THE ATMOSPHERE AND AIR POLLUTION

LAYERS OF THE ATMOSPHERE

• Lower atmosphere – contains 99% of all atmospheric air• Troposphere• Stratosphere

• Ionosphere• Mesosphere• Thermosphere

• Exosphere

TROPOSPHERE

• Layer where we live

• Most of the O2

• Extends to 5-9 miles from the Earth’s surface at sea level

• Most weather occurs here

• Most dense layer of the atmosphere

STRATOSPHERE

• Directly above the troposphere

• Extends from 9 to 31 miles above the Earth at sea level

• The Ozone Layer that traps and scatters UV radiation from the sun occurs here

• Drier, less dense air than that found in the troposphere

IONOSPHERE

• Mesosphere• Directly above the

stratosphere 31-53 miles above the Earth’s surface at sea level

• Thermosphere• Directly above the

mesosphere 53-372 miles above the Earth’s surface

EXOSPHERE

• Outermost layer of the Earth’s atmosphere

• Transition zone between the Earth’s atmosphere and outer space

• Lowest atmospheric pressure of all the layers

COMPOSITION OF EARTH’S ATMOSPHERE

• 78% Nitrogen!!!!

• 21% O2

• 0-7% water vapor (H2O) – varies by climate

• 0.01-0.1% carbon dioxide (CO2) – varies by location

• 0-0.01% Ozone (O3) – varies by location

ATMOSPHERIC INVERSION• Natural temperature gradient of lower atmospheric

air is reversed• Usually warm air closest to Earth and gets cooler as

move away from Earth (convection currents)• When dense cool air gets trapped under a layer of

less dense warm air, the air becomes more still and upward air currents are prevented from developing

• Air pollution can get trapped and build up to harmful levels

• Common in large cities surrounded by hills and mountains• Mumbai, India• Mexico City, Mexico• Los Angeles• Vancouver, British Columbia

WHY DOES IT RAIN?

• Convection• Warm air rises – less dense than

cool air• As warm air rises, it loses heat

and cools• Warm air has a higher capacity

for holding water vapor• As warm air rises, water vapor

condenses

FRONTS

• Warm Fronts• Warmer air moves into an area of cooler air• As warm air rises, get drizzly rain• Adds heat to cooler air and temperature and humidity near the ground

increase

• Cold Fronts• Cold air moves in and pushes warm air upwards• Humidity in air condenses rapidly and falls as precipitation• Usually associated with a line of rain showers and thunderstorms

CONVECTION CELL MODEL OF ATMOSPHERIC CIRCULATION

• Hadley Cells

• Coriolis Effect

OCEAN INTERACTIONS

• Convection currents• Cool dense water from poles sinks and moves towards equator• Warmer, less dense water rises and floats toward the poles

• Ocean currents transport a lot of Earth’s heat

EL NINO SOUTHERN OSCILLATION (ENSO)

• A climate shift in tropical equatorial Pacific Ocean

• Occurs every 3-7 years and can last a few months to up to 4 years

• Occur when trade winds that normally blow east to west reverse• Surface waters become warmer• Nutrient rich upwellings near Peru are suppressed – fish pops decrease

• Can effect worldwide weather patterns

EFFECTS OF EL NINO (1)

• Northern US, Canada, Brazil, Indonesia, Australia, India, Southeast Africa• Less snow (snow fed rivers will decrease in spring because of lack of snow

melt)• Drought• Wildfires• Increase in diseases

• Malaria and dengue fever• Cholera and othe water borne issue

EFFECTS OF EL NINO (2)

• Southern US, Cuba, northern Peru, Ecuador, Bolivia, east Africa• Suppression of hurricanes in Caribbean and Atlantic Ocean• Increased flooding and landslides• Increased diseases from contaminated water

AIR POLLUTION

• Anything added to the atmosphere that can cause harm to life

• Point source• Single, stationary source – smokestacks, methane from landfills, smoke and

ash from forest fires

• Non-point source• Dispersed or mobile sources

Air pollutants are found throughout the entire global system. Air Pollution is

the 5th largest killer in India.

