Understanding 

Our Fragile Environment 

Lessons from 

Geochemical Studies 
All ethics so Jar evolved rest upon a single premise: that the individual is a member of a 

community of interdependent parts. His instincts prompt him to compete for his place in that 

community, but his ethics prompt him also to co-operate (perhaps in order that there may be a 

place to compete for). The land ethic simply enlarges the boundaries of the community to 

include soils, waters, plants, and animals, or collectively: the lands. 

Aldo Leopold-A Sand County Almanac 

Front cover: Fireweed, the state flower of Alaska, is an early colonizer of lands disturbed both naturally and by human activity. 

Following the May 18, 1980, eruption of Mount St. Helens, this wildflower was among the first plant species to colonize volcanic 

ash that was deficient in both organic matter and nutrients. 
Understanding 

Our Fragile Environment 

Lessons frolll 

Geochelllical Studies 

Public Issues in Earth Science 

U.S. Geological Survey Circular 1105 

Compiled by Larry P. Gough 

With contributions from 

Sigrid Asher-Bolinder 

Laurie S. Balistrieri 

George N. Breit 

Thomas J. Casadevall 

James G. Crock 

Kimberley I. Cunningham 

Joseph S. Duval 

James A. Erdman 

Barbara M. Erickson 

Walter H. Ficklin 

Larry L. Jackson 

Rama K. Kotra 

Joel S. Leventhal 

James M. McNeal 

William R. Miller 

James K. Otton 

Douglass E. Owen 

Edited by Carole A. Bales, Sonja K. Runberg, and Robert K. Wells 

Graphics by Marty Simmons, Shawn T. Smith, and Richard P. Walker 

Photocomposition by Barbara J. Ramsey and Joan G. Nadeau 

Geoffrey S. Plumlee 

G. Michael Reimer 

Ronald C. Severson 

Kathleen S. Smith 

Kathleen C. Stewart 

Ronald R. Tidball 

Stephen A. Wilson 

Robert A. Zielinski 
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U. S. Government. 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1993 

Free on application to 

USGS Map Distribution 

Box 25286, Building 810 

Denver Federal Center 

Denver, CO 80225 

Library of Congress Cataloging-in-Publication Data 

Understanding our fragile environment: lessons from geochemical studies I 

compiled by Larry P. Gough; with contributions from Sigrid Asher-Bolinder ... 

[ et al.] ; edited by Carole A. Bales, Sonja K. Runberg, and Robert K. Wells. 

p. em. -(U.S. Geological Survey circular; 1105. Public issues in earth 

science) 

Includes bibliographical references. 

Supt. of Docs. no.: I 19.4/3:1105 

1. Environmental geochemistry. I. Gough, L. P. II. Asher-Bolinder, 

Sigrid. III. Bales, Carole A. IV. Runberg, Sonja K. V. Wells, Robert K. 

VI. Series: U.S. Geological Survey circular; 1105. VII. Series: U.S. 

Geological Survey circular. Public issues in earth science. 

QE516.4.U53 1993 

551.9-dc20 93-15778 

CIP 
FOREWORD 

As part of the special interest series, Public Issues in Earth Science, published by the U.S. 

Geological Survey (USGS), this Circular describes the importance of the earth sciences in the 

investigation of environmental problems. The report focuses on geochemistry-the study of 

the amounts, distribution, and cycling of chemical elements in the Earth and atmosphere-and 

how this science helps to evaluate critical issues that relate to our fragile environment. 

The mission of the USGS is to provide geologic, topographic, and hydrologic information 

that contributes to the wise management of the Nation's natural resources and promotes the 

health, safety, and well-being of our people. Part of this task includes characterizing the 

Nation's geochemical environment and understanding the dynamic processes responsible for 

change in that environment. 

One of our greatest assets at the USGS is our long tradition of excellence in unbiased earthscience research. Part of that legacy is our commitment to supply the geochemical information 

necessary to confront urgent environmental challenges. Geochemistry provides information on 

the distribution of chemical elements to help us define and understand environmental 

problems. This information then allows us to provide answers for their resolution and possible 

remediation. 

This Circular presents an overview of geochemistry and its application to various case 

studies that illustrate the use of geochemistry in examining environmental problems. Some 

new and exciting areas of environmental geochemistry are discussed, involving r(.)ck/water, 

soil/ water, and plant/ soil investigations. These investigations focus on many of our natural 

resources including minerals, soil, water, air, and vegetation and examine environmental 

concerns-such as acid precipitation, mine drainage, and sources of contamination-from a 

"systems" or "holistic" approach. 

As the primary Federal earth-science agency, the USGS leads in the collection, interpretation, and dissemination of earth-science information. This report helps to define one area in 

which the USGS is an active participant-the application of geochemistry to environmental 

concerns. 

Dallas L. Peck 

Director 

iii 
USGS scientist sampling water from a uranium-rich spring in a Colorado wetland. 

iv---------------------------------------------------------------------------------
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CONTENTS 

Foreword iii 

Introduction to Environmental Geochemistry 1 

Minerals, trace elements, contaminants, and hazards 1 

Sources of hazardous element contamination 2 

The future--Possible problems and solutions 4 

Geochemistry and responsible land use 6 

Geochemical Processes in the Environment 8 

The global perspective 8 

Heavy-metal mobilization, transport, and deposition 9 

Baselines and backgrounds-What's natural and what isn't 10 

New technology provides tools for the geochemist 12 

Examples and Case Studies 14 

Plant and animal health 14 

Radon, uranium, and the environment 16 

Mine drainage 18 

Air pollution and biogeochemistry 21 

Volcanogenic and greenhouse gases 24 

Oil and petroleum spills 26 

Point sources of contamination-Industrial and natural 27 

Nonpoint sources of contamination-Agricultural and natural 29 

New areas of concern-A look to the future 30 

Further Reading in Environmental Geochemistry 31 

Information Sources 32 

Glossary 33 

v 

Introduction to Environmental Geochemistry 

Minerals, trace elements, contaminants, and hazards 

An understanding of our fragile environment can begin with a recognition of the 

importance of certain elements, commonly 

called "minerals substances" (such as iron 

and zinc), in the lives of humans and animals 

and in the soils that support plants. This 

recognition is well deserved because these 

elements are essential for the life or optimum 

health of an organism. Some elements such 

as carbon, hydrogen, oxygen, magnesium, 

potassium, and phosphorus are required in 

relatively large amounts by organisms. 

However, others are required in smaller 

quantities; these are referred to as trace elements. Diseases have been related to the deficiency of about 20 elements in animals and 

humans and to the deficiency of approximately 13 elements in plants. 

The biogeochemistry of life--€ssential elements 

At the same time, if these and other elements occur in quantities great enough, toxicity can result. An element, or any substance, 

that occurs in the environment and contains 

concentrations above what are considered to 

be background levels may be considered a 

contaminant. When contaminants occur at 

levels that are potentially harmful to organisms, they are labeled as hazards. Often the 

quantitative difference between essential 

amounts and toxic concentrations of these 

elements is very small. For example, the trace 

element selenium is required at a level of no 

less than 0.4 ppm in the diet of cattle but can 

be toxic at levels greater than approximately 

4ppm. 

Elements that are required for survival 

by animals and plants are termed essential, 

Essential to all Essential to several Essential to a wide Essential to one or Recent work indicates 

animals and plants: classes of animals and variety of species in two species only: essentiality, but of 

plants: one class: unknown function: 

Hydrogen (H) Silicon (Si) Boron (B) Lithium (Li) Rubidium (Rb) 

Carbon (C) Vanadium (V) Fluorine (F) Aluminum (AI) Tin (Sn) 

Nitrogen (N) Cobalt (Co) Chromium (Cr) Nickel (Ni) 

Oxygen (0) Molybdenum (Mo) Bromine (Br) Strontium (Sr) 

Sodium(Na) Iodine (I) Barium (Ba) 

Magnesium (Mg) 

Phosphorus (P) 

Sulfur (S) 

Chlorine (Cl) 

Potassium (K) 

Calcium (Ca) 

Manganese (Mn) 

Iron (Fe) 

Copper (Cu) 

Zinc (Zn) 

Selenium (Se) 

Elements in bold type are generally considered to be trace elements. 

1 
!The ~ 

I biogeochemical 

cycle 

2 

Chemical elements move through 

the environment in 

biogeochemical 

cycles. There are 

three major components to this process: 

(1) an element source 

(where did the element come from?-

for example, rocks, 

soils, waste sites, 

contaminant spills, 

to name a few), (2) a 

transport mechanism (how does it 

move through the 

environment?), and 

(3) a place of deposition (where, how, 

and why does it stop 

moving?). 

