EPA/600/R-04/090
April 2004
Mine Waste Technology Program
Phosphate Stabilization of Heavy Metals Contaminated
Mine Waste Yard Soils, Joplin, Missouri NPL Site
By
Jay Cornish, Project Manager
MSB Technology Applications, Inc.
Mike Mansfield Advanced Technology Center
Butte, Montana 59702
Under Contract No. DE-AC22-96EW96405
Through EPA IAG No: DW89938870-01-0
Norma Lewis, EPA Project Manager
Sustainable Technology Division
National Risk Management Research Laboratory
Cincinnati, Ohio 45268
This study was conducted in cooperation with
U.S. Department of Energy
National Energy Technology Laboratory
Pittsburgh, Pennsylvania 15236
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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Notice
The U.S. Environmental Protection Agency through its Office of Research and Development funded the
research described here under IAG DW89938870-01-0 through the U.S. Department of Energy (DOE)
Contract DE-AC22-96EW96405. It has been subjected to the Agency's peer and administrative review
and has been cleared for publication as an EPA document. Reference herein to any specific commercial
product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily
constitute or imply its endorsement or recommendation. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the EPA or DOE, or any agency thereof.
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Foreword
The U.S. Environmental Protection Agency is charged by Congress with protecting the Nation's land, air,
and water resources. Under a mandate of national environmental laws, the Agency strives to formulate
and implement actions leading to a compatible balance between human activities and the ability of natural
systems to support and nurture life. To meet this mandate, EPA's research program is providing data and
technical support for solving environmental problems today and building a science knowledge base
necessary to manage our ecological resources wisely, understand how pollutants affect our health, and
prevent or reduce environmental risks in the future.
The National Risk Management Research Laboratory is the Agency's center for investigation of
technological and management approaches for preventing and reducing risks from pollution that threatens
human health and the environment. The focus of the Laboratory's research program is on methods and
their cost effectiveness for prevention and control of pollution to air, land, water, and subsurface
resources; protection of water quality in public water systems; remediation of contaminated sites,
sediments, and ground water; prevention and control of indoor air pollution; and restoration of
ecosystems. The NRMRL collaborates with both public and private-sector partners to foster technologies
that reduce the cost of compliance and to anticipate emerging problems. NRMRL's research provides
solutions to environmental problems by developing and promoting technologies that protect and improve
the environment; advancing scientific and engineering information to support regulatory and policy
decisions; and providing the technical support and information transfer to ensure implementation of
environmental regulations and strategies at the national, state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term research plan. It is
published and made available by EPA's Office of Research and Development to assist the user
community and to link researchers with their clients.
Lawrence W. Reiter, Acting Director
National Risk Management Research Laboratory
in
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Abstract
This document summarizes the results of Mine Waste Technology Project 22Phosphate Stabilization of
Heavy Metals-Contaminated Mine Waste Yard Soils. Mining, milling, and smelting of ores near Joplin,
Missouri, have resulted in heavy metal contamination of the area. The Joplin site was listed on the
Superfund National Priorities List in August 1990. High blood levels in young children in the area have
prompted efforts to reduce soil-based lead (Pb) (and cadmium) health threats.
Previous investigations indicate that Pb bioavailability can be reduced via addition of 1% by weight
phosphoric acid (PA) plus 0.05% potassium chloride. The purpose of this study was to determine if the
treatment would be effective in mine waste-affected soils. Bioavailability of Pb is determined by
measuring Pb levels in various tissues from young pigs following ingestion of a known quantity of Pb in
treated and untreated soil or lead acetate. The data collected for the in vivo study were not sufficient to
conclude (at the 95% confidence level) that PA-treatment had any particular effect on Pb bioavailability.
The results of a parallel in vitro study were more encouraging. The extractable Pb was consistently lower
in PA-treated soils compared to untreated soils.
IV
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Contents
Page
Notice ii
Foreword iii
Abstract iv
Figures vi
Tables vi
Acronyms and Abbreviations vii
Acknowledgments viii
Executive Summary ES-1
1. INTRODUCTION 1
1.1 Project Background 1
1.1.1 Site History 1
1.1.2 Bioavailability and Bioaccessibility of Lead (Definitions) 1
1.1.3 Previous Soil Remediation Studies 2
1.2 Project Objectives 3
1.2.1 Assess Reduction of Lead Bioavailability in Test Soils 3
1.2.2 Assess Reduction of Lead Bioaccessibility in Test Soils 4
1.2.3 Assess Reduction of Heavy Metals Phytoavailability in Test Soils 4
2. METHODS 6
2.1 Field Investigations 6
2.1.1 Experimental Design 6
2.1.2 Implementation of Field Investigations 7
2.2 Laboratory Investigations 8
2.2.1 In Vivo Bioavailability Studies 9
2.2.2 In Vitro Bioaccessibility Study 10
2.2.3 Heavy Metals Phytoavailability Study 10
3. RESULTS AND DISCUSSION 15
3.1 In Vivo Bioavailability Studies 15
3.2 In Vitro Bioaccessibility Study 15
3.3 Heavy Metals Phytoavailability Study 16
3.3.1 Plant and Soils Data Presentation 16
3.3.2 Plant and Soils Data Interpretation 17
3.3.3 Brief Evaluation of the Soil and Plant Data from the Smelter Soils Test Plot 19
4. CONCLUSIONS AND RECOMMENDATIONS 23
4.1 In Vivo Lead Bioavailability Studies 23
4.2 In Vitro Lead Bioaccessibility Study 23
4.3 Heavy Metals Phytoavailability Study 23
5. REFERENCES 25
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Contents (Cont'd)
Appendix A: Previous Field Investigations (Mosby, 2000)
Appendix B: First Mine Soil Bioavailability Investigation (Casteel et al., 2001)
Appendix C: Second Mine Soil Bioavailability Investigation (Casteel et al., 2002)
Appendix D: Recalculation and Uncertainty Analysis of Lead RBA Estimates in Untreated and
Phosphate Treated Soils from the Jasper County Superfund Site (Syracuse Research
Corporation, 2003)
Appendix E: Mine Soil Bioaccessibility Investigation (Brown et al., 2001)
Appendix F: Environmental Mobility Study (MSE/HKM, 2001)
Appendix G: Summary of Quality Assurance Activities (MSE, 2003)
Note: Appendixes A through G are available upon request from the MSE MWTP Program Manager.
Please refer to document number MWTP-216R1. Email: mse-ta@mse-ta.com, Phone: (406)494-7100.
Figures
Page
1-1. Joplin County Site Map 4
2-1. Test Plot Layout with Sampling Locations 12
2-2. Photographs of the Mill Waste-Soils Test Plot Site 13
Tables
1-1. General Trends in RBA of Pb, as Affected by Mineral Form 5
2-1. Laboratory Methods used in the Heavy Metals Phytoavailability Study 14
3-1. Statistical Uncertainty in Endpoint-Specific RBA Values 20
3-2. Uncertainty in RBA Point Estimates Combined Across Measurement Endpoints 20
3-3. Bioaccessibility Results forthe PA-Treated Soils from OU3 20
3-4. Laboratory Data for the Soil and Plant Samples Collected in June 2001 20
3-5. Laboratory Data for the Soil Liming Investigation Performed in July 2001 21
3-6. Numerical Criteria for Evaluating the Analytical Laboratory Results 21
3-7. Additional Criteria for Evaluating Toxic Effects of the CoCs on Plants and Herbivores 21
3 -8. Calculated CoC-Specific Concentration Factors for the Smelter- and Mill-Waste Test Plots 22
VI
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Acronyms and Abbreviations
ABA absolute bioavailability
As arsenic
AUC area under the curve
BAF bioaccessible fraction
Ca calcium
Cd cadmium
CF concentration factor
CoC contaminants of concern
DTPA-AB diphenylamine triamine pentaacetic acid-ammonium bicarbonate
EPA U.S. Environmental Protection Agency
EPA/NERL EPA:s National Exposure Research Laboratory (Las Vegas)
Fe iron
H3P04 phosphoric acid
ha hectare
ICP-AES Inductively Coupled Plasma-Atomic Emission Spectroscopy
IEUBK Integrated Exposure Uptake Biokinetic Model for Lead in Children
KC1 potassium chloride
kg kilogram
km kilometer
LSB leaf and stalk biomass
m meter
MDNR Missouri Department of Natural Resources
mg milligram
mg/kg milligrams per kilogram
MSE MSE Technology Applications, Inc.
MWTP Mine Waste Technology Program
NPL National Priorities List
O&M operating and maintenance
OU operable unit
P phosphorus
Pb lead
PA/KC1 phosphoric acid/potassium chloride
PbAc lead acetate
PbB blood lead levels
QA/QC quality assurance/quality control
QAPP quality assurance project plan
RBA relative bioavailability
ROD Record of Decision
SBRC Solubility/Bioavailability Research Consortium
SRC Syracuse Research Corporation
UB upper bound
Mg microgram
Mg/dL micrograms per deciliter
//m micrometer
UM/VMDL University of Missouri (Columbia), Veterinary Medical Diagnostic Laboratory
VMDL Veterinary Medical Diagnostic Laboratory
XRF X-ray Fluorescence Spectrometer
Zn zinc
vn
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Acknowledgments
Work was conducted through the DOE National Energy Technology Laboratory at the Western
Environmental Technology Office (WETO) under DOE Contract Number DE-AC22-96EW96405.
This document was prepared by MSE Technology Applications, Inc. (MSE) for the U.S. Environmental
Protection Agency's (EPA) Mine Waste Technology Program (MWTP) and the U.S. Department of
Energy's (DOE) National Energy Technology Laboratory. Ms. Diana Bless is EPA's MWTP Project
Officer, while Mr. Gene Ashby is DOE's Technical Program Officer. Ms. Helen Joyce is MSB's MWTP
Program Manager.
The organization and execution of this project was a collaborative effort between many participants
without whom this project could not have been completed. Special appreciation is given to the following
individuals:
Mr. J. Keith Nolan (President, Lima Hill Mining Co.) for allowing access to and establishment of the
test plot on his property;
Mr. Mark Doolan (EPA Region VII, Remediation Project Manager, Joplin National Priorities List
Site) for arranging and obtaining funding for the in vitro bioaccessibility study;
Mr. Dave Mosby (Missouri Department of Natural Resources, Joplin Site Project Officer) for
participating in MSE document preparation, for implementing the field treatability study, and serving
as liaison between MSE and EPA/State of Missouri entities involved in this project;
Drs. Stan Casteel and John Yang et al. (University of Missouri, Columbia) for overseeing the in vivo
Pb bioavailability and soils characterization activities, respectively, plus participation in MSE
document preparation;
Dr. Ken Brown (EPA/National Exposure Research Laboratory) for overseeing the in vitro Pb
bioaccessibility study performed by Lockheed-Martin, plus participation in MSE document review;
Mr. Kevin Kissell (Manager, HKM Laboratory) for overseeing the analysis of test plot soil and plant
samples, and follow-on soil liming investigation;
Dr. Vicki Lancaster (Neptune and Company, Inc.) for her critical review of the draft (September
2002) report, and suggestions offered for improving the statistical analysis of the VMDL data sets;
and
Dr. Bill Brattin et al. (Syracuse Research Corporation) for their timely responses to Dr. Lancaster, and
expert reanalysis of the pig dosing data.
