Great Salt Lake’s Mercury: Biogeochemical Cycling of Nevada Gold Mining Emissions Why? How? How long? What effects? What’s Next? Ivan Weber 10-01-05.

Great Salt Lake’s Mercury: Great Salt Lake’s Mercury: Biogeochemical Cycling of Biogeochemical Cycling of

Nevada Gold Mining Nevada Gold Mining EmissionsEmissions

Why? How? How long? What Why? How? How long? What effects? What’s Next? effects? What’s Next?

Ivan Weber 10-01-05

Mercury Moves Mercury Moves like no otherlike no other

• ‘Winged Mercury’ is legendarily elusive and mobile• “Shape-shifting” threat, capable of moving over time from

solid to liquid to gas to hitchhiker on particles and in organisms

• Can be sequestered as stable, metallic form, but be oxidized and mobilized by transport or changing conditions

• A ‘global pool’ of Mercury grows at 1%/year, according to some analysts, as a result of fossil fuel combustion, industrial and consumer products manufacturing, forests and soils releases (and re-releases), open oceans emissions, and from metals mining/processing

Metals Mining Mercury EmissionsMetals Mining Mercury Emissions

• Gold, Silver, Copper – “amalgams” and beneficiation emissions

• Historical and ‘artisanal’ (primitive) mining used mercury to separate gold & silver, then drove off mercury by heating to leave Au & Ag

• “Modern” gold mining roasts ore to oxidize, make available maximum amount of gold particles in ore for cyanide leaching, free gold from binding in carbon-rich and sulfide ores

• Scrubbing only partially successful at capturing Hg; quantities so large allow enormous emissions to air

• Huge quantities of tailings & waste rock placed on land for long-term Hg oxidation, transport (e.g., Carlin tailings dam failure)

Mercury Cycling – Air TransportMercury Cycling – Air Transport

Airborne Mercury Emissions:– Elemental or ‘metallic’ mercury (Hg0)

• Settles into stream, lake and ocean sediments• Is carried gradually into water bodies with limited reactive

potential for conversion to other forms• Vaporizes into atmosphere – uniquely high vapor pressure

among metals – often after long history of earlier transport and re-exposure to changing conditions; long ‘residence time’ in atmosphere

– Inorganic, ionic mercury (bivalent Hg2+ or HgII is most common; also mercuric oxide HgO; particulate and gaseous forms)

• Predominant airborne form• Readily adsorbed to airborne particles• Accounts for most (up to 95%) of ‘wet’ and ‘dry’ deposition

over land, forests, lakes, watersheds• Hg2+ Primary “substrate” for conversion to methyl mercury in

waterbodies

Mercury Biogeochemistry Mercury Biogeochemistry byby Dummies Dummies• As with most other metals released in nature or by industry,

BIO GEO CHEMICAL processes are subject to inorganic chemical processes, but can be ‘mediated’ by microbiological organisms: bacteria, algae, fungi

• If conditions are right (or can be made right) for microbiological activity, then biogeochemical processes can convert metals into compounds of more or less stability, depending on pH, dissolved carbon, available sulfate, and other variables

• Micro-environments in wetlands famously subject metals and other mining contaminants to “reduction-oxidation” (‘redox’) variations, depending on oxygen and organic carbon availability (carbon is often a ‘donor’ of critical electrons for conversion reactions)

• Sulfur affinities and sulfate-reducing or –oxidizing bacteria can alter Hg forms, especially in aquatic environments

Mercury Methylation Happens Mercury Methylation Happens Almost EverywhereAlmost Everywhere

• Sulfate-reducing bacteria seem to play an important role, along with pH, temperature and other factors (somewhat offset by H2S stable mercury sulfides)

• Appears to require methylcobalamine (vitamin B12) donation of methyl groups to Hg2+

• Can occur in soils as well as in dynamic oxic/anoxic zones of water column

• Many microorganisms can methylate Hg: strepto- and staphylococci, lactobacilli, yeasts, fungi and both anaerobic and aerobic bacteria

