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…
Top Related