Class objectives:
• Cover some of the major topics in
Environmental Chemistry
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Energy
Atmospheric Compartment
Water compartment
Soil
1. Some examples of
environmental chemicals
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Polynuclear Aromatic HC (PAHs)
Dioxins
Ketones
PCBs
CFCs
DDT
O3, NO2, aerosols, SO2
Toxic loads
• Scientists have hypothesized that the
fetus is sharing the mother’s toxic
load, and may actually provide some
protection to the mother by reducing
her internal exposure.
• Children get 12% of their lifetime
exposure to dioxins during the 1st
year.
• Their exposure is 50 times greater
than an adult during a very critical
developmental period.
• Firstborns from dolphins off the
coast of Florida usually die before
they separate from their mothers
Mother’s milk
• Human babies nursed by mothers
with the highest PCB contamination
levels in their milk are afflicted with
more acute ear infections than
bottle fed Inuit babies.
• Many of these children don’t seem
to produce enough antibodies for
childhood vaccinations to take.
PCBs and lower intelligence
• There is evidence of lower intelligence
in babies exposed to PCBs.
• In adults, a blood-brain barrier insulates
the brain from many potentially harmful
chemicals circulating through the body
• In a human child this barrier is not fully
developed until 6 months after birth.
2. Energy
SO what is a joule??
Force = mass x acceleration; f = m x a
a = D velocity / D time = dv/dt
velocity = D distance / D time; a= D distance / D time2
Work = force x distance
W=fxd
W= m x a x d and W = m x d2 /t2
Work and energy have the same units
a joule is defined as accelerating 1 kg of
mass at 1 meter/sec2 for a distance of 1 meter
A watt is a unit of power = 1 joule/second or
energy/time
how long will the oil last??
1980 estimate of reserves Oil
1x1022 J
1980 estimate of oil usage /year1.35x1020
J/year
Estimate the # years of oil left if we used at the above
rate from 1980 to 1990 and 2x’s the 1980 rate after
1990 = 3x; we estimated ~50 to 80 years
We used more recent data in class.
Fuel energy
When we burn a fuel where does the energy reside?
Let s take hydrogen in water as an example. If we were
to react H2 with O2 to form water, we would 1st have to
break the hydrogen bonds and the oxygen bonds
This takes energy; in the case of H2 it takes 432 kJ/mole
(~100,000 calories/mole) for H2 2H.
How many days of food will supply you with 100,000
calories?
To break O2 to O. (O2  2O.) requires
494 kJ/mol
When when water forms, however, we get energy back
from the formation of H2O because new bonds are
formed. Which ones??
Combustion energies from different fuels (kJ)
react. per
per
per
moles
heat mole mole gram CO2 per
kJ
O2
fuel fuel 1000kJ
hydrogen 482
2H2+O2 2H2O
482 241
120
0
Gas
810 405 810
CH4 + 2O2CO2 +2H2O
52
1.2
Petroleum 1220 407 610 44
2 (-CH2-)+ 3O22CO2 +2H2O
1.6
Coal
2046 409 512
4 (-CH-)+ 5O24CO2 +2H2O
39
2.0
1257 27
1.6
Ethanol
1257 419
3. Basic concepts
• Where does pV=nRT come from?
• At standard state can you calculate R?
• A+B C+D
(pC )(pD )
DG  RT ln
(p A )(bB )
o
ln Keq =-DH/R x 1/T + const.
4. The atmospheric
compartment
Two important features
the atmospheric
Compartment are
temperature and pressure
Why does the
temperature normally decrease
with height in the troposphere
and increase with height in the
stratosphere??
The pressure or force per unit area
decreases with increasing altitude
The decline in pressure (P) with altitude is
approximately = to
log P= - 0.06 (z); where z is the
altitude in km and P is bars
How thin is the air at the top of
Mt. Everest?
Mt. Everest is 8882 meters high or 8.88 km
high
log P = -0.06 x 8.88
P = 10-0.06x 8.88 = 0. 293 bars
Assume there are 1.01bars/atm.
This means there is < 1/3 of the air
The quantity d is called the dry
the dry adiabatic lapse rate
Air that contains water is not as heavy and has
a smaller lapse rate  and this will vary with the
amount of water
If the air is saturated with water the lapse rate
is often called s
 Near the surface sis ~ 4 oK/km and at 6 km
and –5oC it is ~6-7 oK/km
How does air circulate
At the equator air is heated and rises and
water is evaporated.
