Fugitive Mercury Emissions from Two Gold Mines in Nevada 

On November 20, 2009, Dr. Chris Eckley, a post doctoral researcher working with 

Dr. Mae Gustin presented a preview of his work and that by a graduate student, 

Matthieu Miller, on fugitive mercury emissions from two gold mines in Nevada 

(see the attached slides). The research focused on measuring mercury emissions 

from a variety of surfaces disturbed by mining activities at Newmont’s Twin Creeks 

Mine northeast of Winnemucca, Nev., and Cortez Pipeline, a Barrick property 

located south of Battle Mountain, Nev, and used this information to develop an 

estimate of emissions for the mine surface area. Fugitive emissions from waste 

rock, heap leaches, tailings impoundments, active pit surfaces, stockpiles and 

reclaimed sites were estimated and compared to mercury releases from sites 

undisturbed by mining. 

The results showed that mercury emissions from mining disturbances are 

approximately 20 percent of the total mercury emitted at these two gold mines. The 

study showed heap leaching and tailings impoundments produced the greatest 

emissions and that current reclamation practices can reduce the current emissions to 

near natural levels. 

Importantly, the work showed that the amount of mercury emitted from these types 

of disturbances can vary significantly among mines, depending primarily on the 

mercury concentration at the disturbed site, the moisture content of the tailings and 

whether or not the heaps are actively being leached with cyanide. Because there are 

a variety of factors (such as mercury concentration, age of the materials, climatic 

conditions, weather, ore type, ore processing techniques, etc.) that can affect the 

emission of fugitive mercury from different mining surfaces and the uncertainty 

associated with each of those factors, this data, developed for these two mines, 

cannot be extrapolated to come up with emissions estimates for other mines. 

Additionally since a mine is a dynamic entity with surfaces changing over time, and 

the emission estimates developed in the UNR study represent the surfaces present at 
the two mines s in 2008, the amount of Hg released in future years may differ 

depending on the types and extent of mining related surfaces at each facility. 

The data contained in the attached power point presentation have not been peer reviewed. 
Fugitive Mercury Emissions From 

Nevada, USA Gold Mines

Eckley, CSa, Gustin, Ma, Miller, MBa, Marsik, Fb

a University of Nevada Reno, Department of Natural Resources and Environmental Science

b University of Michigan, Department of Atmospheric, Oceanic and Space Sciences
Acknowledgements

Note: Information presented has not be subjected to final scientific

peer review

Nevada’s mining companies

Fugitive Mercury Emissions Project Oversight committee

Project Participation
Numerous studies have identified Hg enriched 

soils are a source Hg to the air

Transport and Transformation

Hg emissions to air

Methyl-Hg

Mercury exposure through fish

Mercury (Hg) is a pollutant of global concern
Project Context

~$1,000 oz

The modern gold rush

Graphs from Nevada Bureau of Mines 

and Geology

Mineral trends with high gold content 

are often enriched in Mercury (Hg)

NV Cinnabar (HgS)
Hg

Point Source Emissions

Nevada Gold mines contain point sources of Hg 

emissions:

2,000 kg/yr (NDEP 2006/2007)

Nonpoint source Hg emissions from Nevada Gold 

mines: ???? kg/yr
Project Objectives:

