Mercury Management in Mercury Management in Modern Precious Metals Modern Precious Metals

MinesMines

Glenn Miller and Greg JonesGlenn Miller and Greg Jones

Department of Natural Department of Natural Resources and Environmental Resources and Environmental

ScienceScience

University of Nevada, RenoUniversity of Nevada, Reno

Purpose of the StudyPurpose of the Study

Determine the total amount of Determine the total amount of byproduct mercury produced and byproduct mercury produced and how it is managedhow it is managed

Determine and analyze the Determine and analyze the atmospheric emissions both from the atmospheric emissions both from the Toxic Release Inventory and the Toxic Release Inventory and the Voluntary Mercury Reduction Voluntary Mercury Reduction Program in NevadaProgram in Nevada

Historic Use of Mercury in Historic Use of Mercury in Precious Metals MinesPrecious Metals Mines

Gold will dissolve in liquid mercury and this Gold will dissolve in liquid mercury and this process was extensively used for recovery of gold process was extensively used for recovery of gold from ground orefrom ground ore

Generally utilized plates covered with mercury to Generally utilized plates covered with mercury to which an ore slurry was passed overwhich an ore slurry was passed over

Estimated 1 lb of mercury lost for each ton of ore Estimated 1 lb of mercury lost for each ton of ore processed (Comstock)processed (Comstock)

Tailings often eroded into streams or were Tailings often eroded into streams or were deposited directly into streamsdeposited directly into streams

Metallic mercury converted to ionic mercury and Metallic mercury converted to ionic mercury and then methylated to make the toxic methyl then methylated to make the toxic methyl mercurymercury

Mercury Legacy from Historic Mercury Legacy from Historic Mines Mines

•Elevated concentrations of mercury in sediments

•Elevated concentrations of mercury in fish, birds and other wildlife (Lahontan, Carson sink, Walker Lake, Sierra Nevada streams and others)

•Restrictions on the amount of fish that should be consumed by humans

Toxic Issues with MercuryToxic Issues with Mercury

•Neurotoxicity

•Birth defects

•Kidney function

Current Gold MinesCurrent Gold Mines

Mercury is Mercury is notnot used to extract gold or used to extract gold or silver in Nevada mines (although still in silver in Nevada mines (although still in developing countries)developing countries)

Mercury release to the environment is Mercury release to the environment is related to the co-incidence of mercury in related to the co-incidence of mercury in many gold ores in Nevada, and release many gold ores in Nevada, and release during ore processingduring ore processing

Mercury is produced as a byproduct from Mercury is produced as a byproduct from gold mines in Nevada, and is the largest gold mines in Nevada, and is the largest source of new mercury in the U.S.source of new mercury in the U.S.

Byproduct Mercury ProductionByproduct Mercury Production

The Chemistry

Au + O2 + CN- Au(CN)2- (water soluble)

Hg + O2 + CN- Hg(CN)2 + Hg(CN)42-

(water soluble)

Both the gold and mercury cyanide complexes are trapped on carbon and recovered during processing

Mercury is distilled (retorted) from the gold and collected as liquid mercury and sold by the flask (76 lbs)

Previous records for Hg ProductionPrevious records for Hg Productionfrom the Nevada Division of Mineralsfrom the Nevada Division of Minerals

MineMine 19881988 19891989 19901990 19911991 19921992 19931993 19951995 19991999 20002000

HycroftHycroft 5400054000 4000040000 74477447

ParadiseParadise

PeakPeak

237708237708 252000252000 227000227000 164075164075

NewmontNewmont 55485548 1626416264 1238812388 85128512 1687216872 1418714187 1419214192

BorealisBorealis 18241824

Hog RanchHog Ranch 79537953 82088208

McDermittMcDermitt

(primary (primary Hg mine)Hg mine)

846488846488 10082161008216 00 00

Total Mercury By-Product Recovered for Sale (pounds and Total Mercury By-Product Recovered for Sale (pounds and metric tons) (provided by each company)metric tons) (provided by each company)

19991999 20002000 20012001 20022002 20032003

Jerritt Jerritt CanyonCanyon

40414041 43134313 37093709 50455045

Placer DomePlacer Dome 831831 302302 3150531505 00

BarrickBarrick 1362913629 2285022850 5545755457 4920849208

Newmont E.Newmont E. 1419214192** 1948419484 1694416944 1688816888

Newmont W.Newmont W. 79867986 83678367 1189111891

Total Total PoundsPounds

4165741657 118141118141 7956479564

Metric TonsMetric Tons 18.918.9 53.653.6 36.136.1

*total Newmont byprodut (Nev. Div. Of Minerals)

How is Byproduct ManagedHow is Byproduct Managed Sold or transferred to three primary mercury recyclersSold or transferred to three primary mercury recyclers

