Chapter 18

Air Pollution

Lichens

alga/fungus• some are sensitive to specific pollutants

(e.g. SO2)

Atmosphere

1. troposphere (surface - 11mi): 78% N2,

21% O2, <1% Ar, .036% CO2, .01 - 5% H2O a) tropopause: temperature abruptly rises b) each layer ends when temp gradient

reverses) 2. stratosphere (11-30 mi) 1000x less water,

1000x more O3

3O2 + UV ----> 2O3

3. mesosphere (30 - 50 mi) 4. thermosphere (50 - 75 mi) 5. human impact on nutrient cycle

a) we add 1/4 as much CO2 to atm as nature does

b) we add 3x as much NOx (from fossil fuels, fertilizer)

c) SO2 from fossil fuels

Air pollutants

(wrong chemical in the wrong place at the wrong concentration)1. primary pollutants: formed at surface of the earth

2. secondary pollutants: formed from reactions in troposphere

3. motor vehicles produce more pollution than any other activity

6 Criteria Air Pollutants

• Carbon Monoxide (CO)

• Nitrogen Dioxide (NO2)

• Sulfur Dioxide (SO2)

• Suspended Particulate Matter (aerosols)

• Ozone (O3)

• Lead (Pb)

Know health effects of each p 438

Photochemical smog

• a) mix of primary and secondary pollutants influenced by sunlightNOx + VOC’s + light + heat ----->

O3 + aldehydes + PAN’s + HNO3

Note: formaldehyde: H - C = O I

HPAN’s: peroxyacyl nitrates

b) NO ---> NO2 <--- brown, so brown-air smog

Mechanism

• surface: N2 + O2 ---> 2NO (primary)

(at high temp: auto engines, boilers)

2 NO + O2 ---> 2 NO2

3 NO2 + H2O ---> 2 HNO3 + NO

NO2 + UV ----> NO + O

O + O2 ----> O3

O + O3 + CxHy ----> aldehydes

O2 + hydrocarbons + NO2 ----> PAN’s

Click to view animation.

Animation

Acid deposition animation.

Photochemical oxidants

• NO2, O3, PAN’s - b/c they are strong oxidizers (take electrons away)

1. common in warm, sunny climate with lots of cars

- NO,NO2 concentrations increase as traffic builds and unburned hydrocarbons rise and react, in sunlight, to produce photochemical smog (peaks in afternoon)

Click to view animation.

Animation

Formation of photochemical smog.

Industrial Smog

1. Combo of SO2, H2SO4 droplets, suspended

particles

2. Burning coal, oil– S + O2---> SO2

– SO2 + O2---> SO3

– SO3 + H2O---> H2SO4

– NH3 + H2SO4---> (NH4)2SO4, a particulate solid

Combo of (NH4)2SO4 and soot, C, produces gray-air smog

Prevention Cleanup

Reduce air pollutionby improving energyefficiency

Reduce coal use

Increase natural gasuse

Increase use of renewable resources

Burn low-sulfur coal

Remove SO2 particulates, and NOx

from smokestack gases

Remove Nox frommotor vehicular exhaust

Tax emissions of SO2

Add lime to neutralizeacidified lakes

Add phosphatefertilizer to neutralizeacidified lakes

Temperature Inversion

• Warm air mass gets trapped above cooler air mass (acts as a lid), so surface air can‘t rise and dilute pollutants in cleaner air

• Early morning surface air is cool, clouds block sun so ground stays cool, upper air is warmer so there is no convection current

• Tends to happen in cities located in a valley (like Los Angeles)

Warmer air

Inversion layer

Cool layer

MountainMountain

Valley

Decreasing temperature

Incr

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Wind

Transformation tosulfuric acid (H2SO4)and nitric acid (HNO3)

Nitric oxide (NO)

Acid fog

Ocean

Sulfur dioxide (SO2)and NO

Windborne ammonia gasand particles of cultivated soilpartially neutralize acids andform dry sulfate and nitrate salts

Dry aciddeposition(sulfur dioxidegas and particlesof sulfate andnitrate salts)

Farm

Lakes indeep soilhigh in limestoneare buffered

Lakes in shallowsoil low inlimestonebecomeacidic

Wet acid deposition(droplets of H2SO4 andHNO3 dissolved in rainand snow)

Limestone in soil buffers acid depositionLimestone is sometimes added to lakesAdding phosphate to lakes can raise pH.

