MERCURY IN THE ENVIRONMENT

I. Chemistry of Mercury and Adverse Health Effects – Scott Weir, KTIKII. Sources and the Global Pool of Atmospheric Mercury - Scott Weir, KTIKIII. Mercury in the Environment – Scott Weir, KTIKIV. Mercury in the Pacific Northwest - Bob Brunette, NADP-MDN HALV. Deposition – Scott Weir, KTIKVI. Mercury Monitoring Methods – David Gay, ISWS/NADP MercuryVII. Deposition Network & Use of Data – David Gay, ISWS/NADPVIII. The Value of Tribal Monitoring – David Gay, ISWS/NADPIX. Discussion/Questions and Answers

The Chemistry and Adverse Health Effects of Mercury

Presented by

Scott Weir, Air Quality Coordinator

Kickapoo Tribe in KansasKickapoo Environmental Office

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

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

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”)

Elemental Mercury

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

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.

Methylmercury [CH3Hg]+

Toxicity of Mercury

• Mercury poisoningInhalation or ingestion of HgS dustIngestion of water soluble mercuric

chloride (HgCl2) or methylmercury ([CH3Hg]+)

Inhalation of mercury vaporIngestion of contaminated fish/seafood

Toxicity of Mercury• Severity of health effects depends on:

1) the chemical form of mercury;2) dose received;3) duration of exposure;4) age of the person exposed;5) route of exposure (inhalation, ingestion, etc.);6) overall health of the person exposed

Toxicity of Elemental Mercury

• Mercury is a potent toxinVapor 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

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

Sources and the Global Pool of Atmospheric Mercury

Presented by

Scott Weir, Air Quality Coordinator

Kickapoo Tribe in KansasKickapoo 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))

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.

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

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.

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.

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 fishoriginates with coal-fired power plants.

An example…

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

Coal Train1.5 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’s36,694,388,000 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 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.

…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

Mercury in the Environment and Introduction to Deposition

Presented by

Scott Weir, Air Quality Coordinator

Kickapoo Tribe in KansasKickapoo Environmental Office

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.

Mercury Cycle

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.

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.

More About Methylmercury [CH3Hg]+

Methylation of Mercury

• Occurs primarily in wetlands (but also in sediments)Abundant organic matterLow dissolved oxygen levels

• Sulfate-reducing bacteriaBreakdown organic matterUse sulfate for respiration

• Methylmercury is a by-product of the process.

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 ratesdue to rapid decay of organic matter and sulfate reduction.

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

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 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.

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 ProvidesInformation About Mercury Levels

in Local Fish Populations

KTIK has two ponds under a fish consumption advisory to limit mercury

exposure

Mercury Deposition

Presented by

Scott Weir, Air Quality Coordinator

Kickapoo Tribe in KansasKickapoo 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 particle bound Hg)

• It is thought that much 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 contaminants 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” or “dry 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 samples are 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

conversionmore 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 Affect Local Hg

Deposition

1. Concentration2. Precipitation3. 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 AsConcentration 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/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.

Mercury Deposition

• Hg(0) is not water soluble, uptake in cloud water is very slow, and most of it therefore remains in the atmosphere.

• Gaseous reactive mercury (Hg2+) remains in the atmosphere for only 5 to 14 days, during which time it may travel hundreds of kilometers.

• Particulate-bound mercury (Hg(p)) tends to fall out close to its source; larger particles fall out faster than smaller ones.

Poster Session: 2013 National Tribal Forum on Air Quality

For Additional Information:• United Nations Environment Programme (UNEP) publications about

mercury http://

www.unep.org/hazardoussubstances/Mercury/Informationmaterials/ReportsandPublications/tabid/3593/Default.aspx

• UNEP - Global Mercury Assessment 2013: Sources, emissions, releases and environmental transport http://www.unep.org/publications/contents/pub_details_search.asp?ID=6282

• UNEP - Technical Background Report for the Global Mercury Assessment 2013 http://www.amap.no/documents/doc/Technical-Background-Report-for-the-Global-Mer

cury-Assessment-2013/848

• UNEP - Mercury: Time to act http://www.unep.org/publications/contents/pub_details_search.asp?ID=6281

• USGS – publication pending; under peer review The Quality of Our Nation’s Waters: Mercury in the Nation’s Streams – Levels, Trends

and Implications

Scott Weir, Air Quality CoordinatorKickapoo Environmental Office

scott.weir@ktik-nsn.gov

785.486.2601 ext. 2