Chapter 15 Air Pollution and Stratospheric Ozone Depletion

Chapter 15 Air Pollution and Stratospheric Ozone Depletion Our Atmosphere IS a Resource Atmospheric Composition

N2 78.08% O2 20.95% Argon 0.93% Carbon dioxide 0.04% (400 ppm) Ecosystem services

1.Blocks UV radiation 2.Moderates the climate 3.Redistributes water in the hydrologic cycle Air Pollutants: Found Through the Entire Global System

Air Pollution: Found in troposphere. Introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to cause harm. Connected system. Natural or anthropogenic. Natural Sources of Air Pollution

Volcanoes Lightning Forest fires Plants

Pollution: Natural and Human Made Natural Volcanoes: sulfur dioxide, particulate matter, carbon monoxide, and nitrogen oxides. Forest Fires: particulate matter, nitrogen oxides, and carbon monoxide. Living plants: VOCs (ethylene and terpenes). Sulfur dioxide emissions are 30% natural, nitrogen oxide are 44% natural, and VOCs are

89% natural. Anthropogenic Sources of Air Pollution

On-road vehicles Power plants Industrial processes Waste disposal (incineration) Air Pollution Around the World Air quality is deteriorating

rapidly in developing countries China has an especially bad problem with Particulate Matter & smog Developing countries have older cars Still use leaded gasoline 5 worst cities in world

Beijing, China; Mexico City, Mexico; Shanghai, China; Tehran, Iran; and Calcutta, India Major Air Pollutants There are six Criteria Pollutants that are regulated by the Clean Air Act(1970) under National Ambient Air Quality Standards (NAAQS)

SO2 NOx

CO PM O3 Pb (Sulfur Dioxide) (Nitrogen Oxides) (Carbon Monoxide) (Particulate Matter)

(Ozone) (Lead) Primary Primary Primary Primary Secondary Primary

Anthropogenic Emissions Monitored by the EPA. Clean Air Act and amendments require that the EPA establish standards to control pollutants. All criteria air pollutants have decreased in the US over the last two decades.

Other air pollutants not on the NAAQS list (but still important): CO2 Hg VOCs (Carbon Dioxide) (Mercury) (Volatile Organic Chemicals)

17_11.JPG Primary and Secondary Pollutants Primary Pollutants Come directly out of the smokestack, exhaust pipe or natural emission source. CO, CO2, SO2, NOx and most suspended particulate matter.

Includes many VOCs Secondary Pollutants Primary pollutants that have undergone transformation in the presence of sunlight, water, oxygen and other compounds. Occurs more in the day within wet environments. Ozone: Formed as a result of the emission of the primary pollutants NOx and VOCs in the presence of

sunlight. Sulfate (SO42-) and nitrate (NO3-) the main components of acid deposition are secondary Major Air Pollutants Sulfur dioxide (SO2) and sulfuric acid: About 1/3 of SO2 occurs naturally (volcanoes & fires) About 2/3 from human sources (mostly metal

production & combustion of coal and oil). S + O2 = SO2 (Primary Air Pollutant) 2 SO2 + O2 = 2 SO3 (Secondary Air Pollutant) SO3 + H2O = H2SO4 (Sulfuric Acid Acid Rain) SO2 leads to formation of Industrial Smog Major Air Pollutants

Carbon oxides: Carbon monoxide (CO) is a highly toxic gas that forms during the incomplete combustion of carbon-containing materials. 93% of carbon dioxide (CO2) in troposphere occurs as a result of the carbon cycle (7% anthropogenic) Major Air Pollutants Suspended particulate matter (PM):

Consists of a variety of solid particles and liquid droplets Natural sources: Volcanoes, fires, pollen, dust Anthropogenic sources: FF combustion, agriculture The most harmful forms of PM are fine particles (PM10, with an average diameter < 10 micrometers) and ultrafine particles (PM-2.5). PM causes ~60,000 premature US deaths per year Major Air Pollutants Nitrogen oxides and nitric acid:

Nitrogen oxide (NO) forms when nitrogen and oxygen gas in air react at the high-combustion temperatures in automobile engines and coalburning plants. NO can also form from lightening and certain soil bacteria. NO reacts with air to form NO2. NO2 reacts with water vapor in the air to form nitric acid (HNO3) and nitrate salts (NO3-) which are components of acid deposition.

Major Air Pollutants Ozone (O3): Is a highly reactive gas that is a major component of photochemical smog. It is a secondary air pollutant It can Cause and aggravate respiratory illness (soft tissues). Aggravate heart disease. Damage plants, rubber in tires, fabrics, and paints.

Lead (Pb) Trace metal, occurs naturally in rock and added to gas and oil. Traveled in the air and was deposited all over the globe. Phased out in gas and oil from 1975-1996. Mercury (Hg)

Found in coal and oil. Toxic to to central nervous systems. Subject to bioaccumulation. Coal fired electricity generation present the

largest source of mercury release. Major Air Pollutants Volatile organic compounds (VOCs): VOCs include industrial solvents such as acetone, trichloroethylene (TCE), benzene, paints, vinyl chloride and fuels like gasoline. Contribute to formation of Photochemical Smog

Smog Photochemical Smog: oxidants such as ozone, also know as LA-type smog or brown smog. Sulfurous Smog: sulfur dioxide and sulfate compounds also known as London-type smog or gray smog. Atmospheric Brown Cloud: combination of ozone and particulate matter. Comes from combustion of fossil fuels and burning biomass.

Photochemical Smog Smog and Ozone still present problems in the US. Sunlight + Nitrogen Oxides + Few VOCs (forms) =s Ozone When sunlight dies down nitrogen oxide is still present and ozone combines with the NO and reforms into O2 and NO2.

When VOCs are present they combine with nitrogen oxide. This means the nitrogen oxide is not available to break down ozone by recombining with it. Ozone then accumulates. Emissions of VOCs from vegetation increase as temperature increases. NOx increase as air-conditioning demands

increase. Thermal Inversions When a layer of warm air covers cold air. Emissions can be trapped in the lower layer. Chinese city of Tianjin: turned off their central heating then suffered a cold spell. Emissions got trapped. Over 1,000 people suffered carbon monoxide poisoning. 11 people died.

Thermal Inversions make smog worse by trapping it under a layer of cold air

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