In addition to the people listed above, the following agency and contractor personnel contributed their
time and energy in completing this project: Norma Lewis and Lauren Drees, EPA/National Risk
Management Research Laboratory; Gene Ashby, DOE/WETO; and Helen Joyce, Aleta Richardson,
Miriam King, and Pam Mullaney, MSE.
Vlll
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Executive Summary
Mining, milling, and smelting lead/zinc/cadmium (Pb/Zn/Cd) ores in and around Joplin, Missouri over
the past century have resulted in significant adverse impacts to land and water resources in this area. The
Joplin site was assigned final listing on the Superfund National Priorities List in August 1990, and various
investigations have been underway since 1991. Given that unacceptably high blood lead (PbB) levels
have been observed in young children residing near the old workings, a considerable effort has been made
regarding the reduction of soil-based Pb (and Cd) health threats to this population. The June 1996 Record
of Decision identified a number of remedial responses to residential soils contaminated by smelter
emissions within Operable Unit (OU) 2 or by mining/milling-related wastes within OU3. The major
components of the selected remedy included:
excavation and replacement of residential yard soils, with haulage of the excavated soils to a
constructed repository;
conducting a phosphate stabilization treatability study; and
phosphate stabilization of contaminated residential soils if treatability study results are positive.
Previous (1995-1999) investigations indicate that Pb bioavailability in soils contaminated by particulate
fallout (from the historic Eagle-Picher smelter) could be lowered via addition of 1% by weight phosphoric
acid (PA) plus 0.05% potassium chloride. Although these results were encouraging, it was not clear
whether they could be applied to the mine waste-affected soils. Such uncertainties arise, in part, from
potential differences in the types and/or levels of the different minerals (e.g., cerussite) produced by
weathering of smelter fallout versus residual ore particles. As funding from EPA Region VII was not
available to continue these investigations, the follow-on research regarding mine waste-affected soils was
supported by the Mine Waste Technology Program (MWTP).
The study's goal is to evaluate whether PA treatment can reduce the relative bioavailability (RBA),
bioaccessibility, and phytoavailability of Pb in mine waste-contaminated soils at the Joplin, Missouri NPL
site. The RBA of Pb is determined by measuring Pb levels in various tissues from young pigs following
ingestion of a known quantity of Pb in treated or untreated soil, as compared to Pb levels observed in
tissues following ingestion of a known quantity of lead acetate (PbAc). For example, a RBA of 50%
means that one-half of the Pb in soil was absorbed equally as well as lead from PbAc, while the
remaining one-half behaved as though it was not available for absorption. Lead bioaccessibility
assessments use an in vitro approach that estimates the amount of Pb that would probably be released
from a particular soil as it proceeds through a mammalian gastrointestinal tract. Phytoavailability pertains
to comparison of metals levels in collocated rooting zone soil plus leaf and stalk biomass (LSB) samples
collected from sites treated or not treated with PA. Metals levels in LSB are also evaluated regarding
potential risk to herbivores consuming such plant material. Conventional sampling and analytical
methods are used to generate the metals data. Soil and plant phytotoxicity plus herbivore "tolerance"
(plant toxicity) values from the literature are then used to prepare a screening level assessment of
potential adverse effects (and subsequent impact mitigation by PA-treatment) to the area's plants and
herbivores.
The specific study objectives are focused on whether PA treatment lowers:
Pb-RBA by 25% (compared to RBAs in untreated mine waste soils), which approximates the
minimum RBA reductions observed during PA-treatment of smelter-affected soils;
ES-1
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Pb bioaccessibility by > 25%, assuming a general correspondence between the in vivo (pig dosing)
and in vitro (soil extraction) results; and
overall mobility of the target metals (Cd, Pb, Zn) from soil-plant-herbivore, to achieve an
environmentally beneficial result.
With one notable exception, the methods used in the smelter soil and mine waste studies were essentially
the same. Given the potential for greater Pb bioavailability in mine waste-contaminated soils, the lower
dose of PA was increased from 0.5% to 0.75% by weight. The critical difference was the attempted
streamlining of the pig dosing study via comparison of Pb-RBAs in 0.75 vs. 1.0% PA-treated soils, only.
It was assumed that Pb-RBA in untreated (0% PA) mine waste soils would be > to that observed in
untreated smelter-affected soils. The consequence of this deviation from earlier work is presented and
discussed below.
The MWTP-related test site was located in July 2000 on an historic mill tailings impoundment situated
3.6 kilometers northeast of Joplin. The 3 PA treatments (0%, 0.75%, and 1% by weight) were applied to
test plot soils in mid-October 2000; a randomized block design was used with four 2-by-4-meter
vegetated plots per treatment. After adding hydrated lime, treatment-specific pH was monitored between
October and February 2001. Although pH of the treated soils was below the target range (i.e.,
approximately 5.3 versus >6.5), budget and time constraints resulted in sampling these materials in mid-
March. Composite soil samples (one per treatment) were prepared by the University of Missouri:s
Geological Sciences Department; these materials were then given to the University:s Veterinary Medical
Diagnostic Laboratory (VMDL) for use in pig dosing and to EPA:s National Exposure Research
Laboratory (NERL) at Las Vegas, Nevada, for the in vitro (bioaccessibility) studies. Finally, treatment-
specific composite soil and LSB samples were collected in mid-June 2001 and sent to the HKM
Analytical Laboratory for analysis. All results from these various investigations were received at MSE
Technology Applications, Inc., by late September 2001.
Shortly thereafter, EPA Region VII personnel determined that use of PbAc only as the experimental
control in the Pb-bioavailability study produced too much uncertainty (in the results) to support
defensible decision-making. Thus, VMDL performed a second pig dosing study in December 2001-June
2002; this investigation used untreated soil from the test plot and one dosing level of PbAc. However,
independent statistical review (during the winter of 2002-2003) challenged the comparability of the
results from the two pig soil-dosing studies. The principal concerns were that:
the data tended to be heteroscedastic (i.e., tissue lead levels increased in variability with increasing
dose of Pb in soil); and
such occurrence indicated that the data reduction process used originally (i.e., ordinary least squares
regression) was not appropriate.
Subsequently, Syracuse Research Corporation (SRC) reanalyzed the two data sets using improved data
reduction methods (e.g., weighted least squares regression). They also performed qualitative and
quantitative evaluation of the uncertainty associated with the estimates of Pb-RBA in treated and
untreated soils from these two studies.
Table E-l presents the best estimate (BE) plus 2.5% lower bound (LB) and 97.5% upper bound (UB)
RBA values for each of the 4 measurement endpoints. These results utilized all of the data from the 2
ES-2
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VMDL studies, with no exclusion of outliers (i.e., data points outside the 95% prediction interval). The
data set for each endpoint was fit to either a linear model (i.e., response = a + b * dose) or nonlinear
model [response = a + c*(l- exp (- d * dose))] as judged appropriate by Syracuse Research
Corporation.
Table E-l. Statistical uncertainty in endpoint-speciflc RBA values.
%RBA Relative to Lead Acetate
Untreated (0% PA) Soil
Measurement Endpoint
Blood Lead Area Under the
Curve (AUC)
Liver Lead
Kidney Lead
Bone Lead
BE
40
17
16
35
LB
32
10
9
26
UB
48
25
23
45
0.75% PA-Treated Soil
BE
47
28
35
34
LB
36
21
27
27
UB
61
38
44
44
1.0% PA-Treated Soil
BE
40
21
21
25
LB
28
15
15
20
UB
56
28
28
32
Source: SRC, 2003, Table 5 (see Appendix D).
Inspection of these results indicates that the confidence bounds for treated and untreated soils overlap
considerably for each endpoint. Furthermore, with the possible exception of bone lead, there is no
indication of a trend towards lower RBAs as a function of PA-treatment level.
The variabilities within endpoints (above) were then integrated so as to estimate the uncertainties in
RBAs between treatments. These calculations were accomplished via:
use of professional judgment to assign RBA weights of 9/12 to blood lead and 1/12 each to liver,
kidney, and bone; then
perform Monte Carlo simulations in which a value for RBA is drawn from the uncertainty
distribution for each endpoint with a frequency proportional to the weight assigned to that endpoint.
Each uncertainty distribution was assumed to be normal, with known mean and standard deviation (e.g.,
the endpoint-specific BE values in Table E-l).
The uncertainty ranges in the Pb-RBA for each soil treatment level, estimated by Monte Carlo analysis as
described above, are summarized in Table E-2. Inspection of these results shows no reduction in RBA
due to PA-treatment of the mine waste soils.
Table E-2. Uncertainty in RBA point estimates combined across measurement endpoints.
% RBA Relative to Lead Acetate
Treatment Level
Untreated (0% PA)
0.75% PA-Treated
1.0% PA-Treated
2.5th
13
26
18
Mean
36
43
36
97.5th
48
58
51
Source: SRC, Table 6 (see Appendix D).
Therefore, the data from the two relevant VMDL pig dosing studies are not sufficient to conclude that
PA-treatment of mine waste-contaminated soils had any particular effect on Pb-RBA. Subsequently, it
cannot be determined presently whether the objective of 25% reduction in RBA was met by the given PA
treatment levels.
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The Pb bioaccessibility results from the EPA/NERL in vitro study are more encouraging than those from
the VMDL's in vivo investigations. The extractable Pb concentrations in 0.75% and 1.0% PA-treated
soils were 997 and 931 mg/kg, respectively, versus 2,105 mg/kg in untreated soil. These concentrations
exceed the objective of reducing Pb bioaccessibility by a factor of 2 (i.e., > 50% versus > 25%).
The major findings for the heavy metals phytoavailability study are as follows:
1% PA treatment of mine waste-contaminated soils is probably sufficient to mitigate Cd and Pb
phytotoxicities in tall fescue, but not necessarily for Zn, even in soils with paraneutral pH (6.9-7.2);
only Zn appears to occur at levels in LSB that may pose a chronic ingestion hazard to domestic or
wildlife herbivore species (i.e., > 1,100 versus > 500 mg/kg); and
Cd:Zn ratios of < 1:100 in PA-treated soils probably mitigates any food chain Cd transfer concern.
