Air Pollution

Outdoor Air Pollution

Stationary and Mobile Sources of Air Pollution

• Two Sources of Air Pollution1. Stationary Sources: have a relatively

fixed location• Point Sources: • Fugitive Sources: • Area Sources:

2. Mobile Sources: move from place to place while emitting pollutants

• Ex) Airplanes

General Effects of Air Pollution

• Visual quality of the environment• Vegetation, Animals, Soil• Water Quality• Natural and Artificial Structures• Human Health

Primary and Secondary Pollutants, Natural and Human

• Primary Pollutants– Those emitted directly into the air– Hydrocarbons, particulates, etc.

• Secondary Pollutants– Produced through reactions between

primary pollutants and normal atmospheric compounds

– Ozone

Major Air Pollutants

1. Sulfur Dioxide (acid rain)2. Nitrogen Dioxide / Nitrogen Oxide3. Carbon Monoxide4. Ozone and Other Photochemical

Oxidants5. Volatile Organic Compounds6. Particulate Matter7. Hydrogen Sulfide8. Hydrogen Fluoride9. Hazardous Gases10. Lead

Outdoor Air Pollutants – Sulfur Dioxide (SO2)

• Properties: colorless gas with irritating odor• Effects: produces acid rain (H2SO4), breathing

difficulties, eutrophication due to sulfate formation, lichen and moss are indicators

• Sources: burning high sulfur coal or oil, smelting or metals, paper manufacture

• Class: sulfur oxides• EPA Standard: 0.3 ppm (annual mean)• Combines with water and NH4 to increase soil

fertility

Outdoor Air Pollutants – Nitrogen Dioxide (NO2)

• Properties: reddish brown gas, formed as fuel burnt in car, strong oxidizing agent, forms Nitric acid in air

• Effects: acid rain, lung and heart problems, decreased visibility (yellow haze), suppresses plant growth

• Sources: fossil fuels combustion, power plants, forest fires, volcanoes, bacteria in soil

• Class: Nitrogen oxides (NOx) • EPA Standard: 0.053 ppm

Outdoor Air Pollutants – Carbon Monoxide (CO)

• Properties: colorless, odorless, heavier than air, 0.0036% of atmosphere

• Effects: binds tighter to Hb than O2 • Sources: incomplete combustion of fossil fuels.

60 - 95% from auto exhaust• Class: carbon oxides (CO2, CO)• EPA Standard: 9 ppm • 5.5 billion tons enter atmosphere/year

Outdoor Air Pollutants – Ozone (O3)

• Properties: colorless, unpleasant odor, major part of photochemical smog

• Effects: lung irritant, damages plants, rubber, fabric, eyes, 0.1 ppm is unhealthy

• Sources: Created by sunlight acting on NOx and VOC , cars, industry, gas vapors, chemical solvents, fuel combustion products

• Class: photochemical oxidants

Outdoor Air Pollutants – Suspended Particulate Matter (PM10)

• Properties: particles suspended in air (<10 um)• Effects: lung damage, mutagenic, carcinogenic,

teratogenic• Sources: burning coal or diesel, volcanoes,

factories, unpaved roads, plowing, lint, pollen, spores, burning fields

• Class: SPM: dust, soot, asbestos, lead, PCBs, dioxins, pesticides

• EPA Standard: 50 ug/m3 (annual mean)

Size of Selected Particulates

Total Suspended Particulates (TSP)for several large countries

Outdoor Air Pollutants – VOCs (Volatile Organic Compounds)

• Properties: organic compounds that evaporate easily, usually aromatic

• Effects: eye and respiratory irritants; carcinogenic; decreased visibility due to brown haze; liver, CNS, or kidney damage; damages plants

• Sources: evaporation of solvents or fuels, fossil fuels, plants (largest source), aerosols, paint thinners, dry cleaning

• Class: HAPs (Hazardous Air Pollutants)• Concentrations indoors up to 1000x outdoors• 600 million tons of CFCs

Outdoor Air Pollutants – Lead (Pb)

• Properties: grayish metal• Effects: accumulates in tissue; affects kidneys,

liver and nervous system (children most susceptible); mental retardation; possible carcinogen; 20% of inner city kids have [high]

• Sources: particulates, smelters, batteries• Class: toxic or heavy metals• EPA Standard: 1.5 ug/m3

• 2 million tons enter atmosphere/year

US Emissions of Six Major Air Pollutants

Note that there have been significant reductions.

Urban Air Pollution• Potential for Air Pollution

Determined by:– Rate of emission– Downwind distance– Average wind speed– Elevation

• Atmospheric Inversion: – Occurs when warmer air is found

above cooler air and it poses a particular problem when there is a stagnant air mass

Factors that influence Air Pollution formation and intensity

• Topography (hills and mountains)• Local climate (inversions, air pressure, temperature,

humidity)• Population density• Amount of industry• Fuels used by population and industry for heating,

manufacturing, transportation, power• Weather: rain, snow,wind• Buildings (slow wind speed)• Mass transit used• Economics

Smog

• Smog– A mixture between smoke and fog that

produces unhealthy urban air• Two Types

– Sulfurous Smog / Industrial Smog / Fossil Fuels– Photochemical Smog / Sunlight & Pollutants

