Elementary Environmental Chemistry
Environmental Modeling and Homeostasis - Ch. 1, p. 14, W-L textbook.
Visualizing, Aliff guide Ch. 1.
Homeostasis, that is maintaining a steady state, is a fundamental
concept for the understanding of
physiology and disease that can be applied to planet Earth. The "Gaia Hypothesis" assumes that the
earth is a living organism that maintains a steady state of atmospheric gases, temperature, and
geological materials. Balance of these factors is maintained by cause and effect cycles.
There are two types of homeostasis: negative feedback and positive feedback.
Negative feedback homeostasis produces a response or output opposite
to the input stimulus or stress. See figure 1. For instance, you go outside on a cold
January day in Canada without enough clothes on. Your skin and the blood in it are cooled,
the cooled blood flows to the brain, where the hypothalamic thermostat detects the change.
Then the thermostat send a command to constrict the skin's blood vessels, which in turn will
reduce heat loss. The central nervous system stimulates muscles to contract or shiver,
releasing heat. Notice that in negative feedback homeostasis, the sign, positive or
negative, is opposite for the input and output.
Negative feedback in environmental systems (ecosystems) is seen in the
when carbon dioxide increases in the atmosphere. More carbon dioxide encourages
more photosynthesis (see below) that uses up carbon dioxide. Also the formation of
carbonate and carboniferous (coal) rocks speeds up. Both photosynthesis and carbonate
rock formation will lower carbon dioxide. Over time the input, increased carbon dioxide,
is followed by an output, decreased carbon dioxide.
Positive feedback homeostasis is characterized by the same
sign in the input
and output and are many times related to disease processes, e.g., the
vicious cycle of high blood pressure and arteriosclerosis/hardening of the arteries by calcium deposits.
Arteriosclerosis make blood vessels less flexible and narrow. Arteries harden in response to high blood pressure.
High blood pressure, as chronically endured by uncontrolled sugar diabetes causes arteriosclerosis,
arteriosclerosis causes more high blood pressure, and so on in a vicious cycle. An increase in blood pressure causes
a further increase in blood pressure - this is positive feedback or an increase results in a further increase feedback cycle.
A positive feed back loop is usually destructive to the environment.
as the birth and survival rates of human populations increase, resources, such as farm lands,
are used up a greater rate. The feedback can be negative at this point, and starvation will
reduce population by negative homeostasis. This has been happening in Ethiopia, the Sudan
and Eritrea in Africa for many years. The farm area that supported an average family has
been reduced by more than 75%. But what if food is brought in from the outside?
This has had the effect of maintaining the high birth rates that led to the reduction
of farm land. Therefore, increased birth rate ----> increased resource loss ----> increased birth rate
is a positive feedback.
The two great unknowns in greenhouse
climate modeling are whether increased heat resulting in
increased evaporation will cause low clouds to form that decrease surface temperatures
(negative feedback) or high clouds that serve reflect heat back to the surface, e.g., Venus; positive feedback.
Compounded positive feedback due to population increase:
Increasing human population
leads to more burning of fossil fuels and wood (see combustion below), which leads to more
carbon dioxide in the atmosphere, which leads to more heat being trapped in the atmosphere and
global warming and more acid rain. Meanwhile the economic benefits of the use of combustion
allow for a higher number of human beings to be supported which increases demand for
fossil fuels, more carbon dioxide added to the atmosphere. The latter will be explained
further as you read.
Every student of a science or to achieve good citizenship should have
a basic knowledge of chemistry.
Most of the issues that we will deal with in W-b 4th ed. and this study guide depend on understanding
cycles of chemical changes and the energy that accompanies these cycles.
Matter occupies space or volume and
has mass - the latter we call weight where gravity pulls the mass
toward the center of the earth.
Matter is constructed of tiny units called atoms, indivisible by chemical
means. Although the ancient Greeks first
coined the term, they thought were were only four types of elements, Earth, air, fire and water. Men had
more fire and women had more water. In the 19th century Roentgen discovered X-rays, Rutherford
discovered protons, and Thomson described electrons. In the 1930s, Chadwick proved the existence
of neutrons predicted by Rutherford and it was discovered that atoms could be split, according to
Einstein's theory, to release a large amount of energy. When large atoms were split (nuclear fission)
by Hahn and Strassmann, smaller atoms and subatomic particles were produced.
Matter is composed of what is currently recognized as 103 different
kinds of naturally occurring elements
with different numbers of protons, neutrons and electrons. See www.webelements.com
Atoms are the building blocks of matter, the smallest units of matter indivisible by chemical means.
Atomic mass is the weight (on Earth) of all the subatomic particles of a given atom.
Atomic mas number is the number of protons and neutrons added
together. The number of neutrons
may be calculated by subtracting the atomic number from the atomic mass number.
Atomic number is the number of protons in the nucleus of a given
atom: it is always equal to the number of
electrons orbiting at near the speed of light around the atomic nucleus in an unreacted atom.
Elements are substances composed of like atoms, e.g., aluminum foil.
Molecules are composed of two or more atoms, H2 is
a diatomic or homoatomic molecule, but also units of the
element Hydrogen (H). NaCl, sodium chloride or table salt, is a heteroatomic molecule.
Molecular weight is the sum of the atomic weights of all the
atoms in a molecule;
e.g., H2O, water, 2 H (1) + O (16) = 18. What is the molecular weight of octane,
one of the gasoline mixture of molecules, C8H18?
A Mole is a standard unit of measurement for the qualities of
reactants and products of a chemical reaction.
If one carefully measures out the molecular weight of a compound, one will have almost exactly
6.023 x 1023 particles - a very large number! Concentration in chemistry uses molarity as a measure of concentration or the number
of moles of chemical per liter of solution. See acids, below.
Compounds are composed of like molecules, each of which has two
or more different kinds of
a. A true solution is a homogeneous mixture of a smaller amount of chemical,
the solute, with a larger amount of solvent; e.g.,
a teaspoon of pure salt mixed with a quart of water. If the solute particles are very small, kinetic energy
(see below) will keep them mixed up as long as the solvent amount does not decrease.
b. A suspension is composed of larger solute particles that will
settle out of mixture in left standing. However,
smoke, dust, and sulfur aerosols are suspended by moving air, and soil particles (silt) are suspended in
moving water, e.g., a muddy stream.
c. An emulsion is a mixture of oily substances and water. Sludge in automobile engines is an emulsion (not dirty engine oil as suggested in commercials).
d. A colloid consists or larger particles that scatter light. They
will settle out over a long time, e.g., old coffee left standing for weeks.
Atoms are composed of four larger particles and many smaller particles
that will not be discussed:
protons (positive in charge), neutrons (neutral), electrons
(negative in charge) that revolve around the atomic nucleus and their equal in mass but opposite in
charge positrons found in the nucleus.. One proton has a mass of about 1 dalton or atomic mass unit. The neutron is is also
approximately 1 dalton. Electrons and positrons are much smaller in size - about 1/1837 dalton.
The simplest atom and what astronomers regard as the "Building Block
of the Universe" is common
hydrogen, or protium. Hydrogen has three forms or isotopes that have the same number of
protons and electrons (1) but a different atomic mass.