We call this cycle 

biogeochemical 

because, in addition 

to the role of chemical and physical 

processes, the 

cycling of elements 

strongly depends on 

its interaction ith living organismsfrom bacteria to 

humans. 

while those not required are nonessential. Trace essential elements such 

as fluorine, copper, selenium, molybdenum, and others listed in the table on 

page 1 can be hazardous to life forms if 

present at high levels. Nonessential 

heavy metals such as arsenic, lead, mercury, cadmium, and chromium are usually toxic to organisms at much lower 

levels than trace essential elements. 

Depending on the association that these 

nonessential elements may form with 

natural geologic materials such as organic 

matter, other elements or minerals, and 

adsorbers (such as clays), these elements 

can range from being safe to being 

extremely toxic. 

The elemental composition of plants, 

animals, and humans correlates with the 

geologic makeup of the Earth, and life has 

evolved reflecting these natural occurrences. The science of environmental geochemistry examines the interrelationship of 

life with the physical and chemical Earth. 

Sources of hazardous element contamination 

Because of growing public concern 

about environmental contamination, it is 

becoming increasingly important to better understand both the natural and 

human processes that control the movement of elements at the Earth's surface. 

Elements can be quite mobile in water, 

and the majority of our environmental 

problems are ultimately associated with 

the contamination of surface and 

ground water. The natural processes 

that control the behavior of elements in 

water are fundamental to the understanding, prevention, and correction of 

many environmental problems. 

Scientists strive to comprehend these 

natural and human processes and are 

improving models that predict with 

more accuracy the impact of both natural and human-related environmental 

changes. 

When water comes into contact with 

rocks and soils, some of the minerals 

and organic substances dissolve and 

enter the natural waters. Forests and 

grasslands generally contribute only 

small amounts of these dissolved substances. However, it is possible for an 

area to contain unusually high concentrations of minerals, thereby depositing 

them to the waterways. For example, 

swamps and marshes often produce 

acidic and colored water. Other areas 

that contribute natural pollutants to water 

are those containing rocks with sulfide 

minerals, particularly pyrite. When pyrite 

Fluorine, emitted as a gas from phosphate-processing 

facilities in southeast Idaho, contributed to the death 

of these conifer trees. 
Acidic, metal-bearing waters can form in mineralized 

areas that have not been mined. Here, natural ironand aluminum-rich acidic waters flow into South 

Mineral Creek near Silverton, Colorado. The spring 

waters have precipitated a large terrace of iron hydroxide minerals (bottom). Mixing with the main creek 

waters raises the pH of the acid spring waters sufficiently to precipitate aluminum hydroxides, seen as 

white coatings on creek bed rocks (center of photo). 

is exposed to oxygen and water, the water 

becomes acidic and often contains large concentrations of metals such as zinc, cadmium, 

and arsenic. 

Inorganic substances are cycled naturally 

through our environment at concentrations 

that usually do not adversely affect plants 

and animals. However, the combination of 

some natural processes with human activities 

can increase these substances to harmful or 

toxic levels. Therefore, toxic substances may 

have both natural and human sources. These 

sources can range from a mineral deposit 

(natural point source) or industrial processing facility (human point source) to entire 

cities or several counties (nonpoint source). 

Natural sources of toxic substances 

include rocks, volcanoes, sediments, and 

soils. For example, sedimentary rock in central Oklahoma contaminates ground water 

with arsenic, chromium, selenium, and uranium. In Africa, cooling magma beneath 

Lake Nyos in Cameroon produced carbon 

dioxide that bubbled up and suffocated 2,000 

people in 1986. In the West Central United 

States, certain sedimentary rocks contain 

toxic amounts of selenium. Some plants can 

concentrate selenium in their tissue, which 

can result in livestock disease and death. 

Human activities that add toxic substances to the environment include smelting, 

manufacturing, refining, chemical processing, fertilizer application, irrigation, and 

waste disposal. For example, prior to the 

passage of laws designed to protect the environment, the processing of metal ores created 

areas that were highly contaminated with 

heavy metals. These areas have subsequently 

been designated by the U.S. Environmental 

Protection Agency as hazardous waste 

(Superfund) sites. Areas affected by oil spills 

from tankers or wells are also classified in 

this group. 

A large concentration of a substance 

commonly identifies a source of pollution 

but may not necessarily indicate a problem. 

In addition to the concentration, other characteristics of the substance must be considered. These characteristics include the 

amount of the substance released, the rate of 

release, its availability to organisms, and its 

residence time in a particular ecosystem. 

This information is essential to understand 

and to predict the activity of a substance 

under differing geologic and geochemical 

conditions. With this knowledge, the relation 

between the concentration of a substance 

and the magnitude of its environmental 

impact can be determined. 

3 
I More about the 

chemistry and 

cycling of 

selenium 

4 

Like all elements, 

the form of selenium 

in rocks and soils 

governs its bioavailability (its uptake 

and incorporation 

into plant or animal 

tissue). 

Although common 

in rocks and soils of 

the U.S., the form of 

selenium in Western 

U.S. geologic materials makes it far more 

bioavailable in arid 

and semiarid places 

like California and 

Nevada than in New 

York or Virginia. 

Therefore, environmental selenium as a 

human or animal 

health problem is 

only a concern in arid 

regions. 

The future-Possible problems and solutions 

When it hurts 

All too often a problem isn't recognized until something begins to hurt. 

That pebble in your shoe isn't a problem 

until it gets under your foot, but because 

of past experience, when you first notice 

the pebble, you can immediately anticipate future pain. For the solution to any 

problem we must first identify the problem, either from past experience or by 

new inquiry, and understand the process 

by which it came to be. Knowing the 

process suggests why the problem exists, 

and this understanding can possibly lead 

to a solution. 

Geochemistry is for the birds 

An irrigation project in the San 

Joaquin Valley, California, was created in 

the 1970's on a broad slope that extends 

from the foothills of the Coast Range to 

the San Joaquin River in the center of the 

Valley. Early in the project no one knew 

that toxic amounts of selenium had been 

transported for a very long time from 

rock sources in the Coast Range and concentrated in shallow ground water near 

the lower part of the slope. To control irrigation runoff and salt accumulation in the 

soils, this shallow ground water was 

drained away into evaporation ponds. 

During this draining process, the selenium was further concentrated by evaporation and accumulation into aquatic 

plants. A problem with the selenium was 

noticed when birds feeding on the plants 

began to die. Subsequent research 

showed that rainwater that had percolated through the selenium-enriched sedimentary rocks in the mountains had 

gradually dissolved the selenium. The 

element was then transported by the surface streams and through the ground 

water to the evaporation ponds. 

A possible solution to this problem 

would be to speed up nature's own methods by either transforming the selenium 

to an insoluble form that is no longer 

reactive or by flushing it to the ocean, 

where it would be effectively diluted. As 

a result of the research in the San Joaquin 

Valley, developers of new irrigation projects are aware of the potential environmental consequences of toxic amounts of 

selenium. 

Geochemistry is for plants, too 

Geochemistry touches both largescale agriculture activities and home gardening either through natural environmental conditions or by the addition of 

fertilizers. Fertilizers are widely regarded 

as essential for favorable plant yield, but 

there is a negative side. Super-phosphate 

and limestone fertilizers are typically 

derived from natural rock deposits that 

may also contain significant amounts of 

metals. In Missouri, where fertilizer was 

heavily contaminated with lead, it was 

discovered that mine waste derived from 

the mining of lead hosted in limestone 

had been used as an inexpensive source 

of agricultural lime. In another example, 

natural forests in Missouri were cleared 

and planted with grass for cattle pasture. 

The soils were covered with lime to 

improve the grass yield, but the resulting 

increase in soil pH subsequently 

increased the uptake of certain metals by 

plants, which in turn adversely affected 

the health of grazing cattle. 

Sewage sludge and agriculture 

Municipal sewage sludge can be an 

inexpensive source of agricultural fertilizer. Sewage, properly processed, is free of 

harmful bacteria. The resulting sludge 

contains plant nutrients, which crops 

respond to favorably, and organic matter, 

which improves the texture and waterholding ability of the soil. However, scientists know that heavy metals originating in industrial drainage concentrate in 

the sludge and can be toxic to either 

plants or animals. Studies near Denver, 

Colorado, in the early 1970's showed that 
37" 

00' 

360 

45' 

360 

30' 

Idria 

0 5 10 MILES 

I I I I I 

36° 0 5 10 KILOM ETERS 

120°30' 120°00' 

"" Se(ppm) 

0 0.05 

10 .32 

20 .48 

30 .62 

4() .71 

50 .79 

60 . 84 

70 .89 

60 .95 

90 

95 

15 '~------------------_L ________________________ _j 

.... The pattern of selenium (Se) concentration in soils 

collected in an area on the west side of the San Joaquin 

Valley, California. Selenium in the shale bedrock on 

Monocline Ridge was leached into the ground water 

and migrated east (downslope). Warm colors are areas 

of high soil selenium. Kesterson Reservoir, the site of 

selenium poisoning in waterfowl, is in the northern 

part of this region . 

