U.S. Department of the Interior

U.S. Geological Survey

Circular 1317

Understanding Metal Pathways in Mineralized Ecosystems
Understanding Metal Pathways in Mineralized 

Ecosystems

By Laurie S. Balistrieri, Andrea L. Foster, Larry P. Gough, Floyd Gray, James J. Rytuba, and Lisa L. Stillings

The USGS Pathways of Metal Transfer from Mineralized Sources to Bioreceptors Project studied the physical and 

biogeochemical processes that influence the distribution, concentration, and bioavailability of potentially toxic metals at 

historical hard-rock mine sites in the western United States.

Circular 1317

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

Produced in the Western Region, Menlo Park, California

Manuscript approved for publication, August 9, 2007

Text edited by Peter H. Stauffer

Layout and design by Jeanne S. DiLeo

U.S. Geological Survey, Reston, Virginia: 2007

This report and any updates to it are available online at:

http://pubs.usgs.gov/circ/2007/1317/

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report. 

Suggested citation:

Balistrieri, L.S., Foster, A.L., Gough, L.P., Gray, Floyd, Rytuba, J.J., and Stillings, L.L., 2007, Understanding metal 

pathways in mineralized ecosystems: U.S. Geological Survey Circular 1317, 12 p.

Cataloging-in-publication data are on file with the Library of Congress (http://www.loc.gov/).

FRONT COVER

Acidic and metal-enriched mine drainage forms a pond on mine tailings at the historical Elizabeth Copper Mine, South 

Strafford, Vermont. This mine site was listed on the National Priority List (Superfund) in June 2001.
iii

Contents

Abstract .........................................................................................................................................................1

Introduction.....................................................................................................................................................1

The USGS Pathways Project .......................................................................................................................1

Mercury and fish in California ............................................................................................................3

Why was the study done? ..........................................................................................................3

What are the major conclusions?.............................................................................................3

How is the information used? ....................................................................................................3

Lead and endangered waterfowl in Idaho .......................................................................................3

Why was the study done? ..........................................................................................................3

What are the major conclusions?.............................................................................................3

How is the information used? ....................................................................................................6

Cadmium and willow in Alaska...........................................................................................................6

Why was the study done? ..........................................................................................................6

What are the major conclusions?.............................................................................................6

How is the information used? ....................................................................................................6

Selenium in wetlands: Case studies in Idaho and Nevada............................................................6

Why was the study done? ..........................................................................................................6

What are the major conclusions?.............................................................................................7

How is the information used? ....................................................................................................7

Metal transport and climate in Arizona ............................................................................................7

Why was the study done? ..........................................................................................................7

What are the major conclusions?.............................................................................................7

How is the information used? ....................................................................................................7

Discussion.......................................................................................................................................................7

Acknowledgments.......................................................................................................................................12

Sources of Additional Information............................................................................................................12

Abstract

Successful management of ecosystems containing 

historical mine wastes requires understanding of processes 

that are responsible for the distribution, concentration, 

and bioavailability of potentially toxic elements. 

U.S. Geological Survey (USGS) scientists recently 

completed several investigations at historical mine sites 

in the western United States. These investigations have 

improved our understanding of how metals are mobilized 

from mineralized sources, are transported through the 

environment, and become available to humans and other 

biota. The new information is being used by Federal, State, 

and local agencies that manage and remediate abandoned 

mine lands. 

Introduction

The mid 1800s marked the beginning of a long and 

colorful history of mining in the western United States. That 

history has left a legacy of approximately 11,000 abandoned 

hard-rock mine sites. At many of these sites, historical 

mining activities resulted in adverse impacts to the quality 

of water and sediment and to the health of humans and 

other biota. Understanding the processes that influence the 

distribution, concentration, and bioavailability of potentially 

toxic metallic elements, such as arsenic (As), cadmium (Cd), 

lead (Pb), mercury (Hg), selenium (Se), and zinc (Zn), is 

critical for successful management of chronically affected 

ecosystems where total remediation of environmental 

problems is not financially or technically possible. Such 

understanding of processes can be used to identify and 

target those pathways that have the greatest immediate and 

long-term impact on the environment and health of biota. 

