Reconnaissance soil geochemistry at the Riverton Uranium Mill Tailings Remedial Action Site, Fremont County, Wyoming
Soil samples were collected and chemically analyzed from the Riverton Uranium Mill Tailings Remedial Action Site, which lies within the Wind River Indian…
Public-domain full text preserved in the Mountain Man Mining Library. Original source: pubs.usgs.gov.
Reconnaissance Soil Geochemistry at the Riverton Uranium Mill Tailings Remedial Action Site, Fremont County, Wyoming
Open-File Report 2012–1257 U.S. Department of the Interior U.S. Geological Survey
U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director U.S. Geological Survey, Reston, Virginia: 2012
For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS
For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod
To order this and other USGS information products, visit http://store.usgs.gov
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Smith, D.B., and Sweat, M.J., 2012, Reconnaissance soil geochemistry at the Riverton Uranium Mill Tailings Remedial Action Site, Fremont County, Wyoming: U.S. Geological Survey Open-File Report 2012–1257, 23 p.
Contents Abstract 1 Introduction 1 Sample Collection 3 Sample Preparation and Analytical Methods 3 Quality Assurance and Quality Control 5 Estimation of Risk 6 Ecological Soil Screening Levels 6 Human Health Soil Screening Levels 7 Estimation of Background 8 Results 9 Discussion 19 Acknowledgments 19 References Cited 19 Appendix link Figures Figure 1. Location of 19 soil samples collected from the Riverton Uranium Mill Tailings Remedial Action Site, Fremont County, Wyoming 2 Figure 2. Box-and-whisker plots showing the variation of (a) As, (b) Ba, (c) Cd, (d) Co, (e) Cu, (f) Mn, (g) Ni, (h) Pb, (i) Sb, (j) Se, (k) V, and (l) Zn in soils from the Riverton Uranium Mill Tailings Remedial Action Site, Fremont County, Wyoming, and in soils from the 160-sample Statewide dataset. The outer limits of the lower and upper whiskers on the plots represent the 10th and 90th percentiles, respectively. The “X” between the two box-and-whisker plots in each figure represents the median for six soil samples from the Wyoming Statewide dataset that are located within the Wind River drainage 11 Figure 3. Box-and-whisker plots showing the variation of (a) U and (b) Th in soils from the Riverton Uranium Mill Tailings Remedial Action Site, Fremont County, Wyoming, and in soils from the 160-sample Statewide dataset. The outer limits of the lower and upper whiskers on the plots represent the 10th and 90th percentiles, respectively. The “X” between the two box-and-whisker plots in each figure represents the median for six soil samples from the Wyoming Statewide dataset that are located within the Wind River drainage 18
Tables Table 1. Elements determined by ICP–MS and ICP–AES 4 Table 2. Ecological soil screening levels (Eco-SSL) as established by the U.S. Environmental Protection Agency 7 Table 3. Human health soil screening levels for industrial soils (U.S. Environmental Protection Agency, 2011) 8 Table 4. Human health soil screening levels for industrial soils (U.S. Environmental Protection Agency, 2011). [mg/kg, milligrams per kilogram; NA, not available] 9 Table 5. Statistical summary for 41 elements in 0–5 cm soils from the Riverton UMTRA Site 10
Reconnaissance Soil Geochemistry at the Riverton Uranium Mill Tailings Remedial Action Site, Fremont County, Wyoming By David B. Smith and Michael J. Sweat Abstract Soil samples were collected and chemically analyzed from the Riverton Uranium Mill Tailings Remedial Action Site, which lies within the Wind River Indian Reservation in Fremont County, Wyoming. Nineteen soil samples from a depth of 0 to 5 centimeters were collected in August 2011 from the site. The samples were sieved to less than 2 millimeters and analyzed for 44 major and trace elements following a near-total multi-acid extraction. Soil pH was also determined. The geochemical data were compared to a background dataset consisting of 160 soil samples previously collected from the same depth throughout the State of Wyoming as part of another ongoing study by the U.S. Geological Survey. Risk from potentially toxic elements in soil from the site to biologic receptors and humans was estimated by comparing the concentration of these elements with soil screening values established by the U.S. Environmental Protection Agency. All 19 samples exceeded the carcinogenic human health screening level for arsenic in residential soils of 0.39 milligrams per kilogram (mg/kg), which represents a one-inone-million cancer risk (median arsenic concentration in the study area is 2.7 mg/kg). All 19 samples also exceeded the lead and vanadium screening levels for birds. Eighteen of the 19 samples exceeded the manganese screening level for plants, 13 of the 19 samples exceeded the antimony screening level for mammals, and 10 of 19 samples exceeded the zinc screening level for birds. However, these exceedances are also found in soils at most locations in the Wyoming Statewide soil database, and elevated concentrations alone are not necessarily cause for alarm. Uranium and thorium, two other elements of environmental concern, are elevated in soils at the site as compared to the Wyoming dataset, but no human or ecological soil screening levels have been established for these elements. Introduction The effects of soil composition on human and ecological health is well documented (see, for example, Anastasia and Kender, 1973; Rehab and Wallace, 1978; Kaplan and others, 1990; Ainsworth and others, 1991; Angle and Chaney, 1991; Lamersdorf and others, 1991; Jiang and Singh, 1994; Spurgeon and others, 1994; Lehoczky and others, 1996; Oliver, 1997; Abrahams, 2002; Plumlee and Ziegler, 2003; Pierzynski and others, 2005). Soil can be a pathway for potentially toxic elements of natural or anthropogenic origin to enter the human or animal body through ingestion, inhalation, or dermal absorption and to enter plants by absorption through root tissues. Low concentrations of nutrients or elevated concentrations of toxic elements in soil may control the vegetation species that can grow in the soil (Gough and others, 1989; Oze and others, 2004).
