Transcript Air Pollution - AglanChemistry



1)
2)
3)
Pollutant: a substance that has a harmful
effect on the environment when present at
greater concentration than its natural level
Effect of air pollutants depends on
their concentrations
relative toxicity
Average length of time they remain in the environment
before becoming harmless
Primary Pollutant: emitted directly to the
atmosphere
 Secondary Pollutant:
produced when primary
pollutants undergo chemical
change in the atmosphere

• Carbon monoxide is harmful because, once absorbed
through the lungs, it binds to hemoglobin (Hb) in red
blood cells and hinders the transportation of oxygen in the
body. Effects can range from dizziness at low
concentrations to fatality at high concentrations.
Hb + CO ↔ COHb
hemoglobin
carboxyhemoglobin
• Sources:
– Incomplete combustion of fossil fuels and forest fires in
the presence of limited oxygen (ex. Coal, below)
2C(s) + O2(g) ↔ 2CO(g)
– Internal combustion engines
– Decomposition of organic matter
2CH4(g) + 3O2 → 2CO(g) + 4H2O(l)


Lean Burn Engine14/15:1
Catalytic Converters
◦ 2CO2 (g) + O2 -> 2CO2 (g)
◦ 2CO (g) + 2NO (g) -> 2CO2
(g) + N2 (g)

Thermal Exhaust
Reactor
• Nitrogen monoxide (NO), nitrogen dioxide (NO2), and
dinitrogen oxide (N2O) are the main pollutants. They react
with hydrocarbons to form smog and nitric acid which
contributes to acid rain. Nitrogen dioxide, the most toxic,
causes irritation of the nose and eyes and respiratory
problems.
• Sources:
– Natural sources:
• Decomposition of nitrogen-containing
compounds
• Lightning storms
N2(g) + O2(g) → 2NO(g)
lightning
(this reaction also works under high
temperatures, especially in automobile engines)
– Anthropogenic sources:
•
•
•
•
40% from
30% from
20% from
10% from
motor vehicles
power stations that use coal and oil
the industrial burning of fossil fuels
other sources

High fuel content – low
NO, high CO
◦ Lean Burn Engine – 18:1


Catalytic Converters
Exhaust Gas Recirculation
◦ Recirculates exhaust gases
back into the engine
• Sulfur dioxide (SO2), (primary pollutant)
– Sulfur dioxide is produced naturally from volcanoes and decomposing
vegetables
• Oxidation of hydrogen sulfide:
2H2S(g) +3O2(g) → 2SO2(g) + 2H2O(l)
– Anthropogenic sources:
• Burning of sulfur-containing fossil fuels
• Smelting plants, oxidizing sulfide ores to metal oxides
Cu2(s) + 2O2(g) → 2CuO(s) + SO2(g)
• Sulfuric acid plants
• Sulfur trioxide (SO3), (secondary
pollutant)
– Sulfur trioxide is formed in the
atmosphere by the reaction between
sulfur dioxide and oxygen.
2SO2(g) +O2(g) → 2SO3(g)
– The product, sulfur trioxide, dissolves
in water to form sulfuric acid:
H20(l) + SO3(g) → H2SO4(aq)



SO2 and SO3
Pre-combustion
methods
Post-combustion
methods
◦ Alkaline Scrubbing
◦ Fluidized-bed
Combustion




Definition: Solid particulates of carbon or dust or
Liquid droplets of mist or fog suspended in the air
Diameter: 0.001 to 10 µm (Size of Particles: smaller =
more harmful)
Aerosol: gaseous suspension of very small particles of a
liquid that are formed by polar particulates attached to
water
Harm
1) Affect the respiratory system
2) Can act as catalyst to provoke
the productions of secondary
pollutants

Natural Sources
1) Dust from mechanical break-up
of solid matter
2) Sulfur from volcanic eruptions
3) pollen, bacterial, and fungal
species

Anthropogenic Sources
1) Soot from the incomplete
combustion of hydrocarbon
2) Arsenic from insecticides
3) Fly ash from the combustion of
fossil fuels

