Chapter 15 Air Pollution and Stratospheric Ozone Depletion

Air Pollution Air pollution- the introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to harm plants, animals, and materials such as buildings, or to alter ecosystems. Why is air pollution considered a global system? Earth’s atmosphere is a global commons or worldwide public resource.

Major Air Pollutants Sulfur Dioxide Nitrogen Oxides Carbon Monoxide Particulate Matter Lead Volatiles Organic Compounds Ozone Mercury Carbon Dioxide Of the pollutants above what are the criteria pollutants? What does criteria stand for?

Criteria Pollutants vs Primary Pollutants Criteria Pollutants are controlled by the Clean Air Act. The EPA is required to set National Ambient Air Quality Standards (NAAQS) for the six common air pollutants. These commonly found air pollutants (also known as "criteria pollutants") are found all over the United States. Primary pollutants are direct products of combustion and evaporation and can lead to secondary pollutants. On your chart notes mark the primary pollutants.

CompoundSymbolAnthropogenic CauseEffects/ Impacts Criteria Air Pollutants Sulfur Dioxide Nitrogen Oxide Carbon Monoxide Particulate Matter Lead Ozone Other Air Pollutants Volatile Organic Compounds Mercury Carbon Dioxide Primary

Examples of Sources for the Six Criteria Pollutants O3 – Ozone Ozone: Formed by the interaction of sunlight with other other pollutants: NO, CO, and Volatile Organic Compounds (VOCs) NO2 – Nitrogen Dioxide Car exhaust and Electricity Generation produce NO during combustion, which gets converted into NO 2 in the atmosphere CO – Carbon Monoxide All combustion processes such as car exhaust and Electricity Generation Lesson 1: Air Pollution Basics O 3, NO 2, and CO will be discussed further in Lesson

Examples of Sources for the Six Criteria Pollutants PM2.5,10 – Particulate Matter Car Exhaust, Electricity Generation, Fires, and Road dust Pb – Lead Iron smelters and other industrial processes. Before it was banned, leaded gasoline was a major contributor to lead in the atmosphere. SO2 – Sulfur Dioxide Electricity Generation from burning of coal. Lesson 1: Air Pollution Basics O 3, NO 2, and CO will be discussed further in Lesson

**Page 412

Primary and Secondary Pollutants Primary Pollutants are emitted directly from various sources and cause harm in their emitted state. Examples of Primary Pollutants: NO, SO 2, CO, CO 2 Secondary Pollutants result from chemical transformations in the atmosphere. Examples of Secondary Pollutants: O 3, H 2 O 2, HNO 3, H 2 SO 4, Nitrate and Sulfate Particles Lesson 1: Air Pollution Basics

What is the difference between a primary and a secondary pollutant? Primary causes secondary. If society controls primary then secondary pollution will reduce.

Natural Sources of Air Pollution Volcanoes Lightning Forest fires Plants

Anthropogenic Sources of Air Pollution On-road vehicles Airplanes Power plants Industrial processes Waste disposal

How does the Clean Air Act regulate anthropogenic emissions? In developing the Clean Air Act of 1970 and subsequent amendments: The Clean Air Act (CAA) is the comprehensive federal law that regulates air emissions from stationary and mobile sources. Among other things, this law authorizes EPA to establish National Ambient Air Quality Standards (NAAQS) to protect public health and public welfare and to regulate emissions of hazardous air pollutants.

Air Quality Index Levels of Health Concern Lesson 1: Air Pollution Basics A daily measure of the quality of the air generally published along with weather reports based on the amount of the six criteria pollutants in the air.

What is photochemical smog and how does it form? Key Components: Sunlight NO 2 Oxygen VOC’s Ozone Photochemical smog in Denver!

Photochemical Smog

Thermal Inversions: How does an inversion layer influence air pollution events? Thermal Inversion when a relatively warm layer of air at mid-altitude covers a layer of cold, dense air below. The warm inversion layer traps emissions that then accumulate beneath it.

