United Sutn
Environmental Protection
Afieney
Watar
Offica of Wattr
Regulation* and Standard;,
Criteria and Standard! Oivttinr.
Waihirigton DC 20460
December 1987
SCD# 16
SEDIMENT QUALITY CRITERIA FOR METALS: V.
OPTIMIZATION OF EXTRACTION METHODS
FOR DETERMINING THE QUANTITY OF SORBENTS
AND ADSORBED METALS IN SEDIMENTS
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SEDIMENT QUALITY CRITERIA FOR METALS:
OPTIMIZATION OF EXTRACTION METHOOS FOR DETERMINING THE
QUANTITY OF SORBENTS AND ADSORBED METALS IN SEDIMENTS
Work Assignment 77,- Task 9
December 1987
Prepared by:
Eric A. Crecelius, Everett A. Jenne, and J. S. Anthony
Battel1e
Pacific Northwest Laboratories
Richland, Washington
For:
U.S. Environmental Protection Agency
Criteria and Standards Division
Washington, D.C.
Submitted by:
8ATTELLE
Washington Environmental Program Office
Washington, D.C.
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ABSTRACT
The Criteria and Standards Division of the U.S. Environmental Protection
Agency (EPA) is developing sediment quality criteria for nonpolar organic and
metal contaminants. The approach that EPA is considering for developing
sediment criteria for metals requires that the quantities of sorbed metals
and major sorbents be estimated. It has been proposed that the quantities of
these sorbed metals and sorbents be determined by chemical extraction methods.
In this study, a variety of sediments were used to optimize an acidic hydroxy-
1 amine hydrochloride extraction method for determining sorbed metals, and
amorphic iron oxide and manganese oxide sorbents. The results confirm the
usefulness of the procedural aspects of the hydroxy1 amine hydrochloride method,
except that a longer reaction time (60 min rather tharr 30 min) is indicated.
In addition, the efficiency of two alkali methods, ammonium hydroxide
and potassium hydroxide, were compared for determining the quantity of the
reactive particulate organic carbon sorbent. The potassium hydroxide method,
which was found to have advantages over the ammonium hydroxide method, was
optimized. Again, an extraction time of 60 min rather than 30 min is indicated.
iii
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ACKNOWLEDGMENTS
We woulcTlike to thank Dr. John Moore of the University of Montana for
collecting the sediment samples from the Clark Fork River. We also thank Ms.
Robin Canterbury of Clemson University for collecting the samples from Lake
Issaquenna, South Carolina; Pendleton Swamp, South Carolina; and Lake Burton,
Georgia.
iv
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CONTENTS
ABSTRACT i i i
ACKNOWLEDGMENTS iv
INTRODUCTION 1
EXPERIMENTAL METHODS 4
SAMPLES 4
Sources of Sediments and Minerals 4
Sediment Characterization 4
EXTRACTION METHODS 5
Hydroxy!amine Hydrochloride 5
KOH 5
NH40H 6
RECOVERY OF METALS 6
OPTIMIZATION OF EXTRACTION TIMES 6
RESULTS 8
CHARACTERIZATION OF SEDIMENTS .... 8
EXTRACTIONS OF Fe AND Mn OXIDE MINERALS 8
PRECISION OF EXTRACTIONS 10
RECOVERY OF METALS 11
OPTIMIZATION OF NHgOH'HCl EXTRACTION 11
OPTIMIZATION OF EXTRACTION TIME 12
OPTIMIZATION OF KOH EXTRACTION 19
DISCUSSION 23
CONCLUSIONS 26
REFERENCES . 27
v
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APPENOIX A - NH20H-HC1 METHOD FOR EXTRACTING SORBED METALS AND
AMORPHIC Fe AND Mn OXIDES FROM A SEDIMENT SAMPLE .... A.l
APPENDIX B -KiOH METHOD FOR EXTRACTING THE REACTIVE PARTICULATE
ORGANIC CARBON FROM A SEDIMENT SAMPLE B.l
vi
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FIGURES
1 Time Dependent Dissolution of Amorphic Fe Oxides
from Six Sediments, Using the Hydroxylamine
Hydrochloride Method . 14
2 Time Dependent Dissolution of Mn Oxides from Six Sediments,
Using the Hydroxylamine Hydrochloride Method 15
3 Time Dependent Desorption of Zn Oxides from Six Sediments,
Using the Hydroxylamine Hydrochloride Method . 16
4 Time Dependent Desorption of Cu Oxides from Five Sediments,
Using the Hydroxylamine Hydrochloride Method 17
5 Time Dependent Oesorption of Pb Oxides from Three Sediments,
Using the Hydroxylamine Hydrochloride Method 18
6 Reactive Particulate Organic Carbon, as Determined by
Potassium Hydroxide and Ammonium Hydroxide, Plotted
Versus the Total Particulate Organic Content of the
Sediments Studied 20
7 Time Dependent Dissolution of Reaction Particulate Organic
Carbon Determined with Potassium Hydroxide for Five
Sediments 21
TABLES
1 Composition of Sediments 9
2 NH20H*HC1 Extractions of Fe and Mn from Minerals by Two
Sequential Extraction of the Same Sample 10
3 Average Precision of Four Replicate Extractions of Each
Sediment 11
4 Recovery of Metals Simultaneously Spiked into Suspension
at the Beginning of Extraction Period . 12
5 Extraction of Metals at Three SolidrSolution Ratios and
Three HC1 Molar (M) Concentrations 13
vii
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INTRODUCTION
The Criteria and Standards Division of the U.S. Environmental Protection
Agency (EPA) is developing sediment quality criteria for nonpolar organic
contaminants and metals. These criteria will be used in conjunction with
water quality criteria to protect aquatic organisms and man's food chain in
both freshwater and saltwater. The approach selected for developing sediment
quality criteria for metals involves calculating the thermodynamic activity
of the uncomplexed metal in the sediment pore water, and relating this
thermodynamic activity to the toxic level of the metal, which is inferred
from the water quality criteria for individual metals (Jenne et al. 1986).
