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contaminants in the environment.docx

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McMaster University
Life Sciences
Luc Bernier

March 27 , 2013 Life Sci 2H03: Environmental Life Sciences Contaminants in the Environment Mercury in the Environment - Hg is a natural occurrence in Earth’s biogeochemical system - Increased levels in atmosphere, ocean, and terrestrial systems - Combustion of fossil fuel, especially coal Mercury Cycle - elemental mercury distributed through winds - hg can precipitate with acids and move into freshwater and marine environments - or precipitate entering terrestrial systems - deposits in the form of dust - precipitate in the form of rain or snow - enters marine ecosystems - mercury can enter sediments and remain for decades, even centuries - mental mercury is efficiently absorbed by organisms in their fatty tissues - organic mercury can also settle in sediments - biomagnification in the food chain Mercury: A Toxic Chemical - in 1950s: Minamata, Japan - people ate fish contaminated by high levels of mercury - neurological damages - e.g.: visual, auditory, and sensory disturbances, etc. - malformation in utero: children born exposed to high doses of mercury in the womb develop mental disorders Natural Mercury Cycle - primary emissions: volcanoes and related geological processes - land emissions from areas rich in mercury - wetlands may be associated to high levels of mercury - spikes in mercury with land disposal facilities Plate Tectonic Boundaries Geologically Rich in Mercury - concentrated in the areas where tectonic plates are meeting and where there is a lot of volcanic activity Ice Cores Reveal Record of Natural and Anthropogenic Mercury Deposition for the Last 270 Years - high altitudes recovering the cores - each layer corresponds to the position in the atmosphere for a given year - mining and increase in fossil fuels - pre-industrial estimates: amount of mercury moving between atmosphere, water and land ~1000kg/year - anthropogenic: ~4000kg/year - 4-fold increase just attributed to human activity - mercury being released through human activity and changes in terrestrial habitat Hg Emissions Trends - direct, present-day anthropogenic emissions of mercury to the atmosphere range: 2,200-4,00 tonnes year -1 - coal: stationary combustion represents ~60% of year 2000 emissions Total Anthropogenic Emissions
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