It therefore provides the scientific foundation for making 

decisions, developing strategy, and assessing mitigation 

and remediation alternatives by local, State, and Federal 

agencies charged with minimizing the environmental and 

health impacts of the toxic elements.

The USGS Pathways Project

The U.S. Geological Survey (USGS) Pathways Project 

focuses on improving our understanding of the processes 

that redistribute metals from mineralized sources to human 

populations and other biological receptors within ecosystems. 

The major objectives of the Pathways Project are to:

• advance our understanding of the physical, chemical, and 

biological processes responsible for the cycling of potentially 

toxic elements in large-scale ecosystems influenced by 

mineralized deposits and mine wastes,

• identify those pathways that have the greatest chronic or 

long-term adverse impact to the environment and to the health 

of biota, and

• develop conceptual and quantitative transport and 

reaction models that link the concentrations and distributions 

of elements to specific processes.

To meet these objectives, work within the Pathways Project 

examines the behavior of various potentially toxic elements in 

different ecosystems and addresses several interrelated questions:

• How do ecosystem conditions (for example, arid versus 

wet or vegetated versus non-vegetated) influence the transport 

and dispersion of elements?

• How does the speciation (specific chemical form) of 

elements in solution and as particles affect their geochemical 

mobility and availability to biota? 

• How do processes at physical and geochemical 

boundaries affect element speciation, mobility, and 

bioavailability?

• What are the relations among different types of microbial 

communities, the processes that transform elements between 

various chemical forms, and the availability of elements to 

biota? 

• Can conceptual and quantitative models be developed 

that link element concentrations and distributions 

in mineralized ecosystems to specific physical and 

biogeochemical processes and that help us to understand the 

possible impacts of natural and anthropogenic changes on 

element distributions in these systems? 

Selected major accomplishments of the USGS Pathways 

studies that addressed these issues are highlighted in the 

following sections.

By Laurie S. Balistrieri, Andrea L. Foster, Larry P. Gough, Floyd Gray, James J. Rytuba, and Lisa L. Stillings

Understanding Metal Pathways in Mineralized Ecosystems
2 Understanding Metal Pathways in Mineralized Ecosystems

Physical, chemical, and biological processes transport and biogeochemically transform elements 

as they are redistributed from mineralized sources (ore deposits and mine wastes) to biological 

organisms. These processes have been the focus of the U.S. Geological Survey (USGS) Pathways 

Project studies at historical mine sites in the western United States

Metal Pathways in Mineralized Ecosystems

SOURCE in Mineralized Ecosystems

Physical, Chemical, and Biological PROCESSES

Dissolved

Metals

Particulate

Metals

BIORECEPTORS

(humans, wildlife, plants)

• mixing •

• hydrologic transport •

• reduction/oxidation •

• dissolution/precipitation •

• adsorption/desorption •

• organic/inorganic

complexation •

• biological productivity

and respiration •

Bioavailability

Mining and

Processing

Natural

Weathering
The USGS Pathways Project 3

Mercury and Fish in California

Why was the study done?

Historical placer gold dredging in the floodplains of 

many rivers in the western United States has modified river 

geomorphology and impaired the spawning and rearing 

habitats of salmonid species. In addition, the dredge tailings 

contain mercury (Hg), an element used in the mining process 

to concentrate gold. Large-scale river-restoration projects in 

mining-affected watersheds may mobilize mercury from the 

tailings and downstream sediment derived from them and 

consequently lead to increased Hg levels in fish. Knowledge 

of the processes that control Hg cycling in the environment 

is needed to plan and manage river-restoration programs 

in order to minimize Hg release from sediments, chemical 

transformations due to methylation, and accumulation in fish.

