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MERCURY IN THE ENVIRONMENT

MERCURY IN THE ENVIRONMENT. Chemistry of Mercury and Adverse Health Effects – Scott Weir, KTIK Sources and the Global Pool of Atmospheric Mercury - Scott Weir, KTIK Mercury in the Environment – Scott Weir, KTIK Mercury in the Pacific Northwest - Bob Brunette, NADP-MDN HAL

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MERCURY IN THE ENVIRONMENT

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  1. MERCURY IN THE ENVIRONMENT • Chemistry of Mercury and Adverse Health Effects – Scott Weir, KTIK • Sources and the Global Pool of Atmospheric Mercury - Scott Weir, KTIK • Mercury in the Environment – Scott Weir, KTIK • Mercury in the Pacific Northwest - Bob Brunette, NADP-MDN HAL • Deposition – Scott Weir, KTIK • Mercury Monitoring Methods – David Gay, ISWS/NADP Mercury • Deposition Network & Use of Data – David Gay, ISWS/NADP • The Value of Tribal Monitoring – David Gay, ISWS/NADP • Discussion/Questions and Answers

  2. The Chemistry and Adverse Health Effects of Mercury Presented by Scott Weir, Air Quality Coordinator Kickapoo Tribe in Kansas Kickapoo Environmental Office

  3. The Chemistry and Adverse Health Effects of Mercury Liquid metal Vaporizes easily Persistent Elemental - cannot be destroyed Health Effects/Biological damage Mercury in the Environment and Ecosystems Mercury cycle Aquatic systems and methylation Biological amplification up the food chain

  4. Amalgamation • Mercury has a peculiar affinity for certain other metals. • attracted the attention of alchemists. • It forms an amalgam with silver or gold. • was used in dental fillings; • also for reflective surface on antique mirrors; • used extensively in gold mining, past and present. • It rapidly corrodes aluminum when it comes into contact. • possible sabotage of aircraft in World War II.

  5. The unusual properties of mercury created intense interest among alchemists.Symbol for Hg Ouroboros

  6. Elemental Mercury • Generally obtained from cinnabar (HgS), a red ore • The only metal which occurs as a liquid at standard temperature and pressure • Slowly vaporizes at ambient temperatures • Freezes at -38.83o C (-37.89o F) • Was once known as hydrargyrum (from Greek words meaning “silver water”) – hence the chemical symbol Hg • Also called quicksilver (i.e., “live silver”)

  7. Elemental Mercury

  8. Hg occurs in three oxidation states • Hg(0) – Elemental mercury • Metal or vapor • Hg(I) – monovalent mercury ion; Hg22+ • E.g., Mercurous Chloride: Hg2Cl2 • Hg(II) – divalent mercury ion; Hg2+ • E.g., Mercuric chloride: HgCl2

  9. Divalent Mercury: Hg2+ • Divalent mercury is the most common form in organic and inorganic mercury compounds. • Divalent mercury is the form most easily washed out of the air with precipitation. • Divalent mercury is also referred to as reactive gaseous mercury.

  10. Methylmercury [CH3Hg]+

  11. Toxicity of Mercury • Mercury poisoning • Inhalation or ingestion of HgS dust • Ingestion of water soluble mercuric chloride (HgCl2) or methylmercury ([CH3Hg]+) • Inhalation of mercury vapor • Ingestion of contaminated fish/seafood

  12. Toxicity of Mercury • Severity of health effects depends on: • the chemical form of mercury; • dose received; • duration of exposure; • age of the person exposed; • route of exposure (inhalation, ingestion, etc.); • overall health of the person exposed

  13. Toxicity of Elemental Mercury • Mercury is a potent toxin • Vapor is harmful – chronic exposure leads to “Mad Hatter Disease” (erethism mercurialis) • Loss of hair, teeth and nails • Deafness • Lack of coordination • Poor memory • Emotional disturbances • Kidney damage

  14. Toxicity of Mercury • In general, for a given exposure, the younger the patient, the more severe the effects • For fetuses, infants and children, the primary adverse health effect is impaired neurological development • Prenatal exposure can be especially severe • Negative impacts on cognition, memory, attention span, language development, and fine motor / spatial skills are well documented

  15. Sources and the Global Pool of Atmospheric Mercury Presented by Scott Weir, Air Quality Coordinator Kickapoo Tribe in Kansas Kickapoo Environmental Office

  16. Atmospheric Mercury • Mercury occurs in three forms in the atmosphere: • Elemental Vapor (Hg0) • Some is converted to reactive gaseous mercury (Hg2+), the predominant form flushed from the atmosphere by precipitation • Gaseous Divalent (Hg(II)) • Particulate Phase (Hg(p))

  17. Atmospheric Mercury • Most of the mercury circulating in the atmosphere is Hg(0) vapor. • This is readily transported, and remains in the atmosphere for 6 months to 2 years. • Hg(0) is gradually oxidized to water-soluble divalent mercury (Hg2+), which is removed from the atmosphere by wet deposition.

  18. Atmospheric Mercury • It is likely that inorganic compounds containing divalent mercury occur in atmospheric aerosols. • Mercuric chloride: HgCl2 – probably the most prevalent • Mercuric nitrate: Hg(NO3)2 • Mercuric sulfate: HgSO4

  19. Natural Sources of Atmospheric Mercury • In nature, mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide, HgS). • Natural emissions to the atmosphere generally occur through volcanic and geothermal activity (including oceanic vents), with additional input from erosion of geologic surfaces containing mercury.

  20. Natural vs. Anthropogenic Sources of Atmospheric Mercury • Natural sources (e.g., volcanoes) are responsible for about one-third of atmospheric Hg emissions. • Anthropogenic sources (e.g., coal-fired EGUs & gold mining) are responsible for about one-third of atmospheric Hg emissions. • The remaining one-third of emissions are due to recycling of Hg already in the environment.