This approach assumes that the activity of metals in pore water is in
equilibrium with the sorbed metals. The data required are the quantity of
each important sorbent (sorption "sink"), the quantity of sorbed metals, and
surface adsorption constants for the individual sorbents. These data can
then be used with an appropriate algorithm (model) to estimate the activities
of metals in pore water. The most important advantages of this approach are
that sediment quality criteria are related to the water quality criteria and
the problems of determining metal availability and evaluating toxicity are
separated.
Therefore, the objectives of this study are to provide recommended stan-
dard methods for 1) estimating the quantity of sorbed metals and the major
oxide sorbents and 2) determining the reactive particulate organic carbon
(RPOC) content to estimate the surface adsorption constants. These methods
are intended for oxic sediments. Various methods for estimating sorbed metals
and the three major sorbents, amorphic iron (Fe) oxide, manganese (Mn) oxide,
and RPOC, in oxic sediments were reviewed in an earlier paper (Jenne 1984).
To achieve the study's objectives, we 1) evaluated and optimized the
hydroxylamine hydrochloride (NHgOH^HCl) method of Chao and Zhou (1983) for
determining the quantity of sorbed metals and the oxide sorbents, 2) compared
the effectiveness of the potassium hydroxide (KOH) and ammonium hydroxide
(NH^OH) method of Jenne (1984) and Luoma and Bryan (1981), respectively, for
extracting RPOC, and 3) optimized the KOH method for determining the quantity
of RPOC.
1
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The NHgOH-HCl extraction method was evaluated for 1) its extraction
efficiency for Fe and Mn minerals, 2) the possibility for readsorption of
desorbed metaTduring the extraction, 3) the extraction efficiency of various
acid concentrations and solidisolution ratios, and 4) the optimum length of
extraction time.
In addition, reference materials of Fe and Mn were used to determine if
the NH20H*HC1 extraction method will dissolve crystalline Fe and Mn oxides.
The extensive dissolution of .crystalline Fe oxides while the quantity of
amorphic Fe sorbent is being determined is undesirable. If crystalline oxides
are abundant in the sediments and dissolve during extraction, an overestimation
of the amorphic Fe sorbent would result. However, dissolution of the surface
layers of the crystalline oxides may be desirable because these surfaces also
provide sorption sites. If the contribution of the surface layer of crystalline
Fe oxides is included in the estimate of the amorphic Fe adsorbent, a separate
determination of the quantity of crystalline Fe oxides may not be necessary
to model the sorption of metals onto sediments. Although pyrolusite (0-MnO2)
is not a dlgenetic mineral, it was Included in this experiment to test whether
a highly crystalline Mn oxide is dissolved by this method.
This report also presents the results of experimental studies that compared
the effectiveness of the KOH and NH^OH methods for extracting RPGC from
sediment, and that optimized the extraction time for the KOH method. These
studies involved determining the effects of reagent strength and sol id:solution
ratio on extraction efficiency.
Certain criteria were used to select appropriate sediment samples for
this study. To demonstrate the effectiveness of the extractants over a range
of environmental conditions, an effort was made to collect sediments that had
a range of concentrations of Fe, Mn, and organic carbon (OC). Because the
NH20H*HC1 method for extracting sorbed metals, Mn oxide, and amorphic Fe oxide
is intended to be used for oxic sediments, sediment samples were selected to
minimize the content of sulfides and carbonates. Any sediment samples that
were black or had an odor of hydrogen sulfide were not used. The sediment
samples were characterized for chemical content and particle size distribution.
From the 16 samples, three were chosen for use in evaluating the NH 0H*HC1
method because they represented a reasonable range in the concentrations of
2
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metal contaminants and Fe and Mn sorbents. All 16 sediments were used initially
for evaluating the KOH and NH^OH methods for extracting RPOC. Five of the 16
sediments, representing a range in the RPOC and sediment characteristics,
were used for the KOH optimization study.
3
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EXPERIMENTAL METHODS
SAMPLES
Sources of Sediments and Minerals
Fine-grained sediments were collected in the spring and summer of 1987
from the Duwamish River in Washington; the Willamette River in Oregon; the
Clark Fork River in Idaho; Lake Issaquenna and Pendleton Swamp, South Carolina;
and Lake Burton, Georgia. The samples were promptly returned to the laboratory,
spread out on clean polyethylene sheets, and allowed to air-dry. The >60-
mesh (>0.25-mm) material was removed with a nylon screen and stored in plastic
containers.
Standard reference sediments from the National Bureau of Standards
[SRM 1645a (a river sediment), and SRM 1646 (an estuarine sediment)], and
National Research Council of Canada [MESS-1 (a marine sediment)], were used
as received. Magnetite (Fe304, sold as "black iron oxide"), lepidocrocite
(7-Fe00H), and hematite (a-Fe2Q3, sold as "red iron oxide") were obtained
from Reade Metals and Minerals Corp., Rumson, New Jersey, in <6Q-mesh form.
0-MnO2 (tetragonal, presumed to be pyrolusite) was obtained from CERAC, Inc.,
Milwaukee, Wisconsin, in <100-mesh form. Humic acid was used as received
fvom the Aldrich Chemical Company.
Sediment Characterization
The total metal concentrations of Al, Fe, Mn, Cu, Zn, and Pb in the sedi-
ment samples was determined by energy dispersive X-ray fluorescence (XRF)
(Nielson and Sanders 1983). The cadmium concentration was determined by Zeeman
graphite furnace atomic absorption, after total digestion of the sediment in
a Teflon bomb using a mixture of nitric, perchloric, and hydrofluoric acids.
