Chemical Characteristics of Some Southwest Virginia Minesoils

Abstract

A detailed study of the chemical characteristics of minesoils derived from the Wise formation in Southwest Virginia was undertaken usinq a number of standard techniques. The minesoils studied ranged in age from 4 to 20 years, and were derived from sandstones and siltstones hioh in carbonates and iron. The wet acid-dichromate digestion organic matter technique often yields questionably high values in minesoils. In order to evaluate the effects of coal fragments on this technique we added coal fragments to a standard minesoil. The coal contents were varied from 1% to 10% of soil weight. The size of the coal fra9rnents was varied from 0.05 to 2mm. Coal particles finer than O.lmm affected the procedure, but were not completely oxidized. Larger. visible coal fragments had no effect on measured organic matter content. Errors in this procedure may be due to the oxidation of iron compounds rather than coal. In

Full text

1982 SVmpo5ium on Surface Mining
Hydrology,
Sedimentology and
Reel.mation
(University
of
Kenrucky, Lexington, Kencucky 40506·(}()46 -December 5·10, /982)
Chemical Characteristics
of
Some Southwest Virginia Minesoils
by
W.
Lee
Daniels
and
D.
F.
Amos
Department
of
Agronomy
Virginia Polytechnic
Institute
and
State
University
Blacksburg, Virginia 24061
Abstract. A
detailed
study of the chemical
characteristics
of
minesoils derived
from
the
Wise
formation in Southwest Virginia
was
undertaken usinq a
number
of
standard techniques.
The
minesoils studied ranged in age
from
4
to
20
years,
and
were
derived
from
sandstones
and
siltstones
hioh in carbonates
and
iron.
The
wet acid-dichromate
digestion
organic matter technique
often
yields
questionably high values in minesoils.
In
order to
evaluate the
effects
of coal fragments
on
this
technique
we
added
coal fragments to astandard minesoil.
The
coal contents
were
varied
from
1%
to
10%
of soil weight.
The
size
of the coal
fra9rnents
was
varied
from
0.05 to
2mm.
Coal
particles
finer
than
O.lmm
affected
the procedure, but
were
not completely
oxidized. Larger.
visible
coal fragments
had
no
effect
on
measured organic matter content. Errors in
this
procedure
may
be
due
to the oxidation of iron
compounds
rather
than
coal.
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I!lse s011s
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c:
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f"
ese!i
stilll3.
C·
to
EJlc::nan
e
Caoacity
(CEe)
measurements
which
sum
exchan~eable
bases
and
BaC1
2-
TEA
acidity
(titrated
to
pH
8.2)
seriously
overestimate
the
effective
CEC
of
these
soils.
Dilute double acid (0.025 N
H
2
S0
4+0.05
~
HC1)
dissolves carbonates
durin~
extraction
-
procedures
and
seriously
overestimates
plant
available
P.
Bicarbonate
(HC0
3
-)
is
an
effective
extractant
of
readily
available
Pin tnese
soil
systems. Available P
is
quite
low
in
these
soils,
even
immediately
after
fertilization.
The
high P
fixation
potential
of
iron-rich
minesoils
is
likely
to
be
a
serious
limitation
over time.
Care
must
be
taKen
in the
application
of
standard soil
testing
techniques to minesoils
and
in the
interpretation
of
results,
IntrOduction
Surface mining
for
coal
in
hard rock regions
such as the Appalachians
often
results
nthe
complete
destruction
of
natural
soils.
Natural
soils
in these steep areas
are
generally thin
and
infertile.
making
topsoiling
impractic 1, Plants
used
in reclamation must
therefore
rel
on
rock
spoils
as
their
growing media. These rock
spoils
are
usually
~50%
coarse fragments
(~2mm).
but tend
to weather quickly,
once
they
are
reclaimT
d2
Thin
Ahorizons
are
detectable
within 5
years,
•
indicati
ng
atransformation
from
"mine
spai 1"
to
"m
ine
so
i1".
While
several
studies
of
mine
soil
chemis~r5
have
been
done
in
Kentucky3
and
West
Virginia, ,
little
work
has
been
done
in Southwest Virginia.
Early in 1980, Virginia Tech, in cooperation with
the Penn-Virginia Resources Corporation.
began
an
interdisciplinary
study
on
the
Powell
River
Reclamation Research
Project,
comprising
135
ha
of
371
surface-mined land in
Wise
County.
Virginia.
The
initial
soil
mapping
and
characterization
was
completed in
late
1981.
and
the data reported here
are the
results
of subsequent
studies
into the
chemical behavior
of
these
mine
soils.