T California Aqueduct, Fresno County, California. 

Irrigation water from this source is used for agriculture 

throughout the San Joaquin Valley. The selenium 

leached from geologic formations accumulated in biota 

of the Kesterson National Wildlife Refuge. High concentrations of selenium resulted in wildfowl deformities 

and death. 

5 
6 

hard, red, winter wheat absorbed significant 

amounts of cadmium, nickel, and other metals from sludge. Such metal absorption by 

crops fertilized with sewage sludge can be a 

problem. As a result, selection processes are 

now used to determine which crops may 

receive sludge fertilization and still have 

minimal negative effects. Although there are 

some negative aspects to sludge fertilization, 

there are many benefits from the process. 

Successful use of sludge by both developing 

and developed countries demonstrates the 

advantages of its use as a fertilizer. 

Geochemistry and responsible land use 

Modern land-use managers are challenged to accommodate the increasing and 

often conflicting demands of potential users, 

while at the same time they must strive to 

preserve the integrity of natural resources. 

Accurate site-specific geochemical data are 

critical for responsible land-use decisions. 

The data must define the physical and chemical characteristics of the near-surface environment (the area from the Earth's surface 

down to the bedrock) and must describe the 

natural processes that form and modify these 

characteristics. Land-use decisions should be 

compatible with these natural processes or 

should include strategies to reduce any negative impact on the land. 

Geochemical processes 

Geochemical studies by USGS scientists 

have defined the causes and extent of the 

selenium problem in California. However, 

the initial gathering of geochemical data 

could have helped managers lessen this environmental problem. Additional irrigationrelated problems include the leaching of pesticides, herbicides and other potentially toxic 

trace elements, and loss of soil fertility 

through salt buildup (salinization). Land 

managers who consider geochemical and 

other earth-science data in their decisions can 

better anticipate or remediate these potential 

problems. Such data include the local topography, climate, and hydrology, as well as the 

distribution and characteristics of the 

region's soils and bedrock. 

Many biogeochemi- • Biological transfor- bacteria decompose the present and in a dis- tion of elements in an 

cal processes influence mations-Sunlight and plant, and the elements solved form in water environment. 

the quantity and distri- nutrients such as carbon, are released back into when oxygen is absent. • Scavenging or sorpbution of elements in nitrogen, and phospho- the atmosphere, soil, • Radioactive decay- tion-These processes 

our environment. The rus are transformed and water. These reactions involve involve the physical or 

degree of influence of a through photosynthesis • Oxidation/ the spontaneous chemical attachment of 

particular process in plants. Other trace Reduction (Redox) release of gamma rays dissolved elements to 

varies with the type of elements such as boron, reac.tions-These reac- and electrons. The rate the surfaces of partielement, the ecosystem copper, iron, man- tions change the chemi- of this decay is known des. For example, in 

of interest, and the ganese, molybdenum, cal and physical form of for radioactive ele- lakes certain toxic dischemical conditions of and zinc are also incor- elements through the ments and can be used solved elements such 

the system. porated into plant mat- exchange of electrons. in geochemical studies as arsenic can be 

The processes that ter during photosynthe- For example, iron exists to determine how the adsorbed onto sinking 

scientists know exist sis. When plants die, in a solid form (i.e., rate of various process- particles or bottom sedand have studied microorganisms such as rust) when oxygen is es affects the distribu- iments. In the adsorbed 

include: 
state these elements are tions. Certain base- particles and dissolved 

effectively removed metal ores (copper, elements from aquatic 

from being further cir- lead, and zinc) form in systems such as 

culated through the this manner. aquifers, wetlands, and 

system. • Atmospheric depo- lakes. The mixing of 

• Precipitation-This sition-After being car- waters can then redisprocess relies on the ried by wind, elements tribute dissolved elechemical conditions of are deposited by rain- ments in an environa solution and reactions fall or on dust particles mental system. 

whereby dissolved ele- and incorporated into • Volcanic 

ments form solids. plants, soils, and water. emissions-When volMany ore deposits were • Transport by canoes are active, they 

formed by the precipi- water-Rivers, streams, produce gases and 

tation of elements from and ground water can lava, thereby bringing 

hydrothermal solu- supply and remove elements located deep 

~ The general cycle of element 

mobilization, transport, and deposition. Elements that are mobilized 

through processes listed below are both 

physically and chemically transported. 

They eventually are redeposited in lake 

and ocean sediments to be locked away 

until mobilized once again. 

within the Earth to the sophisticated geosurface. chemical tools to 

• Weathering of explain the complicatrocks-Rocks that are ed, intertwined relaweathered chemically tionships. These tools 

and are mechanically include mathematical 

broken down into models, advanced 

smaller pieces form sampling and analytisoils, and the elements cal techniques, and 

are redistributed. both laboratory and 

Many of these field studies, which 

processes are linked to all help to identify the 

one another. Therefore, processes. 

to better understand 

them, researchers use 

7 
8 

Geochemical Processes in the Environment 

The global perspective 

• Lead from a smelter poisons 

nearby children 

• Power plant emits sulfur 

dioxide causing acid rain 

• Arsenic from mine tailings 

pollutes local water supply 

Newspaper headlines such as those 

above describe a few of the pollution problems occurring throughout the world. 

Human activities can have an environmentally destructive effect on the world as a 

whole. For instance, the Chernobyl nuclear 

reactor disaster of 1986 demonstrated that 

there are no political or geographical boundaries to the distribution of harmful elements 

and compounds. During the 20th century, the 

dispersion of numerous elements, largely 

due to human activity, has been "recorded" 

in layers of polar ice and snow. Specifically, 

these recordings have shown the rise of the 

Industrial Revolution and the global circulation of metal contaminants such as lead and 

mercury. Synthetic compounds have also 

been widely dispersed. Some Arctic natives 

have been exposed to unusually high levels 

of polychlorinated biphenyls (PCB's) by consuming fish and aquatic mammals that seem 

to have the material concentrated in their tissues. PCB's are very toxic byproducts of the 

modern plastics and coolant industries that 

remain in the environment for a very long 

time. This is one example of atmospheric and 

hydrologic processes that distribute elements 

and compounds around the planet. As a 

result, a pristine environment is now only a 

relative term. 

Aspects of the major biogeochemical 

cycles of elements such as carbon, nitrogen, 

phosphorus, and sulfur vary from location to 

location but still must be viewed in a global 

perspective. An example of the importance 

of viewing these processes as a whole is the 

current global warming problem. Both 

human activities and natural processes have 

contributed to global warming. Human 

influences include power plants, factories, 

waste disposal, and the processing of raw 

materials. The natural biogeochemical 

cycling of elements has also played a role in 

global warming. Scientists must understand 

the complex linkages among biogeochemical 

cycles, and, in so doing, their studies must 

encompass four dimensions: the two dimensions of the Earth's surface, plus depth and 

time. Hence, environmental geochemistry is 

the study, in time and space, of the concentration, total quantity, and chemical form of 

elements and the physical and chemical 

processes that control their mobility and 

transformation in our environment. 
The Earth can be thought of as having five interconnected 

regions or spheres of chemical, physical, and (or) biological 

activity, each of which plays a role in the mobilization, transport, and deposition of chemical elements. 

Heavy-metal mobilization, transport, and deposition 

Many elements that are a natural part of 

mineral deposits, rock formations, or soils 

are easily mobilized into water as a result of 

specific chemical conditions. The degree that 

an element is dissolved and its ultimate fate 

are dependent on the geochemistry of the 

specific element and the geology of the material from which it came. Iron, manganese, 

copper, lead, arsenic, and cadmium are quite 

often part of mineral deposits and are mobilized naturally or as a result of mining and 

the chemical reactions that cause acidic minedrainage waters. These elements and many 

others can also be found in ground water, 

surface water, and soils as a result of industrial uses. For example, arsenic, which is 

often a byproduct of gold-ore refining, has 

been used extensively in insecticides and 

herbicides. 

The distribution and effect of arsenic in 

the environment from mining and industrial 

waste continue to be an important focus of 

research. As a result of mining, large 

amounts of arsenic-bearing wastes are found 

on the Clark Fork River in Montana and the 

Cheyenne River system in South Dakota. 

Following mining activities, the arsenic was 

mobilized by weathering processes and 

found its way into surface and ground water 

and aquatic life forms. 

9 
What is a 

baseline? 

A baseline is computed as two deviations about the mean. 