What are the major conclusions?

•	 Hg is concentrated in finer grain-size fractions 

(silt and clay sizes) of contaminated sediments, with 

Hg concentrations as much as 300 times higher than in 

the bulk material.

•	 Elemental Hg that was introduced during the 

gold recovery process has been converted to organicbound phases and mercury sulfide, with only 15-40 

percent remaining as elemental Hg. 

•	 Colloidal (submicrometer size) mercury sulfide 

is readily leached from contaminated silts and sands 

by water containing organic acids formed from the 

degradation of plant material.

•	 Contaminated sediments associated with dredge 

tailings, including dredge ponds and constructed 

wetlands ponds in tailings, typically show moderate to 

high rates of Hg methylation. The methylation process 

results in methyl Hg, which is a more bioavailable form 

of Hg.

•	 Sands and silts in dredge tailings may be too 

contaminated to be used in river-restoration projects, 

but coarser tailings can be moved and used to improve 

habitat, if the fine sediment is first removed.

How is the information used?

Study results have been used by the U.S. Bureau of 

Reclamation in the Trinity River Restoration Project and 

by the U.S. Bureau of Land Management and U.S. Bureau 

of Reclamation in the restoration of lower Clear Creek, 

California. In the Trinity River area, tailings and contaminated 

sediments that were removed from open floodplain channels 

were placed above the 100-year flood level and not vegetated 

in order to minimize the potential release of Hg. Wetlands, 

originally planned for areas where contaminated sluice 

sands and silts were found, were sited elsewhere. At Clear 

Creek, tailings that are moved or used for gravel injection 

in floodplain restoration are now routinely evaluated for 

potential release of Hg and, if necessary, treated to minimize 

Hg release.

Lead and Endangered Waterfowl in Idaho

Why was the study done?

A century of historical mining, milling, and smelting 

of world-class silver (Ag), lead (Pb), and zinc (Zn) deposits, 

disposal of mill waste into rivers, and periodic natural 

flooding have resulted in the dispersion of metal-enriched 

water and sediment throughout the Coeur d’Alene River 

Basin, northern Idaho. In 1983, the U.S. Environmental 

Protection Agency (EPA) listed an area of 21 square miles 

in the heart of the basin as a Superfund site. In 1998 the 

EPA began applying Superfund requirements to many other 

areas throughout the basin. Many studies indicate that the 

contaminated materials pose health risks to humans and other 

biota in the basin. Understanding how metals cycle through 

this ecosystem is essential for minimizing those health risks.

Marshes in the lower Coeur d’Alene River valley are 

prime resting and feeding areas for migratory birds. These 

marshes, however, are enriched in toxic metals, and waterfowl 

deaths attributed to Pb poisoning during feeding have been 

reported for this area. During certain seasons of the year, 

reddish-brown material forms along the edge of the river in 

the lower valley. This material is easily re-suspended and 

transported downstream; it adheres to plant surfaces after 

floodwaters recede and may be a potential source of metal 

uptake during feeding by waterfowl. Investigations therefore 

examined this material and the processes responsible for its 

composition and formation.

What are the major conclusions?

•	 Relative to water in the Coeur d’Alene River, 

water that is in the pores of levee-bank sediment along 

the river is acidic and contains high concentrations 

of sulfate (SO4), calcium (Ca), magnesium (Mg), 

and metals, including arsenic (As), cadmium (Cd), 

cobalt (Co), copper (Cu), chromium (Cr), iron (Fe), 

manganese (Mn), lead (Pb), and zinc (Zn).
4 Understanding Metal Pathways in Mineralized Ecosystems