China, India, Africa

WHY DO WE CARE? (HUMANS)

• We inhale 20,000 liters of air each day• Causes 150,000 premature deaths in the world each

year (53,000 in U.S.); aggravates other diseases• U.S. human health costs from outdoor air pollution

range from $40 to $50 billion per year (CDC)• Health impacts - acute – pollutants bring on life-threatening

reactions w/in a period of hours or days; causes headache, nausea, irritation

- Chronic – pollutants cause gradual deterioration of health over years and low exposure, asthma, allergies, low energy, etc

- Carcinogenic – pollutions that causes cancer e.g. benzene

- Expansive settles in water ways, bioaccumulation in food chain, effects our nearby ecosystems

WHY DO WE CARE? (NOT HUMAN)

• Damage to Plants - Agriculture – crops loss ~$5

billion/year - Forests – significant damage to

Jeffrey and Ponderosa Pine along Sierra Nevada; tree growth declined 75% in San Bernardino Mountains

- suspected to increase plant diseases and pests• Damages buildings, bridges,

statues, books• Aesthetics: It looks ugly. We all try

to avoid living in polluted areas (admit it…)

LIST OF AIR POLLUTANTS TO KNOW

• NOX general form refering to N2O (nitrous oxide), NO2 (nitrogen dioxide), N2O4 (dinitrogen tetroxide), etc.

• SOX general form referring to SO2 (sulfur dioxide) and SO3

• CO2 and CO

• Acidic biproducts forming acid rain and dry deposits: H2SO4 (sulfuric acid), HNO3 (nitric acid), HC2H3O2 (acetic acid)

• Tropospheric ozone O3

• Particulate matter (ash, dust, combustion of gas or diesel black smoke)

CO

• Prevents O2 from attaching to hemoglobin in blood.

• Odorless, Colorless,

• It is created by incomplete combustion of gas and is found in car emissions

Particulate Matter (PM)

PM ranges in size from .01μm to PM10. PM2.5, is of great concern, because nose hair does not filter it out and it can become embedded in the lungs. Asbestos.

PM can also scatter light.

Particulate Matter

PM can create what is called a haze or smog.

AMAZON HAS HAZE FROM SLASH AND BURNING OF

RAINFOREST

Major Air Pollutants

• Volatile organic compounds (VOC)

• Ozone in troposphere

• Lead

• Mercury

Sulfates are considered to be secondary pollutants because they are transformed from primary pollutants.

Gas can become a VOC because it evaporates at room temperature, leaving a strong smell, is a hydrocarbon that can leave PM,

The combustion of coal is the primary cause of mercury in the air.

Dry cleaner fluid, spilled gas lighter fluid are additional VOC.

Primary Pollutants

• Primary pollutants: polluting compounds coming directly out of smoke-stacks, exhaust pipes, or natural emission source

• E.g., CO, CO2, SO2, NOx, and most suspended particulate matter

Secondary Pollutants

• Secondary pollutants: pollutants transformed in the presence of sunlight, water, oxygen or other compounds

• E.g., ozone, sulfate, and nitrate

Air pollution comes from both natural and

human sources.

Natural Sources of Air Pollution

• Volcanoes

• Lightning

• Forest fires

• Plants

Anthropogenic Sources of Air Pollution

Anthropogenic: From the Greek,

• Anthropos, “human”

• -genesis, “created”

• Meaning anything caused or created by human activity

Anthropogenic Sources of Air Pollution

• On-road vehicles

• Power plants

• Industrial processes

• Waste disposal

Photochemical smog is still an environmental problem in the United

States.

Smog Formation

• Smog forms when sunlight, nitrogen oxides (Nox), and volatile organic compounds (VOCs) are present.

California smog is mostly due to ozone and called brown smog. London has SO2 smog and is called tea and crumpets smog. Ok, I made that up, it is gray smog.

Smog Formation

• The secondary pollutant ozone is a major component of photochemical smog.

• Sulfur is the main ingredient in sulfurous smog.