The atomic mass is due to the addition of neutrons to the nucleus. See
below. Protium, atomic mass or weight of 1,
has 1 proton and one electron. There are two other, rarer, forms of Hydrogen: Deuterium
(mass = 2) and Tritium (mass = 3). All isotopes of hydrogen have one positive
proton and one negative electron. All unreacted or uncombined atoms have
# protons = # electrons to create a 0 electrical charge.
How many neutrons do Protium, Deuterium and Tritium have? What is the
difference between iodine-131 and I-127?
Carbon-12 and C-14? See the periodic table and webelements below. Atoms with more neutrons than the
most stable form (isotope of the atom) tend to be radioactive - they emit radiation and are called radioisotopes.
Atoms and Energy
Physicists theorized that hydrogen atoms
were being fused in the sun to release atomic energy,
the energy that holds atoms together. Hydrogen fusion (proton chain) powers the Sun:
= 11 H + 11 H + 11 H + 11 H yields -----> 24 He , Helium + radiation
The atomic number is to the left of the atomic symbol and the atomic weight to the right.
Einstein discovered that Mass (an amount of matter, on Earth designated
as weight) can be
converted to energy. Some mass is converted to radiant energy in a nuclear fusion reaction.
Since mass apparently disappeared, this was called the mass defect.
E = mc2
In a hydrogen bomb, deuterium and tritium are fused.
12 D + 13 T ----> Energy
+ 24 He + energy
According to chemists, physicists and astronomers, heavier atoms are cooked up in stars; e.g., carbon, iron,
nitrogen, sulfur, phosphorus, zinc, copper, etc. Since these atoms are in our tissues, the well known astronomer
Carl Sagan called us "Star Stuff."
Periodic Chart: Look up element #19 in the periodic
Here is #12 as an example.
Go to www.chemicalelements.com/show/electronconfig.html for electron configurations.
We will deal with small-medium size atoms. With the Periodic Chart link
or a general biology or chemistry book as an aid, you should be able to
draw Hydrogen (H), Helium (He); Sodium (Na); Chlorine (Cl); Carbon (C)
and Oxygen (O). Keep in mind that the first electron shell contains a maximum
of 2 electrons: the second 8: the third 18, etc. Notice that a vertical column in the periodic table has
elements with similar electron configurations in the outermost (chemical bonding) shell.
That similarity leads to similarities in the chemical properties of the atoms in a vertical
column, particularly in chemical bonding and ion formation. This will be explained as you read.
Mendeleev concluded that the properties of the smaller elements repeated
every eighth one, i.e., Li to Ne (row 2) and Na to Ar (row 3) - "The Rule of
Octets or Eights." A ramification is that after Helium, nonmetal atoms with
eight (8) electrons in their outermost shell are inert. That gives a clue to how atoms react to produce
compounds - they rearrange their electron configurations of their outer shells.
What is a more efficient lifting gas for a blimp, hydrogen or helium?
Why do the Goodyear blimps use helium instead of hydrogen?
Chemical Bonds and Molecules
The reason why atoms react or combine to form molecules is that, in
reacting, they reach a more
stable outer shell electron arrangement, 8, the magic number for atomic stability and lower
energy level. Which electrons have more energy? Those closer to the nucleus, or those farther away?
Which electrons do chemical bonding? The answer is the outermost electrons. Since the positive nucleus
pulls a negative electron towards it, the electron must have enough rotational or centrifugal energy to
continue to orbit the nucleus. Therefore, electrons further away from the nucleus have more energy
than those close in.
Chemical reactions are expressed in equation form. This is similar in
meaning to a recipe.
You take this and add that and make something new, e.g., baking powder + flour + leavening
make bread. When atoms react, they form chemical bonds.
|C , carbon in coal||O2 , oxygen||CO2|
Types of Chemical Reactions
Endergonic (endothermic) reactions store potential energy in
chemical bonds. The process
of photosynthesis makes food molecules that store energy this way by converting the
electromagnetic energy of the sun into chemical bond energy.
Exergonic (exothermic) reactions release energy, usually
the greatest part in heat (breaking
down glucose or ATP). When ATP breaks down to move muscle fibers, much heat is released.
This explains why shivering warms you up.
All Chemical Reactions need Activation Energy added to the
reactants in order to start a Reaction. Types of Activation Energy include these that are of interest for
a. Kinetic Energy - chemical reactions don't occur at a temperature of absolute zero
Anabolic reactions build larger units from smaller atoms or molecules, e.g., when simple sugars
are strung together to make a starch stored in plant roots. Catabolic reactions break larger
molecules into smaller ones, such as when digestion breaks down starches into simple sugars or
when gunpowder explodes.
The kinetic theory of matter also explains the process of diffusion.
Molecules tend to move
from an area of higher concentration to an are of lower concentration. Why? The molecules or atoms
(gas or liquid are good examples) move in straight lines and in random directions. Even solid
metal atoms have some movement. Why does metal expand when it is heated? When water
diffuses into the cells of plant roots, it is a special case of diffusion called osmosis.
Why is it easier to dissolve corn starch or table salt in warm water
rather than cold water? The salt ions
are moved into the solvent by water molecules that surround them. All particles move in straight lines
and random directions.
When atoms react to form molecules, then will try to achive stability
by exchanging or sharing electrons to fill
their outer shells. Atoms are bound closely together to form a molecule in two ways.
1. Ionic bond - If a sodium atom, Na gives away an electron to
a chlorine atom, Cl which keeps it,
notice that both atoms have 8 electrons in their outer shell.
Now, the reacted Na+ ion has a +1 electrical charge
because it lost one negative
electron and Cl- has an extra electron and has a -1 negative charge. Charged atoms, Na+, or groups
of atoms, NH4+ are called ions. Polyatomic ions have more than one atom, e.g., NH4+ , ammonium ion, or SO42, sulfate ion.
Positively charged ions are called cations: e.g., Na+, sodium ion;
Ca2+; Cu+ cuprous ion, calcium ion; Fe3+, ferric iron atom; NH4+ , ammonium ion.
Negatively charged ions are called anions: Cl-, chloride; F-, fluoride; SO42-, sulfate; and CO32-, carbonate.
What is the difference between fluorine gas and fluorine ion? A big
one. Fluorine ion has that extra electron
it wanted for stability. Now it has 8 in the outermost shell of electrons.
Atoms or polyatomic ions that are less oxidized are designated with
the -ous suffix, those that are
are more oxidized are named with the -ite and -ate suffixes.
Ionic bonds are formed when atoms give away or receive electrons.
When atoms lose electrons, an oxidation
results, if atoms gain electrons, they undergo reduction; e.g.,
Na0 ---> Na+ (+) 1e-(Oxidation of Na);
Cl0 + 1e- ----> Cl- (Reduction of Cl)
Consider this example, closer in meaning to the term oxidation.
Cao + O (one atom) -----> CaO, calcium
oxide. The Ca in CaO is now Ca++ ion, it lost two electrons.
The Oxygen went from 00 to 02-, it was reduced.
Or, when coal is combusted, the sulfur contaminating it is oxidized to make sulfur dioxide, an acid rain gas.
S + O2 ----> SO2
Nonmetals generally have 4-8 electrons in the outer shell.
