Dioxide (SO2)

* **Properties of sulfur dioxide**: colorless gas with an irritating odor
* **Effects** **of sulfur dioxide**: produces acid rain (H2SO4), breathing difficulties, eutrophication due to sulfate formation, lichen and moss are indicators
* **Sources of sulfur dioxide**: burning high sulfur coal or oil, smelting or metals, paper manufacture
* **Class of sulfur dioxide**: sulfur oxides
* **EPA Standard of sulfur dioxide**: 0.3 ppm (annual mean)
* Combines with water and NH4 to increase soil fertility Suspend

### Suspended Particulate Matter (PM10)

* **Properties of particulate matter**: particles suspended in air (