• Bethlehem Apparatus Co. Inc., Hellertown, PA;.Bethlehem Apparatus Co. Inc., Hellertown, PA;.• D.F Goldsmith Chemical and Metal Corp, Evanston, ILD.F Goldsmith Chemical and Metal Corp, Evanston, IL• Mercury Waste Solutions, Inc., Mankato, MNMercury Waste Solutions, Inc., Mankato, MN

Each of these companies is regulated by the EPAEach of these companies is regulated by the EPA Current U.S. demand for mercury is 150-200 Current U.S. demand for mercury is 150-200

tons/year; Hg produced in NV is 30-50 tonstons/year; Hg produced in NV is 30-50 tons Price of Hg increased over the past three years from Price of Hg increased over the past three years from

$150/flask to approx. $750/flask$150/flask to approx. $750/flask Management and transfer is conducted in a safe and Management and transfer is conducted in a safe and

reliable mannerreliable manner There is no requirement for supplying data to the There is no requirement for supplying data to the

public on mercury salespublic on mercury sales

Atmospheric Emissions of Mercury from Atmospheric Emissions of Mercury from Precious Metals Mines in the U.S.Precious Metals Mines in the U.S.

Generally not measured until 1998Generally not measured until 1998 Toxics Release Inventory was applied to Toxics Release Inventory was applied to

precious metals minesprecious metals mines Revealed that precious metals mines Revealed that precious metals mines

were some of the single largest sources were some of the single largest sources of atmospheric mercury in the U.S.of atmospheric mercury in the U.S.

Voluntary Mercury Reduction Program Voluntary Mercury Reduction Program (VMRP) initiated in 2001(VMRP) initiated in 2001

Mercury Air Emissions (lbs) from Precious Mercury Air Emissions (lbs) from Precious Metals Mines, 1998-2003 (TRI data)Metals Mines, 1998-2003 (TRI data)

19981998 19991999 20002000 20012001 20022002 20032003

GoldstrikeGoldstrike 15001500 14001400 14671467 12431243 12531253 11221122

PipelinePipeline 22002200 15001500 13511351 13781378

Jerritt Jerritt CanyonCanyon

94009400 94009400 67006700 79907990 47404740 793793

NewmontNewmont

Carlin (S)Carlin (S)5353 7171 8080 490490 513513 565565

Twin CreeksTwin Creeks 22002200 12001200 630630 570570 530530 588588

Total from Total from

NV MinesNV Mines1357613576 1216712167 1250512505 1237412374 87068706 4488 4488

(est)(est)

Total all NV Total all NV IndustriesIndustries

1357613576 1216712167 1291212912 1295912959 92669266

Rank(2002)

State Pounds released(2001)

Pounds released(2002)

1 Texas 14,766 14,505

2 Ohio 11,405 9,625

3 Pennsylvania 9,089 9,177

4 Nevada 12,959 9,069

5 Indiana 7,168 7,645

6 Illinois 5,963 5,610

7 Alabama 5,903 4,729

8 North Carolina 4,164 4,507

9 California 5,668 4,173

10 West Virginia 6,282 4,051

11 Kentucky 5,256 3,670

Ranking of States for Atmospheric Mercury Release

NV Mines 2003 (est) 4500 lbs

Atmospheric Mercury ReleasesAtmospheric Mercury Releases

Nevada was the #2 state nationally Nevada was the #2 state nationally in mercury release in 1998 (after in mercury release in 1998 (after Texas) and dropped to #7 or #8 in Texas) and dropped to #7 or #8 in 2003 and reduced its atmospheric 2003 and reduced its atmospheric emissions by 2/3emissions by 2/3

Nevada still is the second largest Nevada still is the second largest source of atmospheric mercury west source of atmospheric mercury west of the Mississippi (again after Texas)of the Mississippi (again after Texas)

Source Emissions(2001)(Baseline)

Emissions (2002)

Emissions(2003)

Carbon regeneration kilns

1543 294 0.28 Venturi mercury wet scrubbing/carbon polishing system installed in March

Refinery 365 250 (included above)

Emissions routed to carbon regeneration kiln control system in September

Roaster west 4667 2777 599 Sodium hypochlorite injection system installed in September, 2002

Roaster east 1405 1417 188 Sodium hypochlorite injection system installed in September, 2002

Total 7980 4738 787

VMRP Data from Jerritt Canyon (2001-2003)

Source Emissions(2001)(Baseline)

Emissions(2002)

Emissions(2003)