Those with 4-7 hold on to their electrons and
generally "grab for more" when bonding with metal atoms. Those with eight, 2 for helium, are inert. Their electron
needs are satisfied because their outermost shell is full. Metals are weakly electronegative
atoms. That means they give up electrons readily; i.e., Metals generally have 1-3 electrons
in their outer shells.
The electron needs of atoms are stated as valence. If metal atom
like sodium gains
stability by giving away one electron, its valence is +1: it is stable because its underlying shell has 8 electrons.
The oxygen atom with 6 electrons in the outer most shell gains stability by receiving 2 electrons to fill its shell at 8.
Therfore, the valence of oxygen is -2.
Look at your periodic chart. Are Li, Na, K, Mg, Al and Au (gold) metals?
How about S, O, Cl and Ar. What are they, metals or nonmetals? _____ Hydrogen may
exist as a metal on the planet Jupiter when pressures are very high, 2000 times Earth atmospheric pressure or
where temperatures are near absolute zero (-273 Co).
|If you dissolve the ionic compound NaCl in water, Na+ and Cl - ions will float free and be surrounded by spheres of water molecules.|
|NaCl (in water) -----> Na + (+) Cl -|
Water solutions of ions are called electrolytes, essential
for the operation of muscle and
nerve cells, and equally important for conducting minerals like nitrates, phosphates,
potassium and calcium into plant roots.
2. Covalent bonds share electrons. Two electrons form a pair
and share an orbital path; there
are two shared electrons in one covalent bond represented with a dash .
The diatomic gas molecules are covalently bonded:
H-H or with electron dots (Lewis symbol), H . + H . -----> H : H
How many electrons does carbon have in its outermost shell? Notice all carbon atoms share 4 bonds (8e-), e.g., carbon dioxide,
O=C=O, O :: C :: O ; and nitrogen gas N = N, N ::: N
There are two kinds of covalent bonds:
Nonpolar Covalent bonds share electrons evenly by all atoms and
electrical changes are therefore evenly distributed, e.g., Methane, CH4
H -- C -- H
Polar Covalent bonds have at least one atom which is an electron
"bully," the highly
electronegative atom (usually Oxygen) has a greater share of the negatively charged electrons.
Because H--O--H is polar as a molecule, meaning that the Oxygen side
of the molecule has a
negative charge and the Hydrogen side has a positive charge. This characteristic helps water
dissolve NaCl or table salt.
O- Water Molecules stick to each other
/ \ with weak hydrogen bonds. The positive
+H H+ and negative ends of water molecules attract each other.
Water molecules stick to each other with weak hydrogen bonds of
electrical attraction.. The somewhat positive
and negative ends of water molecules draw them together, creating the surface tension that water
strider insects walk on. Hydrogen bonds may draw sections of large molecules together, e.g., protein
helixes and DNA double helixes.
Water as a substance.
What Are the Properties of Water?
Living organisms are mostly composed of water. We are approximately
76% water; jellyfish are over 90% water.
Life may have begun in water. Why is water so important to life existing on Earth.
Consider your engine. As the parts warm up, do they expand? Yes! The
designed to run when hot - the parts fit together best when it is hot. Even atoms in
solid metals move.
facts about water include:
2. To raise the temperature of 1 gram of water, 1 degree C, requires
1 calorie of energy (heat). Food calories are kilocalories or big calories, 1000 times more
than the standard small calorie.
3. To vaporize 1g of water at 100 degrees C requires an additional 540
calories (heat of vaporization) to break Hydrogen bonds. Water requires
a lot of energy input in order to boil (vaporize).
4. Water has a high specific heat (1 Calorie/1 degree C/1 gram)
means that it will store heat and thus it acts as a moderator of climate in
the summer. The Earth is also warmer in the Winter because oceans
release stored heat.
Explain why Bismarck, ND has more temperature extremes as compared
geographically to Seattle, WA? Look at a map or globe.
Why does water and oil separate? Oil is nonpolar covalently bonded,
water is polar.
The two repel each other. Also the density of oil (g/ml) is less that water, so the oil
rises to the top. The rule is "like dissolves like." Does water in your gas tank mix with
the gasoline (nonpolar)? No, it goes to the bottom of the tank and is more likely to cause
engine roughness if you are near empty. Do gasoline and motor oil mix? Yes, both are nonpolar.
You have a problem if your motor oil smells like gasoline.
8. When ice forms over a northern coniferous forest lake or in
the Arctic Ocean, the ice acts
as an insulator for the living organisms below. What would happen if ice were more dense
than liquid water when it freezes? Freezing water from the bottom would push all the fishes
up to be killed by the cold air.
10. Pure water is a poor conductor of electricity unless you dissolve
ions in it. The positive
and negative charges act as electrical poles, just like your car battery that has a positive pole
and a negative pole to conduct electrical current. Ions in solutions are called
electrolytes and are necessary for the operation of the nervous systems. Generally, covalent
compounds are poor conductors.
Which of the preceding characteristics of water can be explained by
its polar nature and
hydrogen bonding? Check out 1-7, above.
Major Water Soluble Plant Nutrients
|NUTRIENT||IONIC FORM||FUNCTION IN PLANTS|
|Nitrogen as nitrate (first number on a bag of general purpose fertilizer) and ammonia, NH3||NO3- (nitrate) and NH4+ ammonium||Very important for stem growth. Needed to make plant proteins, DNA (genetic chemical), RNA (gene copies) and ATP (energy chemical)|
|Phosphorus as phosphate (2nd number)||PO4-3 (phosphate)||Encourages root growth. Needed for DNA and ATP.|
|Potassium (3rd number)
in potash K2O
|K+||Important for retaining water inside cells. Ionic balance.|
|Calcium in limestone, CaCO3||Ca2+||Part of cell walls|
|Magnesium in dolomite, Mg CO3||Mg2+||Needed to make chlorophyll|
|Iron||Fe2+ (ferrous iron)||In photosynthesis and cellular respiration chemicals. Many shrubs need extra amounts.|
|Sulfur||SO42-||In proteins and vitamins|
|Molybdenum||MoO4- (a micronutrient)||Needed for rhizobia bacteria to do nitrogen fixation. See the Materials Cycling chapter.|
|Copper, Manganese, Zinc||Cu+, Mn2+ and Zn2+||In photosynthesis and cellular respiration enzymes.|
|Chloride||Cl-||Needed to make oxygen in photosynthesis. Balances cations in cells.|
The most important non-soluble material in soils is humus, an
amorphous, dark material
that results from the breakdown of plant debris and other organic detritus. It is very
important for holding water and mineral nutrients at root level. Folks add peat moss,
cow manure, "Nature's Helper" and other products to increase the humus content
of Georgia soils. Humus is low in southeastern clay soils because of a combination of high
year-round temperatures that increase microbiological action breaking down humus.
More importantly, high rainfall leaches the minerals into lower soil levels away from
Note: to keep things simple, we have not balanced the reactions that
follow by indicating the relative
amounts of reactants and products involved.
The general form of a chemical reaction:
Reactant A + Reactant B ------> Product C + Product D
For example, Acid (A) and Base (B) ------> Salt (C) and Water (D)
This is called a neutralization reaction as will be explained below, or more precisely,
HCl + NaOH ------> NaCl + H2O
hydrogen chloride (in water, this is called hydrochloric acid)
plus sodium hydroxide
makes sodium chloride (one of many salts) and water.