• Methylating microorganisms occur even in gut of fish, humans and other animals

Mercury GeneralizationsMercury Generalizations• Airborne mercury can be metallic (Hg0) vapor or

inorganic/ionic (Hg2+ – usually oxidized), often adsorbed to particles --- Hg2+ predominates

• Metallic mercury vaporization is temperature-sensitive, often seasonal or dependent on micro-climates (e.g., south-facing, or warmth from sulfide oxidation in waste rock dumps & tailings)

• Metallic mercury is generally not ‘bioavailable’ either to plants or to animals

• Mercury can be ‘sequestered’ in sediments or soils primarily in metallic, sulfide or organically-complexed forms

• Methyl mercury (CH3Hg+) is the form most dangerous to life, most mobile in aquatic environments, most likely to accumulate in water bodies, and to bioaccumulate in aquatic organisms

• Microbiological processes are especially active at water-sediment and aerobic-anaerobic interfaces, which often change very frequently in natural systems (esp. wetlands)

Nevada’s Gold Boom May Be Nevada’s Gold Boom May Be Utah’s Ecological Health BustUtah’s Ecological Health Bust

• USGS Team reports highest mercury readings ever in Great Salt Lake water column, migratory bird tissue, picked up by Salt Lake City press in February, 2005

• 3 fish advisories; DUCK advisory yesterday 9-30-05!• Nevada gold mining escalation over past two + decades has

been indicated quietly in TRI to be responsible for greatly increased mercury air & some solids releases, but great doubt exists about true emissions quantities

• Nevada state environmental quality program has established a ‘voluntary’ mercury emissions reporting and reductions program among four companies / five major mines, only partially successful

• North-central and Northeastern Nevada emissions reported in TRI are among nation’s largest mercury sources, with Utah immediately downwind

• ARE GSL Hg FINDINGS and NEVADA Hg EMISSIONS CONNECTED?

Nevada Sends Emissions Nevada Sends Emissions Downwind, but Keeps the GoldDownwind, but Keeps the Gold

• Utah, Idaho, Wyoming, Colorado are within range of airborne transport

• Average ‘residence time’ of Hg air emissions is ~ one year, plenty of time for regional or global transport

• Only relatively minor portion of Hg vapor falls out close to source

• Gradual re-emission is likely of metallic vapor from tailings, waste rock and from prior or historical releases, esp. to aquatic systems (remember high vapor pressure, sensitivity to temperature of vaporization) – mining’s deadly legacy, worldwide

Great Salt Lake WatershedGreat Salt Lake Watershed

• Immense area of N. Utah, NE Nevada, SE Idaho• High-elevation water bodies tend to be cold receptors of

precipitation, relatively nutrient-poor• Great Salt Lake is ‘terminal basin’ where persistent

compounds accumulate, evaporatively concentrate• One of Western Hemisphere’s most important habitats

for migratory shorebirds and waterfowl, numbering 5-10 million/year, >250 species, many in greater numbers at GSL than anywhere else in the world

• Toxicological risk to human populations largely unknown in time of accelerating growth and probable climate change impacts susceptibility

hypothetical model ofprecip as primary Hg transport vehicle

GSL

Most of precip in high countryAirflow typ. from West(precip. events sometimesfrom NW or SW)

‘Wet’ Adsorbed Inorganic & Elemental Hg

Portion of Hg methylated & transported

Stream & overland flow transport likely

Some flows to ground Water, re-emerge to surface

Surface & Ground water flows - over time - carrying residual elemental Hg and CH3Hg+ultimately to GSL

Large nutrient-rich reservoirs enhance CH3 formation

What are the gradients? What portionof CH3 is dissolved, entrained,and water-borne?

Eutrophic zones atinflows likely methylation areas

SO4-reducers?

Limited de-methylationand ‘evasion’ to air

Where should we look for Mercury Where should we look for Mercury Biogeochemical Activity?Biogeochemical Activity?