On August 11, 2011, 19 soil samples were collected from the Riverton Uranium Mill Tailings Remedial Action (UMTRA) Site about 4 kilometers southwest of Riverton, Wyoming (fig. 1). The Riverton UMTRA Site is located on the Wind River Indian Reservation (Eastern Shoshone and Northern Arapahoe Tribes) and covers an area of approximately 10.4 square kilometers. The land is currently owned by Chemtrade Refinery Services (U.S. Department of Energy, 2011). The mill was constructed in 1958 and closed in 1963. During this period of operation, the mill processed approximately 800,000 metric tons of uranium and vanadium ore (U.S. Department of Energy, 1995, 2011). Solid waste material was transferred to a tailings pile covering about 29 hectares. Between 1988 and 1990, the mill tailings and contaminated soils were removed from the site. However, the Eastern Shoshone and Northern Arapahoe Tribes continue to have concerns about groundwater and soil contamination at the site. The purpose of this investigation was to determine the geochemical variation for 44 chemical elements in soils of the UMTRA site and to compare these soil concentrations with available ecological and human health soil screening levels established by the U.S. Environmental Protection Agency. To put the concentrations observed at the UMTRA site into a more regional context, the site-specific geochemical variation was compared to the variation observed for the entire State of Wyoming as determined from samples collected at 160 sites throughout the State in 2008 as part of the North American Soil Geochemical Landscapes Project (Smith and others, 2011, 2012).
Figure 1. Location of 19 soil samples collected from the Riverton Uranium Mill Tailings Remedial Action Site, Fremont County, Wyoming.
Sample Collection Nineteen samples were collected from sites selected to provide relatively even coverage throughout the UMTRA site. The site was mapped using land-ownership coverages in ArcGIS, and the Chemtrade property (former mill-tailings site) was excluded to determine the surface area available for sampling. A pixilated randomized selection process was then run to determine sampling locations. Land ownership was determined for five sites in each pixel and access requested for the first site in each pixel. If access was denied or not available (not able to contact owner), then the next site owner was contacted. This process continued until access was obtained or until all sites for a pixel were exhausted. For this sampling effort, access was obtained from the first or second property owner in all cases. At each site, a sample was collected from a depth of 0–5 centimeters (cm). This particular sample medium was selected because this near-surface material is the part of the soil with which humans and most animals come into contact most often. Geochemical information for this layer is critical for evaluation of a soil pathway through which potentially toxic elements may enter the bodies of both humans and animals. It also is considered to be the portion of the soil most likely to indicate the influence of uranium milling at the site. Sample Preparation and Analytical Methods Samples were air dried at ambient temperature, disaggregated, and sieved through a 2millimeter (mm) stainless steel screen. Material less than 2 mm in size was crushed to less than 150 micrometers (μm) in a ceramic mill and thoroughly mixed to ensure homogeneity. Prepared samples were sent to a U.S. Geological Survey (USGS) contract geochemical laboratory for major and trace element analysis. Concentrations of the elements aluminum (Al), calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), sodium (Na), sulfur (S), titanium (Ti), silver (Ag), barium (Ba), beryllium (Be), bismuth (Bi), cadmium (Cd), cerium (Ce), cobalt (Co), chromium (Cr), cesium (Cs), copper (Cu), gallium (Ga), indium (In), lanthanum (La), lithium (Li), manganese (Mn), molybdenum (Mo), niobium (Nb), nickel (Ni), phosphorus (P), lead (Pb), rubidium (Rb), antimony (Sb), scandium (Sc), tin (Sn), strontium (Sr), tellurium (Te), thorium (Th), thallium (Tl), uranium (U), vanadium (V), tungsten (W), yttrium (Y), and zinc (Zn) were determined by inductively coupled plasma–atomic emission spectrometry (ICP–AES) by a method similar to Briggs (2002) and inductively coupled plasma–mass spectrometry (ICP–MS) by a method similar to Briggs and Meier (2002). A sample of 0.25 grams (g) was decomposed using a mixture of hydrochloric, nitric, perchloric, and hydrofluoric acids at a temperature between 125 and 150 degrees Celsius (ºC). The four-acid digestion results in an effectively total dissolution of most mineral constituents in soil. However, it does not fully dissolve some of the more refractory or resistant minerals. Examples of such incomplete dissolution include Ba in barite, Cr in chromite, Ti in rutile, Sn in cassiterite, Al in corundum, and rare earth elements in monazite (Briggs, 2002). An aliquot of the digested sample was aspirated into the ICP–AES instrument and the ICP–MS instrument and the concentrations of the optimal elements were determined. The ICP–AES method is best for the major elements, sulfur, and elements with relatively high concentrations not requiring a low detection limit. The ICP–MS method is optimal for trace elements requiring lower limits of determination near or below their crustal abundance and elements not determined by ICP–AES. The lower limits of determination (LLD) are listed in table 1.