The
objectives of
this
report
~re'
1.
To
examine
the
effects
of various
sizes
and
concentrations of coal fragments
on
the
get
acid-dichromate organic matter technique
and
other
basic
soil
chemical
properties.
2.
To
explore the
relationship
among
pH,
acidity
and
base
saturation
in these
soils.
3.
To
evaluate several
methods
of determining
cation exchange capacity in
mine
soiis.
Description of Study
Area
and
Research
Methods
The
Powell
River
Project
Area
is
located
11
km

&
Results
and
Discussion
Table
1.
Chemical
characteristics
of
weathered
<2mm
sandstone fraoments containing 4
l~vels
of
silt-size
«0.05
rom)
coal.
nd
KCl
BaC1
Z-
TEA
CE(:-
Acidity
g,
Exch.
Acidity
Mg
Ca
pH
1.
standard
mine
soil
at
rates
of
0,5%,
1.0%,
2.5%,
5%,
and
10%
of
total
soil
weight. These samples, along
with ablank, were then evaluated
for
organic matter
content
by
the wet acid-dlchromate
digestion
tech-
nique. Additional samples
from
this
experiment were
analyzed
for
pH,
Ca,
Mg
and
K
by
the methods pre-
viously described. Levels
of
KCl
exchangeable
acidity
(Al)
and
BaC1
2
-TEA
acidity
were
also
determined. Cation exchange
capacity
was
determined
in 3
ways:
2.
su
ation
of
Ca,
Mg,
K
and
BaC1Z-TEA
actdi
ty.
3.
saturation
of
5g
samples with
~
CaC1
2
followed
by
displacement with
~
MgC1
2
and
analysis
for
Ca
by
atomic absorption.
The
basic chemical
properties
of
the standard
minesoil used
in
the experiment, along with the
effects
of coal fragments
on
these
properties,
are
presented in Table 1. This
soil
material possessed
relatively
low
levels
of
pH,
exchangeable bases
and
CEC
due
to the
fact
that
the sandstone
from
which
it
was
derived
was
well leached
and
oxidized.
The
addition
of
1%,
5%
and
10%
silt-size
coal to the
samoles
had
no
consistent
effect
on
these proper-
ties.
Increasing coal content did lead to increases
in
BaClz-TEA
acidity
which
will
be
discussed
later.
Coal
northwest
of
Norton, Virginia
on
the flanks
of
a
high mountain
ridge.
Four
levels
of
benches occur
within the
area,
and
the
mine
soils
thereon ranged
from
4to
20
years
in
age
when
they were sampled.
The
underlying bedrock
of
the area
is
of
Pennsylvanian age
and
is
composed
of
horizontally-
bedded
sandstone,
siltstone
and
coal beds
of
the
Wise
fonnation. Several
thin
«2rrrn)
shale beds
are
present,
but comprise
less
than
10%
of
the
exposed
strata.
Thirty
pits
were
excavated,
described
and
sampled in
mine
soils
selected
as
typical
of
the
area.
The
morphological, physical
and
mineralogical
prcperties
yave
been
described
in
detail
by
Daniels
and
Amos. Subsequently,
detailed
chemical
characterization
of
these
minesoils
was
performed using the methods described
in the paragraph below.
All
soil
samples were sieved through a 2
mm
screen to
remove
coarse fragments,
and
then
oven
dried.
Levels
of
orgagic matter
were
determined
by
the
method
of
Peech
which involves awet
sulfuric
acid
digestion,
oxidation
by
potassium
dichromate
and
then
back
titration
of
the unused
dichromate with ferrous
ammonium
sulfate.
The
pH
of the samples
was
determined in a1:1 soil :water
paste. Calcium (Ca),
magnesium
(Mg)
and
potassium
(K)
were
extracted
with
pH
7
NH
OAc,
and
analyzed
by
atomic absorption
(Ca
+
Mg)
~nd
flame photometry
(K). Levels
of
exchangeable
acidity
(Al)
were
determined
by
extraction
with N
KCl
and
base
titration.
Total
acidity
was
determined
Jy
titration
of
pH
8.2
BaCl
-TEA
extracts
and
whole
soil
potentiometric
titr~tion
to
pH
7.0.
Available
phosphorus (P)
was
extracted
in
0.5
~
Na
HC0
3
(pH
8.5)
and
dilute
double acid (0.05 N
HCl
+0.025 N
HZSO
),
and
analyzed
by
ammonium
molybdate -
colo~imetry.
Total S
was
determined
by
combustion
idiometric
analysis.