2) Quantify natural nonpoint source Hg emissions from 

adjacent undisturbed areas

1) Quantify nonpoint source Hg emissions from active 

gold mines
Introduction to Mine Processes

Holes drilled and ore examined for grade and 

metallurgical properties

Based on gold content trucks deliver the 

ore to different processing locations

Blast rock

Schematic pictures 

from Nevada Mining 

Association Brochure
Schematic pictures 

from Nevada Mining 

Association Brochure

Waste Rock/Overburden

High grade ore

Gold Collected on Activated Carbon

Tailings pond

Grinding Mill

Carbonaceous

Oxide

Sulfide Low grade ore

Heap Leach Pad
Two mines chosen for study

Twin Creeks Gold Mine Cortez Gold Mine

0 1,000 m  ̧

0 1,500 m
Two mines chosen for study

Twin Creeks Gold Mine Cortez Gold Mine

Old/Reclaimed

Tailings

Heap Leach

0 1,000 m  ̧

0 1,500 m

Different materials have 

different surface areas that 

change over the life of a mine

Waste rock
Undisturbed Areas: Similar rock types excavated at mines

Outcrops

Valley Alluvium

Twin Creeks Area Cortez Area

Hills Alluvium

0 3,000 m
Method to measure emission:

Flux = (Cinside-Coutside *(Q/A)

Flux is emission or deposition per unit area 

per time

Units 

ng (10-9g) per m2 per hour or

ng per m2 per day

Tekran Total Gaseous 

Mercury Analyzer

ng per m3 of air

Outside air

sample line Inside chamber

sample line

Dynamic Flux Chamber
1) Identify important factors controlling flux using laboratory 

experiments

• 48 tubs—3 from each 

surface type

• Each tub: 24 hr fluxes

twice per season 

• >400 diel flux 

measurements

• Meteorological data

collected on site

• Develop algorithms Active Gold Mine UNR Greenhouse

Methods: General Research Approach
1) Identify important factors controlling flux using laboratory 

experiments

Methods: General Research Approach

2) Measure fluxes at the mines 

compare with laboratory derived data 

develop data for surfaces not represented in lab study

Winter

Summer

Spring

Fall

~ 1 week at each mine each season

24 hours sampled from each surface

Day Night
Methods: General Research Approach

Winter

Summer

Spring

Fall

~ 1 week at each mine each season

24 hours sampled from each surface

Day Night

2 flux chambers 2 Tekrans 

1) Identify important factors controlling flux using laboratory 

experiments

2) Measure fluxes at the mines 

compare with laboratory derived data 

develop data for surfaces not represented in lab study
1) Identify important factors controlling flux using laboratory 

experiments

Methods: General Research Approach

3) Estimate emissions for each mine based on current surface 

areas and environmental conditions over the year of study

Cortez Pipeline

Geographic Information System 

(GIS)

Twin Creeks

2) Measure fluxes at the mines 
Results: Laboratory 

Fluxes vary: 

Daily
Results: Laboratory 

Fluxes vary: 

Daily

Leach (pre-cyanide)Twin Creeks mine (2.7 μg g-1)

Seasonally
Fluxes influenced by:

surface type, material Hg content

Results: Laboratory

-1000

9000

19000

29000

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48

Hg Flux (ng m-2 d

-1

)

Tub #

Winter

Spring

Summer

Fall

Dry Wet
Fluxes influenced by:

surface type, material Hg content

precipitation events—4-fold emission increase

Results: Laboratory

-1000

9000

19000

29000

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48

Hg Flux (ng m-2 d

-1

)

Tub #

Winter

Spring

Summer

Fall

Dry Wet

-100

0

100

200

300

400

500

600

00:00:00 06:00:00 12:00:00 18:00:00 00:00:00

Hg Flux (ng/m2/h)

Time of Day

November, 10 2008

December, 26 2008

January, 1 2009

Dry –November

Wet—December

Dry –January
-1000

9000

19000

29000

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48

Hg Flux (ng m-2 d

-1

)

Tub #

Winter

Spring

Summer

Fall

Daily Hg Flux

(between materials)

Hourly Hg Flux 

(individual materials)