Gravity.
◦ Settling Tanks


Electrostatic
Precipitation
Cyclone Separators
◦ Like a centrifuge




Can have director indirect effect on the air
quality
Direct Effect: extended exposure can lead to
cancer
Indirect Effect: hydrocarbons form secondary
pollutants and photochemical smog
Natural Sources
1) Terpenes: unsaturated hydrocarbons given
out by plants (2-methylbuta-1,3-diene units)

Anthropogenic Sources
1) Unburned petroleum
2) Solvents

Same as CO
◦ Oxidation Catalytic
converter
◦ Thermal Exhaust Reactors
By: Adam Blumenthal
Michael Gropper

Process by which
acidic particles,
gases and
precipitation leave
the atmosphere.
◦ General term

Wet Deposition

Dry Deposition

Caused by sulfur
and nitrogen oxides
◦ Rain, fog, snow, or any
other precipitation
◦ Acidic gases or other
particles

Rain water is naturally
acidic because of
carbonic acid
◦ Standard is 5.5-6.0 pH

Must drop below
certain pH to be acid
rain
◦ pH<5.6

Caused by compounds
of Ammonium, Carbon,
Nitrogen, or Sulfur

Process
◦ Sulfur dioxide is
oxidized to sulfur
trioxide
◦ Sulfur trioxide
dissolves in water
◦ Water falls, panic

Aerosols have
catalytic effect

Process
◦ NO is made by internal
combustion engines
◦ Oxidizes to nitrogen
dioxide
◦ Nitrogen dioxide dissolves
in water
◦ Nitrous and nitric acids
form in solution

Alternate pathway
◦ direct oxidation from
nitrogen dioxide to nitric
acid

A process which
involves
◦ Some solar radiation
replicates back into
space while others are
absorbed by gases in
the atmosphere
◦ The radiation that
passes through is
radiated by the Earth’s
surface as infrared
radiation back into
space.
 However, the CO2 and
water vapor in the lower
atmosphere absorb
much of the radiation.


Some radiation absorbed
by CO2 and water vapor
is reflected back to the
Earth’s surface which is
then re-radiated back
into space.
This is the natural
process known as the
Greenhouse Effect
because the energy is
trapped in the
atmosphere in the same
way light energy is
trapped inside a
greenhouse.


Gases with covalent bonds vibrate at a natural
frequency. When the infrared radiation is
absorbed by the molecule, the bonds within
the molecule vibrate at a higher frequency.
The increased frequency makes the air radiate
heat which in turn makes the air warmer.
While the greenhouse effect occurs naturally,
human activities are escalating its effects.
◦ For example, the amounts of carbon dioxide made
from burning fossil fuels have increased over the
last 150 years.
◦ Mauna Loa


Non-polar diatomic
gases like O2 and N2
aren’t greenhouse gases
because they do not
absorb radiation.
Greenhouse factor: ability
of a gas to absorb infrared
radiation. It compares the
ability of a substance to
absorb infrared to carbon
dioxide
Gas
Main Source
Greenhouse Fa
ctor
Relative
Abundance - %
Overall
Contribution to
increased global
warming %
Water ( H2O)
Evaporation of oceans
and lakes
0.1
0.10
-
CO2
Increased levels
owing to combustion
of fossil fuels and
biomass
1
0.036
50
CH4
Anaerobic decay of
organic matter;
increased levels
caused by intensive
farming
30
0.0017
18
CFCs (e.g.
CCl2F2)
Refrigerants,
pollutants, foaming
agents, solvents
~20,000
~0.00001
14
Ozone (O3)
Secondary pollutants
in photochemical
smog
2000
0.000004
12
N2O
Increased levels
owing to artificial
fertilizers and
combustion of
biomass
160
0.0003
6

Carbon dioxide
affects the average
temperature.
Carbon dioxide
contributes to 50%
of global warming.
Because amounts of
CO2 have increased
over the ages, so
has global
warming.