Stacker cobble tailings

Stacker cobble tailings Sediment & tailings removed from floodplain

Sediment & tailings removed from floodplain deposited on 

stacker cobble tailings & placed above 100 year flood level

Removal of riparian berm and

tailings contaminated sediment

Stacker cobble tailings

Stacker cobble tailings Sediment & tailings removed from floodplain

Sediment & tailings removed from floodplain deposited on 

stacker cobble tailings & placed above 100 year flood level

Removal of riparian berm and

tailings contaminated sediment

Stacker cobble tailings with low Hg concentrations

Sluice

 sands

Contact of stacker cobble tailings

and underlying sluice sands

Silt

Sand

Gravel

0

Grain Size Fraction, in mm

0.5 1.0 1.5 2.0 2.5

Mercury Concentration, in Parts per Million

Bulk

tailings

1.70-

2.83

1.0-

1.7

0.5-

1.0

0.25-

0.5

0.125-

0.25

0.075-

0.125

0.045-

0.075

0.032-

0.045

0.02-

0.032

<0.020

Riparian Berm 

Aerial view of the Trinity River Restoration Project in California. Mercury (Hg) contamination was found to be 

concentrated in the finer grained sediments; coarse, gravely “stacker tailings” show little contamination. This 

information helped the responsible agencies mitigate the toxic impact of the mercury on fish as part of the restoration 

project.

Sluice sands covered by stacker cobble tailings in the Trinity River Restoration Project. The sands and silts 

in the tailings contain much higher concentrations of mercury (Hg) than the coarser cobbly material.

Mitigating the Impact of Toxic Mercury on Fish
The USGS Pathways Project 5

Deaths of migrating waterfowl in the lower Coeur d’Alene River valley have been attributed to poisoning by lead (Pb) 

derived from old mine tailings. U.S. Geological Survey (USGS) scientists have found that the Pb content of different sediment layers downstream from the old mining areas varies—reflecting the history of mining technology. This 

diagram shows the Pb content of sediment in cores collected from the floodplain and river channel in the lower Coeur 

d’Alene River valley. Changes in milling technology (inefficient jigging to more efficient flotation methods) in the mining district helped produce the varying Pb concentrations with depth. Water levels vary seasonally by about 2 meters. 

Reddish-brown flocculent material is observed along the river’s edge as water levels lower in the fall.

Toxic Lead – A Hazard to Waterfowl in 

the Lower Coeur D’Alene River Valley

Scientists with the U.S. Geological 

Survey (USGS) Pathways Project 

analyzed porewater collected from 

metal-enriched levee bank sediments 

along the lower Coeur d’Alene River 

using a sipper array. Sippers, which 

are tubes of variable length with fine 

netting at the bottom, are inserted into 

the sediment, and porewater is pulled up 

the tube using a syringe. Reddish-brown 

flocculent material is seen in the river 

bottom to the upper right of the sipper 

array. This reddish-brown material 

turned out to be an iron oxide that readily 

adsorbs other metals. 

Medium-grained sand

3,000-4,000 ppm Pb

1968 to present

remobilized tailings

Sediment layer

Pb concentrations

Age

Origin

Interbedded fine sand and silt

4,000-10,000 ppm Pb

~1915 to 1968

flotation tailings

Silt and fine sand

15,000-36,000 ppm Pb

1880s to ~1915

jig tailings

Sand and silt

<30 ppm Pb

before 1880s

pre-mining

Sediment Layers and Associated Lead (Pb) Contents

East West

10 meters

5 meters

Winter water level

Summer water level
6 Understanding Metal Pathways in Mineralized Ecosystems

•	 Cd levels in willow are as much as 10 to 100 

times greater than those found in other plants, such as 

green alder, feather moss, and soil lichen, collected 

from the same area. 

•	 Mineralized areas in Alaska are likely sources 

for natural occurrences of potentially harmful 

levels of Cd in willow, which pose a health threat to 

browsing animals. 

How is the information used?