The concentration of total organic carbon (TOC) in sediments was deter-
mined by combustion, using a Leco carbon analyzer after the sediment had been
treated with HC1 to remove inorganic carbon (IC) (such as carbonates). The
4
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IC concentration in sediments was calculated by subtracting tht TOC concen-
tration from the carbon concentration of sediment that had not been treated
with HC1.
EXTRACTION METHODS
The following extraction methods were used over a range of conditions to
optimize the methods. The recommended standard methods are presented in
Appendixes A and B. All containers and filters that came in contact with the
extracting solutions were carefully cleaned. For metals, a 24-h soak in 5%
HC1 was used. For organic carbon, a 24-h soak at 95°C in 1M KOH was used.
Hydroxy1amine Hydrochloride
All extractions contained 0.25M NH20H*HC1 and either 0.1M, 0.25M, or
0.5M HC1. The solution (100 mL) was brought to 50°C in a 250-mL polyethylene
bottle and 0.2, 0.4, or 1.0 g of air-dried sediment was added. The bottle
was placed in a 50°C shaking water bath for times ranging from 1 min to 12 h.
The sample bottles were removed from the hot water bath and an aliquot was
filtered (for evaluation of extraction variables) through an 0.2-/m Gelman
polysulfone Acrodisic (product No. 4192) jembrane filter into a 30-mL poly-
ethylene vial. Filtrates and procedural blanks were analyzed by inductively
coupled plasma (ICP) for Fe, Mn, Cu, Zn, and Pb, and by atomic adsorption
spectroscopy for Cd.
KOH
A 250-mL glass bottle containing 100 mL of 0.25N or 0.5N KOH was heated
to 95°C. Either 0.25, 0.5, or 1.0 g of air-dried sediment was added to the
glass bottle and put into a 95°C shaking hot water bath for times ranging
from 1 min to 8 h. The bottle was removed and placed in cold water bath
(approximately 15°C) for 10 min, and swirled at intervals of 3 to 4 min.
Then 30 mL of suspension was filtered through a 0.2-^m Gelman membrane.
Filtrates and procedural blanks were analyzed for dissolved organic carbon
(DOC) in a Dohrmann Model DC-80 carbon analyzer.
5
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NH4QH
One of tke air-dried sediments was placed in a 250-mL glass bottle, 100 mL
of IN NH^OH was added, and the solution held at 20°C. The solution was swirled
daily for 1 week, then filtered and analyzed for DOC as in the KOH method.
RECOVERY OF METALS
The spike recovery experiment determined if sorbed metals released by
dissolution of amorphic Fe and/or Mn oxides may be adsorbed by another sorbent,
such as GC, thereby underestimating the quantity of sorbed m6ta1. To allow
the maximum opportunity for sorption onto other sorbents, metal spikes were
added at the beginning of the 30-min extraction period. Standard conditions
were used (0.4 g sediment/100 mL solution, 0.25M NH20H*HC1, S0°C, and 30 min)
on three sediments and a procedural blank. Each bottle was spiked with
quantities of individual metals equivalent to those expected to be extracted
from the sediment. The metal spikes were added within 1 min after the sediment
was placed into the preheated extraction solution. Spike recovery was
calculated as the difference between the quantity of the metal in the extract
solution of the recovery experiment and the quantity in the standard 30-min
extract solution.
OPTIMIZATION OF EXTRACTION TIMES
Extraction times were evaluated to optimize the efficiency of the NH 0H*HC1
method in determining the quantity of sorbed metals and sorbents. The
concentrations of metals extracted from sediments versus the extraction times
were determined for six sediments. The extractant was 0.25M NHgOH'HCl, 0.25M
HC1, with a solid:solution ratio of 0.4 g/100 mL, and a temperature of 50°C.~
Ten extraction times of 1, 3, 7, 10, 20, and 30 min, and 1, 3, 6, and 12 h
were used.
To optimize the KOH method for estimating the quantity of RP0C, the
concentration of dissolved organic carbon extracted from the sediments versus
the extraction time was determined for five sediments. The extractant used
6
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was 0.5M KOH, with a solid:solution ratio of 0.4 g/100 ml, at 95°C, and with
time intervals of 1, 3, 7, 10, and 30 min, and 1, 4, and 8 h.
7
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RESULTS
characterization OF SEDIMENTS
The sediment samples were first characterized for total metal concentra-
tions, TOC, IC (carbonates), and particle-size (<63-/im fraction) to verify
that a range of concentrations of Fe, Mn, and TOC were present in these sam-
ples and that the IC concentrations were relatively low. The concentration
of total metals and other constituents of interest in the 16 sediments varied
considerably, ranging over approximately one order of magnitude (Table 1).
Sediments RS-1 to RS-6, which were collected below urban areas, had heavy
metal concentrations typical of sediments from moderately contaminated water
bodies (Salomons and Forstner 1984). The sediments from the Clark Fork River
(CF-1 to CF-4), which were contaminated by earlier mining activities, con-
tained relatively high metal concentrations, as did standard reference mater-
ial SRM 1645, which was from an industrially contaminated river. The
concentrations of metals in the sediments collected from the southeastern
United States (RS-7 to RS-9), and the estuarine and marine reference standard
materials (SRM 1646 and SRM MESS-1) were typical of relatively uncontaminated
sediments.
The total organic carbon (TOC) concentrations ranged from 0.2% to 5.1%.
The relatively low inorganic carbon (IC) concentrations, which ranged from
0.03% to 0.87%, were in accord with the selection criteria of a low carbonate
content.
EXTRACTIONS OF Fe ANO Mn OXIDE MINERALS
Reference oxide minerals were extracted to determine if the NHgOH'HCl
extraction method would dissolve crystalline Fe and Mn oxides. Because the
dissolution of minerals after grinding (the samples were received ground) is
initially high (because of the disordering of the surface layers and the
presence of small particles that adhere to the surfaces of larger particles),
two sequential extractions were carried out on replicate samples. The effects
of disorganized surface layers and fine-sized particles were presumed to be
much less in the second extraction of Fe oxides than in the first.
