Mercury can be used in many different products such as barometers, florescent lamps, and electrical switches and can be in the fish that we eat, whether the fish was caught in a local lake or bought from the grocery store. Mercury is a naturally occurring element in the earth’s crust that can be moved around from volcanoes, coal burning plants, mining, and other natural or human actions. “Mercury is well-documented as a toxic chemical that is atmospherically transported on a local, regional, and global scale by cycling among air, land, and water” (U.S. EPA, 2009). As early as the 1950’s we found that exposure to mercury can be extremely toxic, even deadly to animals and people. Throughout this report I will describe the basic chemical science of mercury, discuss the history and finally the government policies that are being enforced to deal with this problem. Basic Science:
Elemental mercury (Hg), also known as quicksilver, is a unique metal because it is liquid at room temperature. “Mercury’s chemical symbol comes from the Greek word hydrargyrum, which means liquid silver”(Gagnon, 2010). Mercury is commonly found as the mineral cinnabar (HgS), but is rarely found in the elemental form naturally. Mercury tends to alloy easily with many metals called amalgams. Amalgams can be used to extract metals and can be used in dentistry. Mercury exists in three different sources around the world. Manufactured mercury compounds from a laboratory setting, byproducts of mining and refining, and Industrial waste.
“Mercury exists in three oxidation states: Hgo (elemental mercury), Hg22+ (mercurous mercury), and Hg2+ (mercuric mercury)”(COTW, 2010). The last two oxidation states can form inorganic chemical compounds, which are predominantly airborne mercury, and organic chemical compounds such as methylmercury. Mercury compounds have many different uses. “The most important mercury salts are mercuric chloride HgCl2 (corrosive sublimate - a violent poison), mercuric chloride Hg2Cl2 (calomel, still used in medicine occasionally), mercury fulminate (Hg(ONC)2, a detonator used in explosives) and mercuric sulphide (HgS, vermillion, a high-grade paint pigment)”(LWTS, 2009). Airborne mercury from coal burning power plants and volcanoes can be carried in the air globally eventually returning to the ground. Methylmercury is one of the most toxic forms of mercury which affects the immune system and nervous system especially in developing babies. Elemental mercury transforms into methylmercury by the oxidation of Hgo to Hg2+ and then to CH3Hg+. This is a very difficult biogeochemical process. “Humans generally uptake mercury in two ways: (1) as methylmercury (CH3Hg+) from fish consumption, or (2) by breathing vaporous mercury (Hg0) emitted from various sources such as metallic mercury, dental amalgams, and ambient air”(Brigham, 2003). There are many ways that mercury can become airborne into our atmosphere and eventually deposited back to the earth. “Mercury is emitted by natural sources, such as volcanoes, geothermal, geologic deposits, and the ocean. Human-related sources primarily include coal combustion, waste incineration, industrial uses, and mining. During the last 150 years, human activities have more than doubled natural amounts of mercury in the atmosphere”(Brigham, 2003). Once mercury is deposited on the ground it can accumulate in lakes and streams. “It can enter the food chain, where it can be released back to the atmosphere by volatilization. The concentration of dissolved organic carbon (DOC) and pH have a strong effect on the ultimate fate of mercury in an ecosystem”(Krabbenhoft, 2009). The mercury processes in ecosystems are very complex but once methlymercury ends up in the sediments it can move up the food chain. When moving up the food chain mercury can start to accumulate, this is known as Bioaccumulation. “Bioaccumulation is the process by which organisms can take up contaminants more...
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