  21. Anthropogenic Sources of Atmospheric Mercury • The human-generated portion of mercury emissions can be broken down to the following: • 65% from stationary combustion (mostly coal-fired power plants, which account for 40% of U.S. emissions) • 11% from gold mining • 7% from non-ferrous smelters • 6.5% from cement production • 3.0% from waste disposal • 3.0% from caustic soda production • 4.5% from other sources

  22. Part of the problem:Mercury is a natural contaminant in coal.About 40% of the mercury in fishoriginates with coal-fired power plants.

  23. An example…

  24. There are 18 coal-fired Power Plants within 150 miles of the Kickapoo Tribe in Kansas

  25. Coal Train 1.5 miles long 150 cars Car capacity: 102-121 tons Train capacity: 15,300 - 18,150 tons

  26. In 2011, the 6 major power plants to the south of the KTIK reservation burned 18,347,194 tons of coal.

  27. That’s36,694,388,000 pounds of coal.

  28. In 2011, the 6 major power plants to the south of the KTIK reservation emitted 1,512.4 lbs. of Hg.

  29. There is some good news…

  30. …and more… • Mercury accumulation rates in four rural eastern Minnesota lakes and four Minneapolis-area lakes peaked in the 1960s and 1970s, and declined in the 1980s. • The declining mercury accumulation rates in the 1980s are attributed to reductions in regional mercury sources, resulting from: • decreased industrial uses of mercury; • improved technologies at coal-burning facilities; • a shift from coal to natural gas for heating; and • decreased waste incineration.

  31. …and even more… • MERCURY AND AIR TOXICS STANDARDS (MATS) • Replaces Clean Air Mercury Rule (CAMR), which was based on cap and trade • Applicable to new electricity generation facilities • Establishes emission limits for Hg as well as for other metals, particulate matter and acid gases

  32. Mercury in the Environment and Introduction to Deposition Presented by Scott Weir, Air Quality Coordinator Kickapoo Tribe in Kansas Kickapoo Environmental Office

  33. Mercury in the Environment • Mercury is a persistent pollutant. • Mercury remains in the atmosphere for 6 months to 2 years. • Mercury accumulates in soils, sediments, ponds and lakes. • Mercury bioaccumulates efficiently, especially in aquatic systems.

  34. Mercury Cycle

  35. The Mercury Cycle • Inorganic mercury from coal-burning is emitted as gaseous elemental mercury, reactive gaseous mercury and particle-bound mercury. • Gaseous elemental mercury directly enters the global atmospheric pool and circulates for up to 2 years. • Reactive gaseous mercury and particle-bound mercury are generally deposited locally and regionally.

  36. The Mercury Cycle • Inorganic mercury (from coal-fired EGUs or mercury/gold mining operations) enters aquatic systems via deposition and runoff. • Some inorganic mercury attaches to suspended sediment, but... • Some enters organic-rich wetlands and is converted to methylmercury by natural bacterial processes, and then enters streams and lakes with organic matter. • Some inorganic and methylmercury remains in the soil, some leaves via stream flow, and some is re-emitted from the soil to the atmosphere.

  37. More About Methylmercury [CH3Hg]+

  38. Methylation of Mercury • Occurs primarily in wetlands (but also in sediments) • Abundant organic matter • Low dissolved oxygen levels • Sulfate-reducing bacteria • Breakdown organic matter • Use sulfate for respiration • Methylmercury is a by-product of the process.

  39. Methylation of Mercury • Moderate sulfate levels generally enhance formation of methylmercury. • Low sulfate levels limit methylation. • High sulfate levels inhibit methylation because sulfate is converted to sulfide, which binds directly to mercury. • Newly flooded lands and repeated wetting/drying cycles result in high methylation rates • due to rapid decay of organic matter and sulfate reduction.

  40. Methylmercury [CH3Hg]+ • Bioaccumulative environmental toxin • Formed from inorganic mercury by the action of anaerobic microorganisms that live in aquatic systems – sulphate-reducing bacteria are primarily responsible • Methylation predominantly occurs in wetland/floodplain soils and lake sediments • In lakes, methylmercury is also de-methylated in sediments and removed in outlet streams

  41. Methylmercury [CH3Hg]+ • Not readily eliminated from organisms • Biological half-life in aquatic ecosystems is 72 days • Biomagnified in aquatic food chains from bacteria and plankton, through macroinvertebrates, to herbivorous fish and to piscivorous (fish-eating) fish • Predators, i.e., fish-eating birds and mammals (including humans), are at the top of the food chain and receive the highest doses • Concentration of methylmercury in the top level aquatic predators can reach a level a million times higher than the level in the water.

  42. Bioaccumulation

  43. Methylmercury Exposure • Methylmercury levels in freshwater fish vary with the level of deposition of mercury from the air. • Models suggest that about 70% of the mercury deposited into the ocean is re-emitted to the atmosphere, but also that methylmercury stays in the upper ocean for about 11 years. • Research indicates that mercury content in many marine animals is 12 times higher than pre-industrial levels. This implies that much of the mercury in these marine animals comes from anthropogenic sources. • Indigenous populations in the Arctic who consume top marine predators (fish, seals, and whales) have some of the world’s highest exposures to methylmercury.

  44. Biochemistry of Methylmercury [CH3Hg]+ • Readily combines with anions such as chloride (Cl−), hydroxide (OH-) and nitrate (NO3−) • Very high affinity for sulfur-containing anions, particularly the thiol (-SH) groups on the amino acid cysteine • Methylmercuric-cysteinyl complex is recognized in the body as the essential amino acid methionine.

  45. Structural similarity between l-methionine and methylmercury-cysteine

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