Formation of Industrial Smog

Formation of Industrial Smog

Procedure Chemical Reaction

1. Carbon in coal or oil burned

C + O2 −• CO2

2C + O2 −• CO

2. Unburned carbon −• soot C

3. Sulfur in oil and coal reacts with O2

S + O2 −• SO2

Formation of Industrial Smog

Procedure Chemical Reaction4. Sulfur dioxide reacts with O2 to form sulfur trioxide

2SO2 + O2 −• 2SO3

5. Sulfur trioxide reacts with H2O

SO3 + H2O −• H2SO4

6. Sulfuric acid reacts with atmospheric ammonia to form brown, solid ammonium sulfate

H2SO4 + 2NH3 −•(NH4)2SO4

Formation of Photochemical Smog

Formation of Photochemical Smog

Time Description

6 - 9 A.M. Morning commute increases NOx and VOCsN2 + O2 −• 2 NO

NO + VOC −• ΝΟ2

ΝΟ2 −UV−• ΝΟ + Ο

9 - 11 A.M As traffic decreases NOx and VOCs react 2NO + O2 −• 2ΝΟ2

Time Description

11 A.M. – 4 P.M.

As sunlight becomes intense, NO2 breaks down and Ozone increases

ΝΟ2 −UV−• ΝΟ + Ο Ο2 + Ο −• Ο3

Nitrogen dioxide also forms nitric acid3ΝΟ2 + Η2Ο −• 2 Η2ΝΟ3 + ΝΟ

11 A.M. – 4 P.M.

Nitrogen dioxide also reacts with VOCs released by autos, industry, etc.

ΝΟ2 + VOCs −• 2 PANs Peroyacyl nitrates (toxic)

4 P.M. - sunset

As sun goes down the production of ozone haltsNet Result: NO + VOC + O2 + UV −• O3 + PAN

Pollution Control

• Particulates• Automobiles• Sulfur Dioxide

– Coal Gasification: converts coal to gas to remove sulfur

– Scrubbing: gas desulfurization

Air Pollution: Legislation and Standards

• Clean Air Act Amendments of 1990– Comprehensive regulations enacted

by U.S congress that address acid rain, toxic emissions, ozone depletion and automobile exhaust

• Air Quality Standards– Attempt to control air pollution

• Tougher Standards for PM 2.5 and Ozone• Air Quality Index

Specific Air Pollution Treatment Technology

• Traditional– Move factory to remote location– Build taller smokestack so wind blows pollution

elsewhere• New

– Biofiltration : vapors pumped through soil where microbes degrade

– High-energy destruction: high-voltage electricity – Membrane separation: diffusion of organic vapors

through membrane– Oxidation: High temperature combustor

• New continued…– Vapor phase carbon absorption: gases pumped

through series of carbon filled canisters which absorb contaminants

– Electrostatic precipitators: Electrostatically charged surfaces attracts particles

– Sulfur removal: mix crushed limestone with fuel – Nitrogen oxide control: staged burners or

catalytic converters– Hydrocarbon control: closed system to prevent

release before treatment with afterburners– Hybrid, electric and hydrogen powered vehicles

Specific Air Pollution Treatment Technology Continued…

Air Pollution

Indoor Air Pollution

Pathways, Processes and Driving Forces

• Chimney Effect (Stack Effect)– Process whereby warmer air rises in

buildings to upper levels and is replaced in the lower portion of the building by outdoor air drawn through a variety of openings, such as windows doors or cracks in the foundation or walls

Sick Building Syndrome• A condition associated with an

indoor environment that appears to be unhealthy

• The symptoms people report cannot be traced to any one particular cause

Environmental Tobacco Smoke

• Secondhand smoke• 2 sources

– Smoke exhaled by smokers– Smoke emitted from burning tobacco

• The most hazardous indoor pollutant

Radon Gas

• Radon– Naturally occurring radioactive gas– Colorless, odorless, tasteless– Only identified through proper testing

• Health hazard when leaked into homes

• Exposure is associated with lung cancer

How Radon Enters Houses

Major Indoor Pollutants

1, 1, 1-Trichloroethane

Aerosol sprays Dizziness, breathing irregularities

Asbestos Pipe insulation, ceilings, floor tiles, oven mitts

Lung Cancer and asbestosis

Benzo−α− pyrene

Tobacco smoke, woodstoves

Lung Cancer

Carbon MonoxideFaulty furnaces, cigarette smoke

Headache, heartbeat irregularities, death, CO has 250x affinity for Hb than O2

Chloroform Pulp and paper mills, water and wastewater plants

Cancer

Formaldehyde Paneling, particle board, furniture, carpeting, adhesives

Nausea, dizziness, irritation of throat, eyes, and lungs

Methylene chloridePaint strippers and thinner – persistent

Nerve disorders, diabetes

Nitrogen oxides Furnaces, stoves, fireplaces and vents

Headaches, irritated lungs

Para-dichlorobenzene

Air fresheners, mothballs Cancer

Major Indoor Pollutants Continued…

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Radon – 22 Soil and rock near house foundation, concrete

Lung cancer

Styrene Carpets, plastics, Kidney and liver damage

Tetrachlor- ethylene

Dry-cleaning fluid Nerve disorders, damage to liver and kidneys, cancer

Tobacco Smoke Cigarettes and other smoking sources

Lung cancer and heart disease

Organic Material Dust mites, fungal and algal spores, dust (human skin), animal dander, hair, carpet fibers, fur

Allergies, coughs, sneezing, eye irritation, sore throats, difficulty breathing

Major Indoor Pollutants Continued…