CO2 levels as well as temperature has
increased since the 19th century.
Eric You
Salome Mathews

It has been suggested that
the CO2 levels will double in
100 years. This means that
the temperature of the Earth
will rise 2⁰C in 50 years
◦ Changes in agriculture and
biodistribution as the climate
changes
◦ Rising sea-levels owing to the
thermal expansion and the
melting of polar ice caps and
glaciers

Particles like those that
come from volcanic
activity can lower the
temperature of the Earth
because it scatters light.
This means that less
radiation reaches the
Earth. This is exactly
what happened during
the 1960s.
Katy
Sharon


O3 protects earth from UV radiation
Oxygen to oxygen bond weaker than in O2


Stratosphere: where the temperature rises
because of ultraviolet radiation absorption
Chapman Cycle
◦ O2 → 2 O·
 High Energy UV
◦ O2 + O· → O3
 Lower
◦ O3 + O· D 2 O2
 Slow
◦ Exothermic

Steady State

Decreasing
◦ North and South Poles

Nitrogen Oxides
◦ N O· + O3 (g) → N O2· + O2 (g)
◦ N O2· + O (g) → N O· + O2 (g)

Chlorofluorocarbons (CFCs)
◦ Aerosols, refrigerants, solvents, foaming agents,
and plastics
 Can produce chlorine free radicals
◦ CFCs = greenhouse gases

Ozone protects Earth UV Radiation
◦
◦
◦
◦
Skin Cancer
Cataracts and Blindness
Inhibits growth and photosynthesis
Damage to Ocean Life
 Zooplankton and phytoplankton die


Montreal Protocol 1987
Alternatives
◦ Propane and 2-methylpropane refrigerant
coolants
 Decompose less easily because C-H bond is
stronger than C-Cl bond
◦ Fluorocarbons
 Strong C-F bond, doesn’t catalyze ozone depletion,
and no flammable
◦ Hydrochloroflurocarbons
 Most molecules are destroyed in the lower
atmosphere
◦ Hydrofluorocarbons=best alternative
 Doesn’t contain any chlorine atoms, not flammable

ALL GREENHOUSE GASES
Lena and Patrick

Dissolved oxygen

Biological Oxygen Demand (BOD)

Winkler Method

Eutrophication

Thermal pollution
◦ Oxygen that has been dissolved in water; necessarily for
aquatic life
◦ Amount of oxygen (in ppm) needed by bacteria to
decompose the organic matter aerobically in a fixed volume
of water over a set period of time (usually five days)
◦ Method of measuring BOD (explained on next slide)
◦ Excessive addition of nutrients (implications explained
later)
◦ Pollution caused by using water as a coolant in plants

Aquatic life needs oxygen to live
◦ Dissolved oxygen content must be above 0.003 g dm-3
(maximum solubility is 0.009 g dm-3 due to the nonpolarity of the oxygen molecule in the polar water)

Freshwater life cannot survive when the BOD is
greater than the oxygen content
◦ A greater problem in stagnant water, which cannot reoxygenize quickly as a moving body of water can

Winkler method measures BOD by saturating
water and titrating it after five days with a redox
reaction
BOD/ppm
Quality of Water
<1
Almost pure water
5
Doubtful purity
10
Unacceptable quality
100 to 400
Waste from untreated sewage
100 to 10 000
Waste water from meat-processing
plant


