United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S7-84-022 May 1984
Project Summary
Coal Mine Related Stream
Sediment Geochemistry in
Southern Illinois
William C. Hood, Paul D. Robinson, Jean B. Chruscicki, and Thomas A. Delfino
The stream sediment geochemistry of
several elements, specifically cadmium,
cobalt, copper, iron, manganese, nickel
and line, has been examined in a six-
county area of Southern Illinois. This
area has been greatly impacted by coal-
mining activities. Arsenic and chromi-
um were also investigated, but only in
isolated areas. The survey of these
elements in stream sediments indicates
that in most areas having four times the
median value for cadmium, cobalt, iron,
nickel and zinc, are generally
located downstream from areas of coal-
related uses. In detailed study of these
streams, there occur marked relation-
ships among the pH of mine drainage
water, the concentrations of metals in
the water, and the concentrations of
metals in corresponding stream sedi-
ment. Water with low pH reaches sea-
sonal summer highs in metal content
and can enter streams already carrying
large concentrations of metals. In those
parts of a mine-impacted stream where
low pH is maintained, metals can be
leached from the stream sediment to
further increase the concentrations in
water. On the other hand, if the pH of a
stream is increased, metals will tend to
precipitate out of the water and become
part of the stream sediment.
This Project Summary was developed
by EPA's Industrial Environmental Re-
starch Laboratory, Cincinnati, OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Background
Southern Illinois is an area that for
many years has been extensively mined
for coal. Coal-bearing Pennsylvanian-
aged rocks crop out in a broad band that
curves gradually across the southern part
of the state. Where the coal beds in these
rocks are shallow, surface mining has
been widespread. North of the shallow
outcrop area, where the coal beds are
deeper, underground mines are abun-
dant. As of mid-1971,21,987 hectares of
the six-county area of this study had been
affected by surface mining activities and
surface disturbances related to under-
ground mining. This amounts to three
percent of the land area in these counties.
Prior to passage of various State and
Federal reclamation laws, some of the
mining practices used in Illinois resulted
in the creation of problem sites which
have generated large amounts of acid
mine drainage. In the southern Illinois
area, acid mine drainage typically arises
in one of two general settings. First, old,
coarse refuse (gob) piles and fine refuse
(slurry) impoundments which have been
exposed to the weathering processes
have created areas of intense production
of acid drainage and related pollutants.
Second, there are some areas in which
the overburden has a high potential for
the production of acid drainage and little
potential to neutralize it. Strip mines
exposing such material to air and water
can create large non-point source areas
of acid mine drainage.
The polluted waters generated from
these sources are known to carry appreci-
able concentrations of several potentially
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"SW?^*
toxic trace elements. Monitoring pro-
grams by the Illinois Environmental Pro-
tection Agency, the Greater Egypt Re-
gional Planning and Development Com-
mission, and numerous studies of indi-
vidual sites, have shown that appreciable
quantities of zinc, cadmium, nickel, co-
balt, iron, manganese and minor amounts
of copper in the streams are draining
such areas. However, not all of the
contaminants moved by a stream are
dissolved in the water. Many are carried
as part of the paniculate suspended and
bed load of a stream, to be picked up,
dropped, or rolled along as circumstances
dictate. The literature suggests that such
elements may be either removed from
solution to become part of the particulate
load or may be dissolved from solids and
reintroduced into the water, depending
upon the chemical environment. Indeed,
some studies suggest that much of the
trace element load of a stream is carried
in such a non-dissolved state. Thus, a
monitoring program that examines only
the dissolved portions of a polluted stream
may miss large quantities of metals being
transported in another manner. This
study attempts to ascertain the extent of
distribution of metals in the stream
sediment of the mine-impacted portion of
southern Illinois, and to determine the
conditions under which metals move
from the water to become a part of the
sediment, and vice versa.
Approach
This investigation of the geochemistry
of cadmium and other metals related to
coal mining is restricted to a six-county
area of southern Illinois. The counties
involved are Gallatin, Jackson, Perry,
Randolph, Saline, and Williamson (Figure
1). The amount of land that has been
disturbed by surface mining and the
surface effects of underground mining of
coal in these counties range from over
seven percent in Perry County to less
than one percent in Gallatin County. Table
1 indicates the amou nt of surface disturb-
ance related to coal-mining activities.