As the air rises it cools producing large
amounts of precipitation in equatorial
regions.
Having lost its moisture the air mass moves
north and south.
It then sinks and compresses (~30oN and S
latitude) causing deserts
The mean residence time (MRT) can be
expressed as:
MRT = mass / flux
where flux is mass/time
If 75% of the mass/year in the stratosphere
comes from the troposphere

1
MRT = ----------------- = 1.3 years
–
0.75/year
Mt. Pinatubo in the Philippines erupted in
June 1991, and added a huge amount of
SO2 and particulate matter the stratosphere.
After one year how much SO2 was left?
For a 1st order process
C= Coe -1 year/ MRT
C/Co= e -1 year/ MRT = e -1/1.3= 0.47 or ~ 50%
in 4 years, C/Co= e -4 years/1.3 years =
~5%
What happened to global
temperatures after the Pinatubo
eruption?
A lot of SO2 was injected into the
atmosphere
SO2 forms fine sulfate particles that
reflect light back into the
atmosphere and this cools the
upper troposphere
5. What is Global
Warming and how can
it Change the Climate?
How fast are green house
gases increasing???
time trace for the concentration of
carbon dioxide from 1958-1992 at Mt.
Mauna lowa Hawaii
Why does it oscillate up and down as it
generally goes up??
How fast is Global Warming
Occurring?
The rate of global warming over the next
century may be more rapid than any
temperature change that has occurred over
the past 100,000 years!!!
This will cause major geographical shifts in
forests, vegetation, and cause significant
ecological disruption
1979 perennial Ice coverage Nat. Geographic, Sept
2004)
2003 perennial Ice coverage
Doubling Emissions of CO2
Often discussed are the effects of doubling
CO2 concentrations from pre-industrial times
(2xpre-Ind. CO2=550 ppm)
Some times predications are made with the
assumption of CO2 doubling or even
quadrupling.
On the next slide you will see world wide
emissions using different assumptions.
Including Particles in Global
Models
Fine particles, especially sulfate particles
resulting from SO2 emissions from coal,
combustion can reflect light from the sun and
actually cause a negative temp. effect
The next 2 picture from a global circulation
model (GCM by Bob Charleston, UW-Wash,
USA), shows a cooling effect in the
industrialized world.
First without considering particles then with
red= +2oC, yellow =+3oC, blue = +10C
red= +2oC, yellow =+3 oC, blue = +10C
red= +2oC, yellow =+3 oC, blue = +10C
6. Kinetics:
1st order reactions
A ---> B
-d [A] /dt =
krate [A]
- d [A]/[A] = kratedt
,t  t
ln[ A ] A
A, t  0   k Dt
[A]t= [A]0 e-kt
Some time vs conc. data
Hr
Conc [A]
Ln[A]
0
2.718
1
0.3
2.117
0.75
0.6
1.649
0.50
0.9
1.284
0.25
1.2
1.000
0.00
1.5
0.779
-0.25
A plot of the ln[conc] vs. time for a
1st order reaction gives a straight line with
a slope of the 1st order rate constant.
1st order plot
1.2
1
0.8
ln[A]
0.6
0.4
0.2
0
-0.2
0
0.5
1
-0.4
time in hours
1.5
2
ln [A]/[A]o=-k t1/2 ; ln2 /k =t1/2
2nd order reactions
A + B  products
dA/dt = k2nd [A][B]
If B is constant
kpseudo 1st = k2nd [B]
kpseudo 1st = k2nd [B]
ln2 /k =t1/2
1. constant OH radicals
in the atmosphere
kpseudo 1st = k2nd [OH.]
7. Stratospheric o3
The Stratosphere begins about 10k above the surface of
the earth and goes up to 50k The main gases in the
stratosphere, as at the surface, are oxygen and nitrogen
uv light of low wave lengths ( high energy) split molecular
oxygen (O2 )
to split oxygen
O2  O. + O.
requires 495 kJ mole-1 of heat (enthalpy)
What wave length of light can do this??
