Summer Research Program for Science Teachers
Jennifer N. Girard
R. Morrow High School, Brooklyn
Arsenic Contamination Research
poisoning is more often thought of as a topic for a mystery
novel, but it is a grim part of our global reality. All
across the world there are over one hundred million people slowly
being poisoned by their only available water source. Most
recent and devastating problems with contaminated well water were
identified in India. Arsenic tainted water can be found in
as far reaching places as Thailand, Japan, Australia, The United
Kingdom, Inner Mongolia, Hungary, Chile, China, Argentina,
Taiwan, Ghana, Mexico, Philippines, New Zealand, and Canada.
This is not only a problem for distant lands, contaminated water
occurs in the United States as well, in areas such as California,
Washington, and Oregon.
These events, though catastrophic, can make for a great learning experience in a classroom setting. It can obviously apply to a Social Studies lesson where you can discuss geography and the socioeconomic classes in the country that have been stricken. [Teaching Standard A- Work across disciplines]This topic can easily fit into an environmental science classroom where a discussion could develop based on how the surrounding biome is affected by the contaminated water. Also the fact that the arsenic is believed to occur in ground water from the use of outdated pesticides and mine leeching is also a hot topic for debate. A biology teacher could parlay arsenic into his or her lesson simply by discussing its carcinogenic properties. A forensic lesson can be enhanced as well, due to the fact that arsenic remains as part of hair and nail samples even after a person has died. The final class that can draw from this tragedy is a chemistry class.
in the water supply as dissolved particles. This is an example of
solubility. [9-12 Content Standard B- Properties of matter] The question of
why it dissolves can be answered by taking a look at how an
electrolyte interacts with water. There are multiple
oxidation states for arsenic, and, interestingly enough, the +3
state will form more toxic compounds than the +5 state. Changing
the oxidation state of the arsenic can be achieved by a simple
oxidation and reduction reaction, yet another topic tackled by
the chemistry teacher. [9-12 Content Standard B- Chemical reactions] The remediation
techniques that are being used to "filter" the
contaminated water also depend on chemistry to work. Other
substances, such as iron, are added to the water, which causes an
iron/arsenic compound to precipitate out of the solution. The
precipitate is not soluble in the water, which is why it can than
be passed through a fine mesh filtering apparatus. Arsenic
is one of the few elements that are known as a semi metal. So
this means it will have the characteristics of both a metal and
nonmetal. This makes arsenic an even scarier foe, because
it can form a countless number of both organic and inorganic
compounds. The following are some ideas for how a chemistry
lesson/lab can be developed based on this real life problem.
WHERE TO BEGIN?
(and some teachers) find using the Internet for research to be a
frustrating experience. However there is a fantastic
website devoted to arsenic contamination around the world. It
is hosted by Harvard University and is quite user friendly.
The resources it contains are written at many different levels
from scientific journal to local newspaper clippings. This
is where to begin with your students.
Go to this
website, explore different links that interest you. Familiarize
yourself with the tragedy of arsenic contamination around the
through the different techniques being used to remove arsenic
from the drinking water. Choose one of the techniques and
defend why it is the best method for the job. Include such
arguments as the cost for the clean up and its effectiveness.
Then discuss how this method relies on topics we discussed in
on the methods used in India, design an experiment to remove a
dissolved substance from contaminated water.
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