Class objectives:

1
Class objectives

• Cover some of the major topics in Environmental
  Chemistry
• Energy
• Atmospheric Compartment
• Water compartment
• Soil

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1. Some examples of environmental chemicals

• Polynuclear Aromatic HC (PAHs)
• Dioxins
• Ketones
• PCBs
• CFCs
• DDT
• O3, NO2, aerosols, SO2

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Toxic loads

• Scientists have hypothesized that the fetus is
  sharing the mothers toxic load, and may actually
  provide some protection to the mother by reducing
  her internal exposure.

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• 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.

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• Firstborns from dolphins off the coast of Florida
  usually die before they separate from their
  mothers

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Mothers 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 dont seem to produce
  enough antibodies for childhood vaccinations to
  take.

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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.

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2. Energy
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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 f x d 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 D
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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 2xs
the 1980 rate after 1990 3x we estimated 50
to 80 years We used more recent data in class.
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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.) requires494 kJ/mol
• When when water forms, however, we get energy
  back from the formation of H2O because new bonds
  are formed. Which ones??

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Combustion energies from different fuels (kJ)
react. per per per moles heat mole mole gram
CO2 per kJ O2 fuel fuel 1000kJ hydrogen 482
482 241 120 02H2O2? 2H2O Gas 810 405
810 52 1.2CH4 2O2?CO2 2H2O Petroleum 12
20 407 610 44 1.6 2 (-CH2-) 3O2?2CO2
2H2O Coal 2046 409 512 39 2.04 (-CH-)
5O2?4CO2 2H2O Ethanol 1257 419 1257 27
1.6 C2H5OH 3O2?2CO2 3H2O wood 447 447
447 15 2.2(-CHOH-) O2?CO2 2H2O
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3. Basic concepts

• Where does pVnRT come from?
• At standard state can you calculate R?
• AB? CDln Keq -DH/R x 1/T const.

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4. The atmospheric compartment
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Two important features the atmosphericCompartme
nt aretemperature and pressure
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Why does the temperature normally decrease with
height in the troposphere and increase with
height in the stratosphere??
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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

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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 lt 1/3 of the air

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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

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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

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• 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

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• 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

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• 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

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5. What is Global Warming and how can it Change
the Climate?
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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??

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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

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1979 perennial Ice coverage Nat. Geographic, Sept
2004)
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2003 perennial Ice coverage
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Doubling Emissions of CO2

• Often discussed are the effects of doubling CO2
  concentrations from pre-industrial times
  (2xpre-Ind. CO2550 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.

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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

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red 2oC, yellow 3 oC, blue 10C
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red 2oC, yellow 3 oC, blue 10C
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6. Kinetics   1st order reactions
A ---gt B   -d A /dt krate A   - d
A/A kratedt     At
A0 e-kt
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Some time vs conc. data
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A plot of the lnconc vs. time for a 1st order
reaction gives a straight line with a slope of
the 1st order rate constant.
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ln A/Ao-k t1/2 ln2 /k t1/2
2nd order reactions A B ? products dA/dt k2nd
AB If B is constant kpseudo 1st k2nd
B
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kpseudo 1st k2nd B ln2 /k t1/2 1. constant
OH radicals in the atmosphere kpseudo 1st k2nd
OH.
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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??   Lets start with hn E, where h is
Plancks constant and n is the frequency of light
and E is the energy associated with one photon.
 
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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 Plancks 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??  
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  Paul Crutzen in 1970 showed that NO and NO2
react catalytically with O3 and can potentially
remove it from the stratosphere.(he gets a
nobel prize for this in 1995)   NO O3 ?NO2
O2 NO2 O. -gt NO 2O2   So where
would NO come from?? SSTs  
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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.  
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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
ClO-NO2
HCl
Cl2
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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

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Cooking stir-fried vegetables Kamens house,
1987, EAA data
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• Anthropogenic sources
• Primary aerosolIndustrial particles 100x
  1012 g/yearsoot 20forest fires
  80
• Secondary aerosolssulfates from SO2
  140organic condensates 10nitrates
  from NOx 36
• sum of Anthropogenic 390 x1012g/year
• sum of natural sources 3070 x1012g/year

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What are some of the terms used to describe
aerosols?

• Diameters are usually used to describe aerosol
  sizes, but aerosols have different shapes.

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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

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Fresh wood soot in outdoor chambers (0.5 mm scale
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Gas Particle Partitioning
toxic gas
particle
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Langmuirian Adsorption (1918)

• gas
• surface
• ? fraction of total sites occupied
• Rateon kon (Pg) (1-? )
• Rateoff koff ?
• kon/koff Keq

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Langmuirian Isotherm

• if Keq Cgasltlt 1 ?? Keq Cgas

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Yamasaki et al.(1982)

• Langmuirian adsorption
• Assumes total sites ? TSP (particle conc)
• log Ky -a(1/T) b

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Yamasaki (1982)

• Collects Hi-vol filtersPUF
• Analyzes for PAHs

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Partitioning uptake by the lungs

• Nicotine (Pankows group)

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Killer Particles
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Mortality vs. particle exposure
1.3
1.2
mortality ratio
1.1
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

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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