Table 1. Elements determined by ICP–MS and ICP–AES. [LLD, lower limit of determination; ICP–MS, inductively coupled plasma–mass spectrometry; ICP–AES, inductively coupled plasma–atomic emission spectrometry; %, percent; mg/kg, milligrams per kilogram]
Element Analytical method LLD Aluminum ICP-AES 0.01% Calcium ICP-AES 0.01% Iron ICP-AES 0.01% Potassium ICP-AES 0.01% Magnesium ICP-AES 0.01% Sodium ICP-AES 0.01% Phosphorus ICP-AES 50 mg/kg Titanium ICP-AES 0.01% Silver ICP-MS 1 mg/kg Barium ICP-AES 5 mg/kg Beryllium ICP-MS 0.1 mg/kg Bismuth ICP-MS 0.04 mg/kg Cadmium ICP-MS 0.1 mg/kg Cerium ICP-MS 0.05 mg/kg Cobalt ICP-MS 0.1 mg/kg Chromium ICP-AES 1 mg/kg Cesium ICP-MS 5 mg/kg Copper ICP-AES 0.5 mg/kg Gallium ICP-MS 0.05 mg/kg Indium ICP-MS 0.02 mg/kg Lanthanum ICP-MS 0.5 mg/kg Lithium ICP-AES 1 mg/kg Manganese ICP-AES 5 mg/kg Molybdenum ICP-MS 0.05 mg/kg Niobium ICP-MS 0.1 mg/kg Nickel ICP-AES 0.5 mg/kg Lead ICP-MS 0.5 mg/kg Rubidium ICP-MS 0.2 mg/kg Sulfur ICP-AES 0.01% Antimony ICP-MS 0.05 mg/kg Scandium ICP-MS 0.1 mg/kg Tin ICP-MS 0.1 mg/kg Strontium ICP-AES 0.5 mg/kg Tellurium ICP-MS 0.1 mg/kg Thallium ICP-MS 0.1 mg/kg Thorium ICP-MS 0.2 mg/kg Uranium ICP-MS 0.1 mg/kg Vanadium ICP-AES 1 mg/kg Tungsten ICP-MS 0.1 mg/kg Yttrium ICP-MS 0.1 mg/kg Zinc ICP-AES 1 mg/kg
Mercury (Hg) was determined by treating 0.1 g of sample with a mixture of nitric and hydrochloric acids and heating at 110 °C for 30 minutes. Once cooled, solutions of sulfuric acid, potassium permanganate, and potassium persulfate were added followed by sodium chloridehydroxylamine sulfate. The final solution was reduced by stannous chloride and analyzed by atomic absorption spectrometry (AAS). This method is a modification of that published by the U.S. Environmental Protection Agency (1994). The LLD is 0.02 milligrams per kilogram (mg/kg). Selenium (Se) was determined by heating 0.25 g of sample at 175 °C with a combination of nitric, hydrofluoric and perchloric acids. After the solution was cooled, hydrochloric and nitric acids were added, then the solution was heated and cooled again. The sample was diluted and analyzed using hydride-generation AAS in a method similar to Hageman and Brown (2002). The LLD is 0.2 mg/kg. For analysis of arsenic (As), the sample was fused in a mixture of sodium peroxide and sodium hydroxide at 750 °C. The fused mixture was then dissolved in hydrochloric acid and analyzed by hydride-generation atomic absorption spectrometry in a method similar to Hageman and Brown (2002). The LLD is 0.6 mg/kg. Splits of the material less than 2 mm in size were provided to the Colorado State University Soil, Water, and Plant Testing Laboratory for determination of soil pH on a saturated soil paste using the methods described by Richards (1954). Quality Assurance and Quality Control Quality assurance (QA) is mainly the concern of the analytical laboratory. The various components of the QA plan include standard operating procedures, instrument logs, training records, data acceptance and rejection criteria, and laboratory audits. Unlike the unquantifiable QA element, the quality control (QC) element measures, by an analytical method, the accuracy and precision of the data produced. The accuracy and precision are established through the analysis of reference materials (RMs) and sample replicates, respectively. The 19 samples from the Riverton UMTRA Site were processed along with thousands of soil samples collected as part of the North American Soil Geochemical Landscapes Project (Smith and others, 2011, 2012) and were subject to the same QA/QC protocols used in that project as described below. The samples taken through the analytical process in the USGS contract laboratories received QC checks on three separate levels. The first-level QC assessment was made by the USGS contract laboratory. In the next level, quality was assessed by the USGS QC officer, followed by a third-level assessment by the USGS principal investigator for the Riverton UMTRA Site soil geochemistry study. The USGS contract laboratory is accredited to the International Organization for Standardization/International Electrotechnical Commission (ISO/IEC) 17025 standard, which includes both QA and QC protocols. The QC is monitored by analyzing a RM with every batch of 48 samples. The RM most often used is a syenite rock standard (SY-3) developed by the Canadian Centre for Mineral and Energy Technology (Govindaraju, 1989). Shewhart Control Charts (Taylor, 1987) are generated for the RM analyses and reviewed with every report as part of the internal quality audits. The accuracy for elements determined by ICP–MS and ICP–AES was considered acceptable if recovery was within the range of 85–115 percent at five times the LLD. The accuracy for Hg and Se was considered acceptable if recovery was within 80–120 percent at five times the LLD.
