Bangladesh Arsenic Poisoning Scenario
The People's Republic of Bangladesh is surrounded by India to the east, north, and west, and by the Bay of Bengal and the country of Myanmar to the south.
Though relatively poor in natural resources, Bangladesh is unfortunately rich in the poisonous element arsenic. Groundwater flows through sediments rich in arsenic, and by some poorly-understood mechanism the arsenic dissolves in the water. Because surface water is visibly polluted, Bangladesh citizens were encouraged in recent decades to dig "tube wells" to access groundwater for their drinking supply. This project was successful, and approximately 2.5 million of such wells are in use. However, chemists discovered in 1993 that many of these wells contained arsenic levels of greater than 50 micrograms /liter, well in excess of the World Health Organization's suggested limit of 10 micrograms/liter.
Bangladesh has a population of greater than 130 million people, many of whom are exposed to arsenic poisoning through their drinking water. The effects can be noticed most easily on the skin: hyper- and hypopigmentation, gangrene, keratosis (hardening of the skin of the soles and palms), and skin cancer are some of the diseases caused by the ingestion of arsenic. Redness and burning in the eyes resulting from conjunctivitis is also common. Breathing airborne arsenic can cause lung cancer. Doctors are not sure how many other internal problems arsenic ingestion might cause.
Pietro Perona, an electrical engineer at Caltech, has developed an inexpensive instrument to determine the concentration of arsenic in groundwater. His "arsenometer" uses a pair of light-emitting diodes (LEDs) and two photodiode detectors to determine the difference in the intensity of blue light in two solutions of the water sample-one containing an oxidizing agent and one containing a reducing agent. This instrument has the added advantage of being relatively inexpensive; with a selling price of $50, it is accessible to organizations in some of the poorer countries of the world.
While the Virtual Lab does not have an arsenometer in its collection, it does have an instrument that is capable of measuring the intensity of light-the spectrophotometer. In this activity, you will prepare solutions from samples of water sent to us from a chemist in Bangladesh, and use the spectrophotometer and other techniques to determine the concentration of arsenic in the samples.
Gravimetric Determination of Arsenic
Determine the amount of arsenic present in soil samples.
More problems will follow...