Presentation on theme: "MERCURY IN THE ENVIRONMENT: Tribal Challenges and Responses I.Chemistry of Mercury and Adverse Health Effects – Scott Weir, KTIK II.Sources and the Global."— Presentation transcript:
MERCURY IN THE ENVIRONMENT: Tribal Challenges and Responses I.Chemistry of Mercury and Adverse Health Effects – Scott Weir, KTIK II.Sources and the Global Pool of Atmospheric Mercury - Scott Weir, KTIK III.Mercury Deposition – Scott Weir, KTIK IV.Mercury Monitoring - David Gay, ISWS/NADP V.Mercury Deposition Network (MDN) - David Gay, ISWS/NADP VI.TAMS Center Activities – Chris Lee, TAMS Center VII. Tribal Challenges and Responses – Panel VIII. Questions and Answers
The Chemistry and Adverse Health Effects of Mercury Presented by Scott Weir, Air Quality Coordinator Kickapoo Tribe in Kansas Kickapoo Environmental Office
The Chemistry and Adverse Health Effects of Mercury Liquid metal Vaporization Persistence Health Effects/Biological damage Mercury in the Environment and Ecosystems Mercury cycle Aquatic systems and methylation Biological amplification up the food chain
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 -38.83 o C (-37.89 o F) Was once known as hydrargyrum (from Greek words meaning “silver water”) – hence the chemical symbol Hg Also called quicksilver (i.e., “live silver”)
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.
The unusual properties of mercury created intense interest among alchemists. Symbol for Hg Ouroboros
Toxicity of Mercury Mercury poisoning – Inhalation or ingestion of HgS dust – Ingestion of water soluble mercuric chloride (HgCl 2 ) or methylmercury ([CH 3 Hg] + ) – Inhalation of mercury vapor – Ingestion of contaminated fish/seafood
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
Methylmercury [CH 3 Hg] + 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 lake sediments and wetland/floodplain soils In lakes, methylmercury is de-methylated in sediments and removed in outlet streams
Methylmercury [CH 3 Hg] + 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
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 about 90% 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
Biochemistry of Methylmercury [CH 3 Hg] + Readily combines with anions such as chloride (Cl − ), hydroxide (OH - ) and nitrate (NO 3 − ) 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
Structural similarity between l-methionine and methylmercury-cysteine
Human Health Effects of Methylmercury [CH 3 Hg] + Completely absorbed by the human gastrointestinal tract in utero damage: readily transported across the placenta, where it is absorbed by the developing fetus Incorporation in proteins results in abnormal molecular structure and affects cellular structure and function Biological persistence: half-life in human bloodstream is about 50 days Causes severe neurological damage in infants and children Also linked to increased risk of cardiovascular disease in adults
Fish Tissue Sampling Provides Information About Mercury Levels in Local Fish Populations
KTIK has two ponds under a fish consumption advisory to limit mercury exposure
Sources and the Global Pool of Atmospheric Mercury Presented by Scott Weir, Air Quality Coordinator Kickapoo Tribe in Kansas Kickapoo Environmental Office
Atmospheric Mercury Mercury occurs in three forms in the atmosphere: – Elemental Vapor (Hg 0 ) » Some is converted to reactive gaseous mercury (Hg 2+ ), the predominant form flushed from the atmosphere by precipitation – Gaseous Divalent (Hg(II)) – Particulate Phase (Hg(p))
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, with additional input from erosion of geologic surfaces containing mercury.
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 & 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.
Natural vs. 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
…and 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
Mercury Deposition Presented by Scott Weir, Air Quality Coordinator Kickapoo Tribe in Kansas Kickapoo Environmental Office
Mercury Deposition Most atmospheric mercury is elemental (Hg 0 ) Some is converted to reactive gaseous mercury (Hg 2+ ) Hg 2+ is the predominant form flushed from the atmosphere by precipitation (reactive gaseous Hg and particulate bound Hg) It is thought that most atmospheric Hg 2+ is in the form of mercuric chloride (HgCl 2 ) – but we’re not sure
Wet vs. Dry Mercury Deposition Wet deposition is the transfer of a substance from the atmosphere to the surface of the earth with precipitation. Dry deposition is the transport of particulate contaminants from the atmosphere onto surfaces in the absence of precipitation – often referred to as “dust fall.”
Wet vs. Dry Mercury Deposition Dry deposition generally involves amounts of mercury so small that measurement is difficult and samples are subject to contamination – difficult to capture without attracting it by static electrical charge – easily contaminated Wet deposition amounts tend to be much larger than dry deposition, and are therefore easier to measure and protect from significant contamination. – collection method works well – analytical laboratory methods are good
Seasonal Variation of Hg Deposition Hg Concentration and deposition amounts tend to be higher during warm weather because: – higher temperatures increase rate of chemical conversion – more oxidants [e.g., ozone (O 3 ) and hydroxyl ions (OH - )] are present to facilitate conversion from Hg 0 to Hg 2+ – more Hg 0 is present due to higher emissions from power plants – increased precipitation occurs and flushes Hg more efficiently – more particulate matter is present
Three Factors Affecting Local Hg Deposition 1.Concentration 2.Precipitation 3.Location MDN Site KS-03: Sac and Fox Nation - Reserve, KS
1. Concentration “Global pool” - The total amount of Hg from non-local sources circulating in the Earth’s atmosphere. 95% is Hg 0 - circulates from 6 months to 2 years. Local Hg emissions – impact local/regional deposition, especially if emitted as, or rapidly converted to, the reactive form (Hg 2+ )
2. Precipitation “Flushes” Hg from the atmosphere Hg concentrations – higher when it begins to rain or snow and lower near the end of a precipitation event
3. Location Local Hg concentrations – vary with distance from point of measurement to the source Wind direction – influences measured levels depending upon whether the sampling point is upwind or downwind of the source at time of sampling Proximity – in general, the closer a monitor is to a source, provided that it is downwind (“in the plume”) of that source, the higher the Hg concentration
Total Hg Is Reported As Concentration or Deposition
Concentration The amount of mercury present in the water collected by the sampler. Concentration measurements provide a timeline record of mercury levels in precipitation across the nation. In the NADP/MDN, concentration is expressed in nanograms of Hg per liter (ng/L) of precipitation collected.
Deposition The amount of mercury deposited by precipitation on each square meter of ground at the sampling site. Deposition values, expressed in micrograms of Hg per square meter per unit of time (ug/m 2 /year), provide annual estimates of mercury loaded onto the surface of the earth in the vicinity of the sampling site (Hg flux). A portion of this mercury enters bodies of water and ultimately enters the food chain through aquatic systems.