Air Pollution

Air Pollution

Fig. 19-2, p. 440

Atmospheric pressure (millibars)

Temperature

Thermosphere

Pressure

Mesopause

Heating via ozoneMesosphere

Stratopause

Alt

itu

de

(kil

om

eter

s)

Stratosphere Alt

itu

de

(mil

es)

Tropopause

Ozone “layer”

Heating from the earthHeating from the earthTroposphere

Temperature (˚C)

Pressure = 1,000 millibars at ground level

(Sea level)

Layers of the Atmophere

• Thermosphere: Closest to the surface of the Earth. This is where all weather and air travel occurs. Most pollutants affect this layer. Has the highest concentration of molecules

• Stratosphere: Contains the ozone layer which absorbs incoming UV radiation

• Mesosphere: temperature decreases with altitude

• Thermosphere: Warmed by the sun, lowest air pressure of the layers

Major Air Pollutants

• Nitrogen Oxides• Carbon Oxides• Sulfur Oxides• Particulates• Ozone• PANS• Volatile Organic Compounds (VOCs)• Radon (Indoor air pollutant)

Primary Pollutants• Pollutants that retain the same chemical

formula from the source to the atmosphere• methane, SO2, CO, CO2, NO, dust particles,

microorganisms, and chlorofluorocarbons (CFC’s)

• Causes of Primary Pollutants – factories, cars, wind and soil, volcanoes, forest fires, pollen, decaying plants, salt particles from the sea, and refrigerants.

Fig. 19-3, p. 442

Primary Pollutants

CO CO2Secondary Pollutants

SO2 NO NO2

Most hydrocarbons SO3

Most suspended particles HNO3

H2O2 O3 PANs

Most NO3– and SO4

2– salts

Sources Natural Stationary

Mobile

H3SO4

URBAN OUTDOOR AIR POLLUTION

• Industrial smog is a mixture of sulfur dioxide, droplets of sulfuric acid, and a variety of suspended solid particles emitted mostly by burning coal.– In most developed countries where coal and

heavy oil is burned, industrial smog is not a problem due to reasonably good pollution control or with tall smokestacks that transfer the pollutant to rural areas.

Sunlight plus Cars Equals Photochemical Smog

• Photochemical smog is a mixture of air pollutants formed by the reaction of nitrogen oxides and volatile organic hydrocarbons under the influence of sunlight.

Sunlight plus Cars Equals Photochemical Smog

• Mexico City is one of the many cities in sunny, warm, dry climates with many motor vehicles that suffer from photochemical smog.

Figure 19-4Figure 19-4

Temperature Inversions

• Cold, cloudy weather in a valley surrounded by mountains can trap air pollutants (left).

• Areas with sunny climate, light winds, mountains on three sides and an ocean on the other (right) are susceptible to inversions.


Major Air Pollutants• Suspended particulate matter (SPM):

– Consists of a variety of solid particles and liquid droplets small and light enough to remain suspended in the air.

– The most harmful forms of SPM are fine particles (PM-10, with an average diameter < 10 micrometers) and ultrafine particles (PM-2.5).

– According to the EPA, SPM is responsible for about 60,000 premature deaths a year in the U.S.

Major Air Pollutants• Volatile organic compounds (VOCs):

– Most are hydorcarbons emitted by the leaves of many plants and methane.

– About two thirds of global methane emissions comes from human sources.

– Other VOCs include industrial solvents such as trichlorethylene (TCE), benzene, and vinyl chloride.

• Long-term exposure to benzene can cause cancer, blood disorders, and immune system damage.

Major Air Pollutants• Radon (Rn):

– Is a naturally occurring radioactive gas found in some types of soil and rock.

– It can seep into homes and buildings sitting above such deposits.

INDOOR AIR POLLUTION

• Indoor air pollution usually is a greater threat to human health than outdoor air pollution.

• According to the EPA, the four most dangerous indoor air pollutants in developed countries are:– Tobacco smoke.– Formaldehyde.– Radioactive radon-222 gas.– Very small fine and ultrafine particles.

Chloroform

Benzo--pyrene

Styrene

Radon-222

Methylene Chloride

Tobacco Smoke

Carbon Monoxide

Asbestos

Nitrogen Oxides

1, 1, 1-Trichloroethane

Particulates

FormaldehydeTetrachloroethylene

Para-dichlorobenzene

Fig. 19-11, p. 453

INDOOR AIR POLLUTION

• Household dust mites that feed on human skin and dust, live in materials such as bedding and furniture fabrics.– Can cause asthma attacks

and allergic reactions in some people.


Case Study: Radioactive Radon

• Radon-222, a radioactive gas found in some soils and rocks, can seep into some houses and increase the risk of lung cancer.

Sources and paths of entry Sources and paths of entry for indoor radon-222 gasfor indoor radon-222 gas.


Radon Mitigation

• Vent air

Mitigation Techniques

• Wet Scrubbers – removes particulates & Sulfur oxides


• Electrostatic Precipitators

http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect28.gif


• Mechanical Filters• Air filters like your furnace filter, car filter• Remove particulates from the air. Particulates

removes depends on the quality of the filter.

