Notes – Sections C.5-C.7, C.10 – Possible Fish Kill Causes
C.5 Inappropriate Heavy-Metal Ion Concentrations?
General Information
Many metal ions are essential to the health of living things – Fe+2, Mg+2, Ca+2, K+1, etc.
Living things obtain these ions by eating food mostly, but they are also in drinking water.
Not all ions are beneficial: Pb+2 and Hg+2 are hazardous to living things
These ions bind to proteins in living things and do not allow proteins to function
normally – as a result, there can be damage to nerves, kidneys, liver, etc.
Heavy metal ions are not removed as waste in living things – in fact, they become more
concentrated moving up the food chain (little fish get eaten by bigger fish, bigger fish get
eaten by the biggest fish, the biggest fish get eaten by humans). Some of these animals
become hazardous for other animals and humans to eat.
Heavy metal ions are hard to detect at low concentrations in water. They are even harder
to remove (and very costly to remove). The best way to deal with the problem is to
prevent these ions from ever entering water systems.
Specific ion information
Lead ions (Pb+2)
These ions are found in automobile batteries, pesticides (no wonder), and paint. Lead
was even added to gasoline until it was discovered how toxic that practice was. Lead
used to be used in pipes until it was discovered that this caused lead poisoning. It also
was used in fine crystal water pitchers (imagine that).
Mercury ions (Hg+2)
Mercury is used in light switches, thermometers, and fluorescent light bulbs. Mercury
can be absorbed through the skin. Mercury is used in killing bacteria, fungus, and insects
– why? – it’s toxic to living things. In the 1700’s and 1800’s, felt hats (popular at the
time) were made with mercury; many of the workers in these hat factories went “mad.”
(leading to the character of the mad hatter in Alice in Wonderland) Mercury poisoning
leads to numbness, staggering, tunnel vision, and brain damage.
So….What does this have to do with the fish kill?
Heavy metal ions could have been released into the river causing a fish kill.
C.6 Inappropriate pH Levels?
pH – a measure of the acidity of a substance
The pH scale
0
7
14
ACIDIC
NEUTRAL
BASIC
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Students should look at Figure 1.44 to see the pH values of some common substances!
Properties of Acids
1. acid comes from Latin- “acidus” – means sour tasting
2. affect the colors of indicators (an indicator is a chemical that shows one color in an
acid, another in a base) (turn blue litmus red)
3. acids react with bases to produce salt and water
4. acids ionize in water (so…they conduct electricity)
5. acids react with active metals to produce salts and hydrogen
Acids have chemical formulas that start with hydrogen – examples: HCl, HNO3, H2SO4
Properties of Bases
1. bases taste bitter
2. affect the colors of indicators (turn red litmus blue)
3. bases react with acids to produce salt and water
4. bases dissociate in water (so…they conduct electricity)
5. bases feel slippery
Bases (most bases actually) have chemical formulas that end with hydroxide ion
examples: NaOH, Ca(OH)2, Al(OH)3. Ammonia is an important base you should know –
it’s formula is NH3.
So….What does this have to do with the fish kill?
When pH is too low in a stream, lake, or river (too acidic)…fish egg development is
impaired. This also causes more metals to dissolve in the water (see previous section).
When pH is too high (too basic)….Fish skin and scales can be dissolved.
Normally, the Snake River has a pH of 7.0-8.0 (neutral to slightly basic) – maybe the pH
changed causing the fish kill.
C.7 Inappropriate Molecular Substance Concentrations?
Molecular substances – a new kind of chemical we haven’t worked with too much so far
in this course – these are chemicals that don’t have ions – they start with atoms that are
not metals (nonmetals).
Examples of molecular substances: O2, CO2, NH3, CH4 – anything that doesn’t start with
a metal
Molecular substances can be solids, liquids, or gases – it depends on how polar the
substances are – water is very polar which is why it is a liquid at room temperature –
carbon dioxide is not very polar which is why it is a gas at room temperature.
Some of these substances dissolve in water well, while others don’t. What determines
how well they dissolve in water is how polar they are.
“Like dissolves Like” is the phrase to remember when figuring out whether a solute will
dissolve in a solvent. This also relates to cleaning stains – we use dry cleaning fluid to
get out oil stains, while we use water to remove a candy (sugar) stain. Dry cleaning fluid
and oil are both nonpolar, water and sugar are both polar. Of course some substances
will help polar and nonpolar mix (alcohol and soap). This is because these molecules
have both polar and nonpolar parts.
Electronegativity determines how polar substances are – it is your instructor’s opinion
that we shouldn’t learn about this topic yet.
So….What does this have to do with the fish kill?
Is it possible that molecular substances that molecular substances that were dissolved in
the water caused the fish kill? That will depend on what substances were involved and
how much. We’ll see…
C.10 Temperature, Dissolved Oxygen, and Life
Maybe the temperature of the Snake River changed, starting a chain reaction leading to
the fish kill….
Different fish need different amounts of oxygen to survive – these amounts also vary
from season to season with more oxygen needed during the summer.
Some things to know….
a) In warmer water, cold-blooded animals experience: higher body temperatures which
leads to higher metabolism which leads to a need for more oxygen.
b) In warmer water, less oxygen is dissolved in the water.
c) Hot days are not the only cause of a possible temperature rise in the Snake River.
Some industries use cooler river water to cool processes in their plants, then return the
warmer water to the river.
d) If a river doesn’t have enough oxygen dissolved in the water, the fish can suffocate
and die.
So…. If the temperature suddenly rose, this might have killed the fish
Some other things to know….
a) Too much oxygen in the water can also kill fish. The condition that causes death is
called gas bubble trauma.
b) Humans can cause too much oxygen to be dissolved in water at the base of a dam or
hydroelectric plant. As water gets released, it can trap air causing the formation of
“froth,” where large quantities of air will dissolve.