8
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TABLE 1. Composition of Sediments^
TOC
IC
1
Al
Fo
Mn
Cu
Zn
a/9
"b
Cd
Duaaaiah Rivar
RS-1 Lat. 47 32.4'
2 Lot. 47 83.4'
a Lat. 47 83.6'
2.1
1.7
1.1
8.24
8.33
8.13
73
88
68
8.1
8.8
8.8
4.7
4.8
4.8
887
888
874
88
91
39
144
174
87
48
79
19
8.68
8.68
6.38
fillaaatto Rivar
RS-4 Ritar aila 6.8
6 Rivor silo 4.3
8 Rivor silo 8.3
1.6
2.1
2.7
8.13
8.38
8.36
43
68
88
7.9
I.I ,
8.9
4.4
5.8
8.4
768
1819
1228
37
67
87
168
186
148
22
31
28
8.88
6.82
6.38
Clark Fork Rivar^
CF-1 31 In
2 82 In
3 47 In
4 89 ka
1.1
1.7
1.2
1.8
8.42
8.23
8.88
8.32
43
41
48
32
8.3
8.9
8.8
7.1
3.2
3.1
1.4
2.4
1817
1283
267
2118
2718
1388
223
639
1968
1186
283
1333
1231
498
432
117
8.28
2.48
6.67
6.76
Laka Iassouanna^
RS-7
3.9
8.14
49
14.7
3.1
an
24
88
29
6.28
Pandloton Sww^
RS-4
S.l
8.83
48
11.C
12.2
1683
22
98
29
6.16
Lako Burton^
RS-9
1.8
8.83
48
17.3
8.8
S96
61
116
49
8.18
Eatuarino Sodiaont^
NAW
SM 1648
1.8
8.88
8.3
3.4
37S
18
138
28
8.38
Marino Sadiiont^
SRM MESS-1
2.8
8.88
NA
8.8
3.1
813
26
191
34
8.69
Rivor Sodiaont^
SRM 184So
3.8
8.87
NA
2.4
8.S
78«
186
1848
72f
16.66
fa) llotal analysis by XRF, aacapt far Cd, afcieh aaa anslyzod by graphita furnaca atoaic absorption
j. j.ta rooortod on a dry aoiflht tests.
ft) NatancTdoanotroaB fron lara Sprinfls Ponds, colloctod by Or. John Uaoro, Univarsity of Montana.
/,{ rni i.rtM* k> Robin Cantorbury, CI as a on Univorscty
(d) ConeontratKMi of sotals takan from tha eartifieation ahoots providod ait* tho aaoplas.
(a) NA « Not analyiad
9
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This lack of dissolution was confirmed by the results (Table 2), which indicate
that less than 0.5% Fe was dissolved from hematite or magnetite after two
extractions. -However, nearly 30% the lepidochrocite {7-FeOOH) was dissolved,
with about as much dissolved in the second extraction as the first. The almost
total dissolution of the pyrolusite by the first extraction (Table 2) supports
the premise that the NHgOH'HCl extraction solubilizes this Mn oxide.
PRECISION OF EXTRACTIONS
The precision of the NHgOH'HCl extraction procedure was determined by
extracting subsamples of three sediments in duplicate on two days, giving a
total of four data points for each sediment. The coefficients of variation
for Fe, Mn, Cu, and Zn in the three sediments, based on the four data points,
did not exceed 12.1%, and were generally below 10% (Table 3).
TABLE 2. NH20H*HC1 Extraction^ of Fe and Mn from Minerals by Two
Sequential Extractions of the Sane Sample
Fe Extracted Mn Extracted
"Tst 2nd Total 1st 2nd total
Mineral
QaqIi rat®
(b)
Hematite
(a-FegOg)
1
2
avg.
0.24
0.30
~07
0.18
0.24
inr
0.42
0.54
0.48
0.0034
0.0030
<3.0032
0.0005
0.0005
0.0005
0.0039
0.0035
0.OO37
Magnetite
(Fe304)
1
2
avg.
0.074
0.102
O.OSS
0.054
0.070
0:062
0.128
0.172
0.150
0.0004
0.0004
0.0004
0.0002
0.0004
0.0003
0.0006
0.0008
0.0007
Lepidochrocite 1
b-FeOOH) 2
avg.
3.5
18.7
B7T
12.0
14.0
15.5
32.7
<0.001
<0.001
<0.001
<0.001
<0.002
<0.002
Pyrolusite
(0-MnO2)
1
2
avg.
<0.010
0.015
m m
<0.010
0.013
m
<0.010
0.028
m m
62.0
63.0
SO
8.0
4.1
70.0
67.1
SO
(a) Conditions are 0.4 g sediment/100 mL solution, 0.25M NH~0H*HC1 and
0.25M HC1, 50®C, and 30 min. " c
(b) Percentage of initial oven-dry weight of mineral.
10
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TABLE 3. Average Precision of Four Replicate Extractions of E.*ch Sediment^
Fe Mn Cu _ Zn
Sediment
RS-2
RS-6
CF-1
._Mean(b)
%
Cv(c)
%
Mean
/*g/g
CV
%
Mean
mq/q
CV
%
fit c.n
j*g/g
87
CV
%
1.06
5.5
186
11.0
62
7.0
9.9
1.15
6.9
812
5.5
38
6.3
131
12.1
1.06
9.8
377
9.6
2690
12.0
493
3.6
(a) Standard conditions are 0.4 g sediment/100 ml solution, 0.25M
NH2QH*HC1
(b) Ory weight basis
(c) CV is the coefficient of variation (i.e., mean f standard deviation).