At the second tier, the USGS QC officer assessed precision and accuracy on the basis of five RMs that were inserted between every batch of 50 samples. The soil RMs used in this study were SRM 2709 and SoNE-1. SRM 2709, a soil from the San Joaquin Valley of central California, is a certified RM available from the National Institute of Standards and Technology and is used to assess both accuracy and precision (National Institute of Standards and Technology, 2003). The acceptance criteria for accuracy are the same as those used by the contract laboratory. SoNE-1 is a USGS in-house, noncertified soil RM prepared specifically for the North American Soil Geochemical Landscapes Project. It was collected from the Sharpsburg Soil Series (Natural Resources Conservation Service, 2008) in Lancaster County, Nebraska, and is used in this study to assess only precision. The precision for elements determined by ICP–MS and ICP–AES, and for total carbon (C) and carbonate C was considered acceptable if the calculated relative standard deviation (RSD) of duplicate samples is no greater than 15 percent. The precision for Hg, As, and Se was considered acceptable if the calculated RSD of duplicate samples was no greater than 20 percent. The USGS principal investigator for the Riverton UMTRA Site soil geochemistry study initiated the final QC tier, which included two blind SoNE-1 RMs inserted in each batch of 18 samples. In general, one RM was inserted into the first half of the batch and one RM into the second half. The acceptance criteria for accuracy and precision are those stated in the previous paragraph. The Colorado State University Soil, Water, and Plant Testing Laboratory maintains its own rigorous QC program for soil pH determinations including periodic calibration of the pH electrode with standard solutions. Estimation of Risk In this report, risk to biologic receptors and humans from potentially toxic elements in soil within the Riverton UMTRA Site is estimated by comparing the concentration of these elements with soil screening values established by the U.S. Environmental Protection Agency (USEPA). Ecological Soil Screening Levels Ecological Soil Screening Levels (Eco-SSLs) are “concentrations of contaminants in soil that are protective of ecological receptors that commonly come into contact with and (or) consume biota that live in or on the soil” (U.S. Environmental Protection Agency, 2003). USEPA has established Eco-SSLs for many of the soil contaminants that are frequently of ecological concern for plants and animals at hazardous waste sites. These contaminants include the following 15 trace elements that occur naturally in soil: Ag, As, Ba, Be, Cd, Cr, Co, Cu, Mn, Ni, Pb, Sb, Se, V, and Zn (U.S. Environmental Protection Agency, 2006, 2005b, 2005c, 2005d, 2005e, 2008a, 2005f, 2007a, 2007b, 2007c, 2005g, 2005a, 2007d, 2005h, 2007e, respectively). Eco-SSLs have been derived separately for four groups of biological receptors: plants, soil invertebrates, birds, and mammals (table 2). Complete details on how the Eco-SSLs were derived are given in U.S. Environmental Protection Agency (2003). Eco-SSLs are considered to be protective of terrestrial ecosystems and are intended to be applied at the screening stage of an ecological risk assessment. For the current investigation, the values are used to identify those trace elements of potential concern in soils of the Riverton UMTRA Site.
As seen in table 2, Eco-SSL for Cr have been established for Cr(III) and Cr(VI). The chemical analysis performed on the Riverton UMTRA Site samples in this study resulted in total Cr concentrations and did not yield separate concentration values for the two oxidation states. For this reason, Cr will not be considered further in this report. Table 2. Ecological soil screening levels (Eco-SSLs) as established by the U.S. Environmental Protection Agency. [Ag, silver; As, arsenic; Ba, barium; Be, beryllium; Cd, cadmium; Co, cobalt; Cr(III), trivalent chromium; Cr(VI), hexavalent chromium; Cu, copper; Mn, manganese; Ni, nickel; Pb, lead; Sb, antimony; Se, selenium; V, vanadium; Zn, zinc; NA, not available; mg/kg, milligrams per kilogram]
Eco-SSL Eco-SSL Eco-SSL Eco-SSL
Element Plants (mg/kg) Soil invertebrates (mg/kg) Birds (mg/kg) Mammals (mg/kg)
Aga NA
Asb NA
Bac NA NA
Bed NA NA
Cde
Cof NA
Cr(III)g NA NA
Cr(VI)g NA NA NA
Cuh
Mni
Nij
Pbk
Sbl NA NA
Sem
Vn NA NA
Zno
a U.S. Environmental Protection Agency (2006); b U.S. Environmental Protection Agency (2005b); c U.S. Environmental Protection Agency (2005c); d U.S. Environmental Protection Agency (2005d); e U.S. Environmental Protection Agency (2005e); f U.S. Environmental Protection Agency (2005f); g U.S. Environmental Protection Agency (2008a); h U.S. Environmental Protection Agency (2007a); i U.S. Environmental Protection Agency (2007b); j U.S. Environmental Protection Agency (2007c); k U.S. Environmental Protection Agency (2005g); l U.S. Environmental Protection Agency (2005a); m U.S. Environmental Protection Agency (2007d); n U.S. Environmental Protection Agency (2005h); o U.S. Environmental Protection Agency (2007e)
Human Health Soil Screening Levels EPA has developed regional screening levels based on human health risk for both residential and industrial soils (U.S. Environmental Protection Agency, 2011) as shown in tables 3 and 4, respectively. A detailed discussion of the human health soil screening level concept is found in U.S. Environmental Protection Agency (1991; 1996a, b; 2002; 2008b). For some elements, two screening levels have been established, each of which corresponds to fixed levels of risk. One of the screening levels represents a one-in-one million (10–6) cancer risk
(carcinogenic screening level), and the other represents a noncarcinogenic hazard quotient (HQ) of 1. The HQ is defined as the estimated (maximum) concentration of a specific toxic element divided by a screening benchmark regarded as a threshold of toxicity (generally a No-Adverse Effects Level) (U.S. Environmental Protection Agency, 2008b). If the HQ is greater than 1, then harmful effects are likely due to the element in question. If the HQ is less than 1, then harmful effects are not likely. Generally for residential soils, if a substance causes both carcinogenic and noncarcinogenic effects, the 10–6 carcinogenic risk will result in a more stringent screening level.
