Download O 3

Chapter 8
The atmospheric environment
http://www.lpi.usra.edu/education/skytellers/seasons/about.shtml
There is a latitudinal
disequilibrium of heat on the
planet
Global Redistribution of Heat through circulation
without the spin of the Earth
Global Atmospheric Circulation with the spin of the Earth
Polar Cell
Ferrel Cell
Ferrel Cell
Reykjavik, Iceland 64°8’
Boston, MA latitude 42°23’ N
Death Valley, CA 36°34’N
George town, Bahamas 23°51’ N
Khartoum, Sudan 15°62’N
Macapá, Brazil 0°02’N
Wellington, New Zealand 41°26’S
Capitán Arturo Prat, Antarctica 62°33’
http://leslie-questionoftheday.blogspot.com/2010/08/would-you-rather-have-really-hot-summer.html
Hot and sticky – cold and dry
WHY?
The amount of water vapor an air parcel can hold is
temperature dependent
http://www.aviationweather.ws/026_Water_Vapor.php
Water in the Atmosphere
1.
Humidity - describes the amount of water vapor in the
air
2.
Absolute humidity - mass of water vapor in a given
volume of air:
mass of water vapor (gm) / volume of air (cubic m)
[mixed units]
http://www.weatherquestions.com/What_is_evaporation.htm
1.
For every ~10C change in temperature, amount of
water needed for saturation doubles
2.
Rate of evaporation depends on temperature and
vapor pressure in the air
From: Tarbuck and Lutgens (2010) The Atmosphere 11th ed. Pearson
1.
Relative humidity is the ratio of the air's actual water
content to the amount of water vapor required for
saturation at that temp & pressure
2.
Same thing as RH = actual mixing ratio / saturation
mixing ratio
http://www.isavo.com/pic409/jungle-pictures.htm
http://www.panoramio.com/photo/48115818
Relative humidity changes when either the temperature or the
amount of water vapor present in the air parcel changes. When
the temperature changes because of changes in pressure, it is
called adiabatic heating or cooling. This process is responsible
for the formation of clouds, convection cells and redistribution of
the planet’s energy.
http://www.esrl.noaa.gov/psd/outreach/education/science/convection/Sky.html
Hydrostatic Equation: Dp = -rgDh
where Dp is the change in pressure, r is the density of the fluid, g is the
acceleration due to gravity, and Dh is the change in height.
Dry adiabatic lapse rate: the rate at which an air
parcel cools if lifted in the atmosphere or warms if
forced to lower levels, as long as no condensation
occurs in the air parcel. (= ~9.8 K km-1.)
Absolute humidity: the amount of water vapor
actually present in the air.
Relative humidity: the amount of water vapor in
the air divided by the amount of water vapor the
air can hold at any particular temperature,
expressed in percent.
Wet adiabatic lapse rate: the rate at which an air
parcel cools when condensation occurs. It is a
function of temperature and pressure.
Environmental lapse rate: the observed rate at
which temperature changes in a column of air.
Inversion: the reversal of the normal temperature pattern
Radiation inversion: caused by
radiational cooling of the land surface
and a decrease in the temperature of
the atmosphere at low levels.
Subtropical inversion: caused by
sinking air at high pressure center.
*Remember, when air descends its
temperature increases.
Frontal inversion: caused by the
relative movement of warm air over
cold air.
MetEd.ucar.edu
Sources & Types of Air Pollution
• Air pollutants are airborne particles and gases that occur in
concentrations that endanger the health and well-being of
organisms, or disrupt the orderly functioning of the environment
• Pollution is divided into two categories
1. Primary
2. Secondary
Ta ble 8-2. Classification of air pollutants
Major Class
Sub class
Inorganic gases
O xides of nitrogen
N 2 O, NO, N O 2
O xides of sulfur
SO 2 , SO 3
O xides of carbon
CO, CO 2
Other ino rganics
O 3 , H 2S, HF, N H 3, Cl 2 , Rn
Hydro carbons
M ethane ( CH 4), butane (C4 H 10 ), octane (C8 H 18),
benzene (C6 H 6), acetylene (C2 H 2), ethylene (C2 H 4)
Aldehydes and ketones
For maldehyde, acetone
Other organ ics
Chlorofluo rocarbons, PA Hs, alcohols, organic acids
Solids
Fu me, dust, smoke, ash, carbon soot, lead, asbestos
Liquids
M ist, spray, oil, grease, acids
Organic gases
Particulates
Examp les
Types of Air Pollution
• Primary Pollutants are emitted directly from identifiable
sources.