• Ozone-rich urban and forest fire/wildfire atmospheres for Hg oxidation, precursor to methylation in aquatic environments

• Forests for plant uptake, acidic soils (humic acid), animals for ‘bioaccumulation’ effects, especially predators

• Seasonally warm organic-rich aquatic environments; agriculture-eutrophied waterbodies

• Locally acidic aquatic micro-environments that are carbon-rich

• Sulfate-rich aquatic environments• Wetlands water-column / sediment interfaces often harbor

conditions for metallic Hg – methyl mercury conversion, often at micro-environment level

Great Salt Lake:Great Salt Lake:One of the briniestOne of the briniest

COMPARATIVE BRINE COMPOSITIONS

% of dry weight / dissolved solids g/100g

CONSTITUENT GSL OCEAN DEAD SEA

chloride 14.1 / 55.2 1.94 / 55.4 17.5 / 65.1

sodium 7.6 / 29.8 1.08 / 30.8 3.3 / 12.3

sulfate 2.0 / 7.8 0.27 / 7.7 0.7 / 2.6

magnesium 1.1 / 4.3 0.13 / 3.7 3.4 / 12.6

calcium 0.02 / 0.06 0.04 / 1.1 1.4 / 5.2

Approx. 20% = TDS ~ 200 g/l-1

GSL – Dynamic Microbiological GSL – Dynamic Microbiological Soup for Migratory BirdsSoup for Migratory Birds

• No fish in GSL, so we were asleep at the wheel (except at freshwater inlets)

• Wild swings of depth / surface elevation, area coverage, biogeochemistry (dilution, redox potential, organic content, etc.)

• Abundance of sulfate• Dynamic water column variations (anaerobic-aerobic)• Algal and bacterial productivity almost unrivalled for

micro-invertebrates (“plankton”)• Enormously productive of brine shrimp, brine flies: as

much as 170,000 lbs/yr of brine shrimp eggs have been harvested for international markets (prawn/shrimp food)

• Millions of migratory shorebirds and waterfowl feed on this Great Basin “Okavango”

GSL ‘Reactor Vessel’: Microbiological GSL ‘Reactor Vessel’: Microbiological Dynamics and Methyl Mercury Dynamics and Methyl Mercury

• GSL likely receives inflows of MeHg from entire watershed, including eutrophic-tending lakes (e.g., Utah Lake)

• Direct Hg air deposition possibly dominated by inorganic mercury (Hg2+ )

• Hg2+ provides ‘methylation substrate’ combined with biological and inorganic chemical conditions ideal for MeHg formation

• MeHg tends to remain dissolved, accumulates evaporatively, taken up by plankton, algae, plants and invertebrates at base of food chain

• MeHg is readily bioaccumulated in birds (eared grebe found with 25 nanograms/g in liver --- 1 nanogram sets off the alarms)

……hot off the press! (excerpt)hot off the press! (excerpt)Mercury alert: 2 duck species too toxic to eat

Utah health advisory: Tests show some waterfowl that feed on Great Salt Lake marshes fail EPA standards

By Patty Henetz and Brett Prettyman The Salt Lake Tribune Friday, September 30, 2005

Two days before the opening day of the duck hunting season, state officials warned Utah hunters not to eat northern shovelers or common goldeneyes that feed on Great Salt Lake marshes because tests of their flesh show toxic levels of mercury.    The health advisory appears to be the first of its kind in the nation, said state Health Department toxicologist Wayne Ball, who analyzed Utah State University laboratory results of samples state scientists took from seven different duck species on the south end of the lake last year and during the past two months.     All but three of the species in the sample had at least one duck with mercury levels higher than what the U.S. Environmental Protection Agency considers safe to eat. Ten goldeneyes were tested and showed results ranging from below the EPA standard of .3 milligrams of mercury per kilogram of edible tissue to 14 times the standard. Of the 20 shovelers sampled, only one was below the standard, while the rest ranged from about twice the standard to 39 times the safety point.

Two days before the opening day of the duck hunting season, state officials warned Utah hunters not to eat northern shovelers or common goldeneyes that feed on Great Salt Lake marshes because tests of their flesh show toxic levels of mercury.

   The health advisory appears to be the first of its kind in the nation, said state Health Department toxicologist Wayne Ball, who analyzed Utah State University laboratory results of samples state scientists took from seven different duck species on the south end of the lake last year and during the past two months.