Retorts 1,2,3 11 11 11

Mill furnace 1,402 161 161 Carbon column added

Electrowinning cell 613 Included above

Included above

Emissions sent through mill furnace carbon column

Carbon kiln 4380 4380 1927

Autoclave circuit 548 548 548

Roaster 814 814 166

Total 7768 5920 2819

VMRP Data from Barrick Goldstrike

7.3 M oz in 2003, 82% of U.S. and 9% of world production

Value of production up by 11% from 2002 due to higher price

Top 7 years of all time

Estimate of Total Amount of Mercury Estimate of Total Amount of Mercury Emitted from Nevada Mines, 1980-presentEmitted from Nevada Mines, 1980-present

Assume an average of 12,000 pounds per Assume an average of 12,000 pounds per year from 1988-2001 (inclusive), and 5000 year from 1988-2001 (inclusive), and 5000 pounds for 2002 to 2004 (inclusive), and pounds for 2002 to 2004 (inclusive), and ignore the years 1980-1988. ignore the years 1980-1988.

12000 x 14 = 168,000 lbs12000 x 14 = 168,000 lbs 5000 x 3 = 15,000 lbs5000 x 3 = 15,000 lbs Total is 183,000 lbs or 83 metric tons (70-Total is 183,000 lbs or 83 metric tons (70-

100 tons)100 tons) Contributions of Hycroft, Paradise Peak Contributions of Hycroft, Paradise Peak

and Hog ranch are unknownand Hog ranch are unknown

What is the Significance of this What is the Significance of this Mercury ReleaseMercury Release

Largely unknown, although it is much less Largely unknown, although it is much less than the estimated 6000-7000 metric tons than the estimated 6000-7000 metric tons released into the Carson River drainagereleased into the Carson River drainage

Transport of mercury is still not well Transport of mercury is still not well understood, although the areas around the understood, although the areas around the sources will receive the greatest amount sources will receive the greatest amount of falloutof fallout

It is unclear if the elevated mercury in It is unclear if the elevated mercury in Idaho fish is related to mercury releases Idaho fish is related to mercury releases from the mines from the mines

23 major gold mines (8 not on the Carlin trend with > 100 K oz production)

ConclusionsConclusions

1.1. Management of byproduct mercuryManagement of byproduct mercury• Byproduct mercury appears to be managed Byproduct mercury appears to be managed

wellwell• Based on discussions with the recyclers, they Based on discussions with the recyclers, they

feel strongly that a demand for mercury in feel strongly that a demand for mercury in the U.S. exists and byproduct mercury can be the U.S. exists and byproduct mercury can be used to satisfy this need, primarily in lights used to satisfy this need, primarily in lights and electrical equipmentand electrical equipment

• There is currently no legal method for There is currently no legal method for reducing liability to the mining industry for reducing liability to the mining industry for storing mercury, while selling it into storing mercury, while selling it into commerce eliminates the liabilitycommerce eliminates the liability

• No need for any changesNo need for any changes

ConclusionsConclusions

2.2. Atmospheric release of mercuryAtmospheric release of mercury• The gold mining industry previously The gold mining industry previously

was a major source of mercury release was a major source of mercury release to the atmosphereto the atmosphere

• Through the VMRP and other efforts by Through the VMRP and other efforts by the industry, a 2/3 reduction has been the industry, a 2/3 reduction has been realized, although mining sites still are realized, although mining sites still are some of the highest point sources some of the highest point sources

• Further reductions can be realized with Further reductions can be realized with current technologycurrent technology

RecommendationsRecommendations

Atmospheric mercury emissions from mines Atmospheric mercury emissions from mines should be regulated by either the State or EPA. should be regulated by either the State or EPA. While successful, the VMRP remains voluntary, While successful, the VMRP remains voluntary, and does not require new sources to participate.and does not require new sources to participate.

More consistent and more mercury More consistent and more mercury measurements should be required. Because of measurements should be required. Because of the complexity of the mercury emission sources, the complexity of the mercury emission sources, a systematic evaluation of the methods used to a systematic evaluation of the methods used to determine mercury emissions rates and determine mercury emissions rates and concentrations should be undertaken. concentrations should be undertaken.

Recommendations (2)Recommendations (2) New systems for better mass balance are New systems for better mass balance are

recommended for accurate assessments of recommended for accurate assessments of mercury release. This includes more precise mercury release. This includes more precise measurements of mercury in the ore, mercury in measurements of mercury in the ore, mercury in the process fluids, and mercury sent out to the the process fluids, and mercury sent out to the tailings facilities. The amount of mercury in the tailings facilities. The amount of mercury in the ore should be accounted for in a life-cycle ore should be accounted for in a life-cycle assessment. assessment.

Byproduct mercury production and sales should Byproduct mercury production and sales should be reportedbe reported

Fate studies for the mercury deposition need to Fate studies for the mercury deposition need to be expanded. Is the mercury deposition regional be expanded. Is the mercury deposition regional or continental, or global? Who has the burden of or continental, or global? Who has the burden of showing where the mercury goes?showing where the mercury goes?