Acid Deposition What is acid deposition? What are the 2 primary pollutants? Acid deposition- occurs when nitrogen oxides and sulfur oxides are released into the atmosphere and combine with atmospheric oxygen and water. These form the secondary pollutants nitric acid and sulfuric acid. These secondary pollutants further break down into nitrate and sulfate which cause the acid in acid deposition.

How does acid deposition have a negative effect on Earth’s surface? Lowering the pH of lake water Decreasing species diversity of aquatic organisms Mobilizing metals that are found in soils and releasing these into surface waters Damaging statues, monuments, and buildings

Acid Deposition

Ways to Prevent Air Pollution Pollution control methods for SO 2, NO x, and particulates. Removing sulfur dioxide from coal by fluidized bed combustion Better combustion of fuels to reduce NO x Catalytic converters on cars ( NO x ) Scrubbers on smoke stacks Baghouse filters Electrostatic precipitators

Baghouse filters- most efficient

Electrostatic precipitators

Scrubbers on smoke stacks

Catalytic Converter an automobile exhaust-system component containing a catalyst that causes conversion of harmful gases (as carbon monoxide and uncombusted hydrocarbons) into mostly harmless products (as water and carbon dioxide)

Good vs Bad Ozone Even # Tables: Good ozone (blue poster) pages 52-55, Odd # Tables: Bad ozone (orange poster) pages 415,

Good Ozone: Formation and Breakdown of Ozone How does the stratospheric ozone layer form and why is it beneficial? First, UV-C radiation breaks the bonds holding together the oxygen molecule, leaving two free oxygen atoms: 1) O 2 + UV-C -> 2O Sometimes the free oxygen atoms result in ozone: 2) O 2 + O -> O 3 Ozone is broken down into O 2 and free oxygen atoms when it absorbs both UV-C and UV-B ultraviolet light: 3) O 3 + UV-B or UV-C -> O 2 + O

Breakdown of the Good Ozone How does the stratospheric ozone layer deteriorates? Reducing our Good Ozone 4) O 3 + Cl -> ClO + O 2 5) ClO + O -> Cl + O 2 6) O 3 + O -> 2O 2

Stratospheric Ozone The stratospheric ozone layer exists roughly kilometers above the Earth. Ozone has the ability to absorb ultraviolet radiation and protect life on Earth. Ozone = good up high, bad near by!!!

Anthropogenic Contributions to Ozone Destruction What causes the depletion of the ozone layer? Certain chemicals can break down ozone, particularly chlorine. The major source of chlorine in the stratosphere is a compound known as chlorofluorocarbons (CFCs) CFCs are used in refrigeration and air conditioning, as propellants in aerosol cans and as “blowing agents” to inject air into foam products like Styrofoam.

Anthropogenic Contributions to Ozone Destruction When CFCs are released into the troposphere they make their way to the stratosphere. The ultraviolet radiation present has enough energy to break the bond connecting chlorine to the CFC molecule: which can then break apart the ozone molecules.

Anthropogenic Contributions to Ozone Destruction First, chlorine breaks ozone’s bonds and pulls off one atom of oxygen, forming a chlorine monoxide molecule and O 2 : O 3 + Cl -> ClO + O 2 Next, a free oxygen atoms pulls the oxygen atom from ClO, liberating the chlorine and creating one oxygen molecule: ClO + O -> Cl + O 2 One chlorine atom can catalyze the breakdown of as many as 100,000 ozone molecules before it leaves the stratosphere.

Depletion of the Ozone Layer Steps taken to reduce ozone? Montreal Protocol on Substances That Deplete the Ozone Layer in 1987: reduce CFCs by 50% by the year Global Ozone concentrations had decreased by more than 10%. Depletion was greatest at the poles Decreased stratospheric ozone has increased the amount of UV-B radiation that reaches the surface of Earth.

Indoor Air Pollutants Main sources of indoor pollution for developing countries? Wood, animal manure or coal used for cooking and heating in developing countries. Main sources of indoor pollution for developed world? Asbestos Carbon Monoxide Radon VOCs in home products Sick building syndrome? The buildup of toxic compounds and pollutants in an airtight space; seen in newer buildings with good insulation and tight seals against air leaks.