Parameter T-statistic p-value

Median

T-statistic

Median

p-value

Substrate Hg 15.2 <0.001 ----- -----

Substrate moisture 3.4 0.001 ----- -----

Solar radiation 2.2 0.023 8.3 <0.001

Air temperature 3.3 0.001 2.8 <0.001

Relative Humidity 2.5 0.014 -0.3 <0.001

Wind speed 3.3 0.001 -0.2 <0.001

Use statistical analyses to determine most 

important variables and develop model 

equations

Results: Laboratory
Twin Creeks dry tub data Cortez-Pipeline dry tub data

Develop equations that allows us to predict flux

as a function of material Hg concentration and 

solar radiation

y = 71x + 568 r2 = 0.71

y = 99x + 1335 r2 = 0.50

y = 507x + 985 r2 = 0.77

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

0 20 40 60 80

Hg Flux (ng m-2 d

-1

)

Substrate Hg (μg g-1)

low solar

middle solar

high solar

y = 110x + 373 r2 = 0.25

y = 338x - 132 r2 = 0.66

y = 419x + 143 r2 = 0.60

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 5 10 15

Hg Flux (ng m-2 d

-1

)

Substrate Hg (μg g-1)

low solar

middle solar

high solar

Results: Laboratory
Results: Laboratory simulation of surface disturbance

Surface disturbance

Increases flux 7-fold

Effect of disturbance 

decreases over time

(~ 7 days)

0

20

40

60

80

100

0

50

100

150

200

250

300

0 1 2 3 4 5 6 7 8 Solar radiation (W m-2

)

Temperature (C)

Hg Flux (ng m-2 h

-1

)

Days following disturbance 

Hg Flux

DFC Temp

Solar Radiation
Field Measurements:

-Characterize Hg concentrations in substrate

-Collect data from field for comparison with laboratory data 

-Measure flux from surfaces not represented in laboratory study

Tailings material

Reclaimed tailings

Old leach pad

Active leach
Characterization of Hg concentrations in substrate

Twin Creeks Gold Mine Cortez-Pipeline Gold Mine

Results: Field data
Spatial Ave Substrate Hg: 5.9 μg/g Spatial Ave Substrate Hg: 1.3 μg/g

0 -12

12 - 24

24 - 36

36 - 48

48 - 60

60 - 72

72 - 84

84 - 96

96 - 108

108 - 120

Solid Hg (μg/g)

Twin Creeks Gold Mine Cortez-Pipeline Gold Mine

Characterization of Hg concentrations in substrate

Results: Surface area/concentration
Spatial Variability of Hg fluxes 

Lowest Emissions:

• Waste rock materials 

(~10’s to 100’s ng m-2 d

-1

)

Highest Emissions:

• Active leach pads & tailings 

(~1,000’s to 100,000’s ng m-2 d

-1

)

Results: Surface area/flux

Surface Area 

Cortez Twin Cks
>80% of field measurements were within the 95% prediction intervals of the laboratory 

data

y = 507x + 985 r2 = 0.77

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

0 20 40 60

Hg Flux (ng m-2 d

-1

)

Substrate Hg (μg g-1)

high solar--lab

high solar--field y = 419x + 143 r2 = 0.60

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 5 10 15

Hg Flux (ng m-2 d

-1

)

Substrate Hg (μg g-1)

high solar--lab

high solar--field

Twin Creeks Gold Mine Cortez-Pipeline Gold Mine

Old leach

Tailings

Comparison of field data with laboratory derived model
y = 507x + 985 r2 = 0.77

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

0 20 40 60

Hg Flux (ng m-2 d

-1

)

Substrate Hg (μg g-1)

high solar--lab

high solar--field y = 419x + 143 r2 = 0.60

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 5 10 15

Hg Flux (ng m-2 d

-1

)

Substrate Hg (μg g-1)

high solar--lab

high solar--field

Twin Creeks Gold Mine Cortez-Pipeline Gold Mine

Old leach

Tailings

Comparison of field data with laboratory derived model
Hg fluxes from tailings

Heterogeneous 

Hg content (19 to 177 μg g-1),

Moisture (0.1% to liquid solution) 

Flux (889 to 684,000 ng m-2 d

-1

). 

