Air Pollution

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 on1) their concentrations 2) relative toxicity3) 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

Introduction to Air pollution

Carbon Monoxide• 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)

CO Lean Burn Engine-

14/15:1 Catalytic Converters

◦ 2CO2 (g) + O2 -> 2CO2 (g) ◦ 2CO (g) + 2NO (g) ->

2CO2 (g) + N2 (g) Thermal Exhaust

Reactor

Nitrogen Oxide• 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 motor vehicles• 30% from power stations that use coal and oil• 20% from the industrial burning of fossil fuels• 10% from other sources

NO 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 Oxide• 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)

Sulfur Oxide

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

Harm1) Affect the respiratory system2) Can act as catalyst to provoke the productions of secondary pollutants

Particulates 1

Natural Sources 1) Dust from mechanical break-

up of solid matter2) Sulfur from volcanic eruptions3) pollen, bacterial, and fungal

species Anthropogenic Sources

1) Soot from the incomplete combustion of hydrocarbon

2) Arsenic from insecticides3) Fly ash from the combustion of

fossil fuels

Particulates 2

Particulates

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 Sources1) Terpenes: unsaturated hydrocarbons given out by plants (2-methylbuta-1,3-diene units) Anthropogenic Sources1) Unburned petroleum2) Solvents

Volatile Organic Compounds

Volatile Organic Compounds

Same as CO◦ Oxidation Catalytic

converter◦ Thermal Exhaust Reactors

~THE END~

Acid DepositionBy: Adam Blumenthal

Michael Gropper

Acid Deposition

Process by which acidic particles, gases and precipitation leave the atmosphere.◦ General term

Wet Deposition ◦ Rain, fog, snow, or any

other precipitation Dry Deposition

◦ Acidic gases or other particles

Caused by sulfur and nitrogen oxides

Acid Rain

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

Sulfuric Acid

Process◦ Sulfur dioxide is

oxidized to sulfur trioxide

◦ Sulfur trioxide dissolves in water

◦ Water falls, panic Aerosols have

catalytic effect

Nitrous Acid and Nitric Acid

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

What is the Greenhouse effect? 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.

What is the Greenhouse Effect? 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.

Greenhouse Gases 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

Greenhouse Gases

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

How Greenhouse Factor, and the Abundance of the Substance in the air effects Global Warming Gas Main Source Greenhouse Fa

ctorRelative 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

SF6 Used as an insulator in the electrical

industry

22,000 very low 0.05

Global Warming 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.

Influences of greenhouse gases on the atmosphere

CO2 levels as well as temperature has increased since the 19th century.

Greenhouse EffectEric You

Salome Mathews

Influences of greenhouse gases on the atmosphere

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

Influence of Particles on the Earth’s Surface

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.

Ozone Depletion Katy

Sharon

What is Ozone?

O3 protects earth from UV radiation Oxygen to oxygen bond weaker than in O2

Natural Formation of Ozone in Stratosphere 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

Depletion of Ozone 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

Impact of Ozone Depletion Ozone protects Earth UV Radiation

◦ Skin Cancer◦ Cataracts and Blindness◦ Inhibits growth and photosynthesis ◦ Damage to Ocean Life

Zooplankton and phytoplankton die

Alternatives to CFCs for the future 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

Dissolved Oxygen in Water

Lena and Patrick

Vocabulary Words Dissolved oxygen

◦ Oxygen that has been dissolved in water; necessarily for aquatic life

Biological Oxygen Demand (BOD)◦ 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)

Winkler Method◦ Method of measuring BOD (explained on next slide)

Eutrophication◦ Excessive addition of nutrients (implications explained later)

Thermal pollution◦ Pollution caused by using water as a coolant in plants

BOD and the Winkler Method 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 non-polarity 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

re-oxygenize 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 Value Table

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

Worked Example 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.

Example contd.a) Calculate how many moles of Na2S2O3(aq) reacted

with the iodine in reaction (III).b) Deduce how many moles of iodine had been

produced in reaction (II).c) Deduce how many moles of MnO2(s) had been

produced in reaction (I).d) Deduce how many moles of O2(g) were present in

the water.e) Calculate the solubility of oxygen in the water in g

dm-3

f) Assume the maximum solubility of the water is 0.009 g dm-3 and deduce the BOD of the water sample.

Solution

a) Amount of Na2S2O3(aq) = 5.00 x 0.0500/1000 = 2.50 x 10-4 moles

b) Amount of I2(aq) = 0.5(2.50 x 10-4 moles) = 1.25 x 10-4 moles

c) Amount of MnO2(s) = 1.25 x 10-4 moles

d) Amount of O2(g) = 0.5(1.25 x 10-4 moles) = 0.0000625 moles

e) Amount of O2(g) in 1 dm3 = 1.25 x 10-4 moles

Mass in 1 dm3 = 0.004 g dm-3

f) Oxygen used by bacteria (BOD) = 0.009 – 0.004 g dm-3 = 0.005 g dm-3

Aerobic and Anaerobic Decomposition

Organic compound can be reduced instead of oxidized, creating different decay products

Used as a sign of oxygen content

Aerobic and Anaerobic Decay Products

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

Eutrophication 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

Thermal Pollution 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

Exercises14. A stream contains 20 ppm by mass of an organic

material which can be represented by C6H12O6.a) Calculate the mass of organic matter that is dissolved in 1 dm3

of the water.b) Deduce the mass of oxygen needed to oxidize this organic

matter.c) Explain the presence of reduced products such as methane in

the water.

16. 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) Temperatureb) Organic pollutantsc) Nitrates and phosphates

Water TreatmentBy: Flora Kim and Alex Kim

Primary Pollutants 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 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 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 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.

Waste-Water treatment 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

Primary Method 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 Method 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 MethodTertiary 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.

Tertiary Method (cont.) 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 and ozone treatment

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

E.7 SoilNeal Bhavnani and Lara Tucci

Introduction 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 Soil degradation- when human activity

(directly or indirectly) reduces the capacity of the soil to support life

Causes Forms Effects

Salinization Type of soil degradation Cause Effects Treatment

Nutrient Depletion Another type of soil degradation Cause Effects Treatment

◦ Legumes◦ Artificial fertilizer

Soil Pollution Another type of soil degradation Causes Effects

Soil Organic Matter (SOM)

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

SOM Continued

Organic Soil Pollutants

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: Waste

With a big o themeBy: Hunter Burch and Lisa Liu

Environmental

chemistry is cool. You

better learn, fool!

Waste

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)

Waste disposal

Simplest solution: open dumping 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!

Waste disposal methods

Landfill

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

Landfill (Cont.)

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

Incineration 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

Recycling

Recycling

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

metals

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

I bet you didn’t know that Big O is

made of alloys!

Glass

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

Plastics 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 of recycling

plastics Mixture is weaker, degradation

of quality, extra cost of sorting

Paper

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

Nuclear waste

Nuclear waste

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

Storage and disposal of nuclear waste 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!