Chapter 15 Air Pollution and Stratospheric Ozone Depletion

Chattanooga, Tennessee

Declared one of the worst cities in the US for particulate air pollution! due to the economic boom and the fact that Chattanooga is located in a bowl, the city air is found to be highly polluted and causing respiratory diseases well above the nation’s average Clean Air Act and local ordinances, changed the way in which the city operated and put major emission controls in place. Three years later, the city achieved compliance.

Air Pollution Defined as the introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to harm plants, animals, and buildings, or to alter ecosystems in the troposphere (first 10 miles above the surface). Can occur naturally (volcanoes) or it can be anthropogenic. Air pollution is a global issue.

5 Pollutant Sources Natural Sources: – forest fires, volcanoes, and oceanic salt, Anthropogenic Sources: – power plants, newly plowed fields, motor vehicles, etc.

Major Air Pollutants SO 2 - comes from burning fossil fuels. It adversely affects plant tissue and is a respiratory irritant. NO x - with the air being 78% N 2, all combustion leads to formation of nitrogen oxides. Mainly formed from motor vehicles and stationary fossil fuel combustion as well as forest fires, lightening and microbial action in soils. CO x- CO formed during incomplete combustion, CO 2 during complete combustion.

Particulate Matter (PM)- solid or liquid particles suspended in the air. Released from the combustion of fossil fuels, road dust, rock- crushing operations, dust storms, volcanic eruptions and forest fires. It is a respiratory irritant and scatters and absorbs sunlight reducing photosynthesis and producing haze. Photochemical Oxidants including tropospheric Ozone- formed as a result of sunlight acting on compounds of NO x and SO 2

Ozone- O 3 Most frequently measured and abundant photochemical oxidant in the troposphere. Harmful to plants and animals, causes asthma and emphysema Can enhance the formation of particulate matter and create smog (smoke, fog, ) when combined with No x and SO 2.

Smog Formation During the day, the sun heats up the surface of the Earth such that warmer air usually resides closer to the surface of the Earth, with temperatures decreasing with increasing altitude. At night, the situation is reversed with cooler air near the surface and warmer resting on top-resulting in what is known as temperature inversion. Because basic physics dictates that warmer air rises and cooler air falls, air pollutants are simply carried up by the warmer air into the atmosphere where they are dispersed and diluted. Thus, the lower atmosphere is cleansed of any pollutants that accumulate.

In a situation where temperature inversion exists during the day, the air near the surface of the Earth is not hot enough as to allow the warm air to rise into the atmosphere. In such a case, air pollutants accumulate near the surface of the Earth, reaching dangerous threshold levels Because temperature inversion is present, it effectively acts as a thermal lid, thus preventing the air pollutants from rising and dispersing into harmless levels in the atmosphere. As a result, a smog siege can occur.

Pb - occurs as trace metal in rocks and soil. When added to gasoline to enhance vehicle performance and burned it was released into the air. It has since been removed in the US but not globally. Pb is toxic to the CNS and can affect intelligence in children. Hg- another trace metal found in coal and oil and when burned is released into the air. It is toxic to the CNS as it bioaccumulates in fish and in humans.

Volatile Organic Compounds Organic compounds that become vapors at typical atmospheric temperatures Many VOCs are hydrocarbons (gasoline, lighter fluid, dry-cleaning fluid, perfumes) that give off strong odors Play an important role in the formation of photochemical oxidants like ozone.

Primary and Secondary Pollutants Primary- are compounds that come directly out of the smokestacks, exhaust pipes, or natural emission source. They include: CO, CO 2, SO 2, NO x and most suspended particulate matter. Secondary- come from primary pollutants that have undergone transformation in the presence of sunlight, water, oxygen or other compounds. Ex: O 3, SO 4 2-, NO 3 1-

14 Factors affecting transport Wind-Higher wind speeds disperse pollutants more quickly reducing local concentrations Stability -Temperature inversion associated with stable conditions can inhibit the vertical motion of a pollutant Turbulence-is the horizontal and vertical motion of the atmosphere; it can cause mixing and dispersal Topography- can act as a physical barrier to pollution movement.

15 Factors affecting transport

16 What happens in between? TRANSPORT – Global winds – Mixing and Cloud Formation TRANSFORMATION – Chemical reactions

17 Factors affecting Transformation Solar radiation – Aids in the formation of ozone Humidity & Precipitation – Provide moisture content for pollutants to bind to  formation of secondary pollutants – Cloud formation Source: aura.gsfc.nasa.gov/outreach/garden_faq.html

18 Atmospheric Deposition Atmospheric deposition is the process whereby airborne material is deposited on the earth's surface.