A 500 cm3 sample of water was saturated
with oxygen and left for five days. The final
oxygen content was measured using the
following sequence of reactions:
It was found that 5.00 cm3 of a 0.0500 mol
dm-3 solution of Na2S2O3(aq) was required to
react with the iodine produced.
a)
b)
c)
d)
e)
f)
Calculate how many moles of Na2S2O3(aq)
reacted with the iodine in reaction (III).
Deduce how many moles of iodine had been
produced in reaction (II).
Deduce how many moles of MnO2(s) had been
produced in reaction (I).
Deduce how many moles of O2(g) were present
in the water.
Calculate the solubility of oxygen in the water in
g dm-3
Assume the maximum solubility of the water is
0.009 g dm-3 and deduce the BOD of the water
sample.
a)
b)
c)
d)
e)
f)
Amount of Na2S2O3(aq) = 5.00 x 0.0500/1000 =
2.50 x 10-4 moles
Amount of I2(aq) = 0.5(2.50 x 10-4 moles) =
1.25 x 10-4 moles
Amount of MnO2(s) = 1.25 x 10-4 moles
Amount of O2(g) = 0.5(1.25 x 10-4 moles) =
0.0000625 moles
Amount of O2(g) in 1 dm3 = 1.25 x 10-4 moles
Mass in 1 dm3 = 0.004 g dm-3
Oxygen used by bacteria (BOD) = 0.009 – 0.004
g dm-3 = 0.005 g dm-3


Organic compound
can be reduced
instead of oxidized,
creating different
decay products
Used as a sign of
oxygen content
Element
Aerobic Decay Product
Anaerobic Decay
Product
Carbon
CO2
CH4
Hydrogen
H2O
CH4, NH3, H2S and H2O
Oxygen
H2O
H2O
Nitrogen
NO3-
NH3 and amines
Sulfur
SO42-
H2S
Phosphorus
PO43-
PH3

Nutrients such as phosphates and nitrates
added to the water
◦
◦
◦
◦
◦

Promote excess algae growth
Algae then dies due to lack of available oxygen
Decay leads to further decay and anaerobic bacteria
Produces chemicals that poison the water
Process continues until there is no life in the water
Main contributors
◦ Artificial fertilizers, detergents, and acid rain


Does not add any substances to the water
When the water is heated, the solubility of the
oxygen decreases
◦ Thus less oxygen in the water, which upsets
organisms and their life cycles
 Fish eggs
14.
A stream contains 20 ppm by mass of an organic
material which can be represented by C6H12O6.
a)
b)
c)
16.
Calculate the mass of organic matter that is dissolved in
1 dm3 of the water.
Deduce the mass of oxygen needed to oxidize this
organic matter.
Explain the presence of reduced products such as
methane in the water.
In order to survive, fish require water containing
dissolved oxygen. Discuss briefly how an increase in
each of the following factors affects the amount of
dissolved oxygen in a lake.
a)
b)
c)
Temperature
Organic pollutants
Nitrates and phosphates
By: Flora Kim and Alex Kim





Methaemoglobin: Methaemoglobin is an
oxidized form of hemoglobin, and it is not
able to transport oxygen. Ex. Blue Baby
Syndrome
Heavy Metals: Mercury, Lead, Cadmium
Pesticides: DDT
Dioxins: Very toxic chemical
Polychlorinated biphenyls (PCBs): interferes
with nutrient transport




Heavy metals interfere with the behavior of necessary ions in
our body (Ca+2, Zn+2 Mg+2)
Mercury: comes from paints, batteries, and agriculture.
Mercury is considered most dangerous and damages nervous
system, causes depression, blindness, and insanity. Causes
reproductive systems in fish
Lead: comes from lead paint, glasses, pottery, and pipes.
Affects the digestive systems (Ex. Constipation and diarrhea)
Failure of kidneys, liver, and heart. Also some minor brain
damage. Lead is toxic to plants and domestic animals
Cadmium: Rechargeable batteries, pigments. Replaces Zn as
the primary enzyme, it causes Itai-Itai disease,which makes
bones brittle. Cadmium also causes lung and kidney cancer.
Toxic to fishes and produce birth defects in mice.



Pesticides include insecticides, which kill
insects, fungicides, which kill fungi, and
herbicides, which weeds. As they are
poisonous they can cause pollution problems
when they are washed off land into water.
DDT is an example of pesticide. DDT is used
to kill insects. DDT is no longer used by
industries.
Biological magnification: Accumulation of
toxic particles in DDT.