These findings are based upon a follow-on laboratory study (performed in Butte) that simulated metals
phytoavailability in P-treated soils exhibiting the target pH (> 6.5). In this investigation, the pH of treated
test plot soils was raised from about 5.3 to about 6.9 via addition of lime kiln dust. The soils were then
extracted and analyzed in the same manner as done for the as-received (acidic) samples from the test plot.
Thus, the qualitative objective of achieving an "environmentally beneficial" result via PA treatment of
these soils was met.
In conclusion, interpretation of RBA data from the MWTP-funded pig soil-dosing studies is substantially
limited by the lack of simultaneous testing of treated and untreated soils within the same study. The
consequent loss of statistical power precludes quantitation of any reduction in Pb-RBA due to PA
treatment of mine waste-contaminated soils. However, it should be noted that:
there is a consistent tendency for RBA to be somewhat lower in the 1% PA-treated soil than in the
0.75% PA-treated soil; and
given the unusually low absorption of Pb (into pig tissues) from untreated mine waste soil, the RBA
in such soils may be higher than that estimated by VMDL for the MWTP study.
The latter point is supported by a previous (1996) investigation by VMDL, wherein young pigs were
dosed with three different soil types (including those contaminated by mine/mill wastes) from the Joplin
Superfund site. The Pb-RBA results from such testing varied between 58% to 83%. If untreated mine
waste soils indeed exhibit RBAs in this range, it would add credence to both NERL's bioaccessibility
study results and observations of reduced Pb levels in LSB from plants grown in 1% PA-treated soils.
Therefore, further evaluation of whether > 1% PA treatment of mine waste soils actually lowers Pb-RBA
in young pigs, and environmental mobility of Pb in general, appears to be justifiable. Such investigations
should include: direct comparisons of RBAs from pigs dosed with treated or untreated soils (plus pigs
dosed with the full suite of PbAc controls); comparisons of Pb bioaccessibility in PA-treated vs. untreated
soils; and heavy metals phytoavailability study for PA-treated soils having rooting zone pH values of
>6.5.
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1. Introduction
1.1 Project Background
1.1.1 Site History
Heavy metals levels present in residential soils
affected by historic mining, milling, and smelting
activities have been identified as posing significant
threats to human health and the overall
environment at a number of Superfund National
Priorities List (NPL) sites located throughout the
United States. The Oronogo-Duenweg Mining
Belt NPL site is one such instance, being an
inactive lead (Pb) and zinc (Zn) mineral
processing area situated in the southwestern corner
of Jasper County, Missouri (Figure 1-1). Mining
operations began in the Joplin townsite in 1870
with subsequent establishment of numerous ore
milling plus Pb and Zn smelting plants thereafter;
Pb production occurred at the Eagle-Picher
Smelter facility located within the northwestern
corner of the city until the 1970s. Particulate
fallout from smelter emissions resulted in soils
contamination extending predominantly in the
southeastern direction to a distance of
approximately 3.6 kilometers (km), essentially
bounding Operable Unit (OU) 2 (Residential Yard
Soils) of the NPL site. In addition, many other
residences (within and adjacent to Joplin) exist on
or near sites contaminated by mining and milling
wastes; these residences are aggregated under
OU3 (Mine Yard Wastes). Because of the
occurrence of elevated blood lead levels (PbB)
>10 micrograms per deciliter (jWg/dL) in children
less than 7 years of age, residential soils
containing > 800 milligrams per kilogram (mg/kg)
Pb or >75 mg/kg cadmium (Cd) in the upper
12 inches or >500 mg/kg lead (Pb) in the upper
18 inches of garden soils have been excavated and
hauled to nearby repositories. The potential cost
for completing these activities, including
replacement of clean soils, has been estimated to
be $28.6 million [and annual operating and
maintenance (O&M) costs at approximately
$113,000]. Because of the magnitude of such
costs, the U.S. Environmental Protection Agency
(EPA) Region VII and the State of Missouri are
investigating the use of phosphate-based, in situ
stabilization of heavy metals as an alternate
treatment approach. In fact, the June 1996 Record
of Decision (ROD) states that such treatment is
preferable (within OUs 2 and 3), if it can meet the
nine criteria associated with selecting a cleanup
remedy. If implemented, total construction cost
savings could vary from $5 to $24 million,
depending upon the extent that this technology is
applied; annual O&M costs savings are estimated
to be approximately $70,000 (Ref 1).
1.1.2 Bioavailability and Bioaccessibility of
Lead (Definitions)
Bioavailability refers to that portion of a substance
contacting a body portal-of-entry (e.g., via lungs,
gastrointestinal tract, skin) that is then
incorporated into the blood stream (Ref. 2).
Bioavailability is also described as absolute or
relative (Ref.3). Absolute bioavailability (ABA) is
the amount of a substance entering the blood via a
particular route of exposure (e.g., gastrointestinal)
divided by the total amount administered (e.g., soil
lead ingested). Relative bioavailability (RBA) is
indexed as measuring the bioavailability of a
particular substance (e.g., lead carbonate or
phosphate) relative to the bioavailability of a
standardized reference material (e.g., water soluble
lead acetate).
Essentially, bioavailability testing involves dosing
of test animals (e.g., rats, pigs) with a known
amount of the substance of concern per unit body
weight per day (e.g., 100 /u,g PbCO3/kg»d) over a
defined interval of time. Sampling and subsequent
analysis of biological materials obtained during
(e.g., venous blood) and after (e.g., kidney, bone)
the dosing period provides the data necessary for
estimating in vivo bioavailability of the test
substance. Examples of Pb RBA determinations
using rats and young pigs, via oral route of
exposure, are found in References 4 and 5,
respectively.
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Determination of risk-based cleanup levels for Pb-
contaminated soils, that are protective of young
children:s health (<6 years of age), is often
dependent upon output from the Integrated
Exposure Uptake Biokinetic Model for Lead in
Children (IEUBK, Ref 6). For the IEUBK model,
soluble Pb in water and food is estimated to have
50% ABA. Furthermore, the model presumes that
ingestion of Pb in soil results in a RBA of 60%.
Thus, the ABA would be (0.60 x 0.50) or 30%.
However, particle size distribution [particularly
those <250 micrometers (^m) in diameter] and
physicochemical form(s) of Pb present in a given
soil material exert considerable influence on Pb
bioavailability. These parameters have been used
to explain PbB levels observed in children residing
at various Pb mining and smelting sites (e.g., Refs.
7 and 8). EPA Region 8 performed studies
wherein Pb-contaminated soils were fed to young
pigs; the observed trends in Pb RBA are presented
in Table 1-1 (Ref. 2).
In vitro methods have been developed for
measuring the portion of Pb solubilized from soil
materials under simulated gastrointestinal
conditions (e.g., Ref. 9). These results, often
referred to as the bioaccessible fraction (BAF), are
thought to be an important determinant of
bioavailability. Thus, BAF is not necessarily equal
to RBA but depends on the relation between
results from a particular in vitro test system and an
appropriate in vivo model/test animal.
The in vitro tests simulate the gastrointestinal
environment via sequential extraction of Pb (from
soil, etc.) using strong acid and paraneutral
aqueous solutions; these fluids mimic the pH
conditions found in the stomach and small
intestine, respectively. The extract is filtered
(0.45 pm) and then analyzed for its Pb content.
The mass of Pb found in the aqueous phase,
divided by Pb mass introduced into the test,
represents the sample-specific BAF. To date, for
Pb-contaminated soils tested in the EPA pig
studies, the in vitro method has correlated well
with the RBA values (Ref. 10).
1.1.3 Previous Soil Remediation Studies
As part of the EPA:s Remediation Technologies
Development Forum (RTDF), the In-Place
Inactivation and Natural Ecological Restoration
Technologies (IINERT) Soils-Metals Action Team
has been evaluating the reduction of Pb mobility
and bioavailability at Joplin since May 1996. A
consortium of federal agencies, academic
institutions, and private-sector consultants has
established an integrated program of laboratory
and field experiments associated with treatment of
the smelter-contaminated (OU2) soils. In
particular, a 1-acre [0.40 hectare (ha)] test site has
been developed approximately one-quarter of a
mile [1550 meters (m)] west of the Eagle-Picher
Smelter works (Figure 1-1). Randomized block
treatments using various combinations of
phosphorus compounds, iron, and organic matter
(as well as at different rates of applying these
materials) have been applied by various means to
the 2-by-4-m plots within the test site. These field
studies were tied to various laboratory
investigations performed elsewhere, including
those implemented at the University of Missouri
(discussed below).
Laboratory treatment of OU2 soils involved
adding of phosphoric acid (H3PO4; PA) at rates of
0, 1250, 2500, 5000 and 10,000 milligrams (mg)
of P/kg soil, plus constant additions of potassium
chloride (KC1) at 500 mg Cl/0.75 kg soil. The
reaction was followed by measurements of Pb
bioaccessibility, solubility products, and electron
microprobe analyses. Key results are summarized
below, while details of the study are reported in
Yang et al. (Ref. 11):
the mean bioaccessible Pb concentrations in
control and 1% PA-treated soils were 1789
and 564 mg/kg respectively, after 70 days
incubation at room temperature (i.e., a 68%
reduction in bioaccessibility);
the microprobe analyses indicated formation
of a chloropyromorphite-like mineral [Pb5
(PO4)3C1]; wherein
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the calculated and standard solubility products
(-log k = 21.0 and 25.0, respectively) suggest
the reaction product is slightly more soluble
and without the crystalline form associated
with the pure compound; and
the mean Pb concentration in the sand fraction
of the 1% PA-treated soils increased from
3,483 to 6,136 mg/kg (i.e., 46% of total Pb
versus 24% in untreated soil), probably due to
Pb transformation into larger particles of
amorphous-to-crystalline chloropyromorphite.
Collectively, these observations indicated the
potential of phosphoric acid/ potassium chloride
(PA/KC1) as a cost-effective means of in situ
treatment of Pb smelter-contaminated soils.
Phosphoric acid treatments were administered to
certain test plots at the IINERT test site in March
1997, and studies continued there through October
1998. Details pertaining to physicochemical
characteristics of the soils, summaries of the field
and laboratory methods used, and key results are
presented in Appendix A (Ref. 12). The principal
conclusions from these efforts are that:
0.5 to 1.0% by weight (w/w) applications of
PA/KC1 can reduce Pb RBA by 26-38%,
respectively, relative to RBAs in untreated
soils (and probably within 90 days of field
treatment); and
1% PA treatment reduces Pb uptake into
aboveground plant biomass by about 73%,
although it has no significant effects on uptake
of Cd or Zn, relative to metals levels in plants
grown in untreated soils.