General Geology
Coal-bearing formations of the Penn-
sylvanian age crop out across southern
Illinois in a west-to-northwest-trending
arc (Figure 2). Their dip is toward the
north and northeast, resulting in an
older-to-younger progression of forma-
tions from south to north. This simple
pattern is complicated somewhat by
several structural features, including
several fault systems and two major
Study Area
Figure 1. Location of study area.
Table 1. Areas Disturbed by Coal Mining
Activities
Hectares in Area
County County Disturbed Percent
Gallatin
Jackson
Perry
Randolph
Saline
Williamson
84,955
1 56,181
114,740
153,851
99,459
1 10,596
6OO
1.983
8.222
2.195
3.846
5.140
0.71
1.27
7.17
1.43
3.87
4.65
folds. Of the fault systems within the
study area, the Cottage Grove Fault
System, the Wabash Valley Fault System,
and the Fluorspar Area Fault System
displace the coal beds on the order of a
few meters to a few tens of meters. The
Shawneetown Fault, on the other hand,
has displacements estimated to be on the
order of hundreds to thousands of meters.
South of the Shawneetown Fault, the
coal-bearing rocks are folded into a U-
shaped outcrop pattern which has brought
several of the coals to the surface in a
relatively small area. When encountered.
all of these features affect the mining of
the coals to some extent and at times
establish the physical limits of a mining
operation.
Another structural feature of major
importance is the DuQuoin Monocline.
Unlike the previously mentioned features,
this structure was active during the time
of deposition of the Pennsylvanian rocks
and separated a relatively stable area
which was dominated by shallow marine
influences on the west (western shelf
area) from one on the east which was
gradually subsiding. The subsiding east-
ern area was the site of active delta
building during the time of coal deposi-
tion. The different types of environments
resulted in somewhat different over-
burden rocks associated with the coal
beds, and this in turn has influenced the
water quality in the different parts of the
area. West of the monocline, there are
numerous limestone beds; east of the
structure limestones are sparse.
The important coal-bearing formations
are the Spoon and the Carbondale Forma-
tions. The Spoon Formation consists
largely of sandstone, siltstone, and gray
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Geology of Study Area
Cottage Grove
Fault System
P - Pennsylvania!!
Pb - Bond
Pm - Modesto
PC - Carbondale
Ps - Spoon
Pa - Abbott
Pcv - Caseyville
M - Mississippian
Shawneetown
Fault
Eagle Valley
Syncline
Figure 2. Geology of study area.
shale, with very little limestone. Two
important coal beds, the Davis and De-
Koven coals, are commercially important
in the southern parts of Williamson and
Saline Counties. The fact that there is
only about six meters of material between
these two coals allows them to be mined
simultaneously. At some locations, the
stratigraphic sequence between the coals
is partially made up of a pyrite-rich black
shale that contains up to twelve percent
sulfur. When exposed at the surface, this
pyritic shale can produce considerable
amounts of acid. Extensive mining of the
Davis and DeKoven coals has produced
areas of intense pollution because of this
unfortunate stratigraphy.
The Carbondale Formation overlies the
Spoon Formation and differs from it by
having larger proportions of limestone
and shale. The limestones tend to become
more abundantly higher.in the strati-
graphic section and west of the DuQuoin
Monocline. Two important coals are also
present in this formation. These are the
Harrisburg (Number 5) and the Herrin
(Number 6) coals. The Number 6 coal is
stratigraphically above the Number 5.
East of the DuQuoin Monocline, in the
area of Williamson and Saline counties,
the stratigraphic interval between the
two coal beds is on the order of 43 meters,
and the two coals are mined separately.
The generally low dip of the strata in this
area results in the outcrop lines of the two
coals being separated by as much as 1.5
kilometers, giving rise to two series of
parallel strip mines. Further to the west,
particularly in the vicinity of the DuQuoin
Monocline, the stratigraphic interval be-
tween these coals becomes much thinner.
In Perry and Randolph counties, only
about 10 meters of rock separate the beds
and the two coals are commonly removed
in a single mining operation.
Elemental Distribution Results
The regional distribution of metals
within the study area are discussed on an
element-by-element basis.
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Cadmium
In the Saline River area, there are
numerous high cadmium values in the
stream sediments. Most of these are
concentrated along the South Fork, with
another area of concentration in Eagle
Creek. Two high values were noted in the
westernmost part of the area; these occur
downstream from a coal-fired powerplant.
Another cluster of high values occurs in
the northeast part of the basin, associated
with underground coal mines in the area.