    All but three of the species in the sample had at least one duck with mercury levels higher than what the U.S. Environmental Protection Agency considers safe to eat. Ten goldeneyes were tested and showed results ranging from below the EPA standard of .3 milligrams of mercury per kilogram of edible tissue to 14 times the standard. Of the 20 shovelers sampled, only one was below the standard, while the rest ranged from about twice the standard to 39 times the safety point.

Two days before the opening day of the duck hunting season, state officials warned Utah hunters not to eat northern shovelers or common goldeneyes that feed on Great Salt Lake marshes because tests of their flesh show toxic levels of mercury.

   The health advisory appears to be the first of its kind in the nation, said state Health Department toxicologist Wayne Ball, who analyzed Utah State University laboratory results of samples state scientists took from seven different duck species on the south end of the lake last year and during the past two months.

    All but three of the species in the sample had at least one duck with mercury levels higher than what the U.S. Environmental Protection Agency considers safe to eat. Ten goldeneyes were tested and showed results ranging from below the EPA standard of .3 milligrams of mercury per kilogram of edible tissue to 14 times the standard. Of the 20 shovelers sampled, only one was below the standard, while the rest ranged from about twice the standard to 39 times the safety point.

Two days before the opening day of the duck hunting season, state officials warned Utah hunters not to eat northern shovelers or common goldeneyes that feed on Great Salt Lake marshes because tests of their flesh show toxic levels of mercury.

   The health advisory appears to be the first of its kind in the nation, said state Health Department toxicologist Wayne Ball, who analyzed Utah State University laboratory results of samples state scientists took from seven different duck species on the south end of the lake last year and during the past two months.

    All but three of the species in the sample had at least one duck with mercury levels higher than what the U.S. Environmental Protection Agency considers safe to eat. Ten goldeneyes were tested and showed results ranging from below the EPA standard of .3 milligrams of mercury per kilogram of edible tissue to 14 times the standard. Of the 20 shovelers sampled, only one was below the standard, while the rest ranged from about twice the standard to 39 times the safety point.

Two days before the opening day of the duck hunting season, state officials warned Utah hunters not to eat northern shovelers or common goldeneyes that feed on Great Salt Lake marshes because tests of their flesh show toxic levels of mercury.

   The health advisory appears to be the first of its kind in the nation, said state Health Department toxicologist Wayne Ball, who analyzed Utah State University laboratory results of samples state scientists took from seven different duck species on the south end of the lake last year and during the past two months.

    All but three of the species in the sample had at least one duck with mercury levels higher than what the U.S. Environmental Protection Agency considers safe to eat. Ten goldeneyes were tested and showed results ranging from below the EPA standard of .3 milligrams of mercury per kilogram of edible tissue to 14 times the standard. Of the 20 shovelers sampled, only one was below the standard, while the rest ranged from about twice the standard to 39 times the safety point.

What We Don’t Know What We Don’t Know Critical Questions: History Critical Questions: History

• “Natural” mercury flows through region?• What remains of ‘historic’ mercury mining?• Have historical sources been underestimated, under-

reported?• Are current industries’ (esp. mining) Hg accurately

reported, accurately understood quantitatively?• Are Hg emissions from NV and UT waste rock, tailings

understood?• What’s come into the watershed since the advent of gold

mining ore roasting?• What Hg may remain from industrial, commercial and

residential coal use, including power?• What else has been done in the watershed that may

have contributed mercury?