Thus, the field studies also demonstrate that in situ
PA/KC1 applications can be an effective remedial
technology for cleanup of Pb smelter-effected
soils.
However, further research is needed to assess the
efficacy of such treatments of soils contaminated
by mine/mill wastes (in OU3), as Pb RBA in these
materials has been measured up to 80% (Ref. 13).
Such elevated bioavailability levels may be due to
greater amounts of cerussite (i.e., lead carbonate
either naturally occurring or as a weathering
product of lead sulfide) relative to that found in
smelter-contaminated soils. As funding from EPA
Region VII is not available to continue these
investigations using soils from OU3, the follow-on
research was supported by EPA's Mine Waste
Technology Program (MWTP).
1.2 Project Objectives
The overall purpose of this project was to assess
the effect of PA/KC1 additions on the RBA of
lead in OU3 soils at the Joplin, Missouri NPL Site.
More specifically, the primary objective of the
field demonstration project was to achieve an
average 25% reduction in Pb RBA in PA/KC1-
treated soils from OU3, as compared to Pb RBA in
untreated soils contaminated by mine/mill wastes
(Ref. 14). This evaluation was performed in vivo
by dosing young pigs with PA-treated soils from
the test plot.
1.2.1 Assess Reduction of Lead
Bioavailability in Test Soils
The project is a technology demonstration effort
rather than an initiation of on-site remediation of
the Joplin site. However, the project will develop
technical information on the ability of the P-
addition technology to treat residential soils
contaminated by historic mining and milling
activities at this site. Therefore, the envisioned
results will contribute to the ultimate cleanup of
the Joplin site and surrounding area. Reduction in
Pb availability should allow higher soil Pb levels
to remain in residential soils, yet comply with the
National Contingency Plan's two threshold criteria
(i.e., be protective of public health and comply
with Applicable or Relevant and Appropriate
Requirements) for selecting a cleanup remedy at
Joplin.
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1.2.2 Assess Reduction of Lead
Bioaccessibility in Test Soils
An in vitro test was also be used to analyze the
treated soil samples from the site. The purpose of
this testing was to compare these results to those
of in vivo testing to determine whether or not the
results are comparable. Previous studies have
collected similar comparative data. Data from this
study will be added to the overall EPA Region
VII/VIII data base, which could eventually be used
instead of routine in vivo testing.
1.2.3 Assess Reduction of Heavy Metals
Phytoavailability in Test Soils
A third criterion is the reduction of actual or
potential metals uptake of Pb, Cd, and Zn in
residential soils at Joplin. Such reductions will be
assessed through measurements of plant
available/extractable levels of these contaminants
from soil solution and analysis of acid-extractable
metals levels found in aboveground plant biomass
collected from the test plot site.
SCALE 1:100 000
A = Smeller Soils Test Site
= Mine/Mill Waste Soils Test Site
Figure 1-1. Joplin County site map.
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Table 1-1. General trends in RBA of Pb, as affected by mineral form.
Potentially Lower Unavailability Intermediate Bioavailability Potentially Higher Bioavailability
(RBA<25%) (RBA = 25%-75%) (RBA >75%)
Galena (PbS) Pb Oxide (PbO) Cerussite (PbC03)
Anglesite (PbSO4) Pb-Fe-Oxides Pb-Mn-Oxides
Pb-Metal Oxides (Pb-M-Ox) Pb Phosphates/Slags
Native Lead (Pb°)
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2. Methods
This section summarizes the design and
implementation of the field and laboratory
activities associated with this project. Essentially,
the methods and protocols developed previously
for the smelter soils-PA treatment study (see Refs.
11 and 12) were applied to the soils contaminated
by Pb mine/mill wastes. Key on-site support was
provided by Mr. David Mosby from the Missouri
Department of Natural Resources (MDNR)
Hazardous Waste Program (Jefferson City,
Missouri). Mr. Mark Doolan, EPA Region VII:s
Remedial Project Manager for the Joplin NPL
Site, also provided technical and administrative
support in executing the present study (Ref 14).
Dr. Stan Casteel of the University of Missouri
(Columbia), Veterinary Medical Diagnostic
Laboratory (UM/VMDL) was the principal
Investigator for the in vivo Pb bioavailability
studies that dosed young pigs with soils collected
from the field test plot at Joplin. Physicochemical
characterization (including Pb speciation) of these
soils was overseen by Dr. John Yang of UM:s
Department of Geological Sciences. The in vitro
Pb bioaccessibility extractions and subsequent
analyses of the treatment-specific soils were
performed by Lockheed-Martin and their contract
laboratory, respectively. This work was overseen
by Dr. Ken Brown, Director of the Technical
Support Center at EPA:s National Exposure
Research Laboratory (EPA/NERL), Las Vegas,
Nevada. Mr. Kevin Kissell, Manager of HKM
Analytical Laboratory (Butte, MT), led the
extractions and subsequent analytical work
pertaining to estimation of plant availability of
select heavy metals in test site soils, as well as
contaminant uptake into plant biomass from these
soils. Interpretation of the HKM data was
performed by MSE Technology Applications, Inc.
(MSB).
2.1 Field Investigations
2.1.1 Experimental Design
The test site layout with plot-specific sampling
locations is presented in Figure 2-1. Before
beginning the treatment stage, a field XRF
spectrometer was used to establish a baseline for
Pb variability. X-ray fluorescence sampling
locations are denoted by an "X" on Figure 2-1.
The plots were laid out in randomized block
design with four replications for each of the three
treatments:
Treatment A = 10 g H3PO4 + 5 00 mg KC1 per
kilogram of soil;
Treatment B = 7.5 g H3PO4 + 500 KC1 per
kilogram of soil; and
Treatment C = no H3PO4 or KC1.
Treatment C represents the control. After
approximately 5 months of treatment, samples
were collected from five locations within each 2-
by 4-m test plot at locations denoted as "" in
Figure 2-1. These five samples were composited
to obtain one representative sample from each test
plot. The four samples from each treatment were
then composited, resulting in three final samples:
Composite A, Composite B, and Composite C.
These samples were submitted to the UM/VMDL
for in vivo Pb bioavailability studies in young
swine and to EPA-NERL for in vitro
bioaccessibility tests.
After 8 months of treatment, the sampling was
repeated in the same fashion for submittal of soil
samples to the HKM Analytical Laboratory for
analysis. At that time, samples of fresh leaf and
stalk biomass (LSB) were also collected and
submitted to the HKM Analytical Laboratory to
determine the plant uptake of metals during the
study.
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2.1.2 Implementation of Field
Investigations
Mr. Mosby identified a suitable site for the PA
treatment study in mid-July 2000. The site was
located within a historic mill tailings
impoundment, approximately 4.8 km northeast of
Joplin in the SW 1/4NE1/4NE1/4 of Section 29,
R32W T28N. An organic-rich horizon of soil 5-
15 cm thick had developed over the top of
flotation tailings that had a fine-sand to silty
texture. MSB signed an access agreement with the
landowner, Lima Hill Mining Company, in late
August; NEPA compliance approval to proceed
was received from the U.S. Department of
Energy/National Energy Technology Laboratory
(DOE/NETL) in early September 2000.
Before installing treatment plots, site metal
concentrations were characterized with a
Spectrace 9000 XRF to ensure that lead
concentrations were within the desired range. XRF
measurements were made in situ without sieving
or other sample preparation. Lead concentrations
within the selected area ranged from 1,800 to
5,000 mg/kg soil.
A total of 12 treatment plots were installed in
October 2000. Two treatments plus one untreated
control were installed with four replicates for each
treatment (Figure 2-1). Each plot was 2x4 meters
in area. Plots were installed by measuring the
areal dimensions of the treated area, trenching to a
depth of 15 cm around the borders of plots, and
installing 25-cm plastic edging to prevent
splashing of reagents between plots.
After the plots were installed, additional XRF
measurements were made. Lead concentrations
ranged from 1292 to 4375 mg/kg, with a mean
2767 mg/kg. Other important metals detected at
significant concentrations by the XRF include
calcium (Ca), Zn, and iron (Fe). Zinc ranged from
24,510 to 6780 mg/kg, with a mean of 16,128
mg/kg. Iron ranged from 40,830 to 16,770, with a
mean of 32,358 mg/kg. Calcium ranged from
41,750 to 4,790 with a mean of 20,286 mg/kg.
Pretreatment soil characterization was beyond
MDNR:s contract scope of work. Therefore, the
PA application rates were predetermined from
earlier treatments made on smelter-contaminated
soil in Jasper County. The smelter-contaminated
soil PA treatments were applied at 0.5% and 1%
phosphorus (P) as PA (Section 1.1.3). Based on
the high concentrations of Zn and Fe associated
with XRF readings from the mill waste-
contaminated plots, a field decision was made that
the 0.5% P as PA treatment was not high enough
to supply ample free phosphorous for the reaction
with Pb. Zinc, Fe, and Ca will compete with Pb in
the reactions with P (Ref 12). The lower
concentration of P was, therefore, increased to
0.75% as PA.
Phosphoric acid treatments were applied to the
field soils using fertilizer grade (85%) PA
(obtained from Farmens Chemical Co. in Joplin,
MO). Soils were treated to a depth of about 15
cm. About 37.8 L of H3PO4 were applied to each
1% PA plot, and 28.4 L of H3PO4 were applied to
each 0.75% PA plot. About 1.66 kg of fertilizer
grade (45%) KC1 was applied to each PA plot.
The plots were rototilled before applying treatment
reagents. KC1 and half the volume of PA was
added to each plot and rototilled into the soil,
followed by adding the remaining half of the PA,
followed by further rototilling. A minimum of
three passes with a hand rototiller was made for
each half volume of PA. The soil was moist, but
sufficiently dry to till without forming significant
clods.
Soil pH was measured 14 days post-treatment on
composite samples of a 1:1 deionized water
suspension from soil collected 0-15 cm deep. For
the 1% PA plots, pH was 3.94; 4.55 for the 0.75%
PA plots; and 7.58 for the control plots. Hydrated
lime [Ca(OH)2] was added to the plots to raise
target soil pH to 6.5-7.0 on the same day to
minimize mobilization of other metals. Lime was
added at a rate of 3080 mg Ca +2/kg soil [9.1 kg
Ca(OH)2] to the 1% PA plots, and 2310 mg
Ca+2/kg soil [6.9 kg Ca(OH)2] was added to the
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0.75% PA plots. A hand rake was used to work
the lime into the soil to a depth of about 10 cm.