Chemical reactions have to be activated by energy in the form of heat
or other forms of
electromagnetic radiation. According to the kinetic theory of matter, molecules and atoms move.
Gas molecules are an ideal example. They move in straight lines and in random directions,
so that the carbon dioxide we exhale becomes evenly distributed in the room we occupy. Heat
increases kinetic energy so that when reactant chemicals collide, they can undergo a reaction.
Theoretically, no chemical reactions could occur at absolute zero, -273 degrees C.
ACIDS AND BASES
Acids are substances which produce H+
ions in solution that bind to water molecules, they are
proton donors. For example, HCl is a polar covalently bonded gas
molecule but when dissolved in water makes H + ions and Cl - ions. Acids dissolve many compounds (like the limestone in buildings)
(Actually the hydrogen ions bind to water molecules creating hydronium ions, H3O+.)
H2C03 is carbonic acid, H2S04
is sulfuric acid, H2S03 is sulfurous acid,
HN02 is nitrous acid, HN03 is nitric acid.
Why are some acids strong and others weak at a given concentration?
Typically 100 HCl molecules (dissolved in a large amount of H2O) yields ---> 96 H+ ions + 96 Cl - (Chloride) ions:
96 of 100 HCl molecules break into ions, and 4 HCL molecules exist at any point in time.
On the other hand,
100 H2CO3 (in H2O) yields ---> 3H+ions + 3HCO3- (bicarbonate) ions
3 of 100 H2CO3 molecules break up.
Which acid is the strong one? The weak one? The latter reaction happens
in the blood and in
beverages when they are carbonated, and acid rain formation.
Bases are the opposites of acids, or have OH- ions,
or will bond to H+ ions/protons.
For example, if a solution had a lot of H+ ions, you could add OH- ions, react the two
and form HOH or water. NaOH or lye is a common base used for making soap and
cleaning sink drains. For example, if a solution had a lot of H+ ions, you could add
OH- ions, the two will react and form HOH or water. NaOH or lye is a common base
used for making soap and cleaning sink drains. e.g., NaOH (in H2O) ---> Na + (+) OH -
Any compound which produces OH- is a base. But is NH3 (ammonia) a base because
NH3 + H + ---> NH4+ (The answer is yes!)
Bases react with acids to produce water or Acid + Base ---> Salt
This is called neutralization, e.g,
H+ + OH- ---> H2O and
HCl + NaOH ---> NaCl + H2O
Buffers are chemicals that resists change in pH. For example,
limestone contains basic CaCO3 and MgCO3, calcium carbonate and magnesium carbonate, respectively.
These react with acid and neutralize it as follows
H2SO4+ CaCO3 -----> CaSO4 (calcium sulfate) + H2O + CO2.
This can be demonstrated by pouring vinegar or battery acid over various
Bubbling indicates the release of carbon dioxide as the acid is neutralized.
Lakes or soils that have little buffering capacity (without limestone or dolmite) are more
susceptible to the effects of acid rain.
Acids are very damaging to many plants, especially evergreens at high
where the acid cloud moisture soaks them daily. Acids and water will dissolve
chemicals better that water alone. Research has proven that as acids bathe
evergreen needles (leaves), the macronutrients Ca++ and Mg++ are leached out.
The tree is then weakened. Final death of the weakened tree may be enhanced by
the attack of insects (parasitic diseases are more likely to attack weakened organisms,
see Symbiosis). For years the explanation of Schools of Agriculture/Forestry was
that the trees were dying of insect outbreaks that they wanted to control by
spraying insecticide. Schools of Arts and Sciences/Ecologists said that the acid
was at fault. Similar reactions of the two camps were noted when Rachel Carson's book
"Silent Spring" came out in the 1960s. (The "Silent Spring" is a spring without the sounds
of insects and birds.)
pH is an inverse logarithmic scale of H+ ion
concentration in Moles per liter of solution.
Mathematically, pH = 1/log H+ or - log H+ ion concentration in Moles/liter. Because the formula is 1 over
the concentration of H+ ion, as H+ ion conc. increases, pH decreases and vice versa. The pH scale
runs from 0 to 14. A pH of 0 to just below 7, means the solution is acidic and has more H+ ions
than OH- ions. A pH above 7.00 means a basic solution where OH - is more concentrated than H+ . For
examples of pH value. Beware: the scale at first look, appears backwards - if the
pH number is high, H+ concentration is low; if the pH # is low, H+ concentration is high! A
simple rule which relates to our study of the metric system in lab is a pH = 0 means H+
concentration is 100 or 1 mole/liter. A pH of 1 means H+ = 10 -1 mole/l. A pH of 7 means H+ =
10 -7 mole/l. Is 10 -7 a big quantity or a very small quantity? It is 1/10,000,000 of a mole. Each higher
pH number has 10 times less H+ ions than the lower pH number, or conversely a pH of 0 is ten times
more concentrated in H+ ions than a pH of 1.
Remember: Acid (+) Base yields Salt (+) Water is neutralization. The
pH will be 7 if it
was a complete neutralization of equally strong acid and base, with equal amounts
(10 -7M) of H+ and OH- resulting.
HCl (stomach acid) + CaC03 (Calcium Carbonate, in water solution) -----> CaCl2 (a salt) + H20 + C02 (gas)
If the pH changes from 2.7 to 4.7, how much change occurred? One hudred times less acid or 10-2 less.
( H+ ) = hydrogen ion concentration; (OH- ) = hydroxide ion concentration.
Hint: since pH numbers are log rhythmic, log of the number 1 = 0, log
of 0.1 = -1;
log 0.01 = -2, log .001 = -3, etc.
Air Pollution Chemistry - See also W-B Ch. 18.
You have heard of acid rain: it includes carbonic acid, sulfuric acid,
nitric acid. These acids are formed by the reaction of polluting gases with
water and oxygen in the air. Acids dissolve vital nutrients such as calcium and magnesium out of leaves and the soil.
|Acid rain gas||Reaction to make acid||Principle sources|
|CO2, carbon dioxide||CO2 + H2O --->
H2CO3 (carbonic acid)
|Combustion of fossil fuels and wood. CxHx + O2
CO2 + H2O
|SO2, sulfur dioxide
SO3, sulfur trioxide
|SO2 + H2O--->
H2SO3 (sulfurous acid, also present in onions)
SO3 + H2O--->
SO2 + H2O + O2--->
|S + O2 -----> SO2. Coal-burning power plants, autos (this stuff wrecks our exhaust systems over time and decreases the effectiveness of your catalytic converter - Sulfur coats the platinum catalyst)|
|N2O, NO and NO2, nitrogen oxides - nitrous oxide, nitric oxide and nitrogen dioxide respectively.||N2O or NO + H2O
HNO2 (nitrous acid)
NO2 + H2O + O2 ----> HNO3 (nitric acid)
|N2 + O2 (high temp. and pressures) ----> N2O, NO + NO2 . Especially, high compression diesel and gasoline engines and coal burning power plants. The higher the combustion pressure and the higher the temperature, the more oxidation of nitrogen occurs and the more oxygen atoms attached to nitrogen atoms, e.g., NO2. Nitrogen oxides contribute to ozone and SMOG formation in cities.|
Combustion of organic or carbon compounds is an important process to know.