• They pollute the air immediately they are emitted
• Secondary Pollutants are produced in the atmosphere
when certain chemical reactions take place among
primary pollutants, and with natural air & water. e.g.
smog
• Secondary pollutants have more severe effects on
humans than primary pollutants
Primary Pollutants
• What they are:
1. Carbon Monoxide
2. Sulfur oxides
3. Nitrogen Oxides
4. Volatile organics
5. Particulates
Primary Pollutants - 2
• Where they come from:
1. Transportation
2. Stationary source fuel combustion
3. Industrial processes
4. Solid waste disposal
5. Miscellaneous
http://globalenvironment.org.uk/what-causes-air-pollution.html
Particulate Matter (PM)
• Mixture of solid particles and liquid droplets found in the
air
• Particulates reduce visibility. Leave deposits of dirt on
surfaces, and may carry other pollutants dissolved in or
on them
• Some are visible to the naked eye, some are not frequently the most obvious form of air pollution
• Sizes range from fine (<2.5 micrometers in diameter) to
coarse (>2.5 micrometers )
Particulate Matter - 2
• Fine particles (PM2.5) result from fuel combustion
(motor vehicles, power generation, industrial facilities,
residential fireplaces & wood stoves)
• Coarse particles (PM10) result from things such as
vehicles travelling on unpaved roads, materials handling,
grinding & crushing & wind-blown dust
• EPA standards are defined for PM2.5 and PM10
Particulate Matter - 3
• Inhalable particular matter includes both coarse & fine
particles
• Coarse particles lead to diseases like asthma
• Fine particles are associated with heart & lung diseases,
decreased lung function, premature death.
• Sensitive groups include elderly people with
cardiopulmonary disease (e.g. asthma) and children.
Particulate matter
Chemistry and sources of atmospheric particulates (aerosols)
Primarily tropospheric
transport
Figure 8-24. Sources of atmospheric particulates. Arrows with dashed lines indicate that there is a
gaseous emission associated with the source.
Mineral dust
Fine particles
Aeolian transport
Sahara dust
Trace element delivery to remote oceans (e.g. Antarctica)
Sea Salts
Bursting of bubbles
Pure sea salt aerosols have a predictable ratio of the major ions in seawater
Cl/Na , S/Na , N/Na
Sulfates
Sulfate aerosols can be in the form of (NH4)2SO4, or H2SO4 primarily
Sources: Anthropogenic - combustion
Natural – DMS (dimethyl sulfide), volcanoes (SO2 and H2S)
Carbon-derived particle
Black carbon (soot) – incomplete combustion
Soot from coal (fly ash) = high K, Fe, Mn, Zn
Soot from oil = high V
Organic aerosols- VOCs
Bioaerosols – spores, pollen, and volatile bio-organic compounds (Blue mountains)
Dry deposition – dust settling
Rate determined by radius of particle (Stokes Law)
Wet deposition – washout
Precip (rain or snow)
Condensation
Aerosols serve as condensation nuclei for the formation of
clouds
Source tracking for aerosol deposition
Air mass trajectories
Using atmospheric circulation models to reconstruct the history of an
air mass.
Aerosols
Solid particles or liquid droplets ranging in size up to 20mm in radius. Can
either be put into the air directly or created in atm
SO2(g) + H2O  H2SO4(l)
Sulfuric acid aerosol
Ta ble 8-3. Sour ces of aerosols an d c ontri butions of natural versus anthr opog enic
sourc es*
Natural
(1 0 12 g y -1)
An throp ogenic
(1 0 12 g y -1)
Soil and rock dust
3000 - 4000
?