Tall fescue (Festuca arundinacea) grass seed was
hand-planted in all treatment plots the day
following liming, 15 days after PA treatment.
A site visit was made in November 2000, 35 days
post-treatment. Fescue seeds had germinated in all
plots. Grass sprouts were most abundant on the
0.75% PA plots, and the least abundant on the
control plots.
Soil pH was measured on this date to ensure
sufficient lime was added to reach target pH.
Grass had sprouted on all treatment plots. Mean
soil pH (from 3 replicates) was 8.51 for 1% PA,
and 10.39 for 0.75% PA treatment plots.
Soil pH was again measured 50 days post-
treatment. Mean soil pH for the 1% PA was 8.22
and 5.61 for the 0.75% treatments.
The interpretation for this drastic pH change for
the 0.75% treatment was that the soil had not
enough time to reach equilibrium. The decision
was made to allow more time for soil pH to
stabilize and then re-measure in late winter 2001,
prior to the growing season. MSB and MDNR
agreed that, if soil pH had not approached the
target range by that time, then lime or additional
PA would be added to reach the target pH.
The pH of 1:1 deionized water:soil pastes was
measured on March 2, 2001: the soils were
collected from 0-15 cm below ground surface, and
plot-specific subsamples composited for each PA
treatment. For the 1% PA plots, the mean pH was
5.97 and 5.88 for the 0.75% plots; the control plot
pH was not determined. Given the goal of project
completion by September 2001, MSB directed
MDNR to forego any further adjustments in soil
pH, and composite samples were collected for the
bioavailability/bioaccessibility studies in late
March.
A plastic trowel was used to collect five
subsamples of soil (0-15 cm below ground
surface) from within each plot, placed in a plastic
bag, and then mixed. This process was repeated
until there were approximately 2 kg samples from
each plot (i.e.,12 total samples from the test site).
The samples were delivered to the University of
Missouri, Department of Geological Sciences, and
sample preparation activities commenced
immediately thereafter (Section 2.2.1).
Treatment-specific composite soil and LSB
samples were collected by MDNR for use in the
metals mobility/uptake studies in June 2001. The
soil samples were obtained via subsampling the 0-
15-cm rooting zone within each treatment-specific
plot and then mixing together materials from all
four plots to produce the treatment-specific
sample. Plant biomass samples (>3 cm above
ground surface) were collected in the same manner
as used for soils. The six (total) samples were
shipped by overnight delivery to MSB; the soil and
plant materials were then transferred to the HKM
Laboratory (Section 2.2.3).
Photographs of the test site environment are
presented in Figure 2-2.
2.2 Laboratory Investigations
The laboratory evaluation phase used samples
collected from the field test site to determine
whether project objectives were met and to assess
the overall success of the PA-stabilization
technology (Section 1.2). The laboratory
evaluation was oriented toward the following:
demonstrating reduction in Pb bioavailability
in mine/mill waste-contaminated soils to
young swine following soils treatment with
phosphoric acid + KC1 (in vitro studies);
using the Solubility/Bioavailability Research
Consortium (SBRC) in vitro extraction test (as
performed by EPA/NERL, Las Vegas) to
demonstrate reduction in Pb bioaccessibility,
and comparing these results to those from the
young swine study;
evaluating changes in Pb speciation (e.g., from
lead carbonate to chloropyromorphite)
following soils treatment with PA and KC1;
and
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evaluating changes in soil chemistry and
metals uptake by the LSB using the end-of-
season (test-site) samples.
2.2.1 In Vivo Lead Bioavailability Studies
2.2.1.1 First Investigation (June - September
2001)
The dosing of young pigs with Pb-contaminated
soils from the test plots followed the methods
previously approved by the toxicology staff of
EPA Region VIII (Ref 15), with one (critical, in
retrospect) exception. In an attempt to streamline
the pig dosing study, it was assumed that Pb-RBA
for untreated mine waste soils would be > that of
the smelter-affected soils (Section 1.1.3). Thus,
the initial study included only PA-treated soil
types plus PbAc controls. Formal compliance
with study protocols (Ref. 15) would have
combined the untreated (0% PA) soil type along
with each of the PA-treated soils (plus PbAc
controls). Given the capacity for conducting pig
dosing studies at VMDL, this approach would
have required two back-to-back (i.e., 0 + 0.75%
PA and 0 + 1.0% PA) investigations. Because of
the perceived need to complete the project by
September 2001, the project team decided to go
forward with only the one (limited) study.
Critical measurements included: total Pb levels in
soil; time course of pig weight, Pb dosage, and
PbB levels during the 15-day dosing period; and
Pb levels in kidney, liver, and femur tissues
following this period (Ref. 14). The detailed study
design is found in Section 2.0 of the report
prepared by Dr. Casteel et al. (Ref. 16; see
Appendix B).
Determination of Pb levels in soils, plus ancillary
agronomic soil measurements (e.g., cation
exchange capacity) and Pb speciation in soils,
were performed by Dr. Yang et al. as described in
Ref. 11. The materials used in the Pb
bioavailability and bioaccessibility studies were
prepared as follows:
soils samples from each plot were mixed, air-
dried, and ground to pass a 0.25-millimeter
mesh sieve;
equal amounts of materials from the four
replicate plots within each treatment were
composited and thoroughly mixed; and
subsamples of the treatment-specific
composites were then digested/analyzed for
Pb, as well as provided to Drs. Casteel and
Brown for their respective investigations.
Sample preparation was completed by early April
2001, and the in life phase of the pig dosing study
was completed by late April. Preparation and
chemical analysis of the various biological
samples, plus soil samples, occurred between mid-
April through late June, followed by data
validation/interpretation through late July. The
draft report was prepared during August and
September 2001.
2.2.1.2 Second Investigation (December 2001-
June 2002)
In response to EPA Region 7 and MDNR concerns
regarding lack of RBA data for untreated mine
waste soils, the Pb-dosing investigation was
extended into a second phase of activity.
In the second study, groups of five swine were
given target average doses of 75,225, or
675 Aig/kg day of Pb in untreated mine waste
soil, or 225 /kg day of Pb from PbAc.
Otherwise, the methods used were the same as in
the previous study (Appendix B).
The validated, tissue-specific Pb analytical data
were used to prepare best fit (linear or nonlinear)
dose-response equations for the PbAc reference
material plus untreated soil. Because only one
dose group was incorporated into this study for
PbAc, the study-specific results were combined
with PbAc results from many previous studies in
order to establish the dose-response relationship.
The RBA results for the untreated soil from this
investigation are discussed in detail in
Appendix C.
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2.2.1.3 Reevaluation of the VMDL Data Sets
The draft (September 2002) project report was
reviewed by EPA/MWTP personnel and their
contracted statistician, Dr. Vicki Lancaster
(Neptune and Company, Inc.), during November-
December 2002. In a letter report received by
MSB in mid-December, the following concerns
were expressed:
without defined confidence intervals for each
Pb-RBA estimate, one can not firmly conclude
whether or not phosphate addition to mine
waste soils produced a meaningful treatment
effect; and
because the analytical data tended to be
heteroscedastic (i.e., the variability of Pb
levels in pig tissues increased as the Pb-in-soil
dosage increased), use of ordinary least
squares reduction for data reduction was not
appropriate.
After several months of intermittent discussions
between EPA and MSB, Dr. Bill Brattin et al. of
SRC were procured in late March 2003 to address
the above issues. As a result of numerous verbal
and written communications between EPA/Dr.
Lancaster, SRC and MSB personnel, the following
improvements were made to the (original) data
reduction approach:
to better accommodate the heteroscedastic
nature of the data sets, weighted least squares
regression was applied, where the weight
assigned to each data point in a dose group is
equal to the inverse of the variance in
responses for all animals in that exposure
group;
to better meet the specific requirements of the
linear or nonlinear modeling efforts, data sets
for reference and test material were fitted
simultaneously rather than step-wise;
fewer data points were excluded from analysis
via re-defining outliers at those data points
having standardized weighted residual of > ± 3
(vs. those outside the 95% confidence
intervals, as used before);
fiduciary limits for quantitative estimation of
uncertainty for each RBA value were
determined using Fieller's theorem; and
occasional use of linear model for fitting
nonlinear dose-response data (i.e., blood
AUC) in those cases wherein the dataset did
not extend far enough to define the shape of
the curve, or to define the plateau value with
confidence.
Details pertaining to the statistical methods
applied to the VMDL data sets, and derivation of
the uncertainty limits requested by EPA/MWTP,
are presented in Appendix D.
2.2.2 In Vitro Bioaccessibility Study
This study used EPA-approved sample extraction
(Ref 10) and analysis (Ref 17) methodologies,
plus quality assurance/quality control (QA/QC)
guidance (Ref. 18), that were prepared by or for the
SBRC. Essentially, the extraction step uses 100
milliliters of pH 1.5 fluid (prepared using
concentrated hydrochloric acid and containing 0.4
moles/liter glycine) and 1.0 grams of soil. The
mixture is placed in a 125-milliliter high-density
polyethylene bottle, sealed, and then shaken at 30
revolutions per minute for 1 hour at 37 °C on a
modified TCLP extractor. Assuming maintenance
of the above pH, the solution is passed through a
0.45-jwm disk filter, and the filtrate is stored at
4 °C until analyzed. The solution is then analyzed
for arsenic (As) and Pb contents using ICP-AES
(SW846-6010B), ICP-MS (SW846-6020), or ICP-
hydride (SW846-7061A), as appropriate (Ref. 19).
Treatment-specific, composite soil samples were
prepared by the University of Missouri (Dr. Yang
et al.) and then sent to Dr. Brown, EPA/NERL, in
April 2001. The samples were extracted in late
July and analyzed in early August, with the results
reported in late September.
2.2.3 Heavy Metals Phytoavailability Study
This study used methods that were either
developed or approved by the EPA for evaluating
heavy metals uptake into aboveground plant
biomass. The methods used by the HKM
10
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Analytical Laboratory in completing their scope of
work are summarized in Table 2-1.
The soil and plant samples were received from Mr.
Mosby (MDNR) at the HKM Analytical
Laboratory on June 15, 2001; analytical results
were received by MSB on July 11 and forwarded
to Mr. Mosby the next day. Following a review
and discussion of the data on July 23, additional
sample processing and tests were ordered that day.
The pH of the as-received, PA-treated soil samples
was in the 5.2-5.4 range; as noted in Section 2.1.2,
the target soil pH is 6.5-7.0. Thus, the purpose of
the additional testing was determination of plant
available (DTPA-AB extractable) levels in PA-
treated soils having the "optimal" pH of > 6.5.