Table 3. Human health soil screening levels for industrial soils (U.S. Environmental Protection Agency, 2011). [Ag, silver; As, arsenic; Ba, barium; Be, beryllium; Cd, cadmium; Co, cobalt; Cu, copper; Mn, manganese; Ni, nickel; Pb, lead; Sb, antimony; Se, selenium; U, uranium; V, vanadium; Zn, zinc; mg/kg, milligrams per kilogram; NA, not available]
Human health screening level Human health screening level Element
carcinogenic (mg/kg) noncarcinogenic (mg/kg) Ag
NA As
Ba
NA 15,000 Be
1,400 Cd
1,800 Co
Cu
NA 3,100 Mn
NA 1,800 Ni
1,300 1,500 Pb
NA Sb
NA Se
Na U
Na
NA Zn
Na 23,000
Estimation of Background For most investigations of soil geochemistry at potentially hazardous sites, an estimation of the background concentrations of elements in soil is made by collecting a very limited number of samples outside the boundaries of the site. Given that true geochemical background for a given element is not just one concentration value but rather a distribution of concentration values (Matschullat and others, 2000; Reimann and Filzmoser, 2000; Reimann and Garrett, 2005; Reimann and others, 2005); this approach is considered by the authors to be wholly inadequate. For this investigation, a dataset of 160 samples of soils from depths of 0 to 5 cm collected throughout the entire State of Wyoming by the North American Soil Geochemical Landscapes Project (Smith and others, 2011, 2012) was used to determine the regional-scale geochemical background variation to provide context within which to consider the data from the Riverton UMTRA Site.
Results Table 5 presents a statistical summary for 41 elements in 0- to 5-cm soils from the Riverton UMTRA Site. The elements Ag, Cs, and Te are not included in this table because most concentration values are below the LLD. A complete listing of the geochemical data (44 elements and soil pH) is shown in appendix 1. Box-and-whisker plots allow a visual representation of the data distribution for each of the elements showing at least one exceedance of the Eco-SSLs or the human health soil screening levels (fig. 2). Figure 2 also provides a comparison of the UMTRA data with the 160-sample Statewide dataset. Given the history of uranium milling at the site, U and Th are elements of potential environmental concern, and their box-and-whisker plots are shown in figure 3. There are no established EcoSSLs for either element. The noncarcinogenic human health screening level (residential soils) for U is 230 mg/kg and for industrial soils is 3,100 mg/kg, both far exceeding any concentrations found at the Riverton UMTRA Site.
Table 4. Human health soil screening levels for industrial soils (U.S. Environmental Protection Agency, 2011). [Ag, silver; As, arsenic; Ba, barium; Be, beryllium; Cd, cadmium; Co, cobalt; Cu, copper; Mn, manganese; Ni, nickel; Pb, lead; Sb, antimony; Se, selenium; U, uranium; V, vanadium; Zn, zinc; mg/kg, milligrams per kilogram; NA, not available]
Human health screening level Human health screening level Element
carcinogenic (mg/kg) noncarcinogenic (mg/kg) Ag
NA 5,100 As
Ba
NA 190,000 Be
6,900 2,000 Cd
9,300 Co
1,900 Cu
NA 41,000 Mn
NA 23,000 Ni
64,000 20,000 Pb
NA Sb
NA Se
Na 5,100 U
Na 3,100
NA 5,200 Zn
Na 310,000
Table 5. Statistical summary for 41 elements in 0–5 cm soils from the Riverton UMTRA Site. [Al, aluminum; Ca, calcium; Fe, iron; K, potassium; Mg, magnesium; Na, sodium; S, sulfur; Ti, titanium; As, arsenic; Ba, barium; Be, beryllium; Bi, bismuth; Cd, cadmium; Ce, cerium; Co, cobalt; Cr, chromium; Cu, copper; Ga, gallium; Hg, mercury; In, indium; La, lanthanum; Li, lithium; Mn, manganese; Mo, molybdenum; Nb, niobium; Ni, nickel; P, phosphorus; Pb, lead; Rb, rubidium; Sb, antimony; Sc, scandium; Se, selenium; Sn, tin; Sr, strontium; Th, thorium; Tl, thallium; U, uranium; V, vanadium; W, tungsten; Y, yttrium; and Zn, zinc; n 19; UMTRA, Uranium Mill Tailings Remedial Action; MAD, median absolute deviation; %, percent; mg/kg, milligrams per kilogram; less than]
Element Units Minimum Median Maximum MAD Al % Ca % Fe % K % Mg % Na % S % Ti % As mg/kg Ba mg/kg 1,780 Be mg/kg Bi mg/kg Cd mg/kg Ce mg/kg Co mg/kg Cr mg/kg Cu mg/kg Ga mg/kg Hg mg/kg In mg/kg La mg/kg mg/kg Mn mg/kg 1,410 Mo mg/kg Nb mg/kg Ni mg/kg P mg/kg 1,350 Pb mg/kg Rb mg/kg Sb mg/kg
Table 5. Statistical summary for 41 elements in 0–5 cm soils from the Riverton UMTRA Site.—Continued [Al, aluminum; Ca, calcium; Fe, iron; K, potassium; Mg, magnesium; Na, sodium; S, sulfur; Ti, titanium; As, arsenic; Ba, barium; Be, beryllium; Bi, bismuth; Cd, cadmium; Ce, cerium; Co, cobalt; Cr, chromium; Cu, copper; Ga, gallium; Hg, mercury; In, indium; La, lanthanum; Li, lithium; Mn, manganese; Mo, molybdenum; Nb, niobium; Ni, nickel; P, phosphorus; Pb, lead; Rb, rubidium; Sb, antimony; Sc, scandium; Se, selenium; Sn, tin; Sr, strontium; Th, thorium; Tl, thallium; U, uranium; V, vanadium; W, tungsten; Y, yttrium; and Zn, zinc; n 19; UMTRA, Uranium Mill Tailings Remedial Action; MAD, median absolute deviation; %, percent; mg/kg, milligrams per kilogram; less than]
Element Units Minimum Median Maximum MAD Sc mg/kg Se mg/kg Sn mg/kg Sr mg/kg Th mg/kg Tl mg/kg U mg/kg mg/kg W mg/kg Y mg/kg Zn mg/kg
a One sample had a Cd concentration of <0.1 mg/kg. This value was replaced by 0.05 mg/kg for calculation of the MAD. b One sample had an In concentration of <0.02 mg/kg. This value was replaced by 0.01 mg/kg for calculation of the MAD. c Eight samples had Se concentrations of <0.2 mg/kg. These values were replaced by 0.1 mg/kg for calculation of the MAD.