RECOVERY OF METALS
The recoveries of metals added during the Nl^OH^HCl extraction procedure
were evaluated to determine if metals extracted from one sorbent (i.e., Fe
and Mn oxides) were resorbed on other sorbents (i.e., organic carbon), iron
and Mn spikes were used to determine if these metals were sorbed by the
organic carbon, resulting in an underestimation of the quantity of these
sorbents. Spike recoveries for six metals (Cd, Cu, Zn, Fe, Pb, and Mn),
averaged across the three sediments, ranged between 98% and 109% (Table 4).
Thus, the extraction conditions resulted in 100% recovery of the five metals,
within experimental error. Unexplainably, Fe was sightly anomalous with only
an 88% recovery.
OPTIMIZATION OF NH?0H»HC1 EXTRACTION
The extraction efficiency, using Q.25M NHgOH-HCl, was examined for three
concentrations of HC1 (0.1M, 0.25M, and 0.5M) and three solidtsolution ratios
(0.2, 0.4, and 1.0 g/100 mL) of extractant at 50°C for 30 min. The results
of metal extractions from three sediment samples (RS-2, RS-6, and CF-1) at
the three acid concentrations and three solidtsolution ratios are presented
in Table 5. Slightly more Fe (expressed as %) was extracted from the 0.1-
and 0.4-g samples than from the 1.0-g samples. Also, slightly higher solu-
tion concentrations of Cd, Cu, Fe, and Mn occurred in some samples when the
higher HC1 concentrations were used. However, the differences in the metal
11
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TABLE 4.
Metal
Fe
Mn
Cu
Zn
Pb
Cd
(a) Standard conditions are 0.4 g sediment/lOOmL solution,
0.25M NH20H*HC1
(b) NA »~Not analyzed
concentrations for the different samples were insufficient to indicate that
sample sizes less than 1.0 g or HC1 concentrations greater than 0.25M should
be used. This lack of dependence on the sample size permits a desirable
flexibility in the quantity of sediment used for the sorbed metal determi-
nations, which facilitates analyses of metal concentrations well above the
analytical detection limits.
OPTIMIZATION OF EXTRACTION TIME
There is appreciable variation among samples in the slope of the extrac-
tion curve over the 30-to 360-min period (Figures I to 5). For most samples
(RS-2, RS-6, RS-7, CF-1, and SRM 1646), the slope of the Fe extraction curve
is relatively steep over the 30- to 60-min interval. For the SRM 1645a sedi-
ment sample, the 30-min point is anomalously high for most metals when com-
pared to the other time points. These results indicate that 60 min rather
than 30 min be used to estimate the quantity of amorphic Fe oxide. In some
instances, the 60-min extraction period also appears preferable to a 30-min
period for estimating the quantity of other metals [i.e., for Mn (RS-2, RS-7,
CF-1, and SRM 1646), Cu (CF-1), Zn (RS-2, RS-6, and CR-1) and Pb (CF-1)]. If
the CF-1 sample (which contains sulfide and thus is not be oxic) is disre-
garded, there are only three instances in which a 60-min extraction period
Recovery of Metals Simultaneously 5gjked into Suv.ension at
the Beginning of Extraction Period^ '
RS-2 RS-6 CF-1 Average Blank Spike
— %
90
89
86
88
90
115
107
106
109
114
108
102
94
101
100
107
104
94
102
110
100
108
NA
104
104
100
100
94
98
90
12
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TABLE 5. Extraction of Metals at Three So1id:Solution Ratios and
Three HC1 Molar Concentrations
U
Vleiqht (q) of Sample per 100 nL Solution
0.2 0.4 or
Molarity of HC1
Metal* '
0.1
6.25
0.5
0.1
6.25
0.5
0.1
0.25
0.5
SEDIMENT RS-2
Fe (%)
1.17
1.16
1.32
1.07
1.17
1.32
1.01
1.04
1.15
Mn (/tg/g)
196
185
203
182
194
206
181
179
186
Cu (/»g/g)
60
58
68
60
66
66
59
61
62
Zn (/tg/g)
120
105
122
100
114
113
101
102
106
SEDIMENT RS-6
Fe (%)
1.09
1.22
1.29
1.00
1.21
1.33
0.93
1.09
1.22
Mn (/tg/g)
830
810
790
770
815
820
771
761
779
Cu (/tg/g)
34
39
40
33
39
43
33
36
40
SEDIMENT CF-1
Fe (%)
0.96
1.20
1.32
1.02
1.11
1.38
0.82
1.03
1.06
Mn (/tg/g)
324
400
474
348
373
525
283
366
396
Cd (/tg/g)
19
24
24
21
22
24
15
21
21
Cu (/tg/g)
2625
2900
2845
2775
2675
3000
2500
2490
2530
Pb (/tg/g)
389
700
970
375
695
1020
186
630
610
Zn (/tg/g)
580
540
710
588
510
743
436
491
502
(a) Metal concentration in percent or /tg/g dry weight of sediment. Paraneters were
100 nL of 0.25M Hydroxylamine Hydrochloride for 30 min at 50°C.
-------
Time (mint
FIGURE 1. Tine Dependent Dissolution of Aaorphic Fe Oxides from Six
Sediments, Using the Hydroxy!amine Hydrochloride Method
-------
FIGURE 2. Time Dependent Dissolution of Mn Oxides from Six Sediments Using
the Hydroxylamine Hydrochloride Method '
-------
CT»
1600
1400 —
cn
v
a>
a.
1200
1000
800
600
400
RS-2
RS-6
RS-7
CR 1
SRM 1646
SRM 1645a
200
0
•o
0 30 60
tUL
200
400
Time (min)
600
800
FIGURE 3. Time Dependent Desorption of Zn Oxides from Six Sediments, Using
the Hydroxylamine Hydrochloride Method
-------
Time (min)
FIGURE 4. Time Dependent Desorption of Cu Oxides from Five Sediments, Using
the Hydroxy1amine Hydrochloride Method
-------
Time (min)
FIGURE 5. Tine Dependent Oesorption of Pb Oxides fron Three Sediments, Using
the Hydroxy1amine Hydrochloride Method
-------
appears preferable to a 30-min period for metals other than Fe. Although Fe
continued to be extracted after 60 min for the RS-2 and CF-1 s„r..pTes( the
extractions were at a much lower rate than before.