Two deviations 

include about 9.5 percent of the area of the I 

distribution under a 

normal frequency 

curve. 

Backgrounds and I 

baselines are generally developed by: (1) 

defining the population (sample) to be 

described; (2) collecting samples that represent the population; (3) analyzing the 

samples for the constituents of interest; 

and (4) computing 

the range that represents the baseline. 

How can this 

range be used to 

determine whether a 

single sample is 

unusual in composition? For example, if 

several samples of 

soil are collected and 

analyzed, and most 

of them have concentrations of elements 

outside of the expected 95-percent range 

for soils that are representative of the 

general area, then 

there is a good 

chance that these are 

unusual samples, 

perhaps representing 

some type of environmental contamination. 

10 

Baselines and backgroundsWhat's natural and what isn't 

Regulatory limits for safe levels of 

elements in water and foodstuffs are 

established by the U.S. Environmental 

Protection Agency and the U.S. Food 

and Drug Administration. However, 

there are generally no regulatory limits 

that scientists can refer to when dealing 

with plants, soils, rocks, and sediments. 

Therefore, to determine whether a 

plant, soil, rock, or sediment contains a 

"high or unusual" quantity of a specific 

element, it is necessary to determine 

what quantity is "normal or usual." 

These levels are referred to as background or baseline measurements, but 

they may be somewhat different. 

A background measurement represents natural concentrations of an element in natural materials that exclude 

human influence. This measurement 

represents an idealized situation and is 

typically more difficult to measure than 

a baseline. True backgrounds may be 

obtained by sampling and analyzing 

items that have a minimum of human 

influence such as tree rings, deep 

glacial ice cores, or layers of sediments 

from lake or ocean floors. 

A baseline measurement represents 

concentrations measured at some point 

in time and is not generally a true background. Baseline concentrations are 

typically expressed as a range, not a 

single value. 

The three objectives that are generally common to all background and 

baseline studies are: 

• To describe the chemical characteristics and variation of an 

environment-The study should tell 

something about the composition of 

the materials sampled as well as their 

distribution or pattern across the landscape. 

• To assess the extent or intensity of environmental alteration-Baseline studies 

should also evaluate the changes in the environment due to human activities. 

• To provide basic information necessary 

to study environmental processes-The 

background information generated from 

environmental studies may show patterns for 

a certain group of elements. The element distribution or pattern across the landscape, 

together with information regarding the 

area's geology, soils, and plant communities, 

provide useful data that help explain 

processes such as element mobilization, 

transport, and deposition. 

Collecting slash pine needles to determine baseline element concentration values. In the United States, an 

unusual form of slash pine is found only in south 

Florida near Everglades National Park. Slash pine is 

being threatened by agriculture, housing developments, 

and air pollution. 
From the farm fields' checkerboard pattern south of 

Lake Okeechobee, to Miami's speckled concrete patterns 

on the eastern Atlantic coast, this Landsat (satellite) 

photograph shows the human impact on the environment. Color enhancement helps to delineate. land-use 

patterns and, over time, can track vegetation changes 

within Everglades National Park (lower left). These 

changes are caused by natural (Hurricane Andrew) 

and human influences (air contamination from 

Miami, agriculture, and heavy industry). 

(Reproduced with permission from Earth Observation 

Satellite Co., Lanham, Maryland, USA.) 

11 
New technology provides tools for the geochemist 

The defining and understanding of problems in environmental geochemistry often 

require accurate measurement of both organic and inorganic substances. Questions such 

as "What substances are in this sample?" and 

"How much of it is there?" are answered by 

using modern analytical techniques. Two of 

the most important techniques are gas chromatography-mass spectrometry (GC-MS) 

and inductively coupled plasma mass spectrometry (ICP-MS). GC-MS is used to identify and quantify organic compounds, whereHow is a geochemical baseline 

expressed? It is often expressed not 

as a single concentration value but 

as a range. This range is based on a 

normal frequency distribution of the 

concentration values found in some 

sample material and is usually plus 

or minus two deviations about the 

mean value (95 percent expected 

range). 

12 

as ICP-MS is used to identify and quantify 

inorganic substances. Both techniques are 

indispensible to the geochemist. 

Soils, sediments, rocks, air, and water can 

contain a large number of organic substances, 

both natural and manmade. Often they are 

present as complex mixtures made up of 

dozens to many hundreds of individual molecules. To find the needle (a pollutant of 

interest) in the haystack (a complex mixture 

of organic compounds), GC-MS is used. 

Typically, a very small amount of a sample is 
Sample identification 

begins when 

liquefied material is 

injected into the 

column or coil of the 

gas-chromatograph. 