Se a salt
1700 - 4700
Sou rc e
Biogenic
100 - 500
Bio mass burning (soot)
6 - 11
Volca nic
15 - 90
Dire ct e missions - fuel, inc inerators, industry
36 - 154
15 - 90
Gaseous e missions
Su lfa te fro m bioge nic DMS
Su lfa te fro m volc anic SO 2
51
18 - 27
Su lfa te fro m fossil fuel
105
Nitrate fro m NO x
62
128
A mmoniu m fro m NH 3
28
37
Biogenic hydroca rbons
20 - 150
Anthropogenic hydroca rbo ns
Tota l
100
5000 - 9619
421 - 614
* Modified from Be rne r and Be rner (1996)
Factoid: Following large volcanic eruptions, the sulfuric acid aerosol in the atm
increases the earth’s albedo leading to temporary global cooling
Ta ble 8-3. Sources of aerosols an d contri butions of natural versus anthropog enic
sources*
Natural
(1 0 12 g y -1)
An throp ogenic
(1 0 12 g y -1)
Soil and rock dust
3000 - 4000
?
Sea salt
1700 - 4700
Biogenic
100 - 500
Sou rce
Bio mass burning (soot)
6 - 11
Volcanic
15 - 90
Direct emissions - fuel, incinerators, industry
36 - 154
15 - 90
Gaseous emissions
Su lfate fro m biogenic DMS
Su lfate fro m volcanic SO 2
51
18 - 27
Su lfate fro m fossil fuel
105
Nitrate fro m NO x
62
128
A mmoniu m fro m NH 3
28
37
Biogenic hydrocarbons
20 - 150
Anthropogenic hydrocarbo ns
Total
* Modified from Berner and Berner (1996)
100
5000 - 9619
421 - 614
Sulfur Dioxide
• SO2 is a colorless and corrosive gas that originates from the
combustion of material containing sulfur, e.g., coal and oil.
• Acrid and poisonous.
• Frequently transformed into SO3. Add water (H2O), get H2SO4 sulfuric acid
• Leads to acid precipitation (acid rain - q.v.)
Sources of
electrical
generation, USA
2006
Nitrogen Oxides (NOx)
• Form during the high-temperature combustion of fuel,
when nitrogen in the fuel reacts with oxygen.
• Primary sources are power plants and motor vehicles
• N + O -> NO + O -> NO2
• NO2 is a reddish-brown gas
• NOx occur naturally, but in much lower concentrations
• Can contribute to heart & lung problems
• Also contribute to acid rain
• Because they are highly reactive, they play an important
role in the formation of smog
Volatile Organic Compounds (VOC)
•
•
•
•
These are hydrocarbons - hydrogen + carbon
Can be solid, liquid or gas
Most abundant is methane (CH4, greenhouse gas)
VOCs are important in themselves, but also lead to
noxious secondary pollutants
http://www.sustainableyoulgrave.org/moxie/gallery/sustainable-youlgrave-res.shtml
Carbon Monoxide
• CO - colorless, tasteless, odorless and poisonous
• Formed by incomplete combustion of carbon
• The most abundant primary pollutant, caused mostly be
transportation industry
• CO enters the blood stream via the lungs, and reduces
oxygen delivery to the body's organs and tissues (face
turns blue)
• Hazardous in concentrations - e.g. underground parking
stations.
Lead (Pb)
• Can accumulate in bones and tissues
• Can cause damage to nervous system, especially in
children
• Major source - automobiles
• Now use lead-free gas, and lead concentrations have
dropped dramatically
http://top-10-list.org/2009/09/02/great-inventionsthat-went-bad-for-mankind/leaded-gasoline-pumps/
Secondary Pollutants
• Formed by reactions among primary pollutants, and with
H2O and O2 of the air
• For example, SO2 + O -> SO3
• Smog = SMoke + fOG
• Nowadays, used as a general term for air pollution
• Term is usually qualified by a location where that type of
smog is/was common, or by descriptions of the cause.
• e.g., London fog; photochemical smog.
Secondary Pollutants - 2
• Photochemical reactions - sunlight reacts with primary
pollution, causing a chemical reaction.
• Occur during the day, maximizing in the summer depends on sun angle.
• Photochemical smog is a noxious mixture of gases and
particles - very reactive, irritating and toxic.