Figure 2 (following six pages). Box-and-whisker plots showing the variation of (A) As (arsenic), (B) Ba (barium), (C) Cd (cadmium), (D) Co (cobalt), (E) Cu (copper), (F) Mn (manganese), (G) Ni (nickel), (H) Pb (lead), (I) Sb (antimony), (J) Se (selenium), (K) V (vanadium), and (L) Zn (zinc) in soils from the Riverton Uranium Mill Tailings Remedial Action (UMTRA) Site, Fremont County, Wyoming, and in soils from the 160-sample Statewide dataset. The outer limits of the lower and upper whiskers on the plots represent the 10th and 90th percentiles, respectively. The “X” between the two box-and-whisker plots in each figure represents the median for six soil samples from the Wyoming Statewide dataset that are located within the Wind River drainage. Eco-SSL, ecological soil screening level; mg/kg, milligrams per kilogram.
Figure 3. Box-and-whisker plots showing the variation of (A) U (uranium) and (B) Th (thorium) in soils from the Riverton Uranium Mill Tailings Remedial Action (UMTRA) Site, Fremont County, Wyoming, and in soils from the 160-sample Statewide dataset. The outer limits of the lower and upper whiskers on the plots represent the 10th and 90th percentiles, respectively. The “X” between the two box-and-whisker plots in each figure represents the median for six soil samples from the Wyoming Statewide dataset that are located within the Wind River drainage. mg/kg, milligrams per kilogram.
Discussion Within the UMTRA site, all 19 samples exceed (1) the carcinogenic human health screening level for As in residential soils (0.39 mg/kg) and (2) the Pb and V Eco-SSLs (ecological soil screening level) for birds (11 and 7.8 mg/kg, respectively). Eighteen of the 19 samples exceed the Mn Eco-SSL for plants (220 mg/kg), 13 of the 19 samples exceed the Sb Eco-SSL for mammals (0.27 mg/kg), and 10 of 19 samples exceed the Zn Eco-SSL for birds (46 mg/kg). However, to provide perspective, these exceedances are found in soils at most locations in the 160-sample Wyoming Statewide soil database. Therefore, elevated concentrations alone are not necessarily cause for alarm. Elements of most environmental concern to the tribes are U, V, Ni, Zn, and Th. Elements Ni, Zn, U, and Th are enriched in soils at the site compared to the Wyoming Statewide soil database (figures 2G, 2L, 3A, and 3B, respectively). The former mill site processed both U and V (U.S. Department of Energy, 2011), so it might be expected that both elements would be enriched at the site with respect to the Wyoming Statewide soils dataset; however V is depleted compared to the Wyoming soil dataset (fig. 2K). Of interest to the tribes is how these elements in the soils are transported and incorporated into vegetation, biota, and water. The principal surface uses are growing hay, grazing, and subsistence gardening. The Little Wind River runs along the south institutionalcontrol boundary of the UMTRA site and is used for recreation and subsistence purposes. Previous investigations by the Wind River Environmental Quality Commission have found U concentrations in sediments of an oxbow lake as high as 9.23 mg/kg (Shakespeare and Goggles, 2010), similar to the highest soil concentrations found in this study. Concentrations of As, Ni, and V in oxbow lake sediments also were similar to soil concentrations found in this study. This could imply that either eolian transport and (or) surface runoff are the principal transport mechanisms for moving soils toward the Little Wind River. If the former is a principal transport mechanism, then long-term exposure to dust and airborne particulates possibly could present human health concerns. Perhaps of greater interest to the tribes is the subsurface mobilization and transport of these elements through groundwater. A recently completed retrospective analysis of groundwater quality at the UMTRA site (Anthony Ranalli, written commun.) indicates that subsurface mobilization is not a primary consideration in groundwater, although these elements are present in groundwater at detectable concentrations. Acknowledgments Samples were collected with the assistance of Armando Ramirez. References Cited Abrahams, P.W., 2002, Soils: their implications to human health: Science of the Total Environment, v. 291, no. 1-3, p. 1–32. Ainsworth, N., Cooke, J.A., and Johnson, M.S., 1991, Biological significance of antimony in contaminated grassland: Water, Air, & Soil Pollution, v. 57-58, no. 1, p. 193–199. Anastasia, F.B., and Kender, W.J., 1973, The influence of soil arsenic on the growth of lowbush blueberry: Journal of Environmental Quality, v. 2, no. 3, p. 335–337.