Free iron oxides
we~e
extracted
in a
dithionite-citrate-bicarbonate
solution,
analyzed
by
atomic
absorption,
and
are
expressed as %
Fe
Z
03.All analyses
were
performed
in
dupl
icate.
5.18 1.42 1.41 0.12 1.0 3.95 3.78
10
4.95 1.5Z 1.52 0,13
1.0
4.27 5.05
t
CEC
taken as
sum
of
Ca
+
~g
+K+
Exch.
Acidity.
1.0 4.34 3.15
6.15
4.29
meq/100g
54.701,541.520.13
1.1
o
4.821.511.72
0.11
Analysis
of
the chemical
characterization
data
revealed a
number
of
interesting
chemical
relation-
ships in these
soils
which
will
be
discussed
later.
One
property
of
particular
interest,
however,
was
the
relatively
high
levels
of
organic matter deep
in the Chorizons,
beyond
normal
rooting depth
(Table 4).
In
addition,
some
very high val
ues
(>5%)
were
obtained
from
surface horizons. Because
of the
common
occurrence
of
coal fragments through-
out these
soils,
we
devised the following
experi-
ment
to evaluate the
effect
of
coal fraaments
on
the organic matter procedure
of
Peech
6.
A"standard minesoi
1"
l'ias
produced
by
grinding
and
sieving
ahighly weathered
and
oxidized sand-
stone through a
2mm
sieve.
The
chemical
character-
istics
of
the
unamended
soil
are given in Table 1
(as
0%
coal).
Unweathered coal fragments derived
from
the Taggert
seam
of
the
Wise
formation
were
ground
and
sieved into the following
size
classes:
1.
Very
Coarse
Sand
(VCS):
1.0-Z.0
mm
2.
Medium
Sand
(MS):
0.25-0.5
mm
3.
Very
Fine
Sand
(VFS):
0.05-0,10
mm
4.
Silt
(Si):
<0.05
Im1
Each
size
fraction
of
coal
was
then
added
to
~he
The
effects
of
size
and
concentration
of
the
coal fragments
on
the organic matter procedure
are
shown
in
Table
2.
Very
coarse
(l-Zmm)
and
medium
(0.25-0.5
mm)
sized
coal fragments
are
oxidized
only to aminimal degree
by
the procedure.
As
particle
size
is decreased to
<0.05mm,
the coal
fragments
are
increasingly
reactive
in the procedure
but only to a
limited
extent.
Only
at
the higher
concentrations
(>2,5%)
of
the
silt-sized
fragments
does
there
seem
to
be
any
significant
oxidation
of
the coal fraqments,
The
coal used in
this
experi-
ment
was
high grade (>14,000
BTU,
>80%
fixed
carbon)
and
relatively
unweathered. Alower grade
coal with lower carbon
and
~ore
hydroxyls
(OH)
and
other functional groups
would
probably
be
more
reactive.
The
small coal
par:icles
that
did
react
378

I
..
in the procedure
would
also
be
reactive
in the
soil
environment,
and
may
behave
somewhat
like
organic
matter within a
ShOrj
period
of
time.
The
oxi-
dation
of
Fe
2+to
Fe
+
also
interferes
in the
procedure,
and
may
be
responsible
for
errors.
Work
is
currently
in progress to examine
this
possibili-
ty.
Table 3. Cation exchange
capacity
(CEC)
of
weathered
<2mm
sandstone fragments
amended
with four
different
sizes
of coal
as determined
by
3
different
methods.
Cation exchange capacity
(meq/lOOg)
Coal
Particle
Size
(mm)
"
2.0-1.0
.5-.25
.1-.05 <.05
/D
a a 000
0.5 a.14 .07 .17
1.0 0
.14 .14
.34
2.5
.03 .17
.17 .70
5.0 .10 .17 .45 2.72
10.0 I) .30 .
38
6.26
The
chemical
characteristics
of 5
representa-
tive
minesoils
from
the Powell River
Project
Area
are
shown
in Table 4.
Low
levels
of
exchangeable
acidity
were
commonly
associated
with
low
pH
«5.8)
values (see
soil
M15).
Aluminum
species
are
respon-
sible
for
the bulk
of
soil
acidity
in most natural
soils.
Because these
soils
are
relatively
un-
weathered,
little
Al
has
been
released
and
the
acidity
is
probably being
controlled
by
organic
matter
and
coal with minor
contributions
from
iron
compounds
and
traces
of decomposing
pyrite.
The
low
amount
of
Al
generated
acidity
in the majority
Values
for
cation
exchange capacity
by
3
methods
with
differing
coal fragment
sizes
are
given in Table 3.