Photochemical Smog

ACID DEPOSITION• Acidic precipitation and dry

fallout both are corrosive and damaging to biota

pH scale goes 0 to 14 (acid to base)

pH = - log [H+] in a solution. Therefore each number higher on the pH scale is 10X more basic

Acidic- produce H+ ions < pH 7

Basic- OH- (hydroxide ions) > pH 7

Neutral- pure water = pH 7

Normal rain slightly acidic-pH 6.4

Acid rain a pH < 5.5

SOURCES OF ACID RAINNatural: a. Sulfur: Volcanoes, sea spray, microbialb. Nitrogen oxides: lightening, forest fires,

microbialAnthropogenic (human caused) a. Sulfur oxides: coal burning plants, industry,

fossil fuels.b. Nitrogen oxides: power plants, industrial fuel

combustion, transportationc. Effect areas hundreds of miles from the source

of emissions, generally not the whole globed. Both sulfur oxides and nitrogen oxides are

primary components of acid rain.

INDOOR AIR POLLUTANTS1. Types: benzene, formaldehyde,

radon, cigarette smoke

2. Sources: off gassing from furniture, rugs and building materials, dry cleaning, adhesives, cleaning fluids, disinfectants, pesticides, heaters

3. Buildings with too many indoor air pollutants are called “sick buildings” because more than 20% of the people are sick due to occupying the building.

SICK BUILDING SYNDROME ON EPA WEBSITE

Indicators of SBS include:

Building occupants complain of symptoms associated with acute discomfort, e.g., headache; eye, nose, or throat irritation; dry cough; dry or itchy skin; dizziness and nausea; difficulty in concentrating; fatigue; and sensitivity to odors.

And most of the complainants report relief soon after leaving the building.

Causes of Sick Building Syndrome

• Inadequate ventilation

• Chemical contaminants from indoor sources

• Chemical contaminants from outdoor sources

• Biological contaminants

• Solutions to SBS:

pollutant source removal, increasing ventilation rates, air cleaning/filtering, communication and education

REDUCING AIR POLLUTANT EMISSIONS

Best way = Conservation, just use less!• Reducing pollution from

transportation

Input Control (pollution prevention)a. Cleaner burning gasoline, remove

lead Pb which was used as an antiknock substance

b. increased fuel efficiency

c. alternative modes of transportation

-Mass transit, Walking, Bicycling, Electric vehicles

d. decrease the number of miles driven

REDUCING AIR POLLUTANT EMISSIONS (INPUT CONTROL)

e. changes in land use decisions

f. catalytic converter- complete oxidation of hydrocarbons (VOCs) and carbon monoxide to CO2 and H2O, makes for less the VOC and CO pollutants

OUTPUT POLLUTION CONTROLa) Scrubbers on smoke stacks

b) taller stacks to allow for cooling and condensation

c) Coal washing-using large amount of H2O to get rid of sulfur before burning

d) Fluidized bed combustion-produces a waste ash that must be disposed of

REDUCING POLLUTION FROM ELECTRICITY PRODUCTION

• Input Control (pollution prevention)A. Cleaner Burning Fuel by…-Switching to low-sulfur coal-Switching from coal to natural gas-Switching from fossil fuel to renewable

energy sourceB. Increase Energy Efficiency by…-using insulation- using more efficient appliances

OUTPUT CONTROL TECHNOLOGIES

Technological fixes to remove air pollutants

• Scrubbers are “liquid filters”: exhaust fumes through a spray of H2O containing lime

• Also use elctrostatic precipators: SO2 CaSO3 to precipitate out

• Required since 1977 in part due to Clean Air Act of 1970

AIR POLLUTIONS PROBLEMS AND PROGRESS

• Incinerators: used to burn waste, used to do this in open air with no exhaust filtering, very harmful

• Smelting: a form of metallurgy used in mining to heat/melt and add electrolysis to molten ore to isolate the desired mineral/metal

• Since removal of lead from car gasoline, levels of Pb found in the environment, in animals and humans has been reduced significantly.

• In 1960s biggest source of air pollution was factories and industry. But since Clean Air Acts of 1970 and 1990, they have been regulated and there has been a decrease in atmospheric concentrations of VOCs, SOx, CO, NOx and particulate matter (soot, smoke).

• Today biggest source of air pollution is transportation, vehicles.• A few years ago, China surpassed the USA as being the highest

emitter of carbon dioxide. And the Asia/Pacific region is a bigger carbon dioxide emitting region than North America.