Published in J. Environ. Qual. 33:553-558 (2004).
© ASA, CSSA, SSSA
677 S. Segoe Rd., Madison, WI 53711 USA
TECHNICAL REPORT
Heavy Metals in the Environment
Plant-Available Zinc and Lead in Mine Spoils and Soils at the Mines of Spain, Iowa
Monday O. Mbilaa and
Michael L. Thompson*,b
a Dep. of Plant and Soil Science, Alabama A&M Univ., Normal, AL 35762
b Agronomy Dep., Iowa State Univ., Ames, IA 50011-1010
* Corresponding author (Michael_Thompson{at}iastate.edu).
Received for publication April 14, 2003.
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ABSTRACT
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To investigate the forms of Zn and Pb and their plant availability in mine spoil long after its abandonment, we studied seven sites in the Mines of Spain, near Dubuque, IA. Ores of Zn and Pb were mined from dolomitic limestone primarily during the 19th century, and there had been no subsequent remediation of metals-contaminated spoil. From both mine spoil and undisturbed areas, we collected root-zone soil samples as well as samples of the dominant ground-level, native plants, aniseroot [Osmorhiza longistylis (Torr.) DC.] and black snakeroot (Sanicular marilandica L.). We determined Zn and Pb concentrations in both the plant tissue and in the soil samples after strong-acid digestion, and we fractionated the solid-phase forms of Zn, Pb, and P in the soil samples by using sequential extraction. Concentrations of total Zn and Pb were 10- to 20-fold greater in the spoil than in the undisturbed soils. Plants growing in the mine spoil had Zn concentrations two to four times greater and Pb concentrations more than 26 times greater than did plants growing in the undisturbed soils. The highest concentrations of Zn and Pb were in the CBD-extractable and the residual fractions in both undisturbed and mine spoil samples. Although the mine spoil contained large amounts of P, Zn, and Pb were available for uptake by the two plant species in amounts proportional to Zn and Pb concentrations in the rooting zone.
Abbreviations: AAS, atomic absorption spectroscopy • CBD, citrate–bicarbonate–dithionite • DTPA, diethylenetriamine pentaacetic acid • EDTA, ethylenediamine tetraacetic acid • HOAc, acetic acid • ICAP-AES, inductively coupled Ar plasma–atomic emission spectroscopy • OAc, acetate • TEA, triethanol amine
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INTRODUCTION
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ZINC AND PB in soils affected by mining or smelting activities occur in forms that depend on the mode of contamination as well as on soil properties (e.g., pH, organic matter content, and clay content). The kind and amounts of solid-phase Zn and Pb in contaminated soils may influence the bioavailability of the metals. It is often assumed that thermodynamic solubilities of compounds are correlated with solid-phase dissolution rates (Traina and Laperche, 1999). Sparingly soluble forms of metals are expected to contribute little to the free-metal cation pool of the soil solution.
One index of the bioavailability of a metal to plants is the degree to which an extractable solid-phase quantity is correlated with measured tissue concentrations. For example, extractants such as HOAc, CaCl2, EDTA, and DTPA have been used to assess the fraction of the total metal concentration in soils that might be available for plant uptake (Lindsay and Norvell, 1978). Sinaj et al. (1999) have shown that DTPA-extractable Zn correlates well with the amount of soil Zn that is isotopically exchangeable (and presumably bioavailable) over a 15-d period.
Although plant uptake of metals is often well correlated with the activity of the uncomplexed metal cation in soil solution, metal uptake is a function of many other factors, too, such as root length, rate of water uptake, and microbial activity in the rhizosphere. Competing, soluble cations such as calcium and complexing organic anions have been shown to increase the solubility of some metals (e.g., Sauvé et al., 1998; Turpeinen et al., 2000). Moreover, plant species may differ in their need for and tolerance of metals as well as in the physiological mechanisms of metal transport and incorporation in tissue (Barber, 1995). Thus, the quantities of metals in a soil that are actually susceptible to plant uptake remain difficult to predict.
During much of the 19th century, Zn and Pb ores were mined in northeastern Iowa. Classified as Mississippi Valley–type deposits, the ores formed after Zn and Pb were transported in solution by hot, saline brines through caves and fractures in marine Ordovician dolostone, where they precipitated as sphalerite and galena. When subsequent landscape dissection lowered the water table, the metal sulfides were oxidized, dissolved, and reprecipitated as metal oxides and carbonates (Ludvigson and Dockal, 1984). Mining activities in Iowa included deep shafts that linked underground caverns, but much exploration and some ore extraction were also done from relatively shallow pits and trenches dug near the surface. Mining in the area ceased about 100 yr ago.
The objectives of this research were (i) to identify the chemical forms of Zn and Pb in mine spoil at the Mines of Spain, Dubuque County, Iowa, approximately 100 yr after the end of mining activities, and (ii) to assess the bioavailability of Zn and Pb by two species of native plants growing at the site.