In the Crab Orchard Creek area, numerous
high values of cadmium occur. As before,
clusters of high points are located down-
stream from coal mining activities. A pair
of high values occurs in the southern part
of the area. Although no mining is
presently taking place in that area, several
small and very old mines are scattered
around the hills, and it is possible that
these two points are downstream from
one or more of these unmapped mines.
Not shown on the map are several under-
ground mines in the central part of the
area. Several of the high values are below
the old underground mines. In the
Beaucoup Creek area, only four scattered,
high cadmium values occur, and three of
these are clearly associated with strip
mines. The fourth occurs in the northern-
most part of the area and does not appear
to be related to mining activities. In the
Marys River area, several high values are
present. Virtually all of these are adjacent
to or downstream from mines.
Copper
In the Saline River area, only a few
anomalously high copper values occur.
Of these, two are downstream from a
known gob pile, one is adjacent to a strip
mine, and the fourth is not known to be
related to mining. Three high values occur
in the Crab Orchard Creek area. The first
is several kilometers downstream from
mines; however, there are many low
values between it and the mines. The
other two are scattered, apparently un-
related to mines. The two high concentra-
tions which appear in the Beaucoup Creek
area are scattered and are spatially
unrelated to mining. Finally, in the Marys
River area, no high values occur, although
a few scattered intermediate values show
no relationship to mining.
Cobalt
In the Saline River area, six high cobalt
values are present. One of these, located
in the north center portion of the area, is
in the vicinity of an old gob pile and is
likely related to it. A second is located
near the mouth of Eagle Creek, a stream
contaminated by mining, while a third, in
a tributary of the Saline River, receives
drainage from a mining area. Two anom-
alously high values do not appear to be
spatially related to coal mining. In the
Crab Orchard Creek area, there are four
more high values. Three of these four
locations are downstream from mining
activities; however, the fourth is not. In
the Beaucoup Creek area, three high
values occur in the northern part of the
area butappeartobe unrefcrtwdto mining.
Lastly, in the Marys River area, the one
high value is in close proximity to a strip
mine, but is upstream from the mining
activity.
Iron
In the Saline River area, only three
exceptionally high iron values occur. Two
are downstream from mines while one is
not. Several intermediate concentrations
are located downstream from mining
activities. In the Crab Orchard Creek area,
a few high values are present, all of which
occur downstream from coal mines. No
exceptionally high values occur in the
Beaucoup Creek area or in the Marys
River area.
Manganese
In the Saline River area, four high
values of manganese occur in scattered
locations, three of which occur down-
stream from coal mines. If intermediate
values are considered, only a few are
downstream from coal mines. Seven high
values occur in the Crab Orchard Creek
area, mainly downstream from mines;
intermediate values occur frequently. Five
high values occur in the Beaucoup Creek
area, although only two of these are
downstream from mines. Intermediate
values appear to be unrelated to mining.
Finally, two high manganese values occur
in the Marys River area. Both of these are
adjacent to strip mines, but do not appear
to be downstream from them. Interme-
diate values are randomly scattered
across the entire area.
Nickel
It can be seen that most of the twenty
anomalous concentrations of nickel in
the Saline River area and the Crab
Orchard Creek area are downstream from
coal mining activities. In the Beaucoup
Creek area, there are only two high
values, one of which is downstream from
a coal mine. In the Marys River area, the
only high value is adjacent to a coal strip
mining area.
Zinc
Zinc is similar in geochemistry to
cadmium, and not surprisingly the distri-
bution of these two elements is similar.
High zinc values are present in the saline
river area, mostly downstream from strip
mining or downstream from the coal-
fired power plant located in the area.
Other high concentrations occur in Eagle
Creek, an area heavily impacted by min-
ing. Another neighborhood with high zinc
values is located near an old gob pile in
the northeast part of the area. Many high
values also occur in the Crab Orchard
Creek area. With few exceptions, these
are closely associated with mining. High
values in the Beaucoup Creek area, with
two exceptions, are also closely associ-
ated with mining. Lastly, the one high
value of zinc found in the Marys River
area is downstream from a strip mine.
Conclusions
The stream sediment geochemistry of
several elements; specifically, cadmium,
cobalt, copper, iron, manganese, nickel,
and zinc, has been examined in a six-
county area of Southern Illinois that has
been greatly impacted by coal-mining
activities. Arsenic and chromium were
also investigated, but only in isolated
areas.
A regional survey of these elements in
stream sediments indicates that most
areas of anomalously high concentrations
(four times the median value) of cadmium,
cobalt, iron, nickel and zinc generally
occur downstream from coal mines or in
other areas of coal-related land uses.