Carbon dioxide is produced by the the burning of carbon (as in coal)
or hydrocarbons in
fuels or tobacco.
C + O2 -------> CO2
This reads: Carbon and oxygen (plus heat to activate) yields carbon dioxide
HxCx + O2 -------> CO2 + H2O
This reads: hydrocarbons (e.g., propane, C3H8, octane, C8H10 ) plus oxygen yields carbon dioxide and water
HxCx + less O2
CO (carbon monoxide) + H2O
Smoke and soot are unburned/ uncombusted carbon or carbon compounds and aerosols.
The catalytic converter on your car takes hydrocarbons and CO and oxidizes them to CO2,
HxCx + CO + O2 ------> CO2
and it reduces the nitrogen in the nitric oxide pollutant produced as a byproduct of gasoline combustion to nitrogen gas.
NO -----> N2 + O2
This is octane: C8H18. Common hydrocarbons found in liquid petroleum gas are illustrated below.
Sulfur contaminates in coal, gasoline
and other fuels oxidizes to form sulfur dioxide, SO2 (yellow
and sulfur trioxide, SO3. Respectively, these gases dissolve in water to form sulfurous acid;
H2SO3; and sulfuric acid, H2SO4. The acids dissolve the limestone of monuments and buildings,
and dissolve the calcium and magnesium out of conifer needles and soils in general, causing plant
roots to soak up toxic aluminum.
Because car combustion engines compress
high octane gasoline and air previous to an ignition
spark, atmospheric nitrogen is oxidized to NOx (nitric oxides) during the higher temperature explosion.
Naturally, high compression engines make a lot of nitrogen oxide gases
Remember the air we are breathing contains 78 % nitrogen gas. When the first atomic bombs
were exploded in 1945, some feared that the atmosphere would catch fire. It did, but just in the
N2 + O2 ----> NOx gases (nitrogen oxides: N2O, nitrous oxide; NO, nitric oxide; NO2, nitrogen dioxide)
Forty years ago we had high compression/high horsepower auto engines - muscle cars like Pontiac GTOs.
Why aren't these engines made today?
They required highly leaded gasoline for valve lubrication and octane
to prevent preignition due to the heat of compression, and they produced high amounts of nitrogen oxides.
Gasoline without high levels of lead, bromine or benzene additives will
explode in an engine due to the
"heat of compression." When a gas is compressed, it heats up. In a diesel engine, the
heat of compression makes the fuel and air mixture explode (combust) - it needs
no spark plugs! If the gasoline explodes prematurely it causes "ping" or "knock" that is
damaging to it. The exploding gas pushes down on a piston that is coming up.
This is not a good combination for performance or engine life.
Check out How Stuff Works at http://www.howstuffworks.com/engine1.htm
The Ozone layer
The ozone layer
is found in the upper atmosphere about 15 miles high or nearly
twice as high as standard airline jets cruise (40,000 ft. or 8 miles high). Ultraviolet
electromagnetic waves cause O2 to break down into 2 separate Oxygen atoms. One
of these will combine with an O2 to make an O3 or Ozone molecule, which then may
break down again. These reactions are activated by ultraviolet energy.
Why does temperature increase in the thermosphere. Why does the aurora borealis occur in the ionosphere? Seer below.
O2 + UV photons ----> O1 + O1 + Infrared photons (heat)
O1 + O2 + UV ----> O3 (ozone) + Infrared photons (heat)
O3 + UV -------> O2 and O1 + Infrared photons (heat)
Why do temperature inversions happen in the stratospheric ozone layer?
Because heat is
released as ozone is created and break down cyclically.
Various compounds can destroy stratospheric
ozone. Refrigerants or chlorinated fluorocarbons (CFCs) from
spray cans or refrigeration/air conditioning units, carbon monoxide and unburned hydrocarbons
from high altitude jet engine exhausts, methane from large herbivores, and chlorine gases can destroy
the ozone causing "ozone holes" in the atmosphere that leak in increased amounts of
ultraviolet radiation to the earth's surface. If ultraviolet radiation increases, an
increase in the occurrence of skin cancers will be seen in unfortunate humans, more
commonly in light skinned people.
Study Question: in 1973, the U.S. government
decided not to encourage the building of
a high flying Supersonic transport aircraft (SST). What did the ozone layer have to
do with this decision? The SST could have flown at altitudes in the stratosphere where ozone is present.
The ozone hole is near the South
Pole over Antarctica. There are areas of thinning over the
industrial northeast in the U.S. and Canada, and similarly from England over northern Europe
in France and Germany. The ozone hole occurs annually over Antarctica between September
and November, when the Antarctic Spring when sunlight returns.
The circumpolar vortex of cold air forms
ice crystals to which chlorine and bromine adhere.
When the circumpolar vortex breaks up, the chlorine and bromine are dispersed northward
to New Zealand and South Australia. The resultant inning of ozone over New Zealand has
caused increased rates of melanoma and other skin cancers.
Melanoma is the most aggressive and
fatal form of skin cancers is caused by a series of mutations
to melanocytes that make the pigment melanin at the base of the upper cellular of the skin (epidermis).
Once the cancer cells have penetrated into the dermis of the skin where blood vessels and lymphatic
vessels are located, it quickly moves to lymph nodes, and to other tissues and organs. Squamous cell
carcinoma and basal cell carcinoma are also caused by UV-B exposure, the latter are usually not fatal.
In the troposphere, ozone is a secondary
air pollutant produced by photochemical reactions that produce
SMOG, see below. At street level, ozone causes lung diseases, particularly in those who have compromised
lung heath by smoking.
Greenhouse effect - see Ch. 18 and 19 W-L, 5th ed.
Just like glass,
the troposphere is transparent to visible sunlight, but when that sunlight
strikes the Earth,
the photons of Violet-Indigo-Blue-Yellow-Orange-Red are transformed into infrared photons or heat.
Heavier tropospheric gases like nitrogen oxides, carbon dioxide, methane, CFC, and water, reflect these infrared
photons back toward the surface, creating the greenhouse effect.
The combustion of wood, grass, etc.
and fossil fuels, has dramatically increased the CO2
level of the atmosphere as determined in south polar ice samples dating back 158,000 years.
Although there have been periodic rises and falls of CO2 levels that are related to cold glacial
periods (low CO2) and warm interglacial periods (high CO2).
If you want to
see what high CO2 will do for a planet, look at the planet Venus.
oxidized from the rocks on the planet's surface is now suspended as a aerosol (droplets )
of sulfuric acid in thick clouds 100 miles above its surface. Venus has a runaway greenhouse
effect (positive feedback) that has produced temperatures high enough to evaporate all the plant's liquid water
to form a thick cloud layer that hides the surface from optical view. Venus has to be mapped with radar.
The surface temperature is approximately
460oC and the atmospheric pressure is 100 times more
than Earth. By reason of the carbon dioxide currently in the atmosphere and more expected in the future
(see chapter 20), most climatologists predict that the Earth will experience an enhanced greenhouse effect
Methane is a greenhouse gas produced by rotting vegetation in
marshes, swamps and bogs,
and methanogen bacteria in the guts of herbivores. You can see the bubbles of methane popping
to the surface at the Okefenokee Swamp. Can the herbivorous dinosaurs' extinction be attributed
to the "passing of gas?" Extensive volcanic eruptions can increase dust, cooling the Earth for the short term,
but their release of carbon dioxide and sulfur dioxide could increase greenhouse effect for the longer term
as it requires thousands of years to mitigate increased carbon dioxide.
