Transcript MercuryInTheEnvironment

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
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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 -38.83o 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”)
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 (HgCl2) or methylmercury
([CH3Hg]+)
– 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)
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Loss of hair, teeth and nails
Deafness
Lack of coordination
Poor memory
Emotional disturbances
Kidney damage
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 lake
sediments and wetland/floodplain soils
• In lakes, methylmercury is de-methylated in
sediments and removed in outlet streams
Mercury Cycle
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
Bioaccumulation
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
[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
Structural similarity between l-methionine
and methylmercury-cysteine
Human Health Effects of
Methylmercury [CH3Hg]+
• 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
A little mercury goes a long way…
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 (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))
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
Part of the problem:
Mercury is a natural contaminant in coal.
About 40% of the mercury in fish
originates with coal-fired
power plants.
An example…
There are 18 coal-fired Power Plants within 150
miles of the Kickapoo Tribe in Kansas
Coal Train
1.5 miles long
150 cars
Car capacity:
102-121 tons
Train capacity:
15,300 - 18,150 tons
In 2011, the 6 major power plants to the
south of the KTIK reservation burned
18,347,194 tons of coal.
That’s
36,694,388,000
pounds of coal.
In 2011, the 6 major power plants to the
south of the KTIK reservation emitted
1,512.4 lbs. of Hg.
There is some good news…
…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 (Hg0)
• Some is converted to reactive gaseous mercury
(Hg2+)
• Hg2+ is the predominant form flushed from the
atmosphere by precipitation (reactive gaseous Hg
and particulate bound Hg)
• It is thought that most atmospheric Hg2+ is in the
form of mercuric chloride (HgCl2) – 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 (O3) and hydroxyl ions (OH-)]
are present to facilitate conversion from Hg0 to Hg2+
– more Hg0 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 Hg0 - 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 (Hg2+)
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
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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/m2/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.
Contact Information:
Scott Weir
[email protected]
785.486.2601 ext. 2