the atmosphere. composition nitrogen (~78%) oxygen (~21%) argon (~0.93%) carbon dioxide...

THE ATMOSPHERE

Composition Nitrogen (~78%) Oxygen (~21%) Argon (~0.93%) Carbon dioxide (~0.039%) Rest is made of trace gases Water vapor (~1%)

Density and Pressure Sea level is the densest region Atmospheric pressure is the measure

of mass per unit of air Decreases as altitude increases

Basic Layers Thermosphere Mesosphere Stratosphere Troposphere

Troposphere 75-80% of all air in the atmosphere Extends up about 11 mi @ equator & 5

mi @ poles Where all the weather is We live here

Stratosphere Extends from top of troposphere to

about 30 mi above the Earth Less matter, less water vapor, and way

more ozone (O3) Where the “ozone hole” is

Stratospheric Ozone Forms when O2 interacts with UV

radiation Blocks about 95% of harmful radiation Prevents oxygen in the troposphere from

becoming ozone

Ozone Hole First really noticed/ studied in 1970’s Over the Antarctic and Australia Seems to be cyclical (gets bigger then

shrinks) Caused almost entirely by human-made

CFCs (no natural source of CFCs)

Air Pollution Presence of chemicals in the atmosphere

in high enough concentrations to affect both organisms and climate

Effects can range from a minor irritant or cause of death

Natural Sources of Air Pollution Volcanoes Decaying plants Forest fires Sea spray Dust storms

Air Pollutants Natural Stationary Mobile

Sources of pollution in –ED countries Transportation (mostly cars and trucks) Electric power plants that burn coal or oil Industry (especially steel mills, metal

smelters, oil refineries, and pulp/paper mills)

Primary v Secondary Sources Primary pollutants are emitted directly

into the atmosphere and are potentially harmful Soot and carbon dioxide

Secondary pollutants are primary pollutants that have reacted in the air and changed into a new form

Criteria Air Pollutants Most common air pollutants EPA is required to collect scientific and

medical information on their effects National Ambient Air Quality

Standards (NAAQS- known as “nax”) specify the maximum levels of concentration of these pollutants allowable in outside air.

CAP #1 Particulates All airborne

pollutants either liquid or solid

Includes pollen, dust, soot, smoke, acid condensates, etc

Range in size from fly ash (thumbnail) to tiny aerosols (less than 1 µm)

CAP #1 ParticulatesSources

Combustion Forest fires Industrial

processes Vehicle exhaust

Effects Can cause

respiratory disease depends on: Size of the

particle Chemical nature

Air Pollution over China!

CAP #2 Sulfur Dioxide (SO2)Sources

Mainly from burning coal

Metal smelters Industrial boilers Oil refineries

Effects Reacts with water to

form sulfuric acid Acid Rain

Contributes to respiratory illness & aggravates existing heart and lung diseases

Sources

CAP #3 Carbon Monoxide Odorless, colorless, poisonous

Sources Incomplete

combustion from cars and industry

Effects CO has a greater

affinity for hemoglobin that oxygen headaches, drowsiness, and death

CAP #3 Carbon Monoxide (CO) CO is a product of incomplete combustion:

Ex: C8H18 + O2 CO + H20 + hydrocarbons(not enough O2 incomplete combustion)

Ex: C8H18 + O2 CO + H20 (lots of O2 complete combustion)

Amount of incomplete combustion is reduced by a catalytic converter

CAP #4 Nitrogen Oxides (NOx) Nitrogen oxides are formed when

combustion occurs at very high temperaturesSources

Burning fuels in vehicles & power plants

Effects Precursor of ozone/

smog Reacts with water to

form nitric acid acid rain

Contributes to eutrophication

Aggravates respiratory diseases

CAP #5 Lead Excessive exposure to lead may cause

neurological impairments such as seizures, mental retardation, & behavioral disorders.

Even at low doses, lead exposure is associated with damage to the nervous systems of fetuses &young children, resulting in learning deficits & lowered IQ

Leaded gasoline Many countries in Northern Africa, the

Middle East, and former Soviet nations still use leaded gasoline

The US banned leaded gasoline in 1995 (CA in ‘92) NASCAR still used it until 2005…

CAP #6 Ground Level Ozone Ozone, NO2, and PANs are the main

constituents of photochemical smog

NOx + VOCs + sunlight ozone + PANs + hydrocarbons

VOCs= volatile organic compounds from fuels, paints, & glues

PANs= Peroxyacetylnitrate

CAP #6 Ground Level Ozone VOCs, NOx, & sunlight are needed for

ozone The hotter the day, the higher the levels

of ozone and other photochemical oxidants

Ozone “season”: May 1- Sept 30

CAP #6 Ground Level Ozone Exposure causes decreased lung function,

inflammation of the airways, & aggravates lung diseases such as asthma

Ozone also affects vegetation & ecosystems, leading to reductions in agricultural crop & commercial forest yields, reduced growth & survivability of tree seedlings, & increased plant susceptibility to disease, pests, & other environmental stresses (ex: harsh weather)

Photochemical Smog Forms when a mixture of NOx & volatile

organic hydrocarbon compounds react with sunlight to create 100+ secondary pollutants

Trees = Smog? Some tree species (some oaks, sweet

gums, poplars, and kudzu) emit VOCs Only a factor if a forest is near a major

city

Formation of Smog

Industrial Smog Made of sulfur dioxide, sulfuric acid, &

suspended particulates Created when coal & oil are burned Primarily a problem in the late 19th/ early

20th century (London smog) & developing countries

Atmospheric Inversions Atmospheric inversion: cool air (heavier

than warm air) is unable to rise and mix and remain stable

Where and when are thermal inversions likely to occur?