Based on their 

relative sizes, the 

various components 

of the sample are 

retained at different 

rates by the 

presence of a 

gummy substance. 

~~~...It~ 

-+-+-+-+-+-+~-+ 

")) \1 ")) ~ ")) 

Mass Filter 

Next, the separated The ionized 

components of the fragments then pass 

sample pass one by through a mass filter 

one through an ion where they are 

source where they further separated 

are bombarded by based on their 

an electron beam. mass-to-charge ratio 

This beam breaks the :... Only a small 

sample into even :.:. proportion of the ion 

smaller, ionized fragments need to 

fragments. make it through the 

mass filter. 

Detector 

Finally, the detector 

records the electrical 

charge and arrival 

time (as established 

by step one) of each 

passing portion of the 

sample. This 

information is then 

sent to a computer, 

which identifies each 

component of the 

sample. A list 

containing each 

component of the 

sample is then 

provided to the 

analyst. 

injected into the GC-MS instrument. This 

sample is vaporized in an instant and each 

individual molecule type travels through a 

narrow column at a different speed. Each 

molecule comes out of the tube and goes into 

the mass spectrometer, an instrument that 

determines molecular weights, where an 

electron beam breaks the molecule into several pieces. By studying the pattern of the 

pieces and their abundance, the scientist can 

tell what the molecule was and how much of 

it there was in the sample. This, in turn, helps 

assess the concentration of the molecule in 

the mixture. 

When an environmental study is concerned with inorganic substances, ICP-AES 

or ICP-MS is the analytical technique of 

choice. Most elements in the periodic table 

can be ionized at high temperature in a 

"plasma" (high-temperature ionized gas), 

which subsequently is sent into the mass 

spectrometer where signals for individual 

atoms are detected. 

.. ·· 

13 
Examples and Case Studies 

Plant and animal health 

Molybdenum can be too much of a 

good thing 

Molybdenum is a metallic element probably best known as a substance that hardens 

and strengthens steel. It is also used in a dry 

lubricant that is resistant to high temperaThe nutritional imbalance of copper to 

molybdenum in the diet of cattle (a disease 

known as molybdenosis) produces symptoms 

such as hair discoloration and loss, and 

weight loss. The steer above is healthy; the 

steer to the right is suffering from molybdenosis. (Reproduced with permission from 

Dr. Verle Bohman, Professor Emeritus, 

Department of Animal Sciences, University 

of Nevada, Reno, Nevada.) 

14 

tures. However, it is an essential element to 

plant and possibly even animal health. 

At least five distinct enzymes (essential 

proteins) in plants contain molybdenum. 

Two of these enzymes serve to metabolize 

nitrogen, a major plant nutrient. Members 

of the legume family-for example, clover 

and alfalfa- are particularly rich in molybdenum because their roots harbor nodules 

of the bacterium Rhizobium, which biologically transforms nitrogen. 

One negative aspect of molybdenum is 

that in large concentrations it interferes 

with the absorption of copper, an essential 

element; therefore it may have toxic effects 

on certain livestock when ingested in large 

amounts. The resultant effect, or illness, is 

molybdenosis. The symptoms of the illness 

include: anemia, depressed growth, diarrhea, poor reproduction, bone malformation, nervous disorders, and loss of normal 

hair color. For example, the hide of Black 

Angus cattle turns a mouse-gray as a result 
of molybdenosis. Similarly, high levels of 

molybdenum in the diet of sheep may lead 

to defective nervous systems in lambs. 

However, if treated early enough, molybdenosis is reversible through corrective 

nutrition. 

Molybdenosis, cattle; and lignite 

A low-grade coal called lignite has been 

strip-mined for decades in the northern 

Great Plains. Lignite contains appreciable 

levels of molybdenum and uranium derived 

from volcanic rock deposits. Ranchers in 

northwestern South Dakota reported problems that resembled molybdenosis in cattle 

pastured around an abandoned lignite strip 

mine. Results in the area of Flint Butte 

showed that the range grasses contained 

very high levels of molybdenum, but only in 

areas near exposed lignite. The high levels of 

molybdenum resulted from lignite that was 

naturally exposed in the environment as well 

as from lignites exposed during surface mining. The molybdenum was removed from 

the lignite through weathering processes, 

transported by surface-water runoff to the 

nearby pastures, and taken up by the range 

grasses. 

Molybdenosis and humans 

In developed countries such as the 

United States, where food production and 

distribution are widespread, and produce 

grown in one region is often shipped to 

another, molybdenum-related nutritional 

problems in humans probably do not exist. 

However, occurrences of molybdenosis have 

been reported in some developing countries. 

One such incidence occurred in southern 

India where construction of a large dam and 

the resultant reservoir raised the water table 

in the surrounding farming district. 

The pattern of molybdenum concentration in western wheat grass 

collected in the Flint Butte area of South Dakota. Highest concentrations were found to correlate with outcrop of uranium-bearing 

lignite (a soft coal). 

Subsequently, molybdenum levels increased 

in the major crop, sorghum. The local inhabitants rely on sorghum as their dietary staple, 

and following consumption of the food, 

some individuals developed genu valgum 

(knock-knee), a crippling bone deformity 

affecting young people. Although this problem occurred in a relatively small region, the 

impact of the disease on the local population 

was serious. 

15 
16 

Radon, uranium, and the environment 

Uranium map 

based on 

radioactivity 

Radioactivity 

Radon is a radioactive, gaseous element 

that is naturally occurring and results from 

the radioactive decay of uranium and thorium. Uranium and thorium are contained in 

natural geologic materials and are often concentrated, over geologic time, under certain 

environmental conditions (for example, in 

geologic formations high in organic matter 

such as coal and peat and sediments high in 

clay). Public health concerns have focused 

recently on radon in homes constructed over 

so-called "high-risk" geologic regions. The 

USGS has produced radioactivity maps that 

materials. The most altitude with instrucommon type of ments that measure the 

radioactivity map is an radioactive energy radiaero-radioactivity map, ating from the ground. 

which is based on Regions of the counmaps give an indica- radioactivity measure- try that are both high 

tion of the uranium ments made from an and low in radioactivity 

levels of surface aircraft flying at low can be identified in this 

can help identify geographical regions that 

have the potential for high radon in the environment (see map below). 

In addition to being a public health concern, radon has been used in various scientific disciplines. It has been used to explore for 

uranium, monitor the movement of atmospheric air masses, trace the mixing of 

streams and oceans, map geologic faults, 

predict earthquakes and volcanic eruptions, 

and evaluate air movement in caves. This latter use helps scientists determine how caves 

are formed. 

map. For example, west is low due to large 

west-central Ohio areas that are covered 

shows moderately high by volcanic basalts that 

radioactivity due to the are low in uranium. 

spreading of uranium- (Warm colors indicate 

bearing black shales high amounts of uraniover the area by glaci- urn; cool colors indicate 

ers, whereas the north- low uranium content.) 
Guadalupe Ridge 

anticline 

1--

w 

w 

lL 

0 

500 

1000 

1500 

Entrance Passages 

Western Borehole 

F-Survey 

Eastern Megamaze 

Six different microclimatic zones are shown for Lechuguilla 

Cave in Carlsbad Caverns National Park, New Mexico. Radon 

was used for the first time to map and characterize these multiple microclimate zones (air circulation cells) in the various cave 

areas in conjunction with observed airflow data. Suspected surface connections contribute fresh air to remote cave areas as 

demonstrated by low radon values surrounded by higher values, 

as well as the presence of mammalian skeletal remains, 

atmospheric-level carbon dioxide concentrations, cooler than 

normal temperatures, and surface topographic relationships. 

17 
Mine drainage 

What is it? 

Mine drainage is metal-rich water 

formed from reactions between water and 

rocks containing sulfide minerals (types of 

metal-sulfur compounds). This runoff is 

often acidic (has a low pH) and frequently 

flows from areas where ore- or coal-mining 

activities have exposed rocks rich in the 

sulfur-containing mineral, pyrite. Metal-rich 

drainage can also occur naturally in mineralized areas. Potential problems associated 

with mine drainage include contaminated 

drinking water and disrupted growth and 

reproduction of aquatic organisms. The bottom of streams contaminated by mine 

drainage is commonly coated with red, 

orange, or yellow sediment, as seen in the 

photographs on page 19. 

The USGS is currently studying a number of watersheds in 

Colorado to understand the impact of mine drainage on water 

quality. For example, Clear Creek, a major source of water for 

municipalities and industry in the Denver metropolitan area, 

receives drainage water from several historic mining districts. 

This plot demonstrates how the drainage impacts dissolved metals in the water along Clear Creek. Zinc, copper, manganese, 

and iron show variations in concentration that reflect the input 

of mine water. 

18 
How does mine drainage occur? 

Mine drainage is formed when pyrite, an 

iron-sulfide mineral (FeS2), is exposed and 

reacts with air and water to generate sulfuric 

acid (H2S04) and dissolved iron. Some or all 

of this iron can precipitate to form the red, 

orange, or yellow sediment in the bottom of 

streams containing mine drainage. 

The rate and degree by which acid-mine 

drainage proceeds can be greatly increased 

by the actions of certain bacteria. As a result, 

some mine drainage can be more acidic than 

vinegar. During acid-mine drainage, the 

generated acid and iron can cause oxidation 

and dissolution of additional pyrite and 

other sulfide minerals containing metals 

such as lead and copper. These metals are 

<111111 Iron-, zinc-, and copper-rich waters draining from 

the Rawley Tunnel, Bonanza District, Colorado. The 

waters emanate from a collapsed mine ad it in back of 