Most such anomalously high stream
sediments are within eight kilometers of
the coal-related area. Only manganese,
and to a lesser extent copper, show
distribution patterns unrelated to mining.
In three streams singled out for more
detailed study, marked relationships exist
among the pH of mine drainage water,
the concentrations of metals in the water,
and the concentrations of metals in
corresponding stream sediment. Water
with low pH shows seasonal summer
highs in metal content and can enter
streams already carrying large concen-
trations of metals that have either been
released during the oxidation of pyrite or
leached from the rocks with which the
acid drainage has come into contact. In
those parts of a mine-impacted stream
where low pH is maintained, metals can
be leached from the stream sediment to
further increase the concentrations in
water. On the other hand, if the pH of a
stream is increased, metals will tend to
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precipitate out of the water and become
part of the stream sediment. The precipi-
tation reactions can occur at considerable
distances downstream from the source of
pollution, and account for the observed
regional distribution of anomalously high
concentrations of metals in sediment.
Based on the data obtained in this
study, the following conclusions can be
made:
• Various metals such as arsenic, cadmi-
um, cobalt, copper, iron, manganese,
nickel, and zinc are present in the
rocks of the coal mining region of
southern Illinois, in amounts generally
equal to or slightly greater than the
content in similar rocks around the
world.
• Sulfuric acid created by the oxidation
of pyrite can mobilize these elements,
allowing them to move into nearby
surface drainages.
• Once in the stream, the fate of a
particular metal depends on geochem-
ical factors, such as pH, which de-
termine whether it will stay in solution
or become a part of the stream sedi-
ment.
• Those parts of streams less than 8
kilometers downstream from coal min-
ing activities frequently have trace
element contents in bottom sediment
significantly higher than those parts of
the stream not influenced by coal-
related activities.
Parts of streams having low pH values
consistently have higher concentrations
of the trace elements in water than do
areas with high pH values.
Sampling sites with low pH values
commonly show a strong seasonal varia-
tion of concentration of elements in
water, marked by an increase in concen-
tration of all trace elements in the summer
and fall months. Sites with high pH
values do not develop a seasonal trend;
instead they have various peaks and lows
in concentration occurring throughout
the year.
Sites with low pH, and a seasonal trend
in water quality, show strong interele-
mental behavioral similarity. Conversely,
sites with high pH values that lack the
seasonal trend do not have strong inter-
elemental behavioral similarity.
Concentrations of all trace elements in
water decrease with greater distance
from the source, due to dilution from
additional surface water or groundwater
and/or to the precipitation of elements
iut of solution.
Rainfall may dilute the concentrations
of the trace elements in water. The
influence of this factor increases in
streams of greater drainage area.
Sampling sites with low pH values
consistently have lower concentrations
of the trace elements in stream sediment
than sites with high pH values.
None of the streams studied showed
significant seasonal variation for trace
elements in sediments. Most values
fluctuate throughout the year, with erratic
peaks and lows. However, high or peak
values occur more often in summer
months.
Concentrations of most of the trace
elements in sediment decrease with
increasing distance downstream from a
polluting source. When high pH-high
sediment concentration streams mix with
low pH-low sediment concentration
streams, the resulting values for metals
in sediment are not necessarily inter-
mediate. Some elements are of lower
values than either contributing stream,
suggesting a dissolution of these ele-
ments from the sediment. Iron and chro-
mium are frequently in higher concentra-
tion in the sediment below the confluence
than in either contributing stream, indi-
cating precipitation of these elements.
The specific behavior of the metals mainly
depends on the pH of the water below the
mixing zones.
The higher trace element content of
stream sediment below coal mines is a
result of leaching of the elements in or
near the mines by acidic water coupled
with reprecipitation when the acidic
water is neutralized. Consequently, it is
recommended that monitoring stream
sediment for trace element pollutants not
be required, because pH and trace ele-
ment content in the mine effluent will
control mine-related downstream chang-
es in the trace element content of the
sediments.
William C. Hood, Paul D. Robinson, Jean B. Chruscicki, and Thomas A. Delfino
are with Southern Illinois University, Carbondale, IL 62901.
Thomas J. Powers is the EPA Project Officer (see below).
The complete report, entitled "Coal Mine Related Stream Sediment Geochemistry
in Southern Illinois," (Order No. PB 84-153 444; Cost: $13.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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Environmental Protection
Agency
Center for Environmental Research
Information
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