Based on our Cd study and to examine links between 

Cd levels in willow and moose, a database of element 

concentrations in moose tissue was developed by USGS with 

assistance from the Alaska Department of Fish and Game 

and the University of Alaska. Samples of moose kidney 

from harvested as well as road-kill animals are analyzed and 

compared with similar moose data from Sweden and Finland 

and with Cd data from willow. 

Selenium in Wetlands: Case studies in Idaho 

and Nevada

Why was the study done?

Selenium (Se) toxicity, resulting from bioaccumulation 

in their forage, is a serious threat to livestock, particularly 

cattle and sheep, in the western United States. High 

concentrations of Se, released into surface waters during 

the mining of phosphate deposits in southeastern Idaho 

and subsequently taken up by plants, are implicated in the 

deaths of sheep grazing in that area. Wetland soils and plants 

are known to concentrate Se and thereby promote its entry 

into the food chain. Understanding how Se cycles through 

wetland systems will aid in minimizing bioaccumulation by 

plants and consequent health risks to foraging livestock. 

Studies were conducted in two wetlands to assess 

transport and retention of Se within these systems. One of 

the study areas is a wetland downstream from the phosphate 

deposits in Idaho. The other is a wetland in a nature park 

affected by runoff from Las Vegas, Nevada. These wetlands 

were compared by evaluating their Se mass balances. A 

mass balance determines the amount of an element that 

remains or is retained in the wetland by comparing the 

amount of the element that enters the wetland with the 

amount that leaves the wetland. Elements can enter or leave 

the wetlands by surface streams, by ground water, or through 

the atmosphere.

•	 The enrichment of elements in porewater is due 

to oxidation of metal sulfide minerals, dissolution 

of carbonate minerals, and biologically mediated 

decomposition of organic matter in bank sediment. 

•	 During annual lowering of water levels in the 

basin or after floodwaters recede, porewater drains 

from bank sediment and mixes with the Coeur d’Alene 

River water. Chemical reactions during the mixing 

process result in the formation of the metal-enriched, 

reddish-brown material.

•	 Chemical analyses and geochemical modeling 

indicate that the reddish-brown material is an iron 

oxide, which adsorbs other toxic metals.

How is the information used?

The results of this study add to the overall understanding 

of how metals cycle through the Coeur d’Alene River Basin 

and how they may impact the health of humans and other 

biological receptors. That knowledge was used by EPA to help 

develop long-term goals for cleanup and recovery from the 

effects of historical mining in the basin.

Cadmium and Willow in Alaska

Why was the study done?

Previous studies in ecosystems containing mineralized 

deposits have indicated a direct link between high cadmium 

(Cd) concentrations in willow leaves and twigs and the 

occurrence of disease in ptarmigan (grouse) that feed on the 

willow. Because willow is a preferred source of food for 

moose in Alaska, investigations of Cd cycling were conducted 

in both mineralized and nonmineralized areas throughout 

Alaska to determine if willow and other plants accumulate Cd 

and, if so, to define the geochemical conditions that result in 

bioaccumulation of Cd. Understanding of Cd cycling within 

these ecosystems is important for minimizing adverse impacts 

to the health of browsing animals, such as moose, and the 

health of people who hunt those animals. 

What are the major conclusions?

•	 Willow growing in soils developed from 

mineralized bedrock accumulates Cd in concentrations 

4 to 10 times higher than willow growing in 

nonmineralized soil.
The USGS Pathways Project 7

What are the major conclusions?

•	 The two wetlands differ in both flow volume and 

Se concentrations in their inlet and outlet waters. Water 

entering or leaving the Idaho wetland had lower flows, 

but higher Se concentrations, than water entering or 

leaving the Nevada wetland.

•	 The Idaho wetland retained 611 grams of Se (88 

percent of the Se in the inflow) during a five-month 

period, whereas the Nevada wetland retained 5,800 

grams of Se (24 percent of the Se in the inflow) during 

a four-month period. The amount of Se retained in the 

wetland likely represents accumulation of Se by plants 

and wetland sediments, although gains or losses to the 

wetlands from the ground water and atmosphere were 

not measured.