Magnitude of emissions best correlated with % moisture r 2 = 0.55 p=0.001

Twin Creeks
Hg fluxes from substrate actively under leach only obtained at Twin Creeks 

Typical Cortez leach

Twin Creeks Leach

Results: Cyanide Heap Leaching
-2000

0

2000

4000

6000

8000

10000

12000

0:00:00 6:00:00 12:00:00 18:00:00 0:00:00

Time of Day

Hg Flux (ng/m2/h)

Active CN

Pre CN

Post CN

Pre CN CN Addition Post CN

Pre leach: 2,280 ± 1,470 ng/m2/d

Active leach: 101,300 ± 53,400

ng/m2/d

Post leach: 1,750 ± 572 ng/m2/d

Twin Creeks Spring Data

Results: Cyanide Heap Leaching

3 μg/g 4 μg/g 5 μg/g
Daily Emissions increase ~4-fold from the effect of wetting alone

Daily Emissions ~35-fold higher during leaching than from pre and post 

leaching

A component of Hg emitted during active leaching is from the cyanide solution

Results: Cyanide Heap Leaching

Mean Hg Content of leach solution: 

17 μg/L (Cortez)

470 μg/L (Twin Creeks)

Nevada rainwater:0.002-0.4 μg/ L

(Mercury Deposition Network Data Station: NV02, 2007 data)
Emissions from capped tailings Twin Creeks (spring, 2008 data)

Ave flux from tailings: 27,600 ng/m2/d

Ave flux from capped tailings: 1,160 ng/m2/d

Fluxes may be greatly reduced post-reclamation

Results: Material age/reclamation

Data from 5 year old/inactive leach suggest fluxes decline as 

materials age
• 1) Calculate fluxes 

– Use substrate Hg concentrations versus solar radiation relationship for dry and wet 

surfaces

Make adjustments based on field data

 Tailings

– Leach pads during cyanide addition

– Account for surface disturbance 

– Account for surface age

• 3) Scale emissions: Flux (ng/m2/d) X surface area (m2) X days 

• 4) Sum fluxes from each surface for all days of the year = total 

emissions

• 5) Sensitivity and Uncertainty analysis performed on the models

Annual Emission Estimates
Total nonpoint source (NPS) emissions kg/yr:

Twin Creeks: 105 (range 60 to 121) 

Cortez-Pipeline: 19 (range 16 to 43) 

Annual Emission Estimates

% of total mine emissions that are NPS: 

Twin Creeks: 19% (12 to 21%); Cortez-Pipeline: 17% (15 to 31%)

% increase in total mine emissions from NPS: Twin Creeks: 23% (13 to 27%) 

Cortez-Pipeline: 20% (17 to 46%) 

Total emissions point and NPS kg/yr:

Twin Creeks: 554 (509 to 570); Cortez-Pipeline: 113 (110-137)

tailings and active heap leach < 15% area at both mines released >75% of Hg

waste rock/reclaimed/inactive leach >85% area at both mines released <25% Hg

Total point source emissions kg/yr :

Twin Creeks: 449 

Cortez-Pipeline: 94 

(Nevada Division of Environmental Protection data)
Emissions prior to mining kg/yr:

Twin Creeks: 1.5 

Cortez: 0.25 

Annual Emission Estimates

Total nonpoint source emissions kg/yr:

Twin Creeks: 105 

Cortez-Pipeline: 19 

Projected emissions post mine reclamation

Twin Creeks: <8 kg/yr

Cortez-Pipeline: <3 kg/yr
Concluding remarks:

• Large differences in emissions between mines

• Emission estimate reflects one stage in the life of a mine

– Emissions will vary depending on activity, age, and reclamation

• Factors important to consider:

mercury concentration/host rock characteristics

surface area of mining disturbed materials

characteristics of tailings impoundments

climatic conditions

ore-processing techniques (i.e heap leaching)

age of materials and reclamation
Questions?