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MATERIALS AND METHODS
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Research Sites and Sampling Techniques
The research sites were in the Mines of Spain Recreation Area of Dubuque County, in the Paleozoic Plateau region of northeastern Iowa. The sites chosen for study were on a hill slope (18–25% slope) where the undisturbed soil is mapped as Seaton silt loam (a fine-silty, mixed, superactive, mesic Typic Hapludalf) and is developed in loess that was deposited about 13000 yr ago (Boeckman, 1983). Below 0.5 to 2.0 m of loess, there is a clayey, iron-rich paleosol that developed in residuum of Ordovician dolostone. The vegetation is predominantly oak (Quercus ssp.) and hickory (Carya ssp.); aniseroot and black snakeroot are the dominant ground-level plants. Detailed morphological, physical, chemical, and mineralogical properties of soils at the research site have been reported elsewhere (Mbila, 2000).
The local area studied (
0.1 ha) is comprised of surface excavations of various sizes (3–10 m diam.). Historical records are not sufficient to determine exactly when mining occurred at the sites we studied. Few pits were refilled after excavation, and beside most of them piles of excavated spoil remain. These features give the sampling site an irregular microtopography, with many small depressions (0.5–1.0 m deep) over the entire hill slope (Fig. 1)
. Over the years, mine spoil materials and immediately adjacent soil materials have washed into the mining pits, redistributing Zn and Pb derived from the ore and spoil (Mbila, 2000).
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Fig. 1. Schematic diagram of former mining pit, illustrating microtopography of the mine spoil at Mines of Spain Recreational Area, near Dubuque, IA.
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Soil and plant samples were collected from seven sites on the slope. Three of the sites (1, 2, 5) were in mine spoil located at the rims of three excavated pits. Sites 3 and 4 were higher on the slope than the spoil materials and appeared to be physically undisturbed by mining. Sites 6 and 7 were also undisturbed sites but down slope from the spoil materials around the pits. At each site, a quadrant of 1 m2 was laid out on the ground to count and sample the ground-level plants. Within that quadrant, all understory plants were identified and counted. All individuals of the two most abundant understory species, aniseroot and black snakeroot, were carefully excavated; soil from the rooting zone (0–20 cm) was also collected.
Sample Preparation and Analysis
In the laboratory, the plant samples were rinsed with deionized and distilled water to remove debris and dust from leaves and soil particles that clung to the roots. Shoots were then separated from the roots and dried separately at 60°C for 4 d in a forced-air drying oven. Moisture content was determined by drying subsamples at 105°C until constant weight was obtained. The tissue samples were ground to pass a 60-mesh (250-µm) sieve. Total Zn and Pb were determined by reflux digestion of 1-g subsamples of tissue with 15 mL of concentrated trace-metal–grade HNO3 at 100°C for 16 h by using an Al digestion block (Miller and McFee, 1983). After the digestion, 5 mL of 30% H2O2 were added to oxidize resistant organic matter while the digest was cooling. The solution was then filtered through Whatman no. 42 filter paper, diluted to 25 mL, and analyzed for Zn and Pb. Zinc in the solutions was determined by flame atomic absorption spectroscopy, and Pb was determined by inductively coupled plasma atomic–emission spectroscopy (ICP-AES).
Soil samples were air-dried at room temperature for a week and then ground to pass a 10-mesh (2-mm) sieve. Moisture content was determined by drying separate subsamples at 105°C until they reached constant weight. Total Zn and Pb were determined by reflux digestion of 4 g of soil with 20 mL of concentrated trace-metal–grade HNO3 at 100°C for 16 h using an Al digestion block (Miller and McFee, 1983). After the digestion, 5 mL of 30% H2O2 were added to the digest as it cooled to oxidize resistant organic matter. The solutions were filtered through Whatman no. 42 filter paper, diluted to 50 mL, and analyzed for Zn and Pb by atomic absorption spectroscopy. Selected samples were run in triplicate to monitor the precision of the determinations, and average coefficients of variation were 2 and 5% for Zn and Pb, respectively. In addition, a reference sample from a biosolids-amended soil (48 mg Pb kg–1 and 262 mg Zn kg–1) was included in each run for quality control. Recovery of the total Zn and Pb in the sequential fractions is given in Table 5.
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Table 5. Concentrations of sequentially extracted Zn and Pb in mine spoil and undisturbed soil samples at the Mines of Spain research sites.
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On samples ground to pass a 100-mesh (149-µm) sieve, total C and N were determined by dry combustion by using a LECO elemental analyzer, and organic C was determined by using the Mebius method of dichromate oxidation (Nelson and Sommers, 1996). Particle-size distribution was determined with the pipette method (Gee and Bauder, 1986). Soil pH was determined by using a 1:1 soil/water ratio. Bulk densities of undisturbed, field-moist samples were determined in triplicate by the clod method using paraffin (Blake and Hartge, 1986). The DTPA-extractable Zn and Pb were determined by ICP-AES after extraction with a combined solution of 0.05 M DTPA, 0.01 M TEA, and 0.01 M CaCl2, adjusted to pH 7.3 (Lindsay and Norvell, 1978).