Atmospheric Inversions Form in a town/ city that is located in a

valley surrounded by mountains & gets cold, cloudy weather for part of the year Donora, PA

Form in a large metropolis w a sunny climate, light winds, mountains on 3 sides, & an ocean coast Los Angeles, CA

Factors that increase OAP Urban buildings Hills & mountains High temperatures (more smog in hot

climates) Grasshopper effect (send pollutants to

poles) How might this effect polar critters?

Factors that decrease OAP Rain & snow (dry cities have more

photochemical smog) Salty sea spray from the ocean Wind (takes away polluted air & brings in

fresh air) Why might this also be a negative?

Acid Deposition Pollutants expelled from smokestacks

from power plants & factories travel on the wind to other areas (as far away as 600 mi!) and can cause regional air pollution

During their trip, secondary pollutants form

Acid Deposition Wet deposition is acidic precipitation,

snow, fog, and cloud vapor with a pH of less than 5.6

Dry deposition is dry acidic particles that fall from the sky Within 2-3 days, pretty close to emission

source

Acid Rain Generally, rain water has a pH value of

5.6 because of the carbon dioxide from air dissolved in it

Any rainfall has a pH value less than 5.6 is defined as acid rain

Some regions have rain with a pH as low as 2.3! (1000x normal acidity!!!)

Vulnerability to Acid Rain An ecosystem’s sensitivity to acid

preparation is determined by the chemical composition of its soil and bedrock (buffering capacity ability to neutralize acids) Low buffering capacity naturally acidic soil

and/or granite rock High buffering capacity alkaline soils and/or

limestone bedrock Over time, soil’s buffering capacity can be

overwhelmed by acidic inputs

Effect on Aquatic Ecosystems Most freshwater organisms do best in

waters that are slightly alkaline (pH=8) Fish population decline is largely due to

acid induced reproductive failure Acid shock often follows spring snow

melt (also a critical developmental period for many larvae)

Acidified lakes appear extremely clear

Acid Deposition & Heavy Metals As pH decreases, toxic metals (Al, Mn, Pb,

Zn, Hg, & Cd) dissolve out of sediments or soils and can leach into the aquatic environment. These metals can Bioaccumulate in fish tissues making them

dangerous for humans to eat Kill fish by damaging their gills (especially Al)

Acidification can cause the conversion of moderately toxic inorganic Hg to the highly toxic organic methylmercury

Other Environmental Effects Deterioration of buildings, statues, and metals Reduction of crop yields some crops are

diminished and others are stimulated Damage to forest productivity:

Most affected are conifers at high elevations Direct damage to leaves Increase in the solubility and leaching of soil-

bound ions of Al, killing root hairs Loss of essential plant nutrients (Ca, K, Mg) from

the soil

Effects of Acid Precipitation

Pollution Control Efforts By the 1960s large-scale fuel-switching from coal

to natural gas and oil had significantly reduced smoky conditions in most Am. Cities

Bans on home refuse burning & utilization of pollution control devices further reduced air pollution

Early air quality laws relied on voluntary compliance by states, many of which were reluctant to adopt strict controls for fear of driving away industry (jobs, tax-base, etc…)

Pollution levels continued to rise until the public outcried

Clean Air Act Spurred by the environmental movement,

Congress passed the 1970 CAA. Strengthened in early 1990’s by Bush Has the following provisions:

1. Development of the NAAQS for the 6 criteria air pollutants*penalties were set for nonattainment areas

Clean Air Act2. Emission limitations for new stationary

sources (factories and power plants)*NOT retroactive for stationary sources in operation prior to 1970*required stationary sources to obtain operating permits specifying allowable levels of pollutant emission as well as required control measures

Clean Air Act3. Stricter emission standards for automobiles

*Inspection & maintenance programs*Made catalytic converters standard*Loophole allowed SUVs, minivans, and light trucks to emit 2-3 times as much pollution as ordinary vehicles. Emission standards have been made tougher *Reformulated gasoline containing oxygen additives in cities not in compliance with ozone emission standards (required to install vapor recovery systems)

Clean Air Act4. Regulation of HAPs through technology-

based controls*Hazardous air pollutants-asbestos -vinyl chloride-mercury -radionuclides-beryllium -coke oven emissions-benzene

*There are now 188 regulated HAPs (prompted by the accident at Bhopal, India)

Clean Air Act5. Acid deposition controls

*Mandate to cut sulfur dioxide emissions in half *Allowance trading (cap & trade)-let utility companies buy & sell allowances for SO2 emissions-encourages companies to reduce emissions below legal limit- 1 allowance = 1 ton of SO2 annually-market forces control the cost of the allowances

Catalytic Converters Converts hydrocarbons, carbon

monoxide, and nitrogen oxides into less harmful substances (water, carbon dioxide, and nitrogen

Wet Scrubbers Systems used to

remove pollutants from polluted gas streams

Used in industrial plants where gas is released

Gas is forced into contact with a scrubbing liquid to remove the pollutants

Greenhouse Effect Radiation from the sun gets trapped by

the greenhouse gases Gases are too weak to escape the

atmosphere and continue bouncing around in the lower atmosphere

Examples of greenhouse gases: Carbon dioxide, water vapor, methane,

nitrous oxide, & ozone

Global Warming Gradual warming of global atmosphere and

ocean temperatures Caused by a rise in greenhouse gases

Probably from human causes such as industrialization, forest fires, car exhaust, etc…

Will cause a rise in sea level (glaciers melting), changes in ecosystems (due to higher temperatures), coral reef die-off, increased number of storms (higher severity of the storms), etc…