the green shed (top center), traverse mine dump material (center), and flow into Squirrel Creek (bottom). 

As the mine waters flow along the ground surface, 

they become oxygenated and precipitate red, orange, or 

yellow iron hydroxide minerals on the stream bed, 

imparting the "bleeding ground" appearance common 

to many mine drainages. 

T Acidic, metal-bearing waters can also form in 

mineralized areas that have not been mined. Here, natural iron- and aluminum-rich, acidic spring waters 

precipitate terraces of iron hydroxide minerals near 

the headwaters of the Alamosa River, southwestern 

Colorado. The spring waters drain pyrite-rich mineralized rock that has not been subjected to mining. The 

lobate terraces are approximately 2-3 inches high and 

up to 5 or 6 feet wide. 

19 
20 

Mine drainage generation: a two-stage geochemical process 

1~ ~~ Pyrite CFeS2) 

I' -..1 Oxygen C02) 

"'--"'"' 1 Water CH 20) 

Reaction A* 

~ Pyrite + Water+ (Fe3+ or Oxygen) -+ Fe 2+ + Sulfate + Acid 

then released into the water in addition to 

the initial amounts of acid and iron. 

Furthermore, even more chemical elements 

can be released when the rocks that are actually sitting in the water are attacked by the 

acidic solution. 

Geochemists, chemists, and geologists 

are trying to understand factors that control 

the composition of mine drainage. They 

have found that some mine drainages are 

acidic and some are not; some contain a larger quantity of metals than others. Differences 

in the chemical composition of mine 

drainages are a result of several geochemical, chemical, and geological factors such as 

the types and amounts of minerals (particularly pyrite) in the rock and the amount of 

oxygen in the water. Once the factors that 

control mine-drainage composition are 

understood, this information can be used to 

Reaction B * 

Fe3+ + Water -+ Iron Hydroxides + Acid 

*Bacteria that convert Fe2+ to Fe3+ 

can greatly increase the rate of 

acid drainage generation. 

predict the composition of future drainage 

and as an evaluation tool for possible remediation techniques. 

What can be done to clean up mine 

drainage? 

It is difficult to stop the formation of 

mine drainage because it requires keeping 

air and (or) water away from the exposed 

rocks. Scientists are testing prevention techniques such as: (1) trying to find ways to 

hinder the bacteria that speed up the chemical reactions that generate mine drainage, 

and (2) grouting fractures in abandoned 

mines to prevent the inflow of oxygenated 

ground waters. They are also working to 

understand how wetlands can be used to 

scavenge metals and neutralize acid in mine 

drainage. 
Air pollution and biogeochemistry 

The temperate forest, one of the most 

productive ecosystems in North America, is 

particularly sensitive to several types of air 

pollution. The ability of this ecosystem to 

efficiently cycle nutrients results in high forest productivity. Anything that causes a disturbance (stress) in a particular biogeochemical cycle (for example, the cycling of sulfur 

or nitrogen from atmosphere to soil to plant 

and back to the atmosphere) will affect the 

whole system. 

Many areas of North America and 

Europe are experiencing widespread forest 

decline-but is this caused by air pollution? 

Shifts in forest ecosystem productivity are 

natural phenomena and can be accelerated 

or accentuated by the introduction of stresses 

in the system. These stresses can be natural, 

such as precipitation changes, insect infestations, and fires, or can be influenced by manmade disturbances, such as forest clearing, 

soil erosion, and air pollution. 

Three basic types of air pollution can 

cause ecosystem stress: 

• Acid precipitation-caused by sulfur 

dioxide and other acid-forming substances 

from fossil-fuel-burning sources (coal-fired 

power plants) being released into the atmosphere. 

• Oxidizing and chemically reactive 

substances-for example, ozone, carbon 

monoxide and dioxide, and complex organic 

compounds (collectively known as "photochemical" compounds) also originate from 

the combustion of fossil fuels. 

• Heavy metals-such as lead, copper, 

zinc, nickel, cadmium, cobalt, and chromium 

that are released by many industrial activities. 

These three types of air pollutants produce different levels of stress for both individual organisms and for the ecosystem as a 

whole. At low levels, forests act as receptors 

or filters for pollutants. For example, it may 

not be possible to measure the damage 

caused by a toxic metal, such as copper or 

mercury, but the accumulation of the metal 

or its movement through the system may be 

easily measured. At intermediate levels the 

stress that pollutants bring to the system can 

be observed in particularly sensitive species 

and may be manifested as metabolic 

Plantations of seedlings like these of slash pine in 

Everglades National Park, Florida, are used to monitor 

the effect of deteriorating air quality on the local vegetation. 

21 
pH of precipitation 

EXPLANATION 

GJ) pH at sample site 5.6 5.4 5.2 5.0 4.6 4.4 4.2 4.0 

-5.0- Line of equal pH value 

22 

.6. Modern emission-control equipment, such as 

scrubbers for sulfur and precipitators for particulates, 

have made this smoky scene of a coal-fired power plant 

in Wyoming much less common. 

~ "Acid Rain"-This map shows the tendency of 

precipitation in the northeastern United States to be 

more acidic in general than other broad regions of the 

country. Scientists attribute this to emissions from factories and power plants that are high in sulfur. 
changes, predisposition to disease, or nutrient overload (for example, ammonium deposition, which acts as a growth stimulant or 

fertilizer). At high levels, pollutants can 

cause observable symptoms and plant death. 

The introduction of heavy metals into an 

ecosystem can be easily measured, and 

because some plant species like mosses and 

lichens will actually accumulate these metals, plants can serve as "biomonitors" that 

reflect air-quality changes. 

The cause of forest decline and the role of 

air pollution have been compared to 

cancer-the result of multiple stresses that 

wear down components of an ecosystem 

until observable changes occur. The three 

types of air pollution mentioned on page 21 

work in conjunction with natural stresses to 

accelerate forest decline. 

A Spanish moss, pictured here in South Carolina, is 

not a true moss at all, but makes an excellent biomonitor and estimator of overall air quality because it is an 

epiphyte that normally grows on other plants and does 

not obtain its nutrients from either its host or the soil 

but from the atmosphere. 

<111111 Like Spanish moss, lichens and true mosses are 

excellent biomonitors of overall air quality because the 

species (collected here by a USGS volunteer in Denali 

National Park and Preserve, Alaska) obtain all of their 

nutrients from dry and wet deposition from the 

atmosphere. 

23 
24 

Volcanogenic and greenhouse gases 

The atmosphere is a global reservoir that 

mixes across state and national boundaries, 

across oceans, and between hemispheres. 

Natural environmental processes (geologicat 

biologicat and geochemical) produce the 

greenhouse gases carbon dioxide (C02) and 

methane (CH4). These gases, along with 

water vapor, are primarily responsible for 

atmospheric warming, which is the "greenhouse" effect. We know there is a greenhouse 

effect based on at least three types of findings: 

• The Earth would be approximately 30 

degrees Celsius cooler if it did not have its 

present atmosphere; as a result, all the water 

on the surface of the Earth would be frozen. 

• Using the known atmospheres of the 

other planets (Venus and Mars in particular), 

we can predict their surface temperatures 

based on their amounts of greenhouse gases, 

gases which are the same as those found on 

Earth. 

• The record of past atmospheric gases 

(C02 and CH4) trapped in ancient ice core 

samples from glaciers shows correlations 

with past climates (historic records). 

Periodic geological events, such as volcanic eruptions, add large amounts of carbon 

dioxide and other gases to the atmosphere. 

These gases tend to enhance the greenhouse 

effect. Volcanoes also add large amounts of 

aerosol particulates (sulfates and ash) that 

seem to cool the atmosphere. These events 

can be monitored but cannot be accurately 

controlled or predicted. USGS scientists at 

various observatories are monitoring these 

volcanic emissions in an attempt to better 

understand the processes. 

Biological processes produce methane in 

certain geochemical environments, such as 

wetlands and freshwater marshes, where 

there is an absence of oxygen (anoxic). These 

methane emissions are a result of bacterial 

metabolism (decay) of organic matter. 

Warming of the atmosphere, land, and 

oceans by carbon dioxide and methane 

would result in sea-level rise due to thermal 

expansion and glacial melting, and coastal 

regions, including marshes, would be 

flooded. 

Salt marshes also produce methane, but 

not as much as freshwater marshes. This is 

because microorganisms known as "sulfate 

reducers" are abundant in salt marshes and 

inhibit the methane-producing microorganisms. Brackish marshes (water with a salinity 

between that of sea water and fresh water) 

emit 25 to 50 percent less methane than the 

freshwater marshes they succeed. Thus, as 

salt waters flood and destroy freshwater 

marshes, less methane is produced. 

The Gulf Coast of Louisiana has been 

experiencing coastal-wetland loss for 100 

years due to subsidence, oil and gas withdrawat sediment starvation due to river 

diversion, and sea-level rise. The USGS is 

studying methane production in marshes 

with varying salinities to quantify the 

methane emissions as a function of marsh 

type. The results of these measurements will 

be used to project the local and world-wide 

effects of sea-level rise and wetland salinization on methane emissions. 
The 1980 eruption of Mount St. Helens in Washington State 

was a natural source of atmospheric contaminants that included 

particulates, carbon dioxide, forms of gaseous sulfur, and trace 

elements. 

25 
Oil and petroleum spills 

Maritime oil spills from freighters such 

as the Torrey Canyon and the Amoco Cadiz in 

the 1960's and 1970's focused the world's 

attention on petroleum pollution at sea and 

the devastating effects on coastal ecosystems. In March 1989, the United States was 

awakened to the enormity of the environmental impact and cost of such a calamity 

when the Exxon Valdez spewed 11 million 

gallons of crude oil into Prince William 