Dioxins is the general name for a range of
compounds whose framework consists of two
benzene rings connected via one or two
oxygen atoms.
Dioxins are added along with the
organochloro waste materials
Dioxins are present in fat and liver cells. They
deliver damages to heart and memory,
concentration abilities and severe depression.
Chloracne is an type of skin disease that
happens when the body is attempting to
remove the poison.




The purpose is to remove hazardous
materials, reduce BOD, kills microorganisms.
Primary Method: Physical
Secondary Method : biological and chemical
Tertiary Method : chemical, physical, and
biological




Water is filtered through to remove insoluble
solids, and remove floating objects such as
grease.
A sludge is removed when the water runs
through sedimentation tank.
A process called flocculation speeds up the
sedimentation process.
Large flocs are produced by the addition of
Aluminum sulfate and calcium hydroxide


Secondary sewage treatment involves
bacterial activity and requires aeration in
which large blowers are used to bubble air, or
air enriched with oxygen, through waste
water, mixed with bacteria-laden sludge.
Activated sludge process allows bacteria to
mix thoroughly with the sewage, to oxidize
and break down most of the organic process.
 Tertiary
Sewage treatment: Sewage treatment
treats water further to remove remaining
organic materials and toxic inorganic
materials.
 Precipitation:
Removes heavy metal such as
cadmium, lead, and mercury.
 Ion Exchange: The nitrates are all soluble and
so are more difficult to remove. Resins or
zeolites can be used to exchange the nitrate
ions in polluted water with hydroxide ions.
The ion exchange resin can also be used to
remove salt from sea water.



Biological methods: Anaerobic organisms
denitrifying bacteria turn the nitrogen in nitrates
back to atmospheric nitrogen.
Distillation: Distillation removes salt content
from sea water to make it able to drink.
Reverse osmosis: Osmosis is the movement of
water passing from a dilute to a concentrated
solution through a semi-permeable membrane.
Reverse Osmosis is the movement of water
passing from concentrated solution to dilute
solution if a pressure of 70atm osmotic pressure
is applied to the more concentrated salt solution.
Chlorine
Ozone
Effective against bacteria but not
against viruses
Effective against both bacteria and
viruses
Cheaper to produce
More expensive
Longer retention time
Shorter retention time
Can be easily liquefied and
shipped
Must be produced on the site
because of high reactivity
Can form toxic chloro-organic
compounds
Oxidized products are much less
toxic
Leaves a chemical taste behind
Leaves no chemical taste behind
Functions as strong oxidizing
agent
Functions as a strong oxidizing
agent
Neal Bhavnani and Lara Tucci





All plants and land organisms dependent for existence
◦ macronutrients
Formation
Content
◦ Inorganic and organic
Humus- decomposed organic matter important to soil
structure; important source of nutrients
Horizons- layer within the soil
Soil Component
Particle size (mm)
Gravel
2.000-60.000
Sand
.060-2.000
Silt
.006-.060
Clay
.002-.006




Soil degradation- when human activity
(directly or indirectly) reduces the capacity of
the soil to support life
Causes
Forms
Effects




Type of soil degradation
Cause
Effects
Treatment




Another type of soil degradation
Cause
Effects
Treatment
◦ Legumes
◦ Artificial fertilizer



Another type of soil degradation
Causes
Effects

Describes organic constituents of
soil:
◦ Plant and Animal Tissues (Leaves,
Twigs, Limbs, etc.)

Only accounts for about 5% of
mass
◦ Still determines productivity of soil


Made up of polysaccharides and
proteins, as well as sugars,
amino acids, and other
molecules.
Humus- Residue left after
decomposition of organic
material
◦ Effects of soil loosening:

Plants in good soil grow better.
Really, it’s true!!
Top Layer is Humus

RCOOH (humus) + K +(aq) <-> RCOOK (humus) + H + (aq)
◦ Reversible

Cation Exchange Capacity
(CEC)- lets humus act as time
release capsule, meaning
nutrients will be released as
needed
◦ Ex.: Potassium removal



Presence of weak organic acids
and salts in humus means… it
can be a natural… BUFFER!!!!
RCOOH (humus) + H2O(l)
RCOO- (humus) + H3O+ (aq)
Low pH and H3O+ concentration
is high= equilibrium 


Humus attracts organic
compounds w/ low solubility.
Several organic compounds
pollute the soil
◦ Remain in top layer of soil and
adsorbed by humus.