How is the information used?

Land-management agencies are changing their 

management practices in order to decrease the amount 

of Se delivered to the studied wetlands. The U.S. Forest 

Service manages the Idaho wetland; they are now using soil 

amendments and seed mixtures to immobilize Se within the 

waste-rock source, hoping to decrease both the concentration of 

Se in forage plants in the wetland as well as the concentration 

of Se in drainage from the waste to the wetland. The Nevada 

wetland is managed by the Clark County Department of Parks 

and Recreation; they now use another source of inlet water with 

lower Se concentrations in order to decrease the amount of Se 

entering their wetland.

Metal Transport and Climate in Arizona

Why was the study done?

The Patagonia Mountains and southern Santa Rita Mountains in southeastern Arizona were mined for silver (Ag), lead 

(Pb), copper (Cu), and zinc (Zn) intermittently from the 1600’s 

to the mid-1960’s. Our studies examined the transport and 

chemical behavior of metals in several arid to semiarid watersheds (Harshaw Creek and Alum Gulch drainages) containing 

these abandoned mine lands. The goal was to evaluate how 

climate and other ecosystem conditions influence metal cycling 

in mining-affected ecosystems. Such knowledge is vital for 

developing robust models that describe potential environmental 

impacts of mining activity in different climate settings.

What are the major conclusions?

• Seasonal precipitation and acid mine drainage, 

which contains metals, such as cadmium (Cd), 

cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and 

zinc (Zn), are the dominant sources of water to the 

study areas.

• During dry periods, acid rock drainage 

evaporates and readily soluble metal sulfate salts 

are deposited on rocks and stream sediment. During 

storm events, these salts dissolve and release acid 

and metals back to solution.

•	 Downstream decreases in acid and metal 

concentrations after a storm event depend on the 

ability of the ecosystems to neutralize or buffer 

the acid produced during salt dissolution and 

on the volume of water from the storm event. If 

the buffering capacity of the ecosystem is small, 

acid and metals are transported far downstream 

in the dissolved phase. If the buffering capacity 

of the ecosystem is large, neutralization results 

in precipitation of aluminum-iron-oxyhydroxide 

minerals, adsorption of metals, and release of carbon 

dioxide gas.

How is the information used?

A major outcome of the research has been an improved 

understanding of the links among weather conditions, 

landscape, mineral precipitation and dissolution, and metal 

transport. The U.S. Forest Service and State of Arizona 

Environmental Quality Agency are using this information to 

develop remediation plans for this mining-affected area.

Discussion

These case studies conducted under the U.S.

Geological Survey (USGS) Pathways Project have yielded 

important new information about the ways in which metals 

are mobilized from rocks and mining waste, transported 

and chemically modified, and accumulated in various biota. 

Many of the metals, including arsenic (As), cadmium (Cd), 

lead (Pb), mercury (Hg), selenium (Se), and zinc (Zn), 

are potentially toxic to animals and humans. The results 

of these studies provide a better understanding of the 

physical and biogeochemical processes that influence the 

distribution, concentration, and bioavailability of the metals 

in mineralized ecosystems, not only in historical mining 

areas, but also in planning and developing new mines.
8 Understanding Metal Pathways in Mineralized Ecosystems

Willows Concentrate Toxic Cadmium in Alaska

The Mt. Eielson mining district, Denali National Park and Preserve, with Grant Creek and typical mineralized bedrock in the foreground, a historic cabin dating to the days of mineral prospecting in the district in the near background, and the Thorofare River and park road in the far background. This area hosts a number of lead-zinc (Pb-Zn) 

skarn deposits, rich in base metals. Willow leaves and twigs high in cadmium (Cd) are found throughout the area.