Smog
Ta ble 8-4. Types of s mogs an d their characteristics
Characteristic
Industrial
Photoch emical
First occurrence
Londo n
Los Angeles
Principal pollutants
SO x
O 3 , NO x, H C, CO, free radicals
Principal sou rces
Industrial and h ousehold fuel co mbustion
M otor vehicle fuel comb ustion
Effect on hu mans
Lung and throat irritatio n
Eye and respiratory irritation
Effect on co mpounds
Reducing
O xidi zing
Time of worst events
Winter mo nths in the early morning
Su mmer months aroun d midday
Industrial smog – mostly acid aerosols, corrode buildings and retinas
Photochemical smogs – mostly formation of ozone, NOx, and PAN,
respiratory distress– maximum during midday
The Great London Smog of 1952
Volcanic Smog (Vog)
Satellite measurements of SO2 concentration
Satellite Visible Imagery
Ozone - Good or Bad?
• Major component of photochemical smog is ozone.
• Ozone causes eye and lung irritation, lowers crop yields,
damages material such as rubber etc.
• Ozone in the upper atmosphere is a good thing (protects
us from solar UV) – we will discuss this later…
• Ozone at ground level is a bad thing
Ozone
Good ozone – stratosphere
Bad ozone – troposphere
Ozone production requires energy from photons
O2 + hv  O* + O*
O* + O2 + M  O3
(M is a catalyst …e.g. N; DHR0 = -106.5 exothermic)
Net reaction …3O2 + hv  2O3
Ozone destruction also involves photons
O3 + hv O2 + O*
O* + O3 O2 + O2
Why good ozone is good.
Figure 8-13. Absorption cross sections for oxygen and ozone in the 100 to 300 nm
wavelengths. Also shown is the solar flux density and the wavelengths of biologically
harmful radiation (UV-B and UV-C). From vanLoon and Duffy (2000).
The polar vortex is a persistent, large-scale cyclone located near the
Earth's poles, in the middle and upper troposphere and the stratosphere. It
surrounds the polar highs and is part of the polar front.
Nitric acid in polar stratospheric
clouds reacts with CFCs to form
chlorine, which catalyzes the
photochemical destruction of
ozone. Chlorine concentrations
build up during the winter polar
night, and the consequent ozone
destruction is greatest when the
sunlight returns in spring
(September/October). These
clouds can only form at
temperatures below about -80°C,
so the warmer Arctic region does
not have an ozone hole.
Maximal ozone will form where form where gas molecule density and uv photon
denisty are optimal.
Ozone layer
Figure 8-14. Altitude versus variations in photon and molecular densities.
The optimum altitude for ozone formation occurs where these curves cross.
Stratospheric ozone distribution
Higher over poles (stratospheric transport)
Higher in summer vs. winter
The ozone hole
Hole varies in size due
to meteorological factors
Additions of N2O,
CFCs, and bromine
Compounds caused the
decline in ozone
Figure 8-15. Seasonal variation of ozone concentrations (in Dobson units) at Halley Bay,
Antarctica, for two different time periods. From Solomon (1990).
Ozone destroying reactions
N2O
N2O + O*  2NO
NO + O3  NO2 + O2
NO2 + O  NO + O2
O + O3  2O2
CFCl3
CFCl3 + hv  CFCl2’ + Cl’
Cl’ + O3  ClO’ + O2
ClO’ + O  Cl’ + O2
O + O3  2O2
For each of these reactions
the Cl’ and the NO return to their
original state. They are catalysts
only and do not participate in the
reaction
Calculating reaction rates for various ozone destroying chemicals
Ta ble 8-8. Kin etic data for variou s re actan ts in th e catalytic des tru ction of ozon e at 235 K*
X + O3
X
Concen tration
( molecu les cm-3)
A
(cm3 molecules -1 s -1)
Ea
(kJ mol-1)
k 235
(cm3 molecules -1 s-1 )
O
1.0 x 10 9
H
2.0 x 10 1 5
1.4 x 10 -10
3.9
1.9 x 10 -11
OH
1.0 x 10 6
1.6 x 10 -12
7.8
3.0 x 10 -14
NO
5.0 x 10 8
1.8 x 10 -12
11.4
5.3 x 10 -15
Cl
Very small
2.8 x 10 -12
21
6.0 x 10 -17
XO + O
XO Calc reaction
Concen tration rate forA Cl’ + O  ClO’
E
Example 8-3:
+ O3 at k235K.