Sound, Alaska. Although the spill was 

approximately 30 times smaller than the 

Amoco Cadiz, it affected more than a thousand miles of coastline in a highly productive cold-water ecosystem and killed more 

wildlife than any previous spill. The death 

toll of sea birds alone has been estimated to 

be 100,000 to 300,000. 

As the Alaskan oil spill spread, the more 

volatile components were lost to the atmosphere. Oil was emulsified with sea water, 

where it continued to degrade or weather 

and was deposited on shorelines and intertidal zones. In the aquatic and terrestrial 

environments, naturally occurring microorganisms further degraded the petroleum. 

Along portions of the Alaskan coastline, 

"bioremediation" was used to speed up the 

natural bacterial oil degradation by the addition of nutrients and apparently served as a 

safe cleanup alternative. Some of the coastal 

ecosystems appear to be recovering rapidly. 

Oil from the Exxon Valdez spill of March 1989 coats rocks in 

the intertidal zone of a beach on Green Island, Prince William 

Sound, Alaska. (Reproduced with permission from the Alaska 

Department of Environmental Conservation, Juneau, Alaska.) 

26 
However, the true, long-term effects will 

undoubtedly be studied and debated for 

years. 

An oil spill the magnitude of the Exxon 

Valdez occurs about once a year somewhere 

in the world, and spills of 1 million gallons 

occur monthly. For most Americans, however, petroleum spills are as close as their 

neighborhood gas station. Petroleumcontaminated soils are common throughout 

the United States, with spills or leaks occurring at petroleum refineries, fuel transportation or storage facilities, petrochemical 

plants, underground storage tanks at gas stations, and at homes with tanks of heating 

fuel. These spills present a human health 

hazard because of potential contamination of 

drinking water or direct exposure to toxic 

and carcinogenic compounds. The risks associated with petroleum-contaminated soils 

may be great and immediate, or they may be 

minimal, depending upon the nature of the 

contaminant and the geologic and hydrologic 

properties of the site. Understanding the 

physical, chemical, and biological processes 

affecting hydrocarbons in soil and ground 

water is the key to appropriate and costeffective remediation of petroleum 

contamination. 

Point sources of contamination-Industrial and natural 

Point-source pollution comes from a single source located in a small area such as a 

factory, power plant, or natural spring. There 

are many types of point-source pollution that 

degrade the quality of water, air, and soils. 

Examples include: (1) emissions of particulates and acidic gases into the atmosphere 

from active volcanoes, (2) metalliferous 

springs whose waters have interacted with 

unmined mineral deposits, (3) natural oil 

seeps, and (4) acid-mine drainage from mine 

and mill tailings. If pollutants are released 

underground, they can contaminate both 

ground water and the rock aquifers through 

which the ground water flows. 

Air pollution can arise from activities 

such as power generation, mineral smelting, 

or industrial processing. Solid particles (particulates) generated by these sources can 

degrade air quality and visibility, and gases 

released from these sources (such as sulfur 

dioxide and various nitrogen gases) can react 

with atmospheric water to generate rain that 

is acidic or that has other chemically hazardous qualities. 

Soil pollution can result from both airand water-based pollution. For exqmple, high 

concentrations of heavy metals can be found 

in soils near smelters and in soils through 

which metal-bearing surface waters or 

ground waters have flowed. 

To effectively clean up sites that have 

been affected by point-source pollution, it is 

necessary to understand the geochemical 

processes that control how the pollutants 

interact with the environment. 

The following two USGS activities 

involving both general research and specific 

site studies help address the geochemical 

behavior of natural and human (anthropogenic) point-source contaminants. 

In Hawaii, USGS scientists are examining 

the origin of natural, volcano-related, acidic 

aerosols in the atmosphere, which can cause 

respiratory problems among island inhabitants. Chemical and isotopic data on the 

aerosols show whether they resulted from 

the interactions of molten lava from the 

Kilauea Volcano with sea water or from the 

reaction of sulfur dioxide of volcanic origin 

with moisture in the atmosphere. By understanding the origin of the aerosols, health 

officials can recommend measures to help 

humans avoid contact with the aerosols. 

27 
What is wrong with this picture? The sun is shining, 

and an irrigation ditch is bringing life-giving water to 

crops near the Arkansas River in Colorado. However, 

the ditch is also receiving uranium- and salt-laden 

runoff and seepage from nearby irrigated fields. 

Another study showed that springs in 

areas of uranium-rich bedrock can be localpoint sources of dissolved uranium. The uranium is dissolved during normal weathering 

of uranium-rich rocks and can be reconcentrated onto organic matter as the springs 

emerge in organic-rich soils or wetlands. The 

following is an example of one such 

uranium-bearing spring that enters a wetland in the Colorado Rocky Mountains. The 

natural spring waters that help sustain this 

wetland contain 30 to 80 ppb uranium compared to a regional background value of less 

than 5 ppb. The concentration of dissolved 

Agricultural practices improper for a climate or soil 

may exaggerate normal weathering processes, and 

they can contaminate ground and surface waters and 

soils with dissolved salts and harmful trace elements 

such as uranium, selenium, and arsenic. 

uranium by peat is very efficient and produces haloes (peat regions that are high in 

uranium) in the immediate vicinity of the 

emergent source springs. Dried samples of 

peat collected near the spring pools contain 

as much as 3,000 ppm uranium, which represents up to a 100,000-fold concentration. The 

figure on page 29 illustrates the distribution 

of uranium in peat near one of the spring 

pools. 

This direct observation of the extraction 

of uranium by peat provides another example of how wetlands can improve water quality through their metal-sorption capabilities. 
Nonpoint sources of contamination-Agricultural and natural 

Nonpoint-source contamination has no 

single, clearly defined source area and can 

result from both natural and human-induced 

processes. The most commonly studied are 

those either introduced or exacerbated by 

human activities. Agriculture is an important nonpoint source of contamination. This 

is a result of two generalized activities: (1) 

leaching of contaminants that man has 

added to the soil or the crops, such as organic herbicides or pesticides and nitrates or 

phosphates from fertilizers; and (2) leaching 

of naturally occurring pollutants in the soil, 

chiefly as the result of irrigation, which are 

then concentrated to abundances incompatible with plant or animal life. 

The role of the USGS in the study of nonpoint-source pollution studies is focused on 

its ability to understand the chemical and 

physical processes controlling the pollutants 

in the environment. The definition of baselines in both agricultural and native soils 

and parent material has helped define what 

the pollution source is, how large the source 

is, the associated elements, and what the 

controlling processes are. With the knowledge of source and controls, remediation 

steps can be effectively planned and implemented with minimal impact on human 

health . 

Uranium from marine deposits 

Marine shales and sandstones underlie 

large parts of the Western United States. 

Much of the uranium in these rocks is loosely bound and can weather under conditions 

typical of the semiarid West. Irrigation can 

increase the natural loss of the uranium. 

Runoff from irrigation may directly reenter irrigation ditches for reuse. Local 

ponding of runoff waters or creation of 

waterlogged soils can also bring uranium 

and other elements to the surface, where 

they are concentrated by evaporation. Soils 

thus contaminated may be rendered unfit for 

cultivation. Additionally, uranium and other 

elements concentrated at the surface may be 

removed by rainfall runoff and carried 

downstream, thus contaminating waters far 

beyond the irrigated fields. 

Irrigation-return waters, regardless of the 

paths they have followed, may drain into 

their originating rivers via natural or artificial flow paths. Further downstream they 

may be taken out again and again for irrigation. When these waters become unfit for use 

on fields, they may be stored in permanent 

reservoirs and become more saline through 

further evaporation. These reservoirs may 

reach high levels of toxicity for animal or 

plant life. Towns and individuals may get 

their drinking water from aquifers that have 

been recharged, in part, by irrigation-return 

waters. 

0 

lil 

a: W 1 

tLi 

:!: 

z 

2 1-

Q. 

w 

c 

3 

To center +--- of wetland 

wetlands N 

aqJfifer · 

To margin --+ of wetland 

Spring water enters the peat from the underlying sandy horizon shown in 

blue. The ruled pattern indicates the depth distribution of peat containing 

more than 500 ppm uranium that was encountered in two perpendicular 

sampling traverses. Note that the most uraniferous peat is apparently 

confined to within a few meters of the spring pool. 

29 
30 

New areas of concern-A look to the future 

The first Earth Summit in Rio de Janeiro, 

Brazil, in 1992 identified global climate 

change, the sustainable management of land 

and resources, and biodiversity as the major 

international environmental issues of this 

decade. Both developed and developing 

countries perceived these issues to be important to the long-term environmental health of 

the planet. 

We have seen through the principles and 

examples described in this publication that 

geochemistry has become an important tool 

in environmental studies and in understanding the processes that affect our chemical 

environment. Geochemical processes are 

involved in climate-change concerns, landuse practices, and the health of organisms, 

ecosystems, and the entire biosphere. 

As the figure shows, the work of the 

USGS, whether it be geologic studies, waterresources investigations, or national-mapping activities, helps create a body of expertise and earth-science information that is 

used by the public and Government 

agencies. 

USGS RESEARCH IN 

ENVIRONMENTAL 

GEOCHEMISTRY 

+ 

8 /.NVIRONMENTA~ ··'"'''''<\ .. <'\ 

EXPERTISE .Jdldlm 