Willow

N

Mineralized Bedrock

Prospector

Cabin

Grant Creek

Thorofare River

Park Road

ALASKA CANADA

Denali National

Park and Preserve

Fairbanks

Anchorage
USGS Pathways Project 9

Box plots of the concentration of cadmium 

(Cd), plotted on a log scale, in plants and 

soils from the mineralized Mt. Eielson and 

Kantishna mining districts, Alaska, and from 

the nonmineralized Yukon-Tanana Upland, 

Alaska. In the nonmineralized area the 

concentration of Cd in various soil horizons 

(A horizon: topsoil, B horizon: subsoil, and 

C horizon: substratum or unweathered 

geologic material) are reported, whereas 

in the mineralized area Cd data in all three 

soil horizons were combined. Note that Cd 

concentrations in willow in the mineralized 

area are as much as 10 times those in the 

nonmineralized area.

0.01

0.1

1

10

100

0.001

Cadmium Concentration

in Parts per Million, Dry Weight Basis

Leaf

Leaf

Twig

Twig

A

B

C

Nonmineralized Area

(Yukon-Tanana Upland) 

 Willow

 (n=60)

Moss

(n=46)

Alder

 (n=60)

Lichen

(n=8)

Nonmineralized Area

(n=57 each horizon)

Mineralized

(Mt. Eielson and Kantishna)

Leaf

(n=6) Twig

(n=6)

Willow 

 Soil

(n=10)

 

Soil Horizon

 

>90th - 90th

<10th - 10th

75th

median

25th

Percentiles
10 Understanding Metal Pathways in Mineralized Ecosystems

Differences in Retention of Selenium in Two Wetlands

A comparison of the amount of selenium (Se) that is 

retained by wetlands near Las Vegas, Nevada, and 

in southeastern Idaho. The area of each circle is 

proportional to the total Se delivered to each wetland, 

24,100 grams over 4 months, and 695 grams over 5 

months, respectively. The Se retained in the wetland 

likely accumulates in wetland soils and plants.

Selenium concentrations in forage vegetation are a concern for ranchers who 

graze stock in mining- affected areas. These cattle browse on wetland grasses 

at the Idaho wetland. The standpipe is from a former mining operation.

Nevada Wetland

24,100 g Se in surface inflow

Retained

5,800 g Se

(24%)

Surface Outflow

84 g Se

Retained

611 g Se

(88%)

Idaho Wetland

695 g Se in surface inflow

Surface Outflow

18,300 g Se
The USGS Pathways Project 11

Climate Influences Metal Dispersion from Arizona Mining Areas

Map of the Alum Gulch-Flux Canyon watershed, Arizona, showing five defined stream “segments” and 

important mine sites. Segments of the same color have similar pH and concentrations of metals in the 

water; these parameters vary from 0.6 milligrams per liter of copper and pH 4.7 in Trench Camp to 3.5 

milligrams per liter of copper and pH 2.9 in Upper Alum Gulch. An arid climate and low volumes of water 

in each stream segment during base-flow conditions (when only seepage from ground water supplies the 

stream) produce efflorescent metal-enriched salt deposits that can dissolve and release metals and acid 

during storm events.

Photo 1. Acidic, iron-rich stream water in Aztec Gulch. Stream boulders and 

walls are made of ferricrete, an iron-rich deposit. 

Photo 2. The World’s Fair Mine area circa 1908. Reproduced from Schrader, 

F.C., 1915, Mineral deposits of the Santa Rita and Patagonia Mountains, 

Arizona: U.S. Geological Survey Bulletin 582, 373 p. 

Photo 3. Main portal (adit) at the World’s Fair Mine. Discharge from the adit 

passes over a waste pile and into the adjacent stream. 

Photo 4. Water in a drainage pipe from the adit at the January Mine flows into 

constructed wetlands that are part of the Trench Camp Mine complex. 

Photo 5. White, efflorescent metal-enriched salt deposits develop as rings or 

in-stream crusts in the Trench Camp segment.

