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bisc lab assignment
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- Louisiana Tech University
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Environmental PollutionBackground
Pollution can be defined as the introduction of any contaminant to a natural environment, which
has a negative effect on the organisms living there. This is a broad definition because there are many
different types of pollution: contaminants in the air, contaminants in the water, solid contaminants on
land, contaminants that are macroscopic (like litter), contaminants that are microscopic… The list goes
on.
Since there are so many different kinds of pollutants, there are many different experiments that
could be designed to test how they affect living things. In this laboratory exercise you will test the effects
of pollutants on Ankistrodesmus, a genus of green algae that grow in fresh water ponds and lakes. These
are ideal organisms to work with because they are easy to take care of, they grow fairly quickly, and their
growth is easy to measure.
The nature of the pollutant that you will work with will be up to you, although we only have two
available in the lab from which to choose. You could select salt water as your pollutant. Notice that the
definition of pollution made no mention of pollutants being “artificial” or “human-made”, although most
pollutants are. This is because even natural substances, like salt, can cause damage to organisms that live
in environments in which this salt is not normally found (remember that Ankistrodesmus are fresh water
plants!).
Hypothesis: Sodium chloride (salt) will inhibit the growth of Ankistrodesmus algae.
Or, you could choose fertilizer as your pollutant. Fertilizers are, of course, used to enhance plant
growth. However, it is possible for high concentrations of fertilizer compounds to actually be toxic to
living things.
Hypothesis: Miracle-Gro (fertilizer) will inhibit the growth of Ankistrodesmus algae.
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, Materials
Miracle-Gro: A fertilizer. Used as a pollutant in these experiments.
Salt: Sodium chloride. Used as a pollutant in these experiments.
AlgaGro: A solution of nutrients that help algae grow.
Ankistrodesmus: A genus of algae that grow in fresh water. Grown in AlgaGro.
Procedure
Preparing the Salt Solution
If you are using salt as a pollutant, you should prepare a 500 mM sodium chloride solution.
Sodium chloride has a molecular weight of 58.44 g/mol. You should prepare 100 mL of this.
Importantly, you should dissolve this salt in AlgaGro Solution NOT in water! The reason for this will
become apparent later.
Preparing the Miracle-Gro Solution
If you are using Miracle-Gro as a pollutant, you should prepare a 0.03% solution (percentage is
mass/volume). You use % concentration for this solute because Miracle-Gro is a complex mixture of
different things and it therefore does not have a uniform molecular weight. You should prepare 100 mL
of this. Importantly, you should dissolve this Miracle-Gro in AlgaGro Solution NOT in water!
Now, if you have calculated the amount of Dilute With AlgaGro!
Miracle-Gro needed, you will see that this is a If we dilute pollutants in water, then the tubes
VERY small amount. In fact, the amount is so receiving more pollutant would be receiving less of
small, you will not be able to accurately measure it the nutrients found in AlgaGro. By preparing
out. There are two options to get around this pollutant solutions in AlgaGro we ensure that,
problem. You may simply prepare a larger volume regardless of how much pollutant solution and
of solution, increasing the amount of AlgaGro and AlgaGro solution the tubes receive, they all have the
Miracle-Gro until it is at a measurable level. same amount of AlgaGro.
Another possibility is to prepare a solution with a
higher concentration of Miracle-Gro, increasing the amount until it is at a measurable level, and then
diluting this concentrate to get to your desired concentration. Both of these solutions are wasteful of
reagent because you are using more Miracle-Gro than you actually need.
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