There are many theories for dinosaur extinction. One outcome of the
effect is: warming of the atmosphere, that may have caused increased evaporation of water, which
increased cloud cover, which then had a negative feedback effect causing atmospheric cooling,
which caused the collapse of plant populations and the food chains that supported dinosaurs.
The Greenhouse Effect - Carbon
dioxide and methane reflect infrared radiation (heat) back
to the surface, causing increased temperatures at the earth's surface. Notice how
UV-Violet-Indigo-Blue-Green-yellow-Orange-Red light wavelengths come through
the atmospheric gases, but infrared radiation is reflected back to the surface.
Global warming has not increased as
dramatically as carbon dioxide in the atmosphere.
Other than the surface temperature data, evidence that suggests the
atmosphere is warming is the fact that most of the world's glaciers are receding and
seal levels are rising. Another possible outcome of increasing carbon dioxide is an
increase in plant biomass. If, hopefully, we don't destroy the plants, their increase
will mitigate the high carbon dioxide levels. If not, algae will take over, growing
in nutrient rich offshore waters. That could turn into a stinking mess and destroy
Experiments have indicated that increasing biomass is accompanied by
a relative decrease in nitrogen
content of the plant food. Nitrogen would not increase, it would stay the same. Therefore,
herbivores would have to eat more plant material to get the same amount of nitrogen-containing
amino acids to make their cellular proteins. Could this be another dinosaur extinction theory?
The glacier that resided here in Colorado is gone!
Adjusting carbon dioxide
Review the carbon cycle in Aliff Visualizing guide Ch. 6. Nature can dispose of carbon dioxide in two ways:
1. Photosynthesis incorporates carbon
into the bodies of plants and that carbon is passed to animals.
When the plants are buried, the carbon may be stored geologically as coal or oil.
The question for the contrarians to answer is this: "Where does the carbon dioxide go if we are
destroying plants? Will plants be increasingly replaced by algae? If so, we will have a rotting mess
that will destroy commercial fisheries.
2. When carbon dioxide dissolves
in the ocean, it forms carbon acid that then reacts with calcium
ions to precipitate limestone. Also certain protozoa and most mollusks make shells that contain
carbonates. The most important action humans can take in reducing carbon dioxide is to stop
burning fossil fuels and allow plant populations to increase.
- Smoke, sulfur aerosols and
dust as air pollutants
The normal circulation pattern is for
air to be heated at the earth's surface and then
rise as convection currents. Hot air, being less dense, rises; cold air, being more dense,
sinks. However, if there is a layer of warmer air over a layer of colder air, see below,
will the layers mix? Air pollution will fill the lower cold air layer and people with lung
problems will begin to feel the effects. This is a common condition in Denver , Los Angeles ,
New York, and Mexico City. The trapped air will remain until a front or otherwise strong
winds can blow the pollution, the air will clear for a while.
A typical temperature inversion consists
of a warm air layer trapped beneath
a cold air layer. Above the inversion or what pilots call the "haze layer" that usually tops
out at 5,500 ft. or more in the summer. At that altitude, the temperature lapse rate initially
increases instead of showing the normal decrease (temp. lapse rate) with height.
Solid smoke particles,
carbon compounds produced by combustion, volcanic,
sulfur aerosols, desert or farming dust can rise to the top of an air layer and screen out sunlight,
making the underlying layer colder than the upper layer - a temperature inversion.
If there were world wide increases of
particles (including volcanic and
agricultural dusts), the earth would cool. One theory about the mass extinction of
Dinosaurs is that an asteroid or large meteor hit the earth 65 million years ago,
causing widespread fires and high altitude dust bands. High altitude dust bands from
volcanoes block sunlight and create severe winters. When the volcano Krakatoa in
Indonesia erupted over 100 years ago, a very severe winter occurred in Europe as
sunlight was blocked. There is some mineral evidence of a meteor impact in rocks
deposited at the so called K-T (Cretaceous-Tertiary geologic time) boundary. There is a layer
of dust and soot containing the metal Iridium, common in meteors, and glassy
"shock crystals" created by rock impact.
At that time the Dinosaurs disappear
and the small mammals that had been
around for a long time, but in small numbers and size, suddenly become dominant
and enlarge in size tremendously.
What chemical process results in smoke?
Incomplete combustion. Complete combustion with
oxygen produces no smoke.
What is "nuclear winter?" Nuclear winter is a cooling effect produced
by the atmospheric dust
created by the explosions of atomic bombs. Similar, to meteor impacts with the Earth that
apparently caused mass extinctions of plants and animals, 50 nuclear bombs exploding in cities
could produce radical cooling of the atmosphere and collapse of plant populations and the food
chains they depend on.
Unburned hydrocarbons, carbon monoxide,
Oxygen, and NO2 interact to produce
harmful ozone (O3) and peroxyacetyl nitrate (PAN) that are the eye irritating
chemicals in SMOG, especially Mexico City, Los Angeles and New York..
Nitrogen dioxide is formed.
O3 + NO (nitric oxide) -----> NO2 (nitrogen dioxide) + O2
Nitric oxide (NO) acts to remove ozone
( O3) from the atmosphere, this mechanism
occurs naturally in the atmosphere.
NO + HxCxO2 -----> NO2 + other products
Sunlight UV can break down nitrogen dioxide (NO2) back into nitrogen oxide (NO).
NO2 + Ultra-Violet light -----> NO + O
The single atom (nascent) oxygen (O) formed reacts with oxygen in the air producing ozone (O3).
O + O2 -----> O3
Nitrogen dioxide (NO2) can
also react with radicals produced from volatile organic compounds
in a series of reactions to form peroxyacetyl nitrates (PAN) that sting eyes.
NO2 + HxCx (hydrocarbons) -----> PAN
Courtesy of student, Mike Coleman
Global warming, ozone depletion and acid deposition
may change the environment of the future.
Assuming the worst case scenarios for the three, what changes in the health,
numbers and types of organisms, and their habitats are in store?
Health or Environmental effects
1. Decrease in coral reefs.
2. Increase in heat-related deaths.
3. Mid-latitude droughts and desertification.
4. Stronger hurricane with wave related damage to reef and shoreline communities.
5. Further decrease in phytoplankton of the California Ocean current with concomitant loses of sea life.
6. Submersion of some islands and coastal areas.
7. Thawing of permafrost, reduction of lichen food for reindeer. Santa can't get south!
8. Reduction in western U.S. snowfall and stream flow resulting.
9. A mistiming of the flowering and emergence patterns of plants and their pollinators, with a decline in populations of both.
10. An increase in insect vector populations and the diseases they transmit.
11. Decrease in buffalo grass in the prairies with an increase of invasive species.
12. U-V damage to photosynthetic chemicals and concurrent reduction of the ability of plants to mitigate carbon dioxide increase.
13. Increased skin cancers and leaf damage to plants.
14. Further decreases seen in mountaintop trees and in those northeastern areas of North American and Europe due to acid rain.
