Objectives
Mercury is as ubiquitous as it is toxic, but people don't know where it is, what it is, or what we can do to change levels of it in the world around us. To a great extent, we also may not know how to regulate our exposure. The purpose of this unit is to teach learners about the natural and anthropogenic ways that mercury cycles through our environment, to teach about the different types of mercury, and to teach about the different impacts that mercury in the environment has; on top predators in a food chain, on the ecosystem as a whole, and on human health. Additionally, the unit examines that mercury is a known pollutant with health risks, yet is still is widely used to make energy efficient and electronic devices. The final outcome of the unit of study will be an action plan- learners will be active in changing the status of mercury in the environment by building a recycling plan than allows the community to recycle electronics in our school. Additionally, learners will understand that individual choices balance risk, and that to navigate decision making, the risk involved in all factors must be known and assessed.
Mercury is a commonly known heavy metal. It is element number 80 on the periodic table, and it has the unusual property of being a liquid at room temperature. Its chemical symbol is Hg, which hearkens back to its Latin name, hydrargyrum. Mercury is a metal in the d-block of the periodic table. The periodic table is designed in such a way that groups elements with similar properties together, and the elements in the d block have their valence electrons in the d orbitals.
Mercury is a metal whose uses have been known for hundreds of years, and has been prepared from cinnabar for medicinal and ceremonial purposes since at least the fifteenth or sixteenth century. Mercury is now known as a human toxin, and is used widely in industrial applications, weapons manufacturing, mining and smelting, and is used as a preservative. 1Mercury nitrate also has a history of use in hat, fur, and felt industries, where mercury inhalation was an occupational hazard; leading to mercury poisoning that manifested such consequences as gingivitis, excitability, memory loss, and tremors. (Industrial mercury poisoning is the origin of the phrase "mad as a hatter.") Mercury is also in the atmosphere as a result of natural outgassing of the earth's crust, remains in the air for relatively long periods of time, and is frequently deposited on land through precipitation. 2
Generally speaking, I believe that many people know that mercury is bad for you, that it is toxic, but I think that people lack certain knowledge about the dangers of mercury poisoning. Specifically, I think many people can't answer the following questions: Where is mercury? How is mercury released? Where does it go when it is released? How does it move through the food chain? Who is most at risk?
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