3
( molecu les cm )
(cm molecules s )
(kJ mol )
(cm molecules s )
Cl’ conc. = 5.0 E11. O3 conc = 2.0 E12. Reaction rate = k [Cl][O3]
a
-3
3
-1
-1
235
-1
3
-1
O2
5.0 x 10 1 6
8.0 x 10 -12
17.1
1.3 x 10 -15
HO
1.0 x 10 6
2.3 x 10 -11
0
2.3 x 10 -11
7
-11
-11
19
-12
-12
7
-11
-11
-1
-Calc k using Arrhenius eqn
HO
2.5 x 10
2.2 x 10
-0.1
2.3 x 10
k =NOAe-Ea/RT 5.0 x 10
9.3 x 10
0
9.3 x 10
-12
3
-1
-1
–(21
KJ
mol-1)(8.314
kJ
mol-1K-1)(235K)
k =ClO
(2.8 E 2.0
cmx 10 molecules
s
)e
4.7 x 10
0.4
3.8 x 10
3
-1 s-1
k=*The6.0
e-17 cm
con centrations
of themolecules
species are for an altitude
of 30 k m with the exception of ClO which is for an
2
2
-Rate calc
altitude of 35 km. The co ncentration of o zone at 30 k m is 2.0 x 1 0 12 mo lecules cm-3. Fro m van Loon and
Du ffy (20 00)
rate = (6.0 E-17 cm3 molecules-1 s-1)(5.0 E11 molecules cm-3)(2.0 E12 molecules cm-3)
rate = 6.0 E7 molecules cm-3 s-1
Tropospheric ozone
Bad ozone
Photochemical smog
OH radicals or NO is a catalyst for the production of troposhperic ozone
NO (nitric oxide) released during fuel combustion
NO converted to NO2 by a host of reactions
NO2 + hv  NO + O
O + O2 + M  O3 + M …remember M is a catalytic particle
Of which, O3 is one
Figure 8-16. Variation in abundances of various species, on a 24-hour cycle, produced during a
photochemical smog event. From vanLoon and Duffy (2000).
• Air Quality Index (AQI)
• How clean or polluted is the air today?
• Meteorological factors are important.
How does the weather affect air quality?
• The solution to pollution is dilution - disperse the
contaminants
• Spread the contaminants around, keeping the levels
below the toxic levels. (This cannot work forever.)
• Meteorological Factors affecting Dispersion
1. The strength of the wind
2. The stability of the air
• Strong winds blow the pollution away (to someone else's
backyard)
• The stronger the wind, the more turbulent the air, and
the better the mixing of the contaminants with the wind.
• Stable air is associated with high pressure systems.
Acid Precipitation
• Some pollutants end up as acids e.g. SO2 + O + H2O
gives H2SO4 - sulfuric acid.
• Also get nitric acid from NOx + water.
• Some acids fall to Earth as acid rain or snow (acid
precipitation)
• The ph scale is given in fig 13-15.
• Water is naturally somewhat acidic (ph ~ 5.6) - CO2 +
H2O gives carbonic acid (appears in aerated drinks)
Precipitation [pH 5 is good.]
Effects of Acid Precipitation
http://envis.tropmet.res.in/kidscorner/acid_rain.htm
1.
2.
3.
4.
Low pH in lakes and streams
lead to more leaching of
aluminum from the soils, and
aluminum is toxic to fish.
Calcium carbonate helps
(acid breaks it down to CO2 &
H2O) We have covered this in
previous chapters
Reduces crop yields
Impairs the productivity of
forests - damages leaves &
roots, and leaches out the
trace minerals.
Corrodes metals, and
damages stone structures
Figure 8-19. Global SO2 produced by the
burning of fossil fuel, 1940 to 1986, in Tg SO2 S y-1 (1 Tg = 106 metric tons = 1012 g). From
Berner and Berner (1996).
Figure 8-20. Global NOx produced by the burning
of fossil fuel, 1970 to 1986, in Tg NOx - N y-1.
From Berner and Berner (1996).