GSL Watershed Historic MiningGSL Watershed Historic Mining

• Bingham/Barney’s Canyon (Kennecott)• Mercur (Barrick)• Ophir• Gold Hill• Eureka – Tintic• Park City district• Big & Little Cottonwood districts• Others…

Historic Mines in GSL WatershedHistoric Mines in GSL Watershed

MERCURY EMISSIONS "W.A.G." ESTIMATE GREAT SALT LAKE WATERSHED MINES I. Weber 9-29-05

SOURCE Production History: C.L. Ege, Selected Mining Districts of Utah, UGS Misc. Pub. 05-5 2005  

Mine/DistrictHistorical Production Au

& Ag (Lbs)

Avg. Hg Emission Factor Hg/Au + Ag (after de Lacerda &

Salomons 1998, decreased 50% for

industrial process era)Approximate Hg Emissions Lbs. Notes

Bingham Complex & Barneys Canyon (1864-present) 22,405,788 0.75 16,804,341  

Mercur- Barrick Mercur (1869-1996) 236,875 0.75 177,656

produced 3,470 flasks Hg (~132 tons)

Ophir (1870-1972) 1,907,288 0.75 1,430,466  

Gold Hill 1892-1961 53,600 0.75 40,200  

Eureka-Tintic (1869-1987) 17,173,125 0.75 12,879,844  

Park City (1875-1982) 15,903,125 0.75 11,927,344  

Cottonwood Canyons & American Fork Canyon (1868-1976 1,247,850 0.75 935,888  

TOTALS 58,927,650   44,195,738  

Historical Mining’s HgHistorical Mining’s Hg

• We don’t know:– Real ‘emissions factor’ as technology changed for

each mining operation, each smelter, each refinery– Exactly where each mine sent its ore for processing– What Hg species released, what put into solids

storage or into ground and surface waters

• We DO know:– Much of the processing was done IN SALT LAKE

CITY at several major facilities, some of which also processed ore for Butte MT, Park City and other major Western mines

Gradients, mechanisms of transport, Gradients, mechanisms of transport, cycling, ‘fate’? … things to considercycling, ‘fate’? … things to consider• Elevation - temperature and Hg retention• Seasonal precipitation: Snowpack vs. summer rain --

variations in Hg deposition?• Aspect - temperature implications for Hg behavior?

Vegetation differences with aspect, and influence?• Forest types, correlated with other variables?• Nutrient/DO content of waterbodies (degree of

eutrophication, correlated w/methylation potential?• Bacterial community attributes - SO4 reducers?• Influence of urban waste, sewage treatment plant

discharges (Northern cities, especially), Agricultural wastes, on methylation?

What We Don’t Know What We Don’t Know Critical Questions: Human Health & Critical Questions: Human Health &

Ecosystems VitalityEcosystems Vitality• What do GSL data indicate about other possible

problems, incl. human? Which may not be problems?– Direct, ‘first-time’ deposition vs. ‘recycling’ in watershed? Extent of

GSL methylation?– Subsequent exposure to ‘cycled’ elemental or methyl mercury? Autism

vs. ‘Hg poisoning’?– Where are the likely locations of concern for fish bioaccumulation of

Hg? Three recent ‘advisories’ issued– Fish hatcheries, commercial trout farms a concern?– What synergistic interactions and ecological effects are possible with

other ‘COCs’ in GSL? Se? As? Dioxins/Furans? Other organics?

……and then there’s and then there’s global warmingglobal warming: RM/GB : RM/GB projections for much warmer, much much projections for much warmer, much much wetter (Bush Administration’s own 2003 wetter (Bush Administration’s own 2003

regional report regional report Preparing for a Changing ClimatePreparing for a Changing Climate))• Projections are for increased runoff, much higher GSL• Possible increased purging & transport of Hg and other

contaminants from watershed to GSL Is there an accumulating mercury burden in the GSL Watershed’s high country waiting to flush into the GSL?

• May be offset somewhat by dilution in deeper, larger Lake• Transition to ‘greenhouse world’ could mean more decaying

plant matter in waterbodies, therefore increased eutrophication more widespread methylation conditions

• Increased urban heat = increased ozone = increased oxidation of Hg0 = increased deposition into waterbodies = increased methyl mercury --- doesn’t it???

How do we get this monster under control How do we get this monster under control and restore conditions to healthful for and restore conditions to healthful for

ecosystems and people?ecosystems and people?

THANKS!

Ivan Weber

Weber Sustainability Consulting

953 1st Avenue

Salt Lake City, Utah 84103

(801)355-6863 / (801)651-8841 cellular

[email protected]