OPTIMIZATION OF KOH EXTRACTION
Two extraction methods for determining the quantity of reactive partic-
ulate organic carbon (RPOC) were compared, then one method was optimized.
Initially, duplicate samples of all 16 sediments were extracted, with both
0.5M KOH at 95°C for 30 min and 1M NH^OH at 20°C for 1 week. The concentra-
tion of carbon extracted by each method was plotted versus TOC concentration
in the sediment (Figure 6). The TOC concentrations in the sediments were
determined on unextracted sediment samples and compared to RPOC, which was
determined on extracts of sediment samples. The KOH procedure extracted
approximately 41% of the TOC, with a range of 7% to 54%. The NH^OH procedure
extracted about 23% of the TOC, with a range of 2% to 36%. Linear regression
analysis between RPOC and TOC yielded R2 values of 0.71 for KOH and 0.56 for
NH^OH (Figure 6). Because KOH extracted more RPOC and provided a regression
against TOC with much less scatter than the NH^QH regression, further experi-
ments were conducted only with KOH.
To optimize RPOC extraction with the KOH method, solution strengths and
solidtsolution ratios were varied in a series of experiments (data not shown).
The amounts of RPOC extracted from sediment and humic acid (humic acid
represents a solid phase with 100% TOC) were compared for two concentrations
of KOH (0.25M and 0.5M) and three solid solution ratios (0.25, 0.5 and 1.0
g/100 mL) at 95°C for 30 min. No significant effect of the solid:solution
ratio in the range of 0.25 to 1.0 g sediment/100 mL KOH (95°C) was noticed.
Neither was there any apparent difference in extraction efficiency between
0.25M and 0.5M KOH.
To optimize the KOH method, extraction of RPOC as a function of time for
five sediment samples was determined (Figure 7). The quantity of RPOC extracted
increased significantly with time up to 30 min. For two samples, RS-2 and
RS-6, there was approximately a 10% increase in RPOC extracted in the interval
between 30 and 60 min. The 30-min values for RS-7, SRM MESS-1, and SRM 1645a
19
-------
% TPOC in Sediment
% TPOC in Sediment
FIGURE 6. Reactive Particulate Organic Carbon, as Determined by Potassium
Hydroxide (A) and Ammonium Hydroxide (B), Plotted Versus the
Total Particulate Organic Content of the Sediments Studied
20
-------
Time (min)
FIGURE 7. Time Dependent Dissolution of Reaction Particulate Organic Carbon
Determined with Potassium Hydroxide for Five Sediments
-------
are anomalously high in comparison to the 60-min value; hence, they cannot be
used to determine the optimum extraction time. For consistency with the
hydroxy! amine~Tiydrochloride extraction method, we tentatively selected a fin-min
extraction period.
22
-------
discussion
The apprxyach that EPA is considering to develop sediment quality
criteria for metals requires that the quantities of sorbed metals and the
quantities of the major sorbent phases in the sediments be estimated. The
estimation methods must be usable by federal agencies and private companies.
Therefore, the methods for estimating the quantity of sorbed metals and sor-
bent phases should be easily applied and relatively insensitive to variations
in extraction parameters, such as the solidssolution ratio, concentration of
extractants, and time. For ease of application, a single extraction time
that yields the maximum quantity of the target sorbent (e.g., amorphic Fe
oxide) and the minimum amount of other phases with different absorptive
properties (e.g., crystalline Fe oxides) should be selected.
The effects on the extraction efficiency of varying the extraction para-
meters have been used to prepare a recommended method for using NH20H*HC1
extractant to estimate the quantity of sorbed metals, amorphic Fe oxide, and
Mn oxide (Appendix A). The NHgOH-HCl method was effective in extracting
amorphic Fe oxide but not crystalline Fe oxides. The metal recovery experi-
ments indicated that readsorption of soluble metals to other sorbents was not
a problem with this procedure for the sediments studied." These results are
in contrast with the results obtained by Rendell et al. (1980), who used a
series of "selective" extractants. Although the reason for this difference
is not known, it is possible that their use of a dithionate extractant, which
is more of a reducer than the NHgOH-HCl extractant, may have affected the
resorption of the metals. The precision studies with the NH20H*HC1
extraction method suggest that the coefficient of variation between estimates
on the same sediment samples will be 12% or less.
Based on the time curves of Chao and Zhou (1983) and Jenne (1984), it
was expected that there would be little increase in Mn and amorphic Fe oxides
extracted per unit time after about 30 to 60 min. Our results indicated that
this hypothesis is generally true, and that a 60-rain extraction time is
desirable. However, the fraction of the total Mn and Fe dissolved by the
NH20H*HC1 method after 60 min for the RS-7 and CF-1 sediment sample is
significant.
23
-------
The increase in the amount of Mn arid Fe dissolved from the RS-7 sample
after 60 min suggests that an Fe-containing mineral is in the sample. This
mineral is considerably less soluble than the amorphic Fe oxide, but still
dissolves at a significant rate in the acidified NHgOH^HCl. Based on the
results of the extraction of crystalline Fe oxides (Table 2), this Fe-
containing mineral may be lepidochrocite. The possible error introduced into
the estimate of the amorphic Fe oxide sorbent by the presence and dissolution
of lepidochrocite merits further investigation.
As mentioned above, the Clark Fork River sample (CF-1) also showed an
increase in the amount of Mn and Fe dissolved after 60 min. The results do
not indicate whether many or most of these trace metals were released from Mn
and amorphic Fe oxides, or from the oxidation of detrital sulfides. Although
the NH20H*HC1 method is clearly valid with oxic sediments, the extent to which
detrital sulfides confound the estimation of amorphic Fe oxide and sorbed
metals also merits careful further investigation.