Rainwater Chemistry
Ta ble 8-1 0. S ou rces of in di vidu al ions in rain water
Origin
Ion
M arine inputs
Terrestrial inputs
Pollution inputs
Na+
Sea salt
Soil dust
Bio mass burning
Mg 2+
Sea salt
Soil dust
Bio mass burning
K+
Sea salt
Biogenic aerosols
Soil dust
Bio mass burning
Fertilizer
Ca2 +
Sea salt
Soil dust
Cement manufacture
Fuel burning
Bio mass burning
H+
Gas reaction
Gas reaction
Fuel burning
Cl-
Sea salt
None
Ind ustrial H Cl
Sea salt
DM S fro m biological
decay
DM S, H 2S, etc., fro m
biological decay
Volcano es
Soil dust
Bio mass burning
N 2 plus lightning
NO 2 fro m biological d ecay
N 2 plus lightning
Auto emissions
Fossil fuels
Bio mass burning
Fertilizer
NH 3 fro m biological
activity
NH 3 fro m bacterial decay
N H 3 fertilizers
Hu man, ani mal waste
deco mposition
(Co mbustion)
2
SO 4

NO 3

NH 4
3
PO 4
Biogenic aerosols adsorbed Soil dust
on sea salt
Bio mass burning
Fertilizer
HCO 3
CO 2 in air
CO 2 in air
Soil dust
None
SiO 2 , Al, Fe
None
Soil dust
Land clearing

•Compounds found in
rainwater come from
seawater, terrestrial or
pollution sources
•Cl- in rain is assumed to
be from a seawater source
•Cl- and other ions in from
seawater are assumed to
have a constant proportion
•Rain sample can be ‘corrected’
for seawater contribution
Ta ble 8-11. W eigh t r atios of major ions in s ea wate r r elati ve to C l-- or N a++ *
Ion
W eight ratio to Cl -
Weight ratio to Na+
Cl-
1.00
1.80
Na +
0.56
1.00
M g 2+
0.07
0.12
SO 4
0.14
0.25
Ca2+
0.02
0.04
K+
0.02
0.04
2
*So urce of data for ratio calculations, Wilson (1975)
Ta ble 8-12. P ri mary as s oci ation s for r ain w ater*
Origin
Association
Marin e
Cl - Na - M g - SO 4
Soil
Al - Fe - Si - Ca - (K, M g, Na)
Biological
N O 3 - NH 4 - SO 4 - K
Bio mass burning
N O 3 - NH 4 - P - K - SO 4 - (Ca, Na, Mg)
Industrial pollution
SO 4 - NO 3 - Cl
Fertilizers
K - PO 4 - NH 4 - NO 3
*Fro m Berner and Berner (1996)
Excess ion X
= total ion X – [(ratio of ion X
to Cl- in seawater) (Cl- conc)]
Figure 8-17. Average Cl- concentration (mg L-1) of rainwater for the United States from July 1955 to
June 1956. From Berner and Berner (1996).
Marine influence on rainwater chemistry
Figure 8-21. Generalized isoconcentration contours for SO42- (in mg L-1) for atmospheric precipitation over the
contiguous United States in 1995. Source of data is the NADP. From Langmuir (1997).
Figure 8-22. Generalized isoconcentration contours for NO3- (in mg L-1) for atmospheric precipitation over
the contiguous United States in 1995. Source of data is the NADP. From Langmuir (1997).
Two most important species for acid rain
are nitrate and sulfate
Figure 8-23. Average pH for precipitation in 1955-1956 and 1972-1973 for the northeastern United
States and Canada and in 1980 for the contiguous United States and Canada. From Langmuir (1997).
Example 8-7: Calc pH for a stream receiving acid rain.
Calc moles of sulfate and nitrate (from Table 8-13)
sulfate = 2.165 x 10-5 mol L-1
nitrate = 2.355 x 10-5 mol L-1
Calculate H+ produced based on what you know about the normality of sulfuric and
Nitric acid. One mole H+ per mole nitrate, two moles H+ per mole sulfate.
Moles H+ = 6.685 x 10-5 mol L-1
pH = -log [H+] = 4.17
The Nitrogen Cycle
Hog Production in USA
(1 dot= 10,000 Hogs and Pigs)
Most dangerous indoor pollutants
1.