Petroleum Hydrocarbons
Agrichemicals
Volatile Organic Compounds
Solvents
Polyaromatic hydrocarbons
Polychlorinated Biphenyls
Organotin compounds
Semi-Volatile Organic
Compounds
Environmental
chemistry is
cool. You
better learn,
fool!
By: Hunter Burch and Lisa Liu
 Due
to increase in world
population, consumption,
anti-air and anti-water
pollution measures
 Nuclear waste: problem
 3.5 tons of solid
waste/man, woman, and
child each year (western
world)
 Simplest
dumping
solution: open
Inexpensive and
convenient, but causes air
and water pollution and
encourages health hazards
(rodents and insects)
 Waste
used to landfill
disused quarries
 Incineration
Greatly reduces bulk of
waste
But both of these
methods of waste
disposal create
environmental
damage!
 Disused
quarries or
natural pit
 Purpose: bury waste so
it is isolated from
groundwater, dry, and
not in contact w/ air
 Groundwater
monitored up to 30
years after closure
Landfill gas flare
 Leaching:
prevented by
lining the site w/
synthetic materials or
impermeable clay
 Organic matter-hard to
decompose
But w/ anaerobic bacteria
to produce methane
Methane collected and
used as fuel
Non-biodegradable
plastics: not broken down
by bacteria
 Burning
of waste, 800-
1000˚C
 CO2 produced; greenhouse
gas
 CO: incomplete combustion
of plastics; poisonous
 Combustion of PVC: HCl
produced causes acid rain
 Important to control temp.
to reduce production of
dioxins
A toxic compound that is
carcinogenic and teratogenic in
certain animals
 Materials
reused to no
waste produced
 Reduces
Use of raw materials
Energy costs
Level of pollutants
Need of land for waste
disposal
 Main
challenge:
separation and
purification of materials
I bet you didn’t
know that Big O
is made of
alloys!
 Recycling
metals saves
Earth’s reserves of the ores
and reduces energy costs
Aluminum cans
Steel from cars (use of
magnets)
 Separated
by difference in
density
 Recycled metals used as
alloys, reducing need to
purify completely
A solid solution of two
different elements in a metallic
matrix
 Easy
to recycle: can be
broken into small pieces
 Separation of colors
Crushed, melted, molded into
new products
 Reduces
energy costs &
cost of new materials
 Not degraded during
process; can be recycled
many times
 Pyrolysis
Decomposition at high
temperatures; absence of air
so no oxidation occurs
Fractional distillation to
separate products
 Thermoplastics
Plastics that can be melted
down and remolded
 Disadvantages
plastics
of recycling
Mixture is weaker,
degradation of quality, extra
cost of sorting
 Does
not decompose in
landfill sites
 Ink cleaned off & additives
released
 Repulped
separated into fibers
 Recycle
into white paper:
bleached w/ peroxides
 Disadvantages for recycling
paper
Degradation of quality and
strength, energy costs of
transporting paper to recycling
plant  low grade products
 Low
level and high level
waste
Low: treating patients and
research
Activity is low; short half life;
high volume
High: spent fuel rods for
power plants
Activity is high; long half life;
low volume
 Method
of disposal
depends on half life
time it takes for half of
sample to decay

Low level waste
◦ Stored in cooling
ponds b/c produces
heat energy
◦ Water cleansed in ion
exchange resin,
diluted, then released
to sea
◦ Alternate method:
steel containers in
concrete vaults

High level waste
◦ Transferred to deep
pools, then cooled by
water containing a
neutron absorber
◦ Cased in
ceramic/glass,
packed in metal
containers, buried
deep in Earth
Big O: It’s
showtime!