Let’s start with hn = E, where h is Planck’s constant and
n is the frequency of light and E is the energy associated
with one photon.
And, n l = c where c is the speed of light and
l is the wave length of light
Combining we can solve for the wave length
that will break apart oxygen at an enthalpy of
495,000 J mole-1
l= h c/ E
If the value of Planck’s constant is
6.62  10-34 joules sec
c = 2.9979 x108 m sec-1
l= h c/ E = 241 nm
can you verify this calculation? Hint energy E
is for one photon??
Paul Crutzen in 1970 showed that NO and NO2
react catalytically with O3 and can potentially
remove it from the stratosphere.
(he get’s a nobel prize for this in 1995)
NO + O3 NO2 + O2
NO2 + O. -> NO + 2O2
So where would NO come from?? SST’s
CCl3F + uv  Cl. + .CCl2F
but the free chlorine atom can react with O3
Cl. + O3  ClO. (chlorine oxides) +
O2
what is really bad is that
ClO. + O.  Cl. + O2
Remember that:
O.+ O2  O3
(Ozone)
It is estimated that one molecule of chlorine can
degrade over 100,000 molecules of ozone before it is
removed from the stratosphere or becomes part of an
inactive compound.
Molina found in 1985 that HCl could be stored on
the surface of small nitric acid particles in polar
stratospheric clouds (PSC).
The HCl then just had to wait for a
ClO-NO2 to hit the particle
particle

Cl2
Cl2 + uv Cl. + Cl.
These nitric acid particles form under extremely
low temperatures in polar stratospheric clouds
HCl
ClO-NO2
Cl2
8. What are aerosols?
• Aerosols are simply airborne particles
• They can be solids or liquids or both
• They can be generated from some of
the following sources:
1. combustion emissions
2. atmospheric reactions
3. re-entrainment
Cooking stir-fried
vegetables: Kamens
house, 1987, EAA data
Anthropogenic sources
Primary aerosol
Industrial particles
soot
forest fires
100x 1012 g/year
20
80
Secondary aerosols
sulfates from SO2
organic condensates
nitrates from NOx
sum of Anthropogenic
140
10
36
390 x1012g/year
sum of natural sources
3070 x1012g/year
What are some of the terms
used to describe aerosols?
• Diameters are usually used to describe
aerosol sizes, but aerosols have
different shapes.
Often particles are sized by
their aerodynamic diameter
• The aerodynamic diameter of a particle is
defined as the diameter of an equivalent
spherical particle (of unit density)
which has the same settling velocity.
• It is possible to calculate the settling
velocity of a spherical particle with a
density =1
Fresh wood soot in outdoor chambers (0.5
mm scale
Gas Particle Partitioning
toxic gas
particle
Langmuirian Adsorption (1918)
gas
surface
 = fraction of total sites occupied
• Rateon= kon (Pg) (1- );
• Rateoff= koff ;
• kon/koff= Keq
•
Langmuirian Isotherm
•

K eq Cgas
1 K eq Cgas
• if Keq Cgas<< 1;  = Keq Cgas
Yamasaki et al.(1982)
• Langmuirian adsorption
•
[gas]
Ky 
[part ] / TSP
• Assumes total # sites  TSP (particle conc)
• log Ky = -a(1/T)+ b
Yamasaki (1982)
• Collects Hi-vol filters+PUF
• Analyzes for PAHs
filter
BaA
log Ky
PUF
1/Tx1000
OH
Partitioning & uptake
by the lungs
CH (CH ) CH
CH(CH3)2
3
2 18
3
eicosane
2-isopropylphenol
• Nicotine
CH3(CH2)14COOH
palmitic acid
(Pankow’s
group)
benz[a]anthracene
N
Cl
Cl
CH3
N
Nicotine
PCBs
Killer Particles
Mortality vs. particle exposure
1.3
1.2
mortality
1.1
ratio
1.0
10
20
30
40
2.5 mm particle conc. in mg/m3
• On a mass basis urban fine particles may
be more toxic than cigarette smoke
Samet et al. at UNC exposed human
airway epithelial cells to residual oil
fly ash (ROFA) particles
• cells secreted prostaglandins
• Prostaglandins are a class of potent
inflammatory mediators which play a
role in inflammatory, immune and
functional responses in the lung