15. Further increases in the death of amphibians, insect larvae, and fishes in the lakes affected by acid rain.
There are several types of energy which are important for Environmental Sciences.
Atomic energy is stored in atoms, it literally holds the atomic
When atoms are split (as in an Uranium or Plutonium fission bomb or nuclear reactor)
or fused (as in the Sun or laser fusion devices) some mass is converted to energy.
Kinetic energy is the energy that causes atoms or molecules to
Kinetic energy provides the energy to collide reactants A with B to react to make C product.
Heat (thermal energy) increases atomic and molecular motion. See above.
Chemical energy is stored in the chemical bonds made by atoms exchanging or sharing electrons.
Potential energy - potential energy is energy that is stored
and can be released. A good example
is the evaporation of water and its rising against the force of gravity to form clouds. When enough
h water accumulates in a cloud, it falls releasing its potential energy. When water falls through the
turbines of a hydroelectric dam, that energy is converted to electrical energy.
Electrical energy is carried by a current of electrons being
pushed along in house current and,
in batteries, moving toward an area of opposite charge..
Radiant energy travels in waves. It is also called electromagnetic
energy. Electromagnetic waves,
like ocean waves, rise in potential energy and fall in energy. Similarly, electromagnetic waves have
two characteristics, amplitude or power and wavelength.
Atoms and Radiation - see p. 21, W-L, 5th ed.
VIBGYOR = Violet Indigo, Blue, Green, Yellow , Orange, Red
The general relationship of ionizing/mutagenic radiation exposure to disease
The graphed line was not connected at the bottom because cells have
enzymes for limited gene repair.
The energy of the ultraviolet photon is decreased by the collision with
electrons in ozone or melanin
(skin pigment) molecules, or the photosynthetic chemical chlorophyll in plants. See the figure following.
Van Allen Radiation Belts
Radiation, including electrons and protons,
is trapped in the magnetosphere of the earth and circulate
500 + mi. above the surface of the earth. This radiation can be seen at the poles, e.g., the Aurora Borealis.
More distant magnetic belts deflect gamma rays and the "solar wind."
Will skin cancer rates increase as the Ozone layer decreases in O3 concentration?
Who gets more skin cancer due to skin exposure, light skinned or dark skinned people?
Who gets more skin cancer, folks in Michigan or folks in Arizona? Cloud
some UV, but who gets more exposure? People living nearer the equator get even more exposure.
Why wear "sun screens?"
At very high levels of radiation exposure, radiation sickness,
characterized by severe nausea, diarrhea
and resulting dehydration occurs as cells lining the digestive tract and other organs are destroyed.
Many who immediately survived the atomic bomb explosions in Japan died of this condition
some days to a few weeks thereafter. The line is not connected at very low levels. Cells have DNA
repair mechanisms to fix a small number of mutations. Every time we go out in the sun, some DNA mutations occur
in our skin cells due to UV-A and UV-B exposure. We have enzymes that repair the thymine
dimer mutations that result. Some children have inherited mutated genes that do not make these enzymes
and they cannot have their skin exposed to sunlight. Their skin blisters repeatedly and then turns cancerous.
Light, Chemicals, Color and Heat
Chemical such as chlorophyll and other photosynthetic pigments absorb
direct the energy to the process of photosynthesis that makes food and structural
materials for the plants. Why is chlorophyll green? Because it reflects green photons,
but absorbs strongly in the Violet-Blue and OR areas of VIBGYOR. Reflection and
transmittance (light going through a leaf) are opposite to absorbance. A black
surface absorbs all visible wavelengths and makes infra-red heat. A white
surface reflects all wavelengths.
I bet you know this - what happens when sunlight strikes a flat black
surface? In Chicago,
the city government is experimenting with making the tops of buildings, usually covered with black tar
that creates a lot of heat, reflective or planted in thick vegetation. Reflective surfaces reduce
surface temperature, but what about temperature higher in the air? When the heat "sinks"
of tropical rain forests are replaced by more reflective grassy surfaces, the overall effect is
warming of the air.
Which photon has more energy? A blue one or a red one? Blue is correct.
See the electromagnetic
More Radiation Risks
When atomic bombs explode in the atmosphere, a dust of "radioactive
spread downwind of the source of testing. Also materials from leaking bomb making plants like
Hanford, WA have contaminated groundwater. When atoms are split in "fission" reactions,
smaller atoms are formed. Many of these are "radioisotopes," that emit radiation.
Iodine-131 is a common radioisotope found in fallout from nuclear bomb
Natural Iodine, such as in iodized salt, accumulates in the thyroid gland, where it
is incorporated into thyroid hormones.
See the map of I-131 exposure and the map of thyroid cancer distribution.
The hot spot in Idaho is partly due to Hanford, WA groundwater pollution.
Otherwise the distribution pattern follows the general jet stream movement of air
in a serpentine pattern over the country.
On your periodic chart above, identify strontium-90 as an isotope. What
periodic chart column is it in?
It is a relative of calcium found in bones. Caesium-137 is in the same column with sodium
and potassium (closer). That means it will be incorporated into the body as sodium and
potassium ions are. Due to Caesium's similarity to Potassium, it will be found inside cells
where potassium normally accumulates.
If one eats plants that have soaked up I-131, Sr-90 and Cs-137, does
one's radioactivity level increase? Yes. If one acquires radioisotopes then one's level
of radioactivity increases.
When the nuclear plant in Chernobyl, USSR (now the Ukraine) exploded,
a cloud of
radioactive fallout was spread by the wind northwest as far as Sweden. See the map at
for an outline of the distribution of Cs-137 around the site.
In the late 1980s, many of the "big box" hardware stores were selling
radon testing kits.
There is an radioactive isotope of radon that naturally diffuses from rocks containing uranium-238.
formations and accumulates in basements. It is thought to be another cause of lung cancer, second to
exposure to cigarette smoke.
If food is bathed by gamma rays, as in sterilization/preservation, does
that make the food radioactive? Hint: when you are bathed with light
radiation, does that make you glow in the dark?
The Effects of the Nagasaki Atomic Bombing on the Human Body
Most directly heat and other radiation from the blast literally cooked
the skin off some victims.
The death toll within one kilometer from the explosion was 97% among burns cases,
97%% among those with external injuries, and 94% among people who were apparently unscathed.
Those deaths were due to internal damage done by radiation.
The relative risk of subsequent malignancy (by tumor site) is illustrated
A statistically significant increase in risk was recognized in cancer
of the stomach, colon, lung, breast, ovary, urinary bladder, thyroid and liver and in
skin cancer other than melanoma.
The first atomic bombs were fission bombs. Large Uranium atoms
are split with
smaller atoms resulting from the neutrons splitting more atoms in a chain reaction.
Later bombs used atomic fusion like the sun
13H (tritium) + 12H(deuterium)
--------> 24He (helium) +
large amounts of energy
(the superscript is the atomic number and the subscript the atomic weight of the atoms).
In World War II the Germans built a plant in Norway for extracting "heavy
deuterium oxide or D2O. It is thought that they were trying to make an atomic bomb
using the deuterium. Since the plant was in the cliff of a seaside fjord, the British
had to sling aerial bombs at it. Failing at this, saboteurs were parachuted into the
back country and cross-country skied there to set off bombs that put the plant
out of commission.