19 Atmospheric Deposition Wet – Wet deposition is the fraction of atmospheric deposition contained in precipitation –Anything attached to water in some form Dry – Dry deposition is the fraction deposited in dry weather through such processes as settling, impaction, and adsorption. – Anything not attached to water

20 Precipitation The GOOD: – washes pollutant particles from the air – helps to minimize particulate matter formed by activities such as construction and some industrial processes. The BAD: – Acid Rain

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Acid rain causes acidification of lakes and streams and harms aquatic ecosystems Acid rain contributes to the damage of trees at high elevations (for example, red spruce trees above 2,000 feet) and many sensitive forest soils. Acid rain accelerates the decay of building materials and paints, including irreplaceable buildings, statues, and sculptures that are part of our nation's cultural heritage.

Pollution control: prevention, technology and innovation Use fuels that contain fewer impurities (low Sulfur coal and oil) Increase efficiency and conservation Control Sulfur and Nitrogen Oxide emissions Use pollution control devices that remove particulate matter and other compounds after combustion(fabric filters, electrostatic precipitators, and scrubbers)

Scrubber

Electrostatic Precipitator

Innovative Pollution control Reduce the amount of gasoline spilled at gas stations Restrict the evaporation of dry-cleaning fluid Reduction in the use of wood-burning stoves Reduce the number of bakeries in certain areas (rising bread contains VOCs) Restricting automobile use Expand public transportation, carpool lanes Allowance for factories and S emissions

Stratospheric Ozone Layer Ozone in the stratosphere forms a necessary protective shield against radiation from the sun UV-A passes through the atmosphere w/o being absorbed and contributes to skin cancer UV-B and UV-C have enough energy to cause significant damage to the tissues and DNA of living organisms The ozone layer absorbs 99% of UV-B and UV- C

Tropospheric vs Stratospheric Ozone Tropospheric Ozone Ground level ozone Acts as an air pollutant that damages lung tissue and plants Living organisms do not live in the stratosphere so this ozone is not harmful to them Absorbs UV radiation and shields the surface below

Formation and Breakdown of Stratospheric Ozone O 2 + UV-C  2O O 2 + O  O 3 O 3 + UV-B or UV-C  O 2 + O

Anthropogenic Contributions to Ozone Destruction Chlorine acts as a catalyst and can break down ozone. CFCs- chlorofluorocarbons, used in refrigerants, and in aerosols, get released into the atmosphere. When it reaches the stratosphere, one atom of Cl can catalyzes the breakdown of 100,000 ozone molecules.

Depletion of the Ozone Layer in Antarctica

Ozone Hole Each year for the past few decades during the Southern Hemisphere spring, chemical reactions involving chlorine and bromine cause ozone in the southern polar region to be destroyed rapidly and severely. This depleted region is known as the “ozone hole”. As ozone decreases, UV-B radiation increases, this is harmful to cells and reduces photosynthetic activity and neg. impacts ecosystems.

Efforts to reduce ozone depletion Montreal Protocol on Substances that Deplete the Ozone Later- required the elimination of CFCs production and use by the developed world by It also addresses 96 other ozone depleting compounds. As a result, the level of chlorine in the stratosphere has stabilized and the level of ozone depletion should decrease in years to come.

Indoor Air Pollution More than 3 billion people world wide use wood, animal manure, or coal indoors for heat and cooking. Usually there is no exhaust or ventilation so indoor air pollution from CO and particulate matter occurs. WHO estimates that indoor air pollution causes more than 1.6 million deaths annually in developing countries.

Some sources of indoor air pollution in the developed world

Indoor air pollutants Asbestos- once used as an insulating material, this fibrous silicate mineral causes lung cancer and other respiratory diseases. Carbon Monoxide- CO- very dangerous indoor air pollutant, present as a result of malfunctioning exhaust systems on household heaters. When CO builds up in a house, it binds with hemoglobin leading to oxygen deprivation and death. Radon-radioactive gas that seeps into homes through cracked foundations or soil. Second leading cause lung cancer.

VOCs- used in building materials, furniture, glues, and paints. Formaldehyde is used in particle board, carpet glue, pressed wood, and in many places in new homes. Causes irritation to the eyes and nose, breathing difficulty, and asthma. Has been shown to cause cancer in lab animals. Detergents, dry- cleaning fluids, deodorizers and solvents contain VOCs that are released over time. Sick Building Syndrome- caused by products made with synthetic materials and glue and place in new buildings w/o proper ventilation.