Cigarette smoke
2.
(Radioactive) radon gas
3.
Formaldehyde
http://www.americanhomeconsultantsllc.com/indoorair.html
Indoor air pollution
• More than 100 dangerous substances occur in much
greater concentrations indoor than outdoors
• Substances get trapped in houses & offices etc.
• Give rise to " sick building syndrome "
• Buildings are becoming more airtight in a move to cut
energy costs
• People spend 70 to 90% of their time indoors
Indoor air pollution
• Problems caused by cigarette smoke are well
documented
• Radon gas is a natural by-product of the decay
of uranium - causes lung cancer
• Formaldehyde is part of many building
materials - causes breathing problems, rashes,
headaches etc.
• Cleaning products also contaminate the air cleaning products, carpet adhesive, aerosol
sprays, mothballs
Radon – 222Rn
Produced from the 238U decay chain
Problematic when bedrock contains uranium
and 214Po progeny are particle active, particles inhaled, lodged in lungs…
subsequent alpha decay damages lung tissue
218Po
Consider Rn levels inside:
Generalized steady state equation for an inside pollutant
Ri = kexCi – kexCo
Ci = Co + Ri/kex
Ci = inside conc
Co = outside conc
kex = exchange coef
Ri= production rate of pollutant
Since Rn is radioactive, the expression is modified to acct. for decay
Ri= kex Ai + lAi – kexA0
Indoor activity of Rn is:
Ai= (Ri + kexA0 ) / (kex + l)
Example 8-4: Radon release from soils to a basement at a rate of 0.01 Bq L-1 h-1
Outdoor air has Rn acitivity of 4.0 E-3 Bq L-1 h-1. Assume air exchange coeff of 10 h-1
What is the steady state indoor actvitiy of Rn?
Ai= (Ri + kexA0 ) / (kex + l)
Plug and chug…answer is Ai = 5.0 E-3 Bq L-1 h-1
Radon flux depends on any factors that change gas diffusion
-soil moisture
-temp (solubility of Rn)
-freezing (caps Rn)
-barometric pressure
Rn is elevated in groundwaters and can be used as a tracer for gw inputs to
Surface waters
The Greenhouse Effect
Incoming solar shortwave radiation
Radiated out to
space
Reflected
Absorbedback
in the
to
space
atmosphere by
greenhouse gases
Infra-red
long-wave
radiation
from surface
Absorbed by the
Earth’s surface &
atmosphere
What would the world be like without the
Greenhouse Effect?
• The Earth’s black-body temperature is 5ºC.
• With the Earth’s albedo (reflectivity) the
temperature drops to -20ºC.
• The natural Greenhouse Effect brings that
temperature back to a comfortable 15ºC.
Absorption of outgoing Earthlight
Greenhouse Gases: CO2, CH4, N2O & CFCs that absorb
long-wave, out-going radiation causing them to vibrate
and generate heat.
Positive and negative feedbacks of greenhouse effect and
climate change
Hotter world = more water vapor = more heat trapping = positive feedback
Hotter world = more cloud cover = less insolation = negative feedback
Hotter world = less snow = less albedo = more net insolation = postive feedback
Hotter world = faster decomp = more CO2 = more heat trap = positive feedback
More CO2 + temp = more photosynthesis = less CO2 = negative feedback
Geologic record indicates periods of warm wet earth and cold dry earth
The relative effect of an individual gas on the greenhouse
effect over time depends upon:
Molecular scale radiative forcing (how well it converts radiation to heat)
Atmospheric concentration
Rate of increase in the atmosphere
Atmospheric residence time
Ta ble 8-5. Data for greenhouse gases*
Gas
Concen tration
1990 (ppmv)
CO 2
35 4
Positive
radiative
forcing
(W m-2)
% total
radiative
forcing
Relative
instantan eous
Lifeti me radiative forcing
(y)
(molecular basis)
Global
W arming
Potential
(100 y)
1.5
61
50 - 200
1
1
12
43
21
310
CH 4
1.72
0.42
17
H 2 O strat
-
0.14
6
N2 O
0.310
0.1
4
120
250
CF C-11
0.00028
0.062
2.5
65
15,000
3,400
CF C-12
0.00048 4
0.14
6
130
19,000
7,100
Other CFCs
0.085
3.5
Total
2.45
100.0
CF C substitutes
HFC-23
264
650
HFC-152a
1.5
140
50,000
6,500
3,200
7,400
CF 4
C6 F1 4
*Fro m Berner and Berner (1996), IPCC (1996), van Loon and Duffy (2000)
We have reviewed the greenhouse effect and how it is of benefit to the planet.