Angle, J.S., and Chaney, R.L., 1991, Heavy metal effects on soil populations and heavy metal tolerance of Rhizobium meliloti, nodulation, and growth of alfalfa: Water, Air, & Soil Pollution, v. 57-58, no. 1, p. 597–604. Briggs, P.H., 2002, The determination of forty elements in geological and botanical samples by inductively coupled plasma–atomic emission spectrometry, in Taggart, J.E., Jr., ed., Analytical methods for chemical analysis of geologic and other materials, U.S. Geological Survey: U.S. Geological Survey Open-File Report 02–223, chap. G, 18 p., accessed January 3, 2012, at http://pubs.usgs.gov/of/2002/ofr-02-0223/OFR-02-0223.pdf. Briggs, P.H., and Meier, A.L., 2002, The determination of forty-two elements in geological materials by inductively coupled plasma–mass spectrometry, in Taggart, J.E., Jr., ed., Analytical methods for chemical analysis of geologic and other materials, U.S. Geological Survey: U.S. Geological Survey Open-File Report 02–223, chap. I, 14 p., accessed January 3, 2012, at http://pubs.usgs.gov/of/2002/ofr-02-0223/OFR-02-0223.pdf. Gough, L.P., Meadows, G.R., Jackson, L.L., and Dudka, S., 1989, Biogeochemistry of a highly serpentinized, chromite-rich ultramafic area, Tehama County, California: U.S. Geological Survey Bulletin 1901, 24 p. Govindaraju, Kuppusami, ed., 1989, Compilation of working values and sample description for 272 geostandards: Geostandards Newsletter, v. 13, Special Issue, 114 p. Hageman, P.L., and Brown, Z.A., 2002, Arsenic and selenium by flow injection or continuous flow-hydride generation-atomic absorption spectrometry, in Taggart, J.E., Jr., ed., Analytical methods for chemical analysis of geologic and other materials, U.S. Geological Survey: U.S. Geological Survey Open-File Report 02–223, chap. L, 7 p., accessed January 3, 2012, at http://pubs.usgs.gov/of/2002/ofr-02-0223/OFR-02-0223.pdf. Jiang, Q.Q., and Singh, B.R., 1994, Effect of different forms and sources of arsenic on crop yield and arsenic concentration: Water, Air, & Soil Pollution, v. 74, no. 3-4, p. 321–343. Kaplan, D.I., Sajwan, K.S., Adriano, D.C., and Gettier, S., 1990, Phytoavailability and toxicity of beryllium and vanadium: Water, Air, & Soil Pollution, v. 53, no. 3-4, p. 203–212. Lamersdorf, N.P., Godbold, D.L, and Knoche, D., 1991, Risk assessment of some heavy metals for the growth of Norway spruce: Water, Air, & Soil Pollution, v. 57-58, no. 1, p. 535–543. Lehoczky, E., Szabados, I., and Marth, P., 1996, Cadmium content of plants as affected by soil cadmium concentration: Communications in Soil Science and Plant Analysis, v. 27, no. 5-8, p. 1765–1777. Matschullat, Jörg., Ottenstein, R., and Reimann, Clemens, 2000, Geochemical background—Can we calculate it?: Environmental Geology, v. 39, no. 9, p. 990–1000. National Institute of Standards and Technology, 2003, Certificate of analysis—Standard Reference Material® 2709, San Joaquin soil baseline trace element concentrations: Gaithersburg, Md., National Institute of Standards and Technology, 12 p., accessed January 3, 2012, at https://www-s.nist.gov/srmors/certificates/archive/2709%20January%2018,%202002.pdf. Natural Resources Conservation Service, 2008, Sharpsburg series: National Cooperative Soil Survey, unpaged, accessed January 3, 2012, at https://soilseries.sc.egov.usda.gov/OSD_Docs/S/SHARPSBURG.html. Oliver, M.A., 1997, Soil and human health, a review: European Journal of Soil Science, v. 48, no. 4, p. 573–592. Oze, Christopher, Fender, Scott, Bird, D.K., and Coleman, R.G., 2004, Chromium geochemistry of serpentinite soils: International Geology Review, v. 46, no. 2, p. 97–126.
Pierzynski, G.M., Sims, J.T., and Vance, G.F., 2005, Soils and environmental quality (3rd ed.): Boca Raton, Fla., CRC Press, 569 p. Plumlee, G.S., and Ziegler, T.L., 2003, The medical geochemistry of dusts, soils, and other earth materials, in Lollar, B.S., ed., Environmental geochemistry, in Holland, H.D., and Turekian, K.K., exec. eds., Treatise on geochemistry, v. 9: Oxford, Pergamon Press, p. 263–310. Rehab, F.I., and Wallace, A., 1978, Excess trace metal effects on cotton: 2. Copper, zinc, cobalt, and manganese in Yolo Loam soil: Communications in Soil Science and Plant Analysis, v. 9, no. 6, p. 519–527. Reimann, Clemens, and Filzmoser, Peter, 2000, Normal and lognormal data distribution in geochemistry: Death of a myth. Consequences for the statistical treatment of geochemical and environmental data: Environmental Geology, v. 39, no. 9, p. 1001–1014. Reimann, Clemens, and Garrett, R.G., 2005, Geochemical background—Concept and reality: Science of the Total Environment, v. 350, no. 1–3, p. 12–27. Reimann, Clemens, Folzmoser, Peter, and Garrett, R.G., 2005, Background and threshold: critical comparison of methods of determination: Science of the Total Environment, v. 346, no. 1–3, p. 1–16. Richards, L.A., ed., 1954, Diagnosis and improvement of saline and alkali soils: U.S. Department of Agriculture, Agriculture Handbook No. 60, 159 p. Shakespeare, Travis, and Goggles, Dean, 2010, The Riverton Uranium Mill Tailings Remedial Action (UMTRA) Site on the Wind River Reservation Wyoming: Energy Resources and Produced Water Conference, May 25–26, 2010, Web cast accessed April 27, 2012, at http://wyocast.uwyo.edu/wyocast/viewer/?peid=26819d341cc6430abe57ec2ea11fa1a2. Smith, D.B., Cannon, W.F., and Woodruff, L.G., 2011, A national-scale geochemical and mineralogical survey of soils of the conterminous United States: Applied Geochemistry, v. 26, no. 5, p. S250–S255. Smith, D.B., Cannon, W.F., Woodruff, L.G., Rivera, F.M., Rencz, A.N, and Garrett, R.G., 2012, History and progress of the North American Soil Geochemical Landscapes Project, 2001– 2010: Earth Science Frontiers, v. 19, no. 3, p. 19–32. Spurgeon, D.J., Hopkin, S.P., and Jones, D.T., 1994, Effects of cadmium, copper, lead, and zinc on growth, reproduction and survival of the earthworm Eisenia fetida (Savigny): Assessing the environmental impact of point-source metal contamination in terrestrial ecosystems: Environmental Pollution, v. 84, no. 2, p. 123–130. Taylor, J.K., 1987, Quality assurance of chemical measurements: Chelsea, Mich., Lewis Publishers, p. 129–146. U.S. Department of Energy, 1995, Baseline risk assessment of ground water contamination at the uranium mill tailings site near Riverton, Wyoming: U.S. Department of Energy, Environmental Restoration Division, DOE/AL/62350-65, Rev. 1, accessed April 27, 2012, at http://www.lm.doe.gov/Riverton/BLRA_RVT.pdf. U.S. Department of Energy, 2011, Riverton, Wyoming, processing site: U.S. Department of Energy Fact Sheet, accessed April 27, 2012, at http://www.lm.doe.gov/Riverton/Fact_Sheet_-_Riverton.pdf. U.S. Environmental Protection Agency, 1991, Risk assessment guidance for Superfund: Volume 1—Human health evaluation manual (Part B, Development of risk-based preliminary remediation goals): Office of Research and Development, Publication EPA/540/R-92/003, 54 p., accessed January 3, 2012, at http://epa-prgs.ornl.gov/chemicals/help/documents/HHEMB.pdf.