Aztec

World’s Fair

Flux Canyon

Upper Alum Gulch/Homboldt Mine

Trench Camp/January Audit

Other streams

Area of watershed

Elevation contour

Mine site

Stream

Segments

Explanation

0

0

1 km

0.5 mi 

N

1

2

3

4

5
12 Understanding Metal Pathways in Mineralized Ecosystems

This improved understanding of the metal pathways 

allows the land-management agencies responsible for areas 

affected by mining or mineralization—including the U.S. 

Bureau of Reclamation, U.S. Bureau of Land Management, 

U.S. Environmental Protection Agency, U.S. Department of 

Agriculture, U.S. Forest Service, and State agencies such as 

the Alaska Department of Fish and Game and the Arizona 

Environmental Quality Agency—to better plan for mitigating 

the impacts of chemical toxicity in sediment, water, and biota. 

The research results of the USGS Pathways Project have also 

highlighted remaining questions and pointed the way to promising avenues of further research.

Acknowledgments

The work in the USGS Pathways Project was done with 

the support of Kathleen Johnson, Coordinator of the USGS 

Mineral Resources Program, numerous colleagues in the 

USGS Mineral Resources Program, and our various Federal, 

State, and local collaborators. The manuscript benefited from 

the reviews of Steve Box, Tom Frost, Sue Kropschot, and 

Bronwen Wang, from discussions with Dave Frank, and from 

the technical edit by Peter Stauffer, and design and layout by 

Jeanne DiLeo.

Sources of Additional Information

Ashley, R.P., Rytuba, J.J., Rogers, R., Kotlyar, B.B., and 

Lawler, D., 2002, Preliminary report on mercury 

geochemistry of placer gold dredge tailings, 

sediments, bedrock, and waters in the Clear Creek 

Restoration Area, Shasta County, California: U.S. 

Geological Survey Open-File Report 2002–401, 47 p. 

Ashton, K.L., and Duarte, O.A., 2003, Soil characterization 

at the World’s Fair Mine site, Patagonia Mountains, 

Santa Cruz County, SE Arizona; implications for base 

metal transport during storm runoff events [abs.]: 31st

Annual GeoDaze Geoscience Symposium, GeoDaze 

2003, p. 55.

Balistrieri, L.S., Box, S.E., and Tonkin, J.W., 2003, Modeling 

precipitation and sorption of elements during mixing of 

river water and porewater in the Coeur d’Alene River 

basin: Environmental Science & Technology, v. 39, p. 

1547-1554.

Box, S.E., Bookstrom, A.A., and Ikramuddin, M., 2005, 

Stream sediment geochemistry in mining-impacted 

streams; sediment mobilized by floods in the 

Coeur d’Alene-Spokane River drainage, Idaho and 

Washington: U.S. Geological Survey Scientific 

Investigations Report 2005-5011, 57 p.

Gough, L.P., Sanzolone, R.F., Lamothe, P.J., Ager, C.M., 

Foster, A.L., and Crock, J.G., 2003, Bioaccumulation 

and mobility of cadmium in willow and soils, 

Alaska—implications for the health of browsing 

animals [abs.]: U.S. Geological Survey Open-File 

Report 2003-097, p. 22.

Slowey, A.J., Rytuba, J. J., and Brown, G.E. Jr., 2005, 

Speciation of mercury and mode of transport from 

placer gold mine tailings: Environmental Science & 

Technology, v. 39, p. 1547-1554.

Willard, P., and Stillings, L.L., 2005, A mass balance for 

selenium in the upper pond of the Clark County 

Wetlands Park, Nature Preserve, Las Vegas, NV 

[abs.]: Geological Society of America Abstracts with 

Programs, v. 37, no. 7, p. 178.

Additional information about the recently completed 

“Pathways of Metal Transfer from Mineralized Sources 

to Bioreceptors” project is at the USGS Western Mineral 

Resources Web site [http://minerals.usgs.gov/west/projects/

path.htm].