What happens when the amount of greenhouse gasses in the atmosphere
increase, say from burning fossil fuels.
For example the burning of methane:
CH4 + 2O2
CO2 + 2H2O
CO2
Imbalance = (fossil fuel) – (increase in atm CO2) – (ocean storage) + (deforestation)
The ‘missing’ carbon sink. The global CO2 budget is out of balance. We
predict more increase in atm CO2 than what is actually observed.
Figure 8-8. Mean monthly concentrations of CO2 at Mauna Loa, Hawaii. From Berner and Berner (1996).
Net reaction for atm CO2 uptake in ocean
Global C box model
CO2 + CO32-  H2O + 2HCO3-
Fast
slow
Figure 8-9. The carbon cycle. Reservoir concentrations are in 1015 g (Gt) carbon. Fluxes are in
Gt C y-1. From Berner and Berner (1996).
Methane
2nd most important greenhouse gas
Sinks for methane:
1) chemical oxidation in the troposphere
2) stratospheric oxidation
3) microbe uptake
Figure 8-10. Variation in methane abundance from 1841 to 1996. The fitted curve is a sixth-order polynomial. Data from
Etheridge et al. (1994) and IPCC (1966).
Methane
Ta ble 8-7. Sourc es an d sinks for at mos phe ric methane*
Source or Sink
CH 4 (10 1 2 g C y -1)
% tota l
Sources
Natu ra l
How could 14C help tell us
The source of atm methane?
Wetla nds
86
22.5
Te rmites
15
3.9
Ocea ns
8
2.1
La kes
4
1.0
Me thane hydrates
4
1.0
117
30.5
Ene rgy production/use
69
18.0
Ente ric fer menta tion
63
16.4
Rice
45
11.8
Ani mal wastes
20
5.2
La ndfills
29
7.6
Bio mass burning
21
5.5
Do mestic sewa ge
19
5.0
266
69.5
Total natural
Anthropoge nic
Total anthropoge nic
Total fo r sou rc es
383
Sin ks
At mosphe ric re moval
353
88.2
Re moval by soils
23
5.8
At mosphe re
24
6.0
Total fo r sinks
400
* Data fro m Berne r and Be rne r (1996), IP CC (1 992)
Nitrous Oxide…its no laughing matter
N 2O
Sources: denitrification, nitrification, biomass burning & fertilizer production
No N2O sinks in the troposphere
The third largest contributor to global warming behind CO2 and CH4.
Also responsible for stratospheric ozone destruction.
Climate Change and the Geologic Record
Ice cores
Stable isotopes
Direct gas measurement of bubbles
Paleotemp from
isotopes
Figure 8-11. Variation in temperature, CO2, and CH4
concentrations in Antarctica during the past 240,000 years.
From Lorius et al. (1993).
Climate Change and the Geologic Record
Sediment record
Stable isotopes (oxygen and/ carbon)
Oxygen isotopes in carbonates
from a sediment core in the Western
Pacific
Several glacial / interglacial periods
Figure 8-12. Surface temperature of the Pacific Ocean based on
oxygen isotope ratios. From THE BLUE PLANET, 2nd Edition by
B. J. Skinner, S. C. Porter and D. B. Botkin. Copyright © 1999.
This material is used by permission of John Wiley & Sons, Inc.
Climate Change Evidence:
Global
Drought
Source: NOAA/NCDC U.S. Climate Extremes Index
Source: IPCC AR4, Adapted from Dai et al, (2004)
Source: University of Colorado (Seasonal signals removed)
Source: US GCRP, Groisman et al, (2009)
Source: NSIDC
Final Homework Assignment!!!!! Due: December 3
Chapter 8 problem #s: 7, 11, 12, 13, 16, 18, 22, 34, 37, 43, 64
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