Soils
contain aconsiderable
amount
of
pH
dependent
CEC
due
to the presence of
organic functional groups
and
edge
OH
groups
on
silicates
and
the surfaces
of
iron oxides.
These
dissociate
as the
pH
rises,
leading to increased
net negative charge.
The
~
CaCl?
and
MgC1
2used in
the
CalMg
CEC
technique
have
little
effect
on
pH,
and,
therefore,
this
procedure
reflects
the
CEC
of
these systems
fairly
accurately.
The
NH
4
0Ac
used to
extract
exchangeable bases
is
buffered
at
pH
7, and,
therefore,
increases the apparent
CEC
somewhat
when
summed
with
KCl
exchangeable
Al.
When
the
CEC
of these samples
is
calculated
by
summing
NH
40Ac-exchangeable bases
and
BaCl?-TEA
acidity,
alarge
error
is
created.
The
finer
coal
fractions
were
particularly
reactive
with
this
procedure, thus leading to the increases in
BaC1
2-
TEA
acidity
shown
in Table
1.
The
BaCl
-TEA
reagent
reacts
with
all
acidity
up
to
p~
8.2,
and,
therefore.
seriously
overestimates the exchangeable
acidity
of
naturally-acid
mine
soils.
This
is
particularly
important since Federal
and
many
,State
guidelines for
sewage
sludge-loading
rates
are based
on
CEC.
Conclusions
Coal
particle
size
(ltIll)
(1-2)
(.25-.5)
(.05-1)
«.05)
The
BaCl?-TEA
acidity
technique
seriously
overestimates exchangeable
acidity
in
3.
1.
The
coal fragments in
this
study
had
little
effect
on
the
wet
acid-dichromate
digestion
organic matter technique.
Only
extremely
fine
«O.05mm)
particles
reacted to
any
appreciable
extent.
Exchangeable
Al
is
qui
te
low
in the
majority
of
minesoils
studied.
Soil
acidity
in these systems
is
controlled
by
other sources
of
acidity
such as
fine
coal,
organic matter. oxidation
of
Fe
2+
and
traces
of decomposing
pyrites.
Low
pH's coupled with
relatively
high base
saturation
are.
therefore.
common
in
these
soils.
2.
of these
soils
was
confirmed
by
potentiometric
whole-soil
titrations.
By
comparison,
soil
M7
formed
in ahighly acid
(pH
<3.8)
siltstone
spoil
which
is
considerably higher in
sulfur.
Here,
the extremely
low
pH
has
led to rapid weathering
of the
alumino-silicates
and
subsequent
release
of Al.
The
vast
majority of the
soils
studied
were
quite
low
in
Al
and
S,
however
.
The
rocks
of
the
Wise
formation contain
appreciable
amounts
of carbonates
and
iron
com-
pounds'7which
are
present
as
grain cements
and
nodules.
The
majority of Pin these rocks
is
associated with the carbonates, which
are
par-
ticularly
soluble in the
dilute,
double
acid-
(0.05 N
He1
+0.025 NH
SO
)
extractant
used
by
many
soil
testing
labor&to~ies.
This
is
evidenced
by
the
large
differences
between
acid-extractable
P
and
HC0
3-
extractable
P
shown
in Table 4. A
mine
soil
which
tests
medium
to high in P
by
the
dilute
acid
test
may,
in
fact,
contain
no
readily
plant-available
P.
Everett8
and
Smith
4
have
found
HCO
-to
be
an
accurate P
extractant,
and
we
recomm~nd
its
use.
The
overall
low
levels
of
plant-available
Pin these
soils
are
due
to
low
initial
levels
in the rocks,
relatively
low
ferti-
lization
rates,
and
fixation
by
iron oxides.
Mine
soils
forming in
spoils
which
are
high in iron will
face severe P
availability
problems
as
the rocks
weather
and
iron oxides accumulate.
NH
OAc
bases +
Baf1
2
-TEA
acidity
4.69 5.26 7.40 9.34
NH
OAc
bases +
Kc1
exch.
acidity
4.00 3.95 4.51 4.29
~
CaCl
r
M9c1
23.53 3.09
3.16
3.17
Exch
nge
Method
of
CEC
determination
Apparent Organic Matter
(%)
Effect of
particle
size
and
total
amount
of coal
on
apparent organic matter
levels
as determined
by
wet
acid-dichromate
digestion.
Table
2.
379

Table 4. Selected chemical
characteristics
of
5
representative
minesoi1s.
Organic
Exch.
CEC+
Base
Total Acid
HC0
3-
Hori
zon
Depth
pH
Matter
Ca
t~g
KAcidi
ty
Sat.