Comparison of two methods for estimating the quantity of RPOC indicated
KOH is superior to NH4OH and that the method, in the range investigated, is
not sensitive to the sol id:solution ratio and extractant concentration. Under
the test conditions used, KOH extracted twice-as much organic carbon as NH4OH
and produced a higher correlation between RPOC and TOC in sediments than NH4OH.
There also may be occasions when timeliness is important, making extraction
in 1 h instead of 1 week an advantage. Appendix B gives the recommended
standard method for the KOH extraction method.
While the methodology evaluations reported here are important, they are
only a first step in evaluating the effectiveness of the extractions. In
this study, our analysis was restricted to oxic sediments that have a specific
range in characteristics. As these methods are applied to additional sediments,
a better evaluation of the strengths and limitations of the extraction methods
will result. One issue that will need to be addressed in using the extracted
quantity of Fe, Mn, and RPOC in sorption models is the correlation between
these quantities and the density of sorption sites. If there is no correlation,
then the extracted quantities may be used in empirical models. If there is a
correlation, then classical models (e.g., the triple-layer adsorption model)
can be used. The next step in the sediment criteria development effort will
24
-------
be to evaluate alternative algorithms for estimating the interstitial water
activity of the metal contaminants and then choose the most appropriate
procedure. —
25
-------
CONCLUSIONS
The methods tested are suitable for estimating the quantifies of sorbed
metals and the major sorbent phases in sediments. Recommended standard
methods for estimating the quantities of sorbed metals and major oxide
sorbents, and for determining the RPOC content of sediments, are given in
Appendixes A and B, respectively. Other conclusions are:
• Recoveries of the metal spikes were 90% or better, indicating that
the metals were not readsorbed by other sorbents.
• Extractions of Fe and Mn minerals indicate amphoric Fe and Mn oxides
are dissolved while the dissolution of crystalline Fe oxides is
minimal.
• Variation in the solidzsolution ratio (0.25 to 1.0 g/100 ml) did not
significantly affect the estimation of sorbed metals, oxide-
sorbents, or RPOC on the sediments investigated.
• Variation in the HC1 or KOH concentrations did not significantly
affect the NHgOH^HCl or KOH extraction methods. The use of 0.25M
HC1 rather than a more dilute 0.101J HC1 will permit sample sizes to
range from 0.2 to 1.0 g with only minor changes in metal extraction
efficiencies. This insensitivity facilitates obtaining metal
concentrations in an appropriate concentration range for analysis by
varying the sample size.
• No benefits were found for the use of NH4OH (20°C for 1 week)
instead of KOH for determining RPOC.
• There is merit in extending the extraction time for both the metals
and RPOC extractions from 30 to 60 min.
26
-------
REFERENCES
Chao, T, T.,-«and L. Zhou. 1983. "Extraction Techniques for Selective
^irvf4^&'r°n 0x1d" fro" Son Md son sci.
Jenne, E. A. 1984. "Quantitative Determination of Sorption Sinks " Tn
Radionuclide Migration in Sroumfaater. pp. 43-54. HUREG/CR-3712 (PNL-5040)
U.S. Nuclear Regulatory Commission, Washington, D.C. w''
Jenne, E. A., D. M. DiToro, H. E. Allen, and C. S. Zarba. 1986 "An dr+,-w,+
Based Model for Developing Sediment Criteria for Metals: I. *A New
ln. Proceedings of the Chemicals in the Environment: Internation!??
eds. J. N. Lester, A. Perry, and R. M. SterHtt. pp. helper Ltd
London. K
Luoffla, S. N., and G. *•.Bryan. 1981 'A Statistical Assessment of the Form
of Trace Metals in Oxidized Estuarine Sediments Employing Chemical
Extractants." Sci. Total Environ. 17:165-196.
Nielson, K.K., and R.W. Sanders. 1983. "Multielement Analysis of Un**inh*H
Biological and Seological Samples Using Backscatter aJS ^dl^nta 9
Parameters." Adv. X-ray Anal. 26:385-390.
Rendell, P. S., S. E. Batley and A. J. Cameron. 1980. "Adsorption a« » r«n+ „i
on.Metal Concentrations in Sediment Extracts." Environ. Sc7. T*rh.M.S?! 1
318. ~
Salomons, W., and U. Forstner. 1984. Metals in the Hvdrocvcle.
Verlag, Berlin. 1 K '"aer
27
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APPENDIX A
NH?0H«HC1 METHOD FOR EXTRACTING SORBED METALS AND
AMORPHIC Fe AND Mn OXIDES FROM A SEDIMENT SAMPLE
-------
APPENDIX A
NH?0H*HC1 METHOD FOR EXTRACTING SORBED METALS AND
AMORPHIC Fe AND Mn OXIDES FROM A SEDIMENT SAMPLE
SUMMARY OF METHOD
Air-dry, sieve, and homogenize the sediment sample. Add a portion of
the sample (0.40 g) to 100 mL of hot (50°C) extraction solution (0.25M NH20H*HC1
and 0.25M HC1) and shake for 60 min. Filter approximately 25 mL of the
suspension through a 0.2-/im membrane filter. Store the filtrate in a
polyethylene bottle. Analyze the filtrate for metals by inductively coupled
plasma (ICP), atomic adsorption spectroscopy (AA) or equivalent method.
EQUIPMENT
• shaker hot water bath
• analytical balance with 0.1-mg accuracy
• reagent grade hydroxylamine hydrochloride
• reagent grade hydrochloric acid
• 250-mL and 30-mL polyethylene bottles
• 1-L wide-mouth polyethylene bottles
• 100-mL graduated cylinder
• 30-mL plastic syringes
• 0.2-/im in-line membrane filters (Gelman polysolfone Acrodisic, product
no. 4191)
• 60-mesh (0.25-mm) sieve with nylon screen
• inductively coupled plasma, atomic adsorption spectrometry or
equivalent equipment
A.l
-------
EQUIPMENT PREPARATION
• To clean-polyethylene bottles, graduated cylinder, and syringes,
soak in 5H HC1 for 24 h and rinse five times with double-deionized
water. Air-dry in laminar flow hood.