Acid Deposition and Humans

Respiratory diseases Respiratory diseases

Toxic metal leaching Toxic metal leaching

Decreased visibility Decreased visibility

Damage to structures, especially containing calcium carbonate

Damage to structures, especially containing calcium carbonate

Decreased productivity and profitability of fisheries, forests, and farms

Decreased productivity and profitability of fisheries, forests, and farms

Potential problem areasbecause of sensitive soils

Potential problem areas because of air pollution: emissions leading to acid deposition

Current problem areas(including lakes and rivers)

Indoor air pollution

1. sick building syndrome- def: 20% of occupants get better when they go outside

(coughing, dizziness, flu-like symptons)2. most dangerous indoor pollutants: cigarette smoke, formaldehyde, radon-222, very fine particles3. Radon enters through cracks in foundationand openings around pipes, inhaled into lungs

Reading Prong

Outlet vents for furnaces and dryers

Slab joints

Wood stove

Cracks in floorClothesdryerFurnace

Radon-222 gasSlab

Soil

Uranium-238

Sumppump

Cracks in wallCracks in wall

Open windowOpen window

Openingsaroundpipes

Openingsaroundpipes

Asbestos

1) best to wrap it

2) 1998, foam invented that binds fibers together, nontoxic, still fireproof

radon - 222

1) produced by radioactive decay of U - 238

2) outside diperses, indoors collects

3) radon is 55% of radiation dose in US

4) acceptable dose? 4 - 20 picocuries/L• NOTE: 1 Ci = 3.7 x 1010 disintegrations/s

– a 1g sample of radium has this activity

1 rad is the absorption of 10-5 joule per gram of tissue

Effects of air pollution on living organisms

A. Humans 1. CO takes up receptor site in hemoglobin so

molecule cannot transport O2

2. 1997 study by World Bank and WHO says 2.7 million people die each year from air pollution (2.2 million from indoor pollution)

B. Plants

1. air pollution (esp O3) can break down waxy coating on leaves

a) water loss, loss of protection from pests and frost, etc

Effects of air pollution on living organisms

C. Aquatic life 1. acid shock = sudden runoff of highly acidic water and consequently, aluminum ions a) can kill fish and inhibit reproduction, stimulates excessive mucus clogging fish gills b) mildly eutrophic lake can turn into a clear blue oligotrophic lake c) 16,000 lakes in Norway and Sweden have no fish due to xs acidity

Effects of air pollution on living organisms

D. Materials

1. soot and grit ---> cleaning costs

a) paint, roofs

b) marble statues, historic buildings

c) damage to buildings = $5 billion in US

Natural Defense

• Soil containing Ca2+, Mg2+ salts (buffering ions) can neutralize acid rain to a certain extent

• Limestone, CaCO3 deposits

Solutions

1. Laws: Clean Air Acts of 1970, 1977, 1990 have led to federal regulations

a) clean air act requires EPA to set national

emission standards for toxic air pollutants

(302) compounds) standards not met

b) stricter car emission standards by 2002

c) required cleaner burning fuel (oxygenated) in 9 cities, including Philadelphia

Clean Air Act (cont)

d) Clean Air Act is successful. b/w 1970 and 1997 air pollutants levels have dropped 31%

e) problems with Clean Air Act of 1990 (most recent)

1) relies on cleanup not prevention2) no tightening of emission standards for cars

and light trucks3) no restriction of fine particles4) municipal trash incinerators get 30 year

leases5) weak incinerator emission standards

Market Place

a) 110 power plants in 20 states may buy and

sell SO2 emission rights

b) SO2 credits may be sold and used in the future

c) b/w 1994-1997 SO2 emissions dropped by 30% d) emission credits are also proposed for NOx

Particulate reduction

a) Electrostatic precipitator, baghouse filter and wet scrubber are used technologies

b) catalytic converter in a car’s exhaust system:

2 NO + 2 CO -- (Pt)---> N2 + CO2

c) 50% of emission control systems have been disabled (estimate)

d) controls are needed for outboard motors, lawn mowers, etc

e) b/w 1982 and 1993, US smog levels dropped by 8%

Electrostatic Precipitator

Dirty gas

Dust discharge

ElectrodesCleaned gas