5PP
cm
"meq/l
DOg
%%-
ppm--
.~
Soil
M~
A0-14 5.75 1.26 2.79 1.
32
0.27 0.05 4.43
99
.010 25.0
3.0
Cl
14-60 6.05 0.68 2.86 1.45 0.12 0.05 4.48
99
.008 15,0 1.5
C2
60-90+
5.84 0.78 2.79
1.
78
0.09 0.05 4.71
99
.008 15.0 1.5
Soil
M7
A0-5 3.65 0.58 1.
92
2.80 0,25 4.65 9.62
52
.114 23.0 3.5
C
5-37
3.79 0.58 2.47 3.10 0.26 4.45 10.28
57
.095
8.0
9.0
R
37+
Soil
L7
A0-7 6.48
0.61
2.24
1.
69
0.16 0,10 4.19
98
.012 43,0 1.5
C7-45 6.67
0.41
2.44 1.60 0.15 0,0 4.19
100
.001
34,0 0
IIC
45-120+
4.98 0.30 1.
03
0.92 0.12 0.65 2.72
78
.009 7.0 0
Soil
L2
Al
0-10
6.01
2.30 4.20 3.70 0.25 0.05 8.20
99
.027 47,0
1.5
AC
10-22 6.00 2.24 4.07 4.20 0.19 0.05 8.51
99
.020 23.0
1.5
lIe
22-100+
5.08 0.30 1.40 1.88 0.20 0.65 4.13
84
.002
7.0
1.5
son
M15
A0-13 5.05 2.77 3.75
1.
81
0.40 0.15
6.11
98
.016 12.0 5.1
B13-35 5.59 1.96 3,25 1.74 0.13 0.15 5.27
97
.015 9,0 1.B
C
35-80+
5.40 2.58 3,62 2.00 0.13 0.15 5.90
97
.019
11
.0 0.9
Q
naturally
acid minesoi1s. Therefore,
etC
techniques using
this
acidity
value
seriously
overestimates the
effective
CEC
of
these
soils.
4.
The
disparity
between
dilute-double
acid
and
bicarbonate-extractable
Pconfirms
that
most
standard
soil
testing
techniques
are
designed
for
use
on
weathered natural
soils.
Great care must
be
taken in the
application
of
these techniques to
rela-
tively
unweathered minesoils,
and
in the
interpretation
of the
results.
References
1.
W.
Lee
Daniels
and
D.
F.
Amos.
"Mapping,
characterization
and
qenesis
of
mine
soils
on
areclamation research area in
Wise
County,
Virginia".
Proceedings,
1981
Symposium
on
Surface Mining Hydrology,
Sedimentology
and
Reclamation. Univ. of
Kentucky, Lexington,
KY.,
pp. 261-265.
1981.
2.
L.
R.
Sweeney,
Soil genesis
on
relatively
young
surface
mined
lands in southern
West
Virginia,
M.S.
Thesis, Virginia
Polytechnic
Institute
and
State
University.
1979.
3.
R.
1. Barnhisel
and
H.
F.
Massey.
Chemical
mineralogical
and
physical
properties
of
380
eastern
Kentucky acid-forming coal spoil
materials.
Soil Science 108:367-372, 1969.
4.
R.
M.
Smith,
E.
H.
Tryon
and
E.
H.
Tyner.
Soil development
on
mine
spoil.
West
Virginia University. Agric. Exper.
Station
Bulletin
604T.
47
p' 1971.
5.
R.
M.
Smith, A..
A.
Sobek,
1.
Arkle
Jr.,
J.
C.
Sencindiver,
and
J.
R.
Truman.
Extensive overburden
potentials
for
soil
and
water
quality.
U.S.
Environ.
Protect.
Agency,
Office
of
Res.
and
Deve!.
Industrial
Environ. Res.
Lab.
Cincinnati,
OH,
EPA
600/2/-76-184.
310
p.
1976.
6.
M.
L.
Peech,
L.
A.
Dean
and
J.
Reed.
Methods
of
soil
analysis
for
soil
fert
i1
ity i
nves
tigation. U.S. Dept.
of
Agric. Cir.
757.
1947.
7.
J.
L.
Howard.
Physical, chemical
and
mineralogical
properties
of
mine
spoil
derived
from
the
Wise
Formation,
Buchanan
County,
Virginia.
M.S.
Thesis, Virginia
Polytechnic
Institute
and
State
University.
1979.
8.
C.
J.
Everett.
Effects
of
biological
weathering
on
mine
soil
genesis
and
fertility.
Ph.D.
Dissertation,
Virginia Polytechnic
Institute
and
State
University, 1981.