• To clean in-line filters, force 30 mL of 5% HNO3 through the filters
and rinse with 90 ml of double-deionized water.
SAMPLE PREPARATION
To avoid developing anoxic conditions, promptly return sediment samples
to the laboratory and spread out on clean polyethylene sheets to air-dry. i„
drying, the sediment can form a hard pancake, which should he broken up using
a mortar and pestle. Sieve the sediment to remove material >0.25 ran (>6o
using a nylon screen, and store the sieved samples in wide-mouth polyethylene
containers.
ANALYTICAL PROCEDURE
• Prepare an aqueous extraction solution of 0.25M.hydroxy1 amine
hydrochloride (NH20H*HC1) and 0.25M hydrochloric acid (HC1).
• Place 100 mL of extraction solution in a 250-mL polyethylene bottle.
• Warm solution to 50°C in a hot water bath.
• Add 0.40 g of sieved sediment to warm solution. (Up to 1.0 g/100 ml
of sieved sediment may be used to increase the soluble concentration
of metal, if necessary.)
• Return sample bottle to hot water bath (50°C) and shake for 60 min.
• Remove sample bottle from the hot water bath.
• Withdraw 25 mL of solution from sample bottle using a 30-mL plastic
syringe and filter through a 0.2 jm in-line filter (Gelman polysul-
fone Acrodisic, product no. 4192).
• Collect filtrate in a 30-mL polyethylene bottle.
A.2
-------
• Cap filtrate bottles tightly.
• Analyze-filtrate for metals by ICP, AA or equivalent method.
QUALITY CONTROL
• Analytical balances should be inspected and calibrated on a preassigned
schedule.
• The equipment used for analysis of the filtrates for metal
concentrations should be calibrated on a preassigned schedule following
the manufacturers specifications.
• 10% of samples should be analyzed in duplicate.
• Prepare procedural blanks by following the procedure, but without
adding sieved sediment. One procedural blank for each ten samples
should be included.
• Spike replicates of three sediment samples with quantities of
individual metals equivalent to that expected to be extracted from
the sediment should be analyzed. Add spikes immediately after placing
the sediment into the preheated extraction solution. Calculate spike
recovery as the excess in the recovery experiment compared to that
in the standard extraction.
-------
APPENDIX B
KOH METHOD FOR EXTRACTING THE REACTIVE
PARTICULATE ORGANIC CARBON FROM A SEDIMENT SAMPLE
-------
APPENDIX B
KOH METHOD FOR EXTRACTING THE REACTIVE
PARTICULATE ORGANIC CARBON FROM A SEDIMENT SAMPLE
SUMMARY OF METHOD
Air-dry, sieve, and homogenize the sediment sample. Add a portion of
the sample (0.50 g) to 100 mL of hot 0.5M KOH solution and shake for 60 min.
Filter approximately 25 mL of the suspension through a 0.2-/*m membrane filter.
Store the filtrate in a polyethylene bottle. Analyze filtrate for dissolved
organic carbon.
EQUIPMENT
• reagent grade potassium hydroxide
• shaker hot water bath
• analytical balance with 0.1-mg accuracy
• 250-mL and 30-mL polyethylene bottles
• 1-L wide-mouth polyethylene bottles
• 100-mL graduated cylinder
• 30-mL plastic syringe
• 60-mesh (0.25-mm) sieve with nylon screen
• 0.2-^m in-line polycarbonate membrane filters (Gelman)
• deionized, distilled water
• carbon analyzer (e.g., Dohrmann Model DC-80)
EQUIPMENT PREPARATION
Clean all labware to be used in this extraction by filling with 1.0M KOH
and heating to 95°C overnight. Rinse three times with distilled, deionized
water and dry in a laminar flow hood.
B.l
-------
SAMPLE PREPARATION
To avoicLdeveloping anoxic conditions, promptly return sediment samples
to the laboratory and spread out on clean polyethylene sheets to air-dry. In
drying, the sediment can form a hard pancake, which should be broken up using
a mortar and pestle. Sieve the sediment to remove material >0.25 mm (>60
mesh) using a nylon screen, and store sieved samples in polyethylene containers.
ANALYTICAL PROCEDURE
• Prepare an aqueous solution of 0.5M potassium hydroxide (KOH).
• Place 100 mL of KOH solution into a 250-aL polyethylene bottle.
• Warm solution to 95°C in a hot water bath.
• Add 0.50 g of sieved sediment to sample bottle. (Up to 1.0 g/100 ml
of sieved sediment may be used to increase the concentration of DOC,
if necessary.)
• Return sample bottle to hot water bath (95°C) and shake for 60 min.
• Transfer sample bottles to cold water bath for 10 min. Swirl solutions
at 3- to 4-min intervals.
• Withdraw 25 mL of solution from sample bottle using a 30-mL plastic
syringe and filter through a 0.2-jim in-line filter (Gelman
polycarbonate membrane).
• Collect filtrate in a 30-mL polyethylene bottle.
• Cap bottle tightly and store in refrigerator.
• Analyze for dissolved organic carbon using carbon analyzer.
• Rinse the syringe three times with deionized, distilled water between
uses.
S.2
-------
QUALITY CONTROL
• Prepare-procedural blanks by following the procedure, but without
adding sieved sediment. One procedural blank for each 10 samples
should be included.
• Calibrate the carbon analyzer on a preassigned schedule following
manufacturers specifications.
• 10% of samples should be analyzed in duplicate.
• All analytical balances should be inspected and calibrated on a
preassigned schedule.
B.3
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