The North Koreans are operating a breeder reactor that can make make
fuel plutonium or plutonium for making fission bombs. The second atomic bomb that was dropped on
Nagasaki was a plutonium bomb.
Medical imaging and radiation
Many imaging techniques use forms of radiation produced by decaying
excited atomic nuclei. Some forms are more dangerous than others. See
the figure above. In general, short wavelength forms have very high energy and can,
therefore, mutate the chemical of inheritance, DNA, and cause cancers or
the death of cells. In radiation therapy, beams of gamma rays are focused
on a tumor to 'burn out' the cancer cells. One goal of physicians has been
to lower the dosage of medical imaging X-rays or gamma rays which patients
are exposed to during their lifetime. Unfortunately, the threat of malpractice
causes the ordering of more X-rays and CT scans than are medically necessary.
X-rays are produced when a high voltage electron current strikes
a metal plate
in a cathode ray tube. Structures which absorb X-rays, like solid organs and
bones, produce white images on the negative. Problems include exposure to mutagenic radiation,
above, and the overlapping of two dimensional structures.
CAT or CT scans (Computerized Axial Tomography) apply X-rays
in an arc around the body and fed into a computer. A sectional view of organs can be obtained.
Again, X-ray exposure is a problem.
What cant pregnant women get X-rays? No. X-ray exposure to a fetus can
miscarriages and birth defects.
PET (Positron Emission Tomography) scans are produced when a
is injected with a radioactive substance, e.g., sugar, that produces positrons.
Positrons are positive electrons usually found in the nucleus, but are emitted
during the disintegration of certain radioisotopes.
When the positrons collide with electrons, they destroy each other and
low levels of gamma rays which are imaged. The technique is highly useful for
diagnosing brain area dysfunction.
MRI (Magnetic Resonance Imaging) uses a magnetic field
to cause protons to realign and
radio waves that increase the energy of the protons. The radio wave reflections are
then "read" by the image monitor. Radio waves are the least damaging form of
radiation. They are used to produce the MRI image. There is some debate
about whether high energy magnetic fields are dangerous or not, but most think not.
In radiation therapy, beams of gamma rays are focused
on a tumor to "burn out"
the cancer cells. Radiation therapy or gamma knife surgery can reach tumors that are
Are there any medical procedures or treatments which do not have risk?
No. Are cancer patients
who have been treated successfully with radiation therapy more likely to get tumors of a new
source (different cells)? Yes!
Therefore, is it contradictory that X-rays are used to
treat cancer but that they can cause cancer? No!
But those treated have increased risk of getting new tumors.
Photosynthesis and chemosynthesis as a foundation for animal life
CO2 + H2O +
Sunlight (electromagnetic, VIBGYOR wavelengths) energy ------>
(used to make cellulose/food fiber and other solid compounds, and food for the plant)
+ 02 gas.
Most people think that most of the mass of a tree comes
from the soil. That is not correct.
The mass mostly comes from the carbon in the carbon dioxide of the air that is turned into solid carbon
compounds in wood.
Sunlight provides the electromagnetic energy that is absorbed
by the green chemical chlorophyll and
accessory pigments, such as those seen when sugar maple leaves die in the fall. The electromagnetic
energy is converted to chemical bond energy in the glucose molecule. Where there is a C-C or a C-H
covalent bond, energy is stored in that bond that can be extracted in cellular metabolism..
The food energy we acquire in eating originally came from
the sun's atomic energy transformed into
radiant energy. Plants trap the electromagnetic energy from sunlight and transform it into chemical energy. Our food energy is chemical energy.
However, some bacteria living near volcanic vents in the
Pacific and Atlantic Oceans,
too deep, at 10,000 feet down, to receive sunlight, nevertheless they are produce food for a
whole community of organisms from tube worms to crabs and fishes. These bacterial producers
do chemosynthesis: H2S (hydrogen gas from volcanic vents) is oxidized to yield SO2 and H2O
and the important energy currency of all cells, ATP.
Besides using their ATP for cell movement, transport,
etc. ATP is used to produce light or
bioluminescence in some of these sea bottom dwellers. If life is found on Mars, it
will likely be chemosynthetic bacteria, so called "rock eaters" that can derive the
energy to make food from the oxidation of chemicals in the rock like sulfur.
On Mars, the chemosynthetic bacteria are the most likely sulfur or iron bacteria.
Sulfur bacteria thrive at 170 degrees F at the edge of this
Yellowstone geyser pond. Aliff photo.
"The Grand Balance of Life"
In the biosphere, to maintain stable populations of all organisms,
Photosynthesis and Chemosynthesis = Cellular Respiration
CO2 + H2O + sunlight energy -----> glucose (C6H12O6) and other food molecules + O2
Electrons are acquired from the water molecule to replace those energized
in chlorophyll. Those energized electrons make
chemical bonds in food molecules used in the metabolism of the plants and stored in the leaves, stems, seeds and roots of the plant. Remember that plants do photosynthesis and cellular respiration at the same time.
Chemosynthesis (two examples):
Iron bacteria: Fe2 + ------->
Fe3+ + 1 e-
(the high energy electrons acquired are used to make the food for cells)
Sulfur bacteria: H2S + 02 ------>
SO2 or SO42- (sulfate) +
2 H+ (protons) + 2e-
(the high energy electrons acquired are used to make energy containing C-H and
C-C covalent bonds in the food of cells)
Glucose (C6H12O6) and other food molecules
+ O2 -----> CO2 + H2O
+ chemical energy (ATP) for cells.
The chemical energy stored in glucose is chemical bond energy which is transferred to ATP. ATP then powers cell
activities like movement, growth and transport. All creatures do this process when they utilize food made by
themselves (algae and plants) or food made by other organisms (animals) that consume them..
Debate this statement, :"Plants can survive without animals, but animals
cannot survive without plants."
Plants can live using cellular respiration and photosynthesis. Animals can only do cellular respiration. The food
chain must start with photosynthesis or chemosynthesis.
Will homeostasis of carbon dioxide levels be possible if plant and algae
populations decrease? No!
To see a good on-line periodic chart, go to http://www.webelements.com
For another dinosaur extinction theory, see http://www.knowledge.co.uk/frontiers/sf080/sf080g12.htm
For more information on radioactive fallout, thyroid cancer and radiation risks, see http://www.epa.gov/rpdweb00/assessment/index.html
To study the radiation effects of the atomic bombs dropped
on Japan, see
For more on global warming and climate change, go to http://www.epa.gov/globalwarming/index.html
What are the potential effects of global warming on cities
and plant and animal communities?
Catalytic converters: see http://en.wikipedia.org/wiki/Catalytic_converter
Acid Rain: go to http://www.epa.gov/acidrain/
Magnetic belts deflect
gamma rays and the
"solar wind." See http://en.wikipedia.org/wiki/Van_Allen_radiation_belt http://ozonewatch.gsfc.nasa.gov/meteorology/index.html
Ozone hole: go to http://ozonewatch.gsfc.nasa.gov/meteorology/index.html
For a discussion on the effects of air pollution on tree
communities in Appalachia see:
for the effects of global warming and
what we can do about it.
Study Questions1. What is a radioactive isotope? How is it different from the most common
Email:john.aliff @ gpc.edu