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.

Fig. 1

Negative feedback in environmental systems (ecosystems) is seen in the biosphere
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. For instance,
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.


Subatomic Particles

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.



There are several types of energy which are important for Environmental Sciences.

Atomic energy is stored in atoms, it literally holds the atomic nucleus together.
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 move.
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. 

Radioactive atoms have unstable nuclei that emit radiation as they disintegrate. Radiation includes
various forms of energy emitted by a radioisotope or form a nuclear fission or fusion reaction.
Radiation consists of two general types: atomic particles, e.g.,  electrons, positrons, neutrons
or protons; and electromagnetic waves, actually particles but their mass is not measurable.
The wave forms include gamma rays, X-rays, ultraviolet, visible light spectra, infrared
or heat , microwaves and radio waves.
  Gamma rays, X-rays, and ultraviolet rays are mutagenic; that is, they mutate DNA,
the chemical in our cells that carries the messages of inheritance that regulate cell
growth, reproduction and metabolic activities.

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.

These gamma rays,  X-rays and ultra-violet (UV C, shorter wavelength, and UV-B, longer wavelength)
rays are more precisely packets of electromagnetic energy called photons. This ionizing radiation knocks off the electrons
of gas atoms in the upper atmosphere, specifically the ionosphere, producing the northern or southern
"auroras," they collide with Ozone in the stratosphere and  with the melanin in your skin - there these high
energy photons are degraded into low energy infra red photons (heat) that are not mutagenic. See above.

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.

The electron moves away entirely in the ionosphere and in chlorophyll in living cells, or  returns to the nucleus in
a phosphorescent mineral. In auroras and phosphoresence/flourescence visible light photons are also produced.

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 cover absorbs
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 light and
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
spectrum above.

More Radiation Risks

When atomic bombs explode in the atmosphere, a dust of "radioactive fallout" is
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 testing.
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?  www.webelements.com
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 below.

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 water,"
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 the nuclear
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 or
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 are taken
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 cause
miscarriages and birth defects.

PET (Positron Emission Tomography) scans are produced when a patient
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 produce
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.

Photo of two contradictory road signs, one reads keep right and the arrow points left

Photosynthesis and chemosynthesis as a foundation for animal life

CO2  +  H2O  + Sunlight (electromagnetic, VIBGYOR wavelengths) energy ------> C6H1206/ glucose  (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..


Energy transformations

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


CO +  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)

Cellular Respiration:

Glucose (C6H12O6) and other food molecules +  O----->  CO +  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  http://www.solarstorms.org/Hiroshima.html
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?
See http://www.epa.gov/globalwarming/index.html

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:

See http://www.nwf.org/climate for the effects of global warming and
what we can do about it.

Study Questions

1. What is a radioactive isotope? How is it different from the most common
form of the atom?
2. What forms of electromagnetic radiation are dangerous?
3. How is acid from coal mines a form of water pollution?
4. What does the pH of soil have to do with fertility?
5. How is acid rain formed? What is in it. What damages to structures or biotic
environments result from acid rain?
6. If living organisms are found on Mars, what are they most likely to be?

 Email:john.aliff @ gpc.edu