U.S. Environmental Protection Agency, 1994, Method 7471B (revision 2)—Mercury in solid or semisolid waste (manual cold vapor technique), in Inorganic analytes, chap. 3 of Test methods for evaluating solid wastes: U.S. Environmental Protection Agency SW-846, accessed January 4, 2012, at http://www.epa.gov/epawaste/hazard/testmethods/sw846/pdfs/7471b.pdf. U.S. Environmental Protection Agency, 1996a, Soil screening guidance: User’s guide (2nd ed.): Office of Solid Waste and Emergency Response, Publication 9355.4-23, 39 p., accessed January 3, 2012, at http://rais.ornl.gov/documents/SSG_nonrad_user.pdf. U.S. Environmental Protection Agency, 1996b, Soil screening guidance: Technical background document: Office of Solid Waste and Emergency Response, Publication EPA/540/R95/128, 168 p., accessed January 3, 2012, at http://rais.ornl.gov/documents/SSG_nonrad_technical.pdf. U.S. Environmental Protection Agency, 2002, Supplemental guidance for developing soil screening levels for Superfund sites: Office of Solid Waste and Emergency Response, Publication 9355.4-24, 93 p., accessed January 3, 2012, at http://epa-prgs.ornl.gov/chemicals/help/documents/SSG_nonrad_supplemental.pdf. U.S. Environmental Protection Agency, 2003, Guidance for developing ecological soil screening levels (Eco-SSLs): Office of Solid Waste and Emergency Response Directive 92857-55, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/SOPs.htm. U.S. Environmental Protection Agency, 2005a, Ecological soil screening levels for antimony: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-61, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_antimony.pdf. U.S. Environmental Protection Agency, 2005b, Ecological soil screening levels for arsenic: Office of Solid Waste and Emergency Response, OSWER Directive 9285-62, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_arsenic.pdf. U.S. Environmental Protection Agency, 2005c, Ecological soil screening levels for barium: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-63, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_barium.pdf. U.S. Environmental Protection Agency, 2005d, Ecological soil screening levels for beryllium: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-64, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_beryllium.pdf. U.S. Environmental Protection Agency, 2005e, Ecological soil screening levels for cadmium: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-65, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_cadmium.pdf. U.S. Environmental Protection Agency, 2005f, Ecological soil screening levels for cobalt: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-67, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_cobalt.pdf. U.S. Environmental Protection Agency, 2005g, Ecological soil screening levels for lead: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-70, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_lead.pdf. U.S. Environmental Protection Agency, 2005h, Ecological soil screening levels for vanadium: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-75, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_vanadium.pdf. U.S. Environmental Protection Agency, 2006, Ecological soil screening levels for silver: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-77, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_silver.pdf.
U.S. Environmental Protection Agency, 2007a, Ecological soil screening levels for copper: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-68, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_copper.pdf. U.S. Environmental Protection Agency, 2007b, Ecological soil screening levels for manganese: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-71, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_manganese.pdf. U.S. Environmental Protection Agency, 2007c, Ecological soil screening levels for nickel: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-76, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_nickel.pdf. U.S. Environmental Protection Agency, 2007d, Ecological soil screening levels for selenium: Office of Solid Waste and Emergency Response, Directive 9285.7-72, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_selenium.pdf. U.S. Environmental Protection Agency, 2007e, Ecological soil screening levels for zinc: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-73, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_zinc.pdf. U.S. Environmental Protection Agency, 2008a, Ecological soil screening levels for chromium: Office of Solid Waste and Emergency Response, OSWER Directive 9285.7-66, accessed January 3, 2012, at http://www.epa.gov/ecotox/ecossl/pdf/eco-ssl_chromium.pdf. U.S. Environmental Protection Agency, 2008b, Superfund ecological risk assessment 8-step process: 2. Screening level exposure estimate and risk calculation, accessed January 3, 2012, at http://www.epa.gov/region05/superfund/ecology/erasteps/erastep2.html. U.S. Environmental Protection Agency, 2011, Regional screening levels (Formerly HHMSSL— Human Health Medium-Specific Screening Levels), accessed January 3, 2012, at http://www.epa.gov/earth1r6/6pd/rcra_c/pd-n/screen.htm/.