SCHOOLS , " INDUSTRY 

NON-GOVERNMENT 

ORGANIZATIONS 

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II II II II 

GOVERNMENT 

AGENCIES 

USGS activities in geologic studies, water-resources 

investigations, and national-mapping services all 

contribute to a body of knowledge and information 

used by the public and other Government agencies. 

By providing material such as interpretive maps, 

predictive models, and risk assessments, the USGS 

actively serves the environmental information needs 

of various educational institutions; non-government 

organizations; local, State, and Federal agencies; 

and industrial consortia. 
.,----------------------------------------------------------------------------------

~'~urther Reading in Environtnental Geochetnistry 

The atmospheric environment 

Schulz, E.D., Lange, O.L., and Oren, L.R., eds., 

1989, Forest decline and air pollution: New 

York, Springer-Verlag. 

Smith, W.H., 1990, Air pollution and forests, (2d 

ed.): New York, Springer-Verlag. 

Treshow, M., ed., 1984, Air pollution and plant 

life: New York, John Wiley and Sons. 

The terrestrial environment 

Adriano, D.C., 1986, Trace elements in the terrestrial environment: Harrisburg, Va., R.R. 

Donnely and Sons, Co. 

Bear, F. E., 1986, Earth-The stuff of life: Norman, 

Okla., University of Oklahoma Press. 

Cunningham, K.I., and LaRock, E.J., 1991, 

Recognition of microclimate zones through 

radon mapping, Lechuguilla Cave, Carlsbad 

Caverns National Park, New Mexico: Journal 

of Health Physics, v. 61, no. 4. 

Doe, B.R., ed., 1990, Proceedings of a U.S. 

Geological Survey workshop on environmental geochemistry: U.S. Geological Survey 

Circular 1033. 

Hillel, D.J., 1991, Out of the Earth-Civilization 

and the life of the soil: New York, The Free 

Press. 

Kabata-Pendias, A., and Pendias, H., 1992, Trace 

elements in soils and plants (2d ed. ): Boca 

Raton, Fla., CRC Press, Inc. 

Otton, J.K., 1992, The geology of radon: 

Washington, D.C., U.S. Geological Survey 

Public Information Series. 

Reimer, G.M., and Tanner, A.B., 1991, Radon in the 

geological environment, in Nierenberg, W.A., 

ed., Encyclopedia of Earth System Science, v. 

3: San Diego, Calif., Academic Press. 

Robinson, G.D., and Spieker, A.M., eds., 1978, 

"Nature to be commanded ... " -Earth science 

maps applied to land and water management: U.S. Geological Survey Professional 

Paper 950. 

Severson, R.C., Fisher, S.E., Jr., and Gough, L.P., 

1991, Proceedings of the 1990 Billings Land 

Reclamation Symposium on selenium in arid 

and semiarid environments, Western United 

States: U.S. Geological Survey Circular 1064. 

The aquatic environment 

Drever, J.I., 1988, The geochemistry of natural 

waters: Englewood Cliffs, N.J., Prentice Hall. 

Furness, R.W., and Rainbow, P.S., eds., 1990, 

Heavy metals in the marine environment: 

Boca Raton, Fla., CRC Press. 

Moore, J.W., and Ramamoorthy, S., 1984, Trace 

metals in natural waters-Applied monitoring and impact assessment: New York, 

Springer-Verlag. 

Stumm, W., and Morgan, J.J., 1981, Aquatic chemistry-An introduction emphasizing chemical 

equilibria in natural waters: New York, John 

Wiley and Sons, Inc. 

General 

Albright, H.M., ed., 1988, Conservators of hope: 

Moscow, Idaho, University of Idaho Press. 

Dunnette, D.A., and O'Brien, R.J., 1992, The science of global change-The impact of human 

activities on the environment [ASC 

Symposium Series 483]: Washington, D.C., 

American Chemical Society. 

Ehrlich, P.T., and Ehrlich, A.H., 1991, Healing the 

planet-Strategies for resolving the environmental crisis: Stanford, Calif., Center for 

Conservation Biology. , 

Gough, L.P., Shacklette, H.T., and Case, A.A., 

1976, Concentrations of elements toxic to 

plants, animals, and man: U.S. Geological 

Survey Bulletin 1466. 

Hill, C.L., Ryan, B.J., McGregor, B.A., and Rust, 

M., eds., Our changing landscape-Indiana 

Dunes National Lakeshore: U.S. Geological 

Survey Circular 1085. 

Lag, J., 1990, Geomedicine: Boca Raton, Fla., CRC 

Press. 

Owen, D.E., ed., in press, Wetlands-Processes, 

functions, and dynamics: U.S. Geological 

Survey Circular 1095. 

31 
32 

Inform.ation Sources 

(This list is by no means complete or all inclusive-there are many other government 

and nongovernment organizations that provide valuable data, interpretations, and 

trend analyses in the field of environmental geochemistry.) 

American Chemical Society, Washington, D.C.-Publishes popular as well as scientific treatises on several different perspectives related to the environment. 

( 800-333-9 511) 

American Society for Surface Mining and Reclamation, Princeton, West VirginiaPublishes treatises, newsletters, and general information booklets on topics 

related to surface mining and land reclamation. (304-425-8332) 

Council for Agricultural Science and Technology, Ames, Iowa-CAST is a nonprofit 

organization composed of 29 member scientific societies that provides scientific information on key national issues in food and agriculture to policy maker~,. 

the news media, and the public. It is a non-advocacy, educational organization. (515-292-2125) 

Council on Environmental Quality (Executive Office of the President), Washington, 

D.C.-Source of trends and general statistics on various topics of national 

interest including water; wetlands and wildlife; mining, minerals, and energy; 

land resources; population; and environmental risks and hazards. 

(202 -395-5750) 

Electric Power Research Institute, Palo Alto, California-EPRI operates under the voluntary sponsorship of the Nation's electric utility industry for the purpose of 

expanding electric energy research and development. Environmental considerations are a major area of research funding. (415-855-2150) 

Office of Surface Mining, Reclamation, and Enforcement (Department of the 

Interior), Washington, D.C.-Publishes guidebooks, holds classes, and serves 

as an information source for surface-mine reclamation, regulation, and remediation. (202-208-2553) 

Society for Environmental Geochemistry and Health, University of Missouri-Rolla, 

Rolla, Missouri-Publishes reports on diverse topics related to environmental 

geochemistry including naturally occurring geochemical hazards, risk assessment, drinking-water quality, land reclamation, recycling, and human health 

effects. (314-341-4862) 

Soil Science Society of America, Madison, Wisconsin-Publishes books, journals, anc1 

popular treatises on environmental geochemical issues including macro- and 

micro-nutrients, analytical methods, pesticides and herbicides, metal mobility, 

land reclamation and remediation, geographical information systems (GIS), 

and land-use planning. (608-273-8080) 

Society of Wetland Scientists, Wilmington, North Carolina-Professional society and 

the source of information on wetlands research, conservation, and legislation. 

(913-343-1221) 

U.S. Bureau of Mines Research Center, Denver, Colorado-Provides information on 

research in mine safety, reclamation, and environmental science as well as 

trends and analyses concerning mining productivity. (800-238-4274) 

U.S. Environmental Protection Agency, Center for Environmental Research 

Information, Cincinnati, Ohio-Publishes and distributes both technical and 

popular publications on a variety of environmental topics that focus on 

human health and risk assessments. (513-569-7562) 

U.S. Geological Survey Earth Science Information Center-Provides information, 

both hard-copy and digital, for all map subjects including satellite, geologic, 

hydrologic, land use, and aerial. A fee is usually required. (800-USA-MAPS) 
Glossary 

adit-A nearly horizontal entrance to a mine. 

background-In environmental geochemistry, this refers to a chemical level that has 

not been influenced by man's activities. 

baseline-In environmental geochemistry, this refers to a chemical level that is typical 

for an area that probably has been influenced by man's activities. 

bioavailability-The ability of a chemical form of an element to be incorporated into 

plant or animal tissue. 

Celsius (or centigrade)-Measure of temperature where 0 and 100 are the freezing and 

boiling points of water, respectively. 

deposition-Process of depositing or settling. 

EPA-U.S. Environmental Protection Agency. 

FDA-Food and Drug Administration. 

leach-Removal (usually by water) of the easily dissolvable part or mineral fraction. 

mg/L-Milligrams per liter (equivalent to parts per million). 

pH-Scale of hydrogen ion (H+) concentrations; equals the negative log of the H+ concentration; measure of acidity of a solution. The lower the number, the higher 

the acidic content. 

ppb-Parts per billion (microgram per liter; microgram per kilogram); a term used to 

describe concentrations; a ppb has been described as a family of five in a world 

with a global population of five billion-which is the approximate current 

world population. 

ppm-Parts per million (milligram per liter; microgram per gram); a term used to 

describe concentrations. 

ppt-Parts per trillion; a term used to describe concentrations. 

solution-A liquid (usually water) with its dissolved components (example, salt in 

water). 

Superfund-Areas designated by the EPA as heavily contaminated and in need of 

remediation and that are part of the National Priorities List (NPL). 

suspension-A liquid (usually water) with its undissolved solid components (example, fine silt in water). 

toxicity-the extent, quality, or degree of being poisonous. Because of dose and exposure requirements, a substance may be toxic but not necessarily hazardous to 

either plant or animal health. 

trace element-Elements of the Periodic Chart that usually occur in common materials 

(rocks, soils, plants, water) at concentrations of less than 1 percent. 

USDA/ARS-U.S. Department of Agriculture, Agriculture Research Service. 

USGS-U.S. Geological Survey, Department of the Interior. 

33 
Mount Spur, the farthest peak to the left, seen here 80 miles 

southwest of Anchorage, Alaska, is an active volcano. The volcanic ash particles that periodically rain down over this area are 

responsible for the very deep soils that support the tundra vegetation. Recent geochemical studies of the area that is underlain 

34 

by massive coal deposits have shown that (1) there is little 

regional geochemical change across the landscape, and (2) the 

ash contains very small concentrations of environmentally 

important heavy metals. 

tr U.S. GOVERNMENT PRINTING OFFICE: 1993-774-049/66,048 REGION NO.8 
Back cover: Industrial pollution created by an ore smelter in an otherwise pristine Arizona desert ecosystem. Scientific 

monitoring of point sources of contamination is a topic of study in environmental geochemistry.