The data from this second round of work were
received at MSB on August 10, 2001 and
transmitted to MDNR shortly thereafter.
11
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TEST
PLOT
LAYOUT
TEST SITE BOUNDARY
2m x 4m TREATMENT PLOTS
A= TREATMENT 1
(I0g H3K> 4 5GOmg KCL/Kg SOIL)
Q= TREATMENT 2
(5g HuPQ, 4 5QGmq KCL/Kq SOIL)
C= CONTROL
(NO HsPO< OF KCL)
4 REPLICATIONS OF EACH TREAT ME NT /CONTROL
':<- DENOTES APPROXIMATE SAMPLE LOCATIONS
FOP XRF SAMPLING WORK.
DETAIL
- DENOTES APPROXIMATE COMPOSITE LOCATIONS
FOP EACH TEST PLOL THE 5 SAMPLES FROM
EACH TEST PLOT WILL BE COMPOSITED, THE
4 COMPOSITE SAMPLES FOR EACH TREATMENT
WILL THEN BE COMBINED TO RESULT IN 3 SAMPLES:
COMPOSITE A, COMPOSITE B & COMPOS FT E C.
S f
. TA. IHC.
PP3MZ01
PEV: - 2/9/QO
DPAF1EP: KJB3
Figure 2-1. Test plot layout with sampling locations.
12
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Figure 2-2. Photographs of the Mill Waste-Soils Test Plot Site (source: D. E. Mosby,
June 2001).
13
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Table 2-1. Laboratory methods used in the heavy metals phytoavailability study.
Parameter HKM Standard Source Comments
Operating (detailed method)
Procedure
Preparation of SP00388/389 Ref. 20, Chap. 28 Produces soil particles <2 mm and
soil/plant materials plant particles <0.85 mm.
1:1 pH/Eh (in soil SPO18A Ref. 19 (9045C)/ Ref.20 Glass electrode/probe.
paste) Chap. 42
Plant available metals SP003A/B Ref. 20, Chaps. 26,28; Ref. DTPA-AB extraction, then ICP-AES.
(in soils) 19(6010B)
Total metals (in soils, SP001E Ref. 19 (3050A/6010B) Nitric acid-hydrogen peroxide digest,
biomass) then ICP-AES.
14
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3. Results And Discussion
This section presents the important findings
associated with the Pb bioavailability,
bioaccessibility, and heavy metals
phytoavailability investigations. The raw data for
these studies are presented in Appendices B
through F, respectively. Study-specific methods
used are summarized in Section 2.0. As
documented in Appendix G, all reasonable efforts
were made to abide by the project quality
assurance project plan (QAPP) (Ref 14).
3.1 In Vivo Lead Bioavailability Studies
The databases for VMDL's pig dosing studies
(Appendices B and C) were re-evaluated by
Syracuse Research Corporation using EPA-
approved statistical methods (Appendix D), and
the results of their work are summarized below.
Fieller's theorem was used to calculate the
approximate 95% confidence interval around each
tissue-specific RBA estimate. Table 3-1 presents
the best estimate (BE) plus 2.5% lower bound
(LB) and 97.5% upper bound (UB) RBA values
for each of the 4 measurement endpoints
associated with each of the PA treatment levels
(including the control). These results utilized all
of the data from the two VMDL studies (i.e., no
exclusion of outliers), and the data set for each
endpoint was fit to either a linear or nonlinear
model as judged appropriate. Linear models (i.e.,
response = intercept + slope * dose) are used for
the kidney, liver, and bone (femur) endpoints,
while a nonlinear model [response = intercept +
constant * (1 - exp (- constant * dose))] is used
for the blood area under the curve (AUC) data.
However, in the case of untreated soil, the dose-
response data did not extend far enough out to
define either the slope of the curve or plateau
value with confidence. Thus, in this one instance,
the data were fit using a linear model.
Inspection of these results (Table 3-1) indicates
that the confidence bounds for treated and
untreated soils overlap considerably for each
endpoint. Furthermore, with the possible
exception of bone lead, there is no indication of a
trend towards lower RBAs as a function of PA-
treatment level.
The variabilities within endpoints (above) were
then integrated so as to estimate the uncertainties
in RBAs between treatments. These calculations
were accomplished via:
use of professional judgment to assign RBA
weights of 9/12 to blood lead and 1/12 each to
liver, kidney, and bone; then
perform Monte Carlo simulations in which a
value for RBA is drawn from the uncertainty
distribution for each endpoint with a
frequency proportional to the weight assigned
to that endpoint.
Each uncertainty distribution was assumed to be
normal, with known mean and standard deviation
(e.g., the endpoint-specific BE values in Table
3-1).
The uncertainty ranges in the Pb-RBA for each
soil treatment level, estimated by Monte Carlo
analysis as described above, are summarized in
Table 3-2. Inspection of these results shows no
reduction in RBA due to PA-treatment of the mine
waste soils.
Therefore, the data from the two relevant VMDL
pig dosing studies are not sufficient to conclude
that PA-treatment of mine waste-contaminated
soils had any particular effect on Pb-RBA.
Subsequently, it can not be determined presently
whether the objective of 25% reduction in RBA
was met by the given PA treatment levels.
3.2 In Vitro Bioaccessibility Study
The statistical summary for As and Pb
bioaccessibility values for the three levels of PA
treatment are shown in Table 3-3; the raw data
(including those associated with QA/QC) are
provided in Appendix E.
15
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Using the mean Pb values, the 1% and 0.75% PA
treatments reduce Pb bioaccessibility by about
56% and 53%, respectively, as compared to the
untreated mine waste soils. Regarding the 1% PA
treatment level, the percent reduction in
bioaccessibility is about the same magnitude as
reported for smelter soils (i.e., 60% reduction),
despite use of different Pb extraction methods (see
Ref 11).
Given the reasonable assumption that As loading
from the PA solution is insignificant relative to As
present in the receiving soils (calculations not
shown), it is hypothesized that PA treatment
enhances the mobility and bioaccessibility of this
element. This hypothesis is supported by the
relatively low (17%) recovery of As observed in
the matrix spike sample (Appendix E); the As
levels may be even higher than those reported in
Table 3-3. It is suggested that the concentration of
the H2PO4: ion is far greater than that of the
H2As(V ion (at pH -5.2, Eh -330 millivolts) in
the PA-treated soils (Ref. 22). Subsequently, the
P-ion outcompetes the As-ion for adsorption sites
on particles of hydrous Fe/Al oxides,
aluminosilicates, etc. (Ref. 23).
3.3 Heavy Metals Phytoavailability Study
The ROD identified Pb and Cd as being the
principal contaminants of concern (CoC) in
residential soils at the Joplin NPL Site (Ref. 1).
However, zinc ore mining/milling and smelting
activities were of major economic importance also
within the study area (Ref. 24). Thus, this metal
was also included as a CoC in the original research
proposal (Ref. 13).
This section of the report first presents the CoC
and ancillary laboratory data for plant and soil
materials sampled during this study. These data
are then interpreted from the perspectives of
potential phytotoxicity and food chain concerns.
Finally, the results from the present investigation
are compared to those generated by the previous
smelter soils-related study(ies) at Joplin.
3.3.1 Plant and Soils Data Presentation
The physicochemical characterization of untreated
(0% PA) soil, plus selected physicochemical
properties of 0.75% PA and l%PA-treated soils,
all from samples collected at the test site in March
2001, are presented in Appendix B (Table 2-1).
The analytical results for the treatment-specific
soil and plant composite samples, collected in June
2001, are presented in Table 3-4. Data from the
follow- on laboratory investigations performed in
Butte in late July 2001 are shown in Table 3-5.
Documentation for the June and July sample
analyses are found in Appendix F.
Inspection of the soils data in Table 3-4 indicates
the following trends:
pH remains > 1 log unit below the target range
(6.5-7.0) approximately 8 months after PA
treatments;
1% PA treatment lowers plant available Cd to
34% of that observed in untreated soil;
1% PA treatment lowers plant available Pb to
18% of that observed in untreated soil; and
1% PA treatment lowers plant available Zn to
63% of that observed in untreated soil.
In regards to the plant data (Table 3-4, Part B), 1%
PA treatment appears to reduce Cd, Pb, and Zn
levels to about 42%, 34%, and 85%, respectively,
of those concentrations observed in plants growing
in untreated soils. Table 3-5 shows adjustment of
pH to within the target range appears to further
reduce plant available metals levels. The percent
plant available metals levels (relative to 100%
presence in the controls) in pH 7, 1% PA-treated
soils are as follows: Cd, 20%; Pb, 17%; and Zn,
47%.
Overall, the effectiveness of PA treatment
(>0.75% by weight, pH >6.5) in reducing CoC
bioavailability/plant uptake appears to be
Pb>Cd>Zn. Assuming predominance of hydroxy-
chloro-phosphate mineralization under these
conditions, the above ranking appears to be driven
by relative solubility of these compounds. The
16
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trend in treatment effectiveness is reflected in the
solubility products (-log Ksp) of such compounds,
from least to most soluble: Pb (62.8-84.4), Cd
(42.5-49.7), andZn (37.5-49.1) (Ref.25).
3.3.2 Plant and Soils Data Interpretation
The above data were evaluated using the
phytotoxicity and herbivore risk assessment
criteria presented in Table 3-6. These criteria
represent literature review-based judgements made
by MSB; key references are cited in this table.
The plant-related values are (believed to be)
applicable to physiologic ecotypes of common
grass and forb species that are neither intolerant or
strongly tolerant of the given CoCs, and are yet
able to grow in the given soil conditions.
Phytotoxicity is defined in terms of > 15% to 20%
reduction in aboveground biomass yields, relative
to those for nonstress conditions. Given their
derivation, the herbivore-related criteria are
probably applicable to both livestock (e.g., cattle)
and wildlife (e.g., elk) species.
The element-specific strong acid extractable
("total") metals levels in soils represent
interpolations between guidelines commonly
reported for agricultural species (e.g., Ref. 26),
and those reported for apparently metals tolerant
ecotypes of uncultivated grass species present in
or near the study area (Ref. 27). Similar efforts
were made in developing the DTPA-AB
extractable ("plant available") metals levels, using
Refs. 27 and 28 for establishing the upper and
lower bounds for each of the three CoCs. Given
the observed CoC concentrations (Tables 3-4 and
3-5), the plant available fractions of these elements
may exceed the capacity of the extraction system
to reliably predict plant available concentrations
(Ref. 29). Thus, the criteria in Table 3-6 (Part A)
should be viewed as rough approximations of
metals levels indeed toxic to the tall fescue
growing in the test plot soils.
