4    BACKGROUND CONCENTRATIONS OF METALS AND
CYANIDE IN LOWER MICHIGAN SOILS
Kimberly A. Kesler-Arnold, Principal Hydrogeologist
Michael O'Hearn, Manager
Geosciences C-E Environmental, Inc.
Farmington Hills, Michigan 48331
INTRODUCTION
Soil can become contaminated by a wide variety of waste disposal or handling practices, and
numerous industrial processes utilize raw materials that contain metals. Although soil contamination
is a serious environmental problem itself, contaminated soils can also lead to another potential
environmental threat —groundwater contamination. As a result, soil remediation is often required at
sites of environmental contamination.
Interpreting soil chemistry data can be difficult because many metals of environmental concern
(e.g., arsenic, lead, and chromium) occur naturally in soil and rock. During a contamination assessment, it is often necessary to establish background concentrations of metals in soil to provide a
standard for assessing the magnitude of contamination in other samples. In cases where remediation
must attain background levels, concentrations of naturally occurring metals and other inorganics
must be estimated to set realistic cleanup goals. At sites where contamination by inorganics is not a
concern, a knowledge of background soil chemistry can be essential for understanding the fate and
transport of other contaminants (e.g., organic chemicals) in the soil/water system.
For purposes of this paper, the term "soil" refers to all unconsolidated geologic materials. The
background concentrations of metals in soil are determined largely by the nature of the parent rock
material and the soil's depositional environment. While numerous references on background concentrations of metals in soils are available,1,2,3,4'5 most apply to large geographic areas. This general
information is of limited use for estimating the background chemistry of soils at specific sites because
background soil chemistry is dependent on location. No references are available that provide specific
information on the average background concentrations of metals in Michigan soils.
To provide information on typical concentrations of several metals (and cyanide) in lower Michigan
soils, the authors compiled data collected during numerous environmental contamination assessments. Although cyanide is not expected to occur naturally in soils, it is sometimes detected in soil
samples that might otherwise be considered representative of background conditions. In the absence
of site-specific background data, the results presented in this paper can be used to develop preliminary
estimates of background concentrations based on general soil type and location within the State of
Michigan.
Michigan Geology
The basic composition and origin of soils in Michigan is directly related to the geologic history of
the State. Lower Michigan is underlain by the Michigan Basin-a large, bowl-shaped structure
comprised of sedimentary rocks including sandstones, shales, limestones, dolomites, and evaporites6
(see Figure 1). Overlying the bedrock surface, glacial drift deposits averaging 200 to 300 feet in
thickness cover most of the State. In some locations, the drift is as thick as 1,200 feet.7
Michigan's present-day landforms are predominantly the result of the last major series of glacial
advances and retreats —the Wisconsinan Stage of the Pleistocene Epoch-which began approximately
110,000 years ago.8 The ice sheet of the Wisconsinan Glaciation originated in the Laurentian Highlands of Canada east of Hudson Bay. The glaciers moved from Canada, across the State of Michigan,
and reached as far south as the Ohio River. As a result, the surficial geologic deposits of Michigan are
a complex sequence of glacial tills, outwash deposits, ice-contact deposits, and lake sediments9 that
originated predominantly from local bedrock. In addition, crystalline rocks and minerals from the
Canadian Shield are commonly found in Michigan.
44th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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