Mitigation Techniques• After-burners – used for VOCs and particlute

pollution control• Breaks down the molecular structure into CO2

and Water Vapor• Used often for Methane (CH4)• May be used for energy

http://depts.washington.edu/centc/research_methane.htm

Acid Deposition

• Acid Rain caused by sulfur dioxide emissions• Sulfur dioxide in the atmosphere reacts with

water vapor to form sulfuric acid:

SO2 + H2O -> H2SO4

ACID DEPOSITION

• Acid deposition consists of rain, snow, dust, or gas with a pH lower than 5.6.


ACID DEPOSITION

• pH measurements in relation to major coal-burning and industrial plants.


ACID DEPOSITION• Environmental Effects:• Erosion• Leaching of toxic metals (such as lead and

mercury) from soils and rocks into acidic lakes used as sources for drinking water

• Disruption of aquatic ecosystems

ACID DEPOSITION• Health effects: • Acid deposition contributes to chronic

respiratory disease and

ACID DEPOSITION


ACID DEPOSITION



• Add neutralizing base to acidic water – Lime is a good base to use

• Add phosphate fertilizer which raises the pH level of the water

Fig. 19-10, p. 452

Solutions

Acid Deposition

Prevention Cleanup

Reduce air pollution by improving energy efficiency

Add lime to neutralize acidified lakes

Reduce coal use

Add phosphate fertilizer to neutralize acidified lakes

Increase natural gas use

Increase use of renewable energy resources

Burn low-sulfur coal

Remove SO2 particulates & NOx from smokestack gases

Remove NOx from motor vehicular exhaust

Tax emissions of SO2

Seasons

OZONE DEPLETION IN THE STRATOSPHERE

• Less ozone in the stratosphere allows for more harmful UV radiation to reach the earth’s surface.– The ozone layer keeps about 95% of the sun’s

harmful UV radiation from reaching the earth’s surface.

– Chlorofluorocarbon (CFCs) have lowered the average concentrations of ozone in the stratosphere.

– In 1988 CFCs were no longer manufactured.

Fig. 20-18, p. 486

A free oxygen atom pulls the oxygen atom off the chlorine monoxide molecule to form O2.

Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl3, breakingoff a chlorine atom and leaving CFCl2. Sun

Repeated many times

The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO).

Summary of ReactionsCCl3F + UV Cl + CCl2FCl + O3 ClO + O2

Cl + O Cl + O2

UV radiation

The chlorine atom attacksan ozone (O3) molecule, pulling an oxygen atom offit and leaving an oxygen molecule (O2).

Once free, the chlorine atom is off to attack another ozone moleculeand begin the cycle again.

Cl


• During four months of each year up to half of the ozone in the stratosphere over Antarctica and a smaller amount over the Artic is depleted.



• Since 1976, in Antarctica, ozone levels have markedly decreased during October and November.



• Ozone thinning: caused by CFCs and other ozone depleting chemicals (ODCs).– Increased UV radiation reaching the earth’s

surface from ozone depletion in the stratosphere is harmful to human health, crops, forests, animals, and materials such as plastic and paints.

Human Health• Worse sunburn• More eye cataracts• More skin cancers• Immune system suppression

Food and Forests• Reduced yields for some crops• Reduced seafood supplies from reduced phytoplankton• Decreased forest productivity for UV-sensitive tree species

Wildlife• Increased eye cataracts in some species• Decreased population of aquatic species sensitive to UV radiation• Reduced population of surface phytoplankton• Disrupted aquatic food webs from reduced phytoplankton

Air Pollution and Materials• Increased acid deposition• Increased photochemical smog• Degradation of outdoor paints and plastics

Global Warming• Accelerated warming because of decreased ocean uptake of CO2 from atmosphere by phytoplankton and CFCs acting as greenhouse gases

Effects of Ozone DepletionNatural Capital Degradation

Fig. 20-21, p. 488

Case Study: Skin Cancer

• Structure of the human skin and relationship between radiation and skin cancer.


Law – Clean Air Act

• 1963 - first passage • 1970, 1977 and 1990 - amended• Involves EPA• Sets standards for acceptable levels of sulfur

oxides, nitrogen oxides, ozone, carbon monoxide, hydrocarbons, lead, & more

• Provides pollution credits for industries that utilize pollution-control devices

• It established NAAQS and AQI• Clean Air Act: EPA

http://www.epa.gov/air/caa/

National Ambient Air Quality Standards (NAAQS)

• Sets acceptable concentrations for 6 “criteria” pollutants that:– Threaten public health/the environment

over broad areas (non-point)– Are emitted in large quantities– CO, Pb, Nitrogen Oxides, Ozone,

Particulate Matter and Sulfur Dioxides

Air Quality Index (AQI)

• Measures levels of 5 criteria pollutants• Forecast of daily air pollution levels• Purpose to educate and protect public-

focuses on health effects• Categories: green= good, yellow=

moderate, orange= unhealthy for sensitive groups, red= unhealthy, purple= very unhealthy

National Emissions Standards for Hazardous Air Pollutants

• Regulates emissions (from point sources)

• For specific substances (air toxics w/ known or suspected serious health effects (mutagens, carcinogens, neurotoxins)

• Tend to be localized, from point sources• Examples: Ammonia, chlorine, asbestos,

arsenic, mercury, benzene

Documents

Air Pollution