Site-specific biogeochemical interactions between
rooting zone soils and the vascular plants growing
in them (Refs. 30, 31), as well as species-specific
physiological characteristics regarding metals
uptake and processing (Refs. 32-34), greatly
complicate establishment of accurate CoC
phytotoxicity values in LSB. Nevertheless,
general guidance developed for agricultural
species (e.g., Refs. 35, 36) plus data relevant to the
study area (Ref. 27) were used to generate the
credible criteria shown in Part B of Table 3-6.
The criteria document prepared by the U.S.
Bureau of Land Management (Ref. 37), and
several of the references cited therein, served as
the principal source for preparing the herbivore-
related values shown in Table 3-6 (Part B). A
formal ecorisk assessment using species- and
contaminant-specific toxicity reference values was
beyond the scope of this project.
Comparison of the laboratory (soil/plant) data in
Table 3-4 with the phytotoxicity assessment
criteria in Table 3-6 indicates that:
plant available and acid extractable levels of
Cd and Zn are potentially phytotoxic to plant
growth in all soils sampled, even after PA
treatment; while
PA treatment probably mitigates Pb-related
phytotoxicity, as judged by the reduction in
plant available Pb levels; and
1% PA treatment may be sufficient to mitigate
Cd and Pb phytotoxicity in plants, but
probably not for Zn (at least in nontolerant
species).
The soils data in Table 3-5 indicates that
adjustment of pH to within the target range (6.5-
7.0), following PA treatment, will result in the
following effects:
occurrence of further reductions in plant
available Cd and Pb levels, possibly to the
degree that phytotoxicity is no longer likely;
while
plant available Zn levels may remain
phytotoxic to the more sensitive plant species.
Given the likelihood that plant available aluminum
levels would need to be >3 mg/kg at pH -5.2 (Ref.
17
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38) to be phytotoxic, this element is not believed
to pose a problem in test plot soils. Furthermore,
PA treatment may be precipitating out soluble
aluminum species (e.g., hydrated Al+2, A10FT2) as
Pb/Zn-aluminophosphates of varying solubility
(Ref. 25). Total aluminum levels in dry leaf and
shoot biomass of grass/forb species are typically
< 100 mg/kg (Ref. 3 9) and can range up to 300
mg/kg without presenting phytotoxicity in
nonaccumulator species (Ref. 40). The relatively
low aluminum concentrations also supports the
view that detergent/water rinsing of biomass
during sample preparation removed most of the
surficial soil contamination, prior to digestion and
analyses of the plant materials.
Plant available (Bray-1 extractable) P is probably
low for agricultural production activities (i.e., 1.2
mg/kg; Appendix A); however, total P in plant
biomass taken from the "control" plot(s) does not
indicate a deficiency for this element (i.e., 2900-
3400 mg/kg "expected"; Ref. 40). Furthermore,
total P levels in biomass collected from the PA-
treatment plots are certainly elevated (i.e., >5500
mg/kg P) but are probably not phytotoxic to
grass/forb species (i.e., > 10,000 mg/kg P) (Ref.
40).
As noted previously, at least Zn may exceed
phytotoxicity threshold levels in plant biomass,
following PA treatment of test soils. However, the
above screening level criteria are neither:
based on long-term statistical evaluation of
species-specific biomass production data
acquired from the various PA treatment
conditions; nor
do they recognize potential interelement (e.g.,
antagonistic) effects in overall phytotoxicity
response (e.g., Ref. 41).
The criteria presented in Table 3-6 are probably
conservative, in the sense that they would not fail
to detect an environmental condition of potential
concern to regulators or public health officials.
However, situations exhibiting nearly certain
phytotoxicity to non-metallophyte/
hyperaccumlator plant species and/or pose
unacceptable threat to herbivores will require CoC
levels in soil/biomass as shown in Table 3-8
(Ref. 43).
Comparison of the test plot data (Table 3-4, Part
B) with the criteria in Table 3-8 indicates that Zn
levels in biomass remains of concern regarding
plant production (especially for common
grass/forb reclamation species) and to sheep
consuming such biomass. However, such potential
hazards would be self-limiting, if the quality
("taste") and quantity (i.e., dry matter/m2) are
sufficiently poor to discourage use of such lands
for grazing purposes.
The calculated Cd:Zn ratios in test plot soils are
approximately 0.5:100, 0.6:100, and 0.5:100 for
the 0% PA, 0.75% PA and 1% PA treatments,
respectively (Table 3-4, Part A). There is no
evidence that soil Cd can cause the first human
health effect (renal tubular proteinuria) when
Cd:Zn is <1.5:100, "even when smelters have
contaminated soils to as high as 100 mg/kg"
(Ref. 44, Abstract). Chaney and Ryan also argue
that co-occurrence of Zn strongly reduces Cd
retention in animal (particularly muscle) tissues,
(Ref. 44, Abstract). Assuming the above Cd:Zn
ratio applies equally to monogastric (human) and
digastric (elk, cattle) species then:
the CoC levels in test plot biomass (Table 3-4,
Part B) are probably safe;
the CoC levels in biomass from PA-treated
soils (pH^6.5) are probably acceptable for
consumption by herbivores; and
the above Cd:Zn ratios in PA-treated soils
mitigates the food chain transfer concern,
footnote d in Table 3-6.
Although the database is presently small, the
overall weight-of-evidence indicates that PA
treatment of mine/mill waste-contaminated soils
exhibits significant positive effects on reducing the
environmental mobility of the 2 principal CoCs
(Cd and Pb). Therefore, as the benefits of in situ
PA treatment/ revegetation (i.e., reduced
18
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contaminant transport via wind/water erosion)
exceed the subsequent environmental risks, such
approach to remediation of the OU3 soils appears
to be technically viable.
3.3.3 Brief Evaluation of the Soil and Plant
Data from the Smelter Soils Test Plot
Comparison of the smelter plot soils data
(Appendix Table A-l) with that from the present
study (Table 3-4) indicates that:
the mean-of-the-mean acid extractable Cd
levels are slightly higher, while Pb and Zn
levels are slightly lower, in the smelter soils
(versus mill waste soils); and
the untreated smelter soil has somewhat higher
total organic carbon and cation exchange
capacity levels than does the untreated mill
waste soil (Appendix B, Table 2-1).
The latter observation may indicate slightly lower
bioavailability of Pb (and possibly Cd) in smelter
plot soils; the suggested mechanism would be
preferential displacement of small cations (e.g.,
Ca+2 and Mg+2) by larger ones (e.g., Pb+2 and Cd+2)
on both organic and inorganic (mineral) ion
exchange sites (Ref 45). Alternatively, if plant
available CoC levels in mill waste-contaminated
soils far exceed those in smelter soils, then such
differences in soil characteristics would be
immaterial; the "excess" metal ions available for
plant uptake would be reflected in higher CoC
levels in aboveground biomass due to mass action
effects alone (i.e., "swamping out" the above
exchange sites). There are no plant available or
metals-specific partitioning data presently
available to test these hypotheses.
Nevertheless, the concentration factor (CF) data
presented in Table 3-8 indicates that Cd and Pb are
more readily taken up into plants growing in mill
waste, than smelter soils. Inspection of these data
also shows that CF values for Cd and Pb decrease
with increasing levels of PA treatment at both test
sites. This observation provides additional
evidence (to that found in Section 3.3.2) that such
treatment significantly reduces plant availability of
these two elements. It is possible that some
benefit is achieved also for Zn, particularly when
present at relatively low bioavailable
concentrations (as is surmised for smelter plot
soils). At 1% PA, there also appears to be
sufficient molar excess of reagent to ensure nearly
equal effectiveness in immobilizing Cd and Pb at
potentially "low" and "high" plant available levels
of these metals.
Finally, comparison of soil/plant data from the
smelter plot against relevant screening criteria
found in Table 3-6 indicates that:
acid extractable metals levels in soils may be
phytotoxic, especially Pb and Zn;
acid extractable metals levels in leaf and shoot
biomass are probably not phytotoxic, even in
plants grown in untreated soil; and
CoC levels in the biomass sampled are
probably safe for long-term consumption by
most domesticated and undomesticated
herbivore species.
Therefore, in situ PA treatment/revegetation of
OU3 soils would have at least neutral
environmental benefit, and no appreciable
environmental risks, following its implementation.
19
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Table 3-1. Statistical uncertainty in endpoint-speciflc RBA values.
%RBA Relative to Lead Acetate
Untreated (0% PA) Soil
Measurement Endpoint
Blood Lead Area Under the
Curve (AUC)
Liver Lead
Kidney Lead
Bone Lead
BE
40
17
16
35
LB
32
10
9
26
UB
48
25
23
45
0.75% PA-Treated Soil
BE
47
28
35
34
LB
36
21
27
27
UB
61
38
44
44
1.0% PA-Treated Soil
BE
40
21
21
25
LB
28
15
15
20
UB
56
28
28
32
Source: SRC, 2003, Table 5 (see Appendix D).
Table 3-2. Uncertainty in RBA point estimates combined across measurement endpoints.
% RBA Relative to Lead Acetate
Treatment Level
2.5th
Mean
97.5th
Untreated (0% PA)
0.75% PA-Treated
1.0% PA-Treated
13
26
18
36
43
36
58
51
Source: SRC, Table 6 (see Appendix D).
Table 3-3. Bioaccessibility results for the PA-treated mine waste soils (Ref. 21).
Treatment Level
As
Bioaccessibility (mg/kg)a
Pb
0% PA
0.75% PA
1%PA
0.7 ± 0.1 (2)b
2.8 ±0.1 (3)
2.8 ± 0.1(3)
2105 ±7(2)
997 ± 124(3)
931 ± 148(3)
Notes: ashows arithmetic mean ± standard deviation and (sample number).
bthe mean of duplicate samples LM201 and LM211 was used in calculating this statistic.
Table 3-4. Laboratory data for the soil and plant samples collected in June 2001.
Part A. Soil Samples
Treatment l:lpH/Eh
0% PA
0.75% PA
1%PA
7.2/299
5.2/343
5.4/315
P/TA1
0.737/4100
0.174/4170
0.113/3900
Parameters3
P/TCd
51.7/122
26.1/123
17.4/89
P/TP
18.3/1240
505/16,600
602/16,000
P/TPb
66.7/3850
15.7/3540
12.1/3390
P/TZn
982/23,800
659/20,900
619/16,900
PartB. Plant Samples
Treatment
0% PA
0.75% PA
1%PA
TA1
191
91.1
64.2
TCd
22.4
14.4
9.5
Parameters'"
TP
3100
5800
6500
TPb
118
50.7
40.7
TZn
1300
1250
1100
Notes: a pH/Eh of 1:1 soil:water extract are in standard units and millivolts, respectively; plant available (P; DTPA-
AB) and strong acid extractable (T) levels are in mg/kg, oven dry weight.
b strong acid extractable (T) levels are in mg/kg, oven dry weight.
20
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Table 3-5. Laboratory data for the soil liming investigation performed in July 2001.
Parameters3
Treatment 1:1 pH Before Liming 1:1 pH After Liming P Cd PPb P Zn
0.75% PA 5.26 6.90 8.8 9.8 474
l%Pa 5.08 6.86 10.1 11.3 464
Note: a pH values are in standard units; plant available (DTPA-AB extractable) metals in mg/kg, oven dry weight.
Table 3-6. Numerical criteria for evaluating the analytical laboratory results.
Part A. Phytotoxicity of Rooting Zone Soils
Analytical Parameter Acid Extractable Levels3 Plant Available Levels'*
Cd 10-80 4-12
Pb 400-600 10-25
Zn 500-7000 70-800
Part B. Acid Extractable Levels in Leaf and Shoot Biomass
Analytical Parameter Phytotoxicity0 Herbivore (Plant Ingestion) Risk*1
Cd 5-15 (si) >5.0
Pb 20^0 (< 15) >40.0
Zn 250^50 (< 100) >500
Notes: a Levels are in mg/kg dry soil (Refs. 26 and 27).
b Levels are in mg/kg dry soil (Refs. 27 and 28).
0 Levels are in mg/kg dry plant material (Refs. 27, 35, and 36); "expected" concentrations for plants
growing in uncontaminated, but somewhat mineralized, soil are shown in parentheses.
d Levels are in mg/kg dry plant material (Ref 37); dietary limitations of 0.5 mg/kg Cd and 30 mg/kg Pb
(e.g., in cattle feed) have been suggested, based on human food residue considerations (Ref. 42.)
Table 3-7. Additional criteria for evaluating toxic effects of the CoCs on plants and herbivores (Ref. 43).
Part A. Likely upperbound phytotoxicity threshold criteria for nonmetallophyte species.
CoC Levels in Biomass3
Analytical Parameter Cd Pb Zn
Acid extractable metals" 50 200 500
Part B. Likely upperbound metals-tolerance criteria (chronic intake) for livestock species.
CoC Levels in Biomass3
Livestock Species Cd Pb Zn
Cattle 50-500 5-300 >2500
Horses not determined 80-1000 >1500
Sheep 50-500 5-300 >1000
Notes: ain mg/kg of leaf and shoot biomass, dry weight.
bdetermined by such methods as strong acid digestion followed by ICP-AES.
21
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Table 3-8. Calculated CoC-speciflc concentration factors for the smelter- and mill-waste test plots."
Part A. Smelter Soils Test Plotb
PA Treatment Level (pH)
CoC 0% PA (7.1) 0.5% PA (5.6) 1% PA (6.3) % CF Reduction (1% PA vs. 0% PA)
Cd 0.071 0.043 0.041 42
Pb 0.003 0.002 0.001 67
Zn 0.053 0.108 0.042 21
Part B. Mill Waste Soils Test Plotc
PA Treatment Level (pH)
CoC 0% PA (7.2) 0.75% PA (5.2) 1% PA (5.4) %CF Reduction (1% PA vs. 0 % PA)
Cd 0.184 0.117 0.107 42
Pb 0.031 0.014 0.012 61
Zn 0.055 0.060 0.065 C
Notes: Concentration factor = acid extractable CoC level in dry plant material ^ acid extractable CoC level in dry soils (both
inmg/kg).
bSoil and plant data are found in Appendix Tables A-l and A-3, respectively.
°Soil and plant data are found in Table 3-4.
22
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4. Conclusions And Recommendations
4.1 In Vivo Lead Unavailability Studies
Data produced by the two MWTP-funded pig soil-
dosing studies (by VMDL) are not sufficient to
conclude, with any statistical confidence, that PA
treatment(s) significantly lowered Pb-RBA in
mine/mill waste-contaminated residential (OU3)
soils from the Joplin, Missouri Superfund site.
Such conclusions are precluded due to performing
separate, rather than simultaneous, dosing of
young swine with untreated versus PA-treated
soils. The basis for this finding is presented
below.
Historical data for Pb-RBA in OU3 soils indicates
point estimates of about 80%, as compared to
those around 58% in residential soils affected by
smelter stack fallout (with OU2) (Ref. 51). Thus,
an attempt was made to streamline the initial
(2001) study by dosing young swine with PA-
treated soils, only; the historical data (RBAs >
58%) from previous investigations would serve as
the untreated controls.
Given the variability of Pb-RBA observed in
Joplin site soils, the project team decided to
perform a second investigation in 2002. This
abbreviated study used untreated soil from the
field plot, plus one level (225 jog/kg.d) of PbAc
dosing as compared to the 3 levels utilized in the
initial study.
During review of the draft (September 2002
report), EPA/MWTP personnel identified concerns
regarding methods used for statistical analysis of
the 2 data sets, plus absence of 95% confidence
limits around each of the treatment-specific Pb-
RBA point estimates. Subsequently, the VMDL
data were reanalyzed using improved, and more
defensible, statistical methods. The key finding
was that overlap in confidence limits between
treatments prevents firm conclusions regarding
effectiveness of PA treatment in lowering Pb-
RBAs in OU3 soils. However, the higher RBAs
observed historically, plus unusually low Pb
absorption from untreated study plot soils (into pig
tissues), suggests that 1% PA treatment does
reduce Pb bioavailability in these soils.
In retrospect, study design should have involved
direct comparison of RBAs from untreated soil to
0.75% PA-treated soil, first; this effort would be
followed by comparison of RBAs from untreated
soil to those treated with > 1% PA. In both
studies, all 3 dosing levels of PbAc would also be
used. Performing such investigations, particularly
on soils treated with PA at least 2 years ago, would
provide the evidence needed regarding long-term
viability of this in situ technology at Joplin.
4.2 In Vitro Lead Bioaccessibility Study
The mean Pb bioaccessibility results for the 1%
and 0.75% PA soil treatments of OU3 soils were
about 44% and 47%, respectively, of that observed
in untreated soils. Regarding the 1% PA treatment
level, the 56% reduction in Pb bioaccessibility is
similar to the 44% reduction observed for Pb RBA
(Section 4.1). It is also about the same magnitude
as reported for smelter soils (i.e., 60% reduction),
despite use of different Pb (in vitro) extraction
methods.
Therefore, these study results lend credence to the
potential for PA treatment of the smelter- and
mine waste-affected residential soils.
4.3 Heavy Metals Phytoavailability Study
Treatment of OU3 soils with 1% PA is probably
sufficient to mitigate Cd and Pb phytotoxicities in
tall fescue, but probably not for Zn phytotoxicity,
even at optimal pH (> 6.5). Only Zn appears to
occur at levels in leaf and shoot biomass that may
pose a chronic ingestion hazard to domestic or
wildlife herbivore species. However, the Cd:Zn
ratios in PA-treated soils probably mitigates any
food chain Cd transfer concerns.
Although the phytoavailability database is
presently small, the overall weight-of-evidence
indicates that PA treatment of mine/mill waste-
contaminated soils exhibits significant positive
23
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effects on reducing the environmental mobility of
Cd and Pb. Therefore, as the benefits of in situ PA
treatment/revegetation (i.e., reduced contaminant
transport via wind/water erosion) exceed the
subsequent environmental risks, such approach to
remediation of the mine waste-affected soils to
appears to be technically viable. However,
additional confidence in this conclusion would be
gained by implementing at least some of the
following activities:
continued monitoring of field pH plus plant
vigor, canopy cover, aerial biomass production
and CoC levels in LSB over one to several
additional growing seasons;
evaluation of metals partitioning in untreated
and treated soils, plus ecotoxicity evaluations
using alternative test species, while using
more sophisticated methods than applied
during this study (e.g., Refs. 46-48); and
correlating these findings (above) with metals
speciation data generated by electron probe
microanalysis of particles retrieved from
treated and untreated soil samples.
Collectively, this information would provide
considerable insight into the likely variation in
treatment effectiveness over both time and space,
and subsequently, be useful for optimizing
treatment effectiveness at the Joplin (or other Pb-
contaminated) site.
24
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5. References
1. U.S. Environmental Protection Agency (EPA),
Record of Decision: Residential Yard and
Mine Waste Yard Soils, Operable Units 02
and 03, Oronogo-Duenweg Mining Belt Site,
Jasper County, Missouri, prepared by EPA
Region 7, Kansas City, Kansas, June 1996.
2. EPA, IEUBKModel Bioavailability Variable,
prepared by the Office of Emergency and
Remedial Response, Washington B.C., as
publication EPA 540-F-00-006, October 1999.
3. EPA, Guidance Manual for the Integrated
Exposure Uptake Biokinetic Model for Lead in
Children, prepared by the Office of
Emergency and Remedial Response,
Washington D.C., as publication EPA/540/R-
93/081, February 1994.
4. Schoof, R.S.; M.K. Butcher; C. Sellstone et
al., "An Assessment of Lead Absorption from
Soil Affected by Smelter Emissions",
Environmental Geochemistry and Health 17:
189-199, 1995.
5. Casteel, S.W.; RP. Cowart; C.P. Weis et al.,
"Bioavailability of Lead to Juvenile Swine
Dosed with Soil from the Smuggler Mountain
NPL Site of Aspen, Colorado", Fundamental
and Applied Toxicology 36: 177-187,1997.
6. EPA, Users:Guide for the Integrated
Exposure Uptake Biokinetic Model for Lead in
Children (IEUBK) Windows 7 Version,
prepared by Syracuse Research Corporation,
N. Syracuse, NY for the Technical Review
Workgroup for Lead, publication no. EPA
40-K-01-005, May 2001.
7. Ruby, M.V.; R. Schoof; W. Brattin et al.,
"Advances in Evaluating the Oral
Bioavailability of Inorganics in Soil for Use in
Human Health Risk Assessment", Environ.
Sci. Tech. 33(21): 3697- 3705, 1999.
8. Rieuwerts, J.S.; M. Farago; M.Cikrt et al.,
"Differences in Lead Bioavailability between
a Smelting and Mining Area and the Influence
of Physicochemical Form and Other Factors",
Water, Air and Soil Pollution 122 (1-2): 203-
229, 2000.
9. Ruby, M.V.; A. Davis; R. Schoof et al.,
"Estimation of Lead and Arsenic
Bioavailability Using a Physiologically Based
Extraction Test", Environ. Sci. Tech.30 (2):
422-430, 1996.
10. Solubility/Bioavailability Research
Consortium, In Vitro Method for
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