A sequential extraction scheme was used to partition Zn and Pb in the soil samples into nominal solid-phase forms; details are presented in Table 1. We modified the method of Tessier et al. (1979) by using Mg(NO3)2 to extract exchangeable metals (Shuman, 1985) and by using the citrate–bicarbonate–dithionite extraction method to extract sesquioxide-bound metals (Jackson et al., 1986). We used Na acetate to dissolve carbonate-bound metals, H2O2 to oxidize organic matter, and concentrated HNO3 to dissolve Zn and Pb that were held in crystalline structures of resistant primary or secondary minerals. The concern of Shuman (1985) that Na dithionite may be contaminated with Zn was addressed by preparing standard solutions with blanks that received exactly the same treatment as the soil samples. Phosphorus was also determined in the sequential extracts by ICP-AES, and the total P content reported is the sum of P removed in the extractions. Sample replications and inclusion of a reference soil sample with each set of analyses (as described above) were used to check the precision and reliability of our methods.
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RESULTS AND DISCUSSION
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Soils Properties and Plant Inventory
Soil properties at the undisturbed sites (3, 4, 6, and 7) reflected the nature of the loess parent material, e.g., silt loam textures, moderately high organic C contents, and little if any inorganic carbonate content (i.e., total C less organic C) (Table 2). Mining activities, which involved excavation and placement of subsurface materials at the soil surface, had mixed clayey, dolomitic materials from the weathered residuum with the loess. Therefore, soil surface horizons at the mine spoil sites (1, 2, and 5) generally had more clay, less organic C, higher inorganic carbonate, higher bulk density, and higher pH than did surface horizons at the undisturbed sites (Table 2). Aniseroot and black snakeroot were the most abundant of the ground-level, understory species at most of the sites, but understory species at the undisturbed sites were more diverse than at the mine spoil sites (Table 3).
Concentration of Zinc and Lead in Soils
Total concentration of Zn in soil at the undisturbed sites (56–70 mg Zn kg–1 soil) were similar to the geometric mean concentrations in agricultural soils of Iowa reported by Holmgren et al. (1993) (59 mg Zn kg–1). Lead concentrations at the undisturbed sites (24–35 mg Pb kg–1 soil) were somewhat greater than those reported by Holmgren et al. (13 mg Pb kg–1) but comparable to those of uncontaminated soils in other parts of the world (Kabata-Pendias and Pendias, 2001). In contrast, metal concentrations in soil at the mine spoil sites (550–1032 mg Zn kg–1 soil and 650–955 mg Pb kg–1 soil) were more than 10- to 20-fold greater (Table 2). The DTPA extraction is often used as an index of plant-available metals in soils, and by that measure the concentration of plant-available Zn was four times greater in the mine spoil than in the undisturbed soil. In the undisturbed soil, DTPA-extractable Zn was several times greater than the "critical" values that predict Zn deficiency (Brennan et al., 1993). The mean concentration of DTPA-extractable Pb was 37 times greater in the mine spoil than in the undisturbed soil. Thus, both total and potentially plant-available Zn and Pb concentrations in the mine spoil were greater than in most soils uncontaminated by human activities.
Concentrations of Zinc and Lead in Plants
Aniseroot and black snakeroot are perennials with shallow root systems, and they had slightly different root/shoot biomass ratios, 1.2 and 0.8 for aniseroot and black snakeroot, respectively (data not shown). Consistent with concentrations of Zn and Pb in the soil and the fact that Zn is an essential micronutrient, Zn concentrations in plant tissues were considerably greater than those of Pb (Table 4). Concentrations of Zn in both aniseroot and black snakeroot growing in the mine spoil was two to four times greater than those in the tissues of both species growing in the undisturbed soil (Table 4). In contrast, there was more than a 26-fold difference in Pb concentration between plants growing in the mine spoil and those in the undisturbed soil.
Uptake of Zn and Pb differed somewhat for each species. For example, the mean Zn concentrations in the roots of black snakeroot were greater than those in the roots of aniseroot, although the differences were not large (Table 4). In the root tissue of both species, the mean concentrations of Zn and Pb were greater than concentrations in the shoots; the difference was more pronounced in the plants growing in the mine spoil. Similar differences between root and shoot concentrations of Zn and Pb have been observed for other plant species (Dahmani-Muller et al., 2000, among others). The difference between root and shoot concentrations of Zn and Pb suggests the presence of a physiological mechanism in the plants that excludes Zn and Pb from shoots and reproductive tissue by retaining metals in the roots (Baker, 1981). This mechanism may have been one reason for the successful growth of the two species in the mine spoil. The relative abundance of these species on the mine spoil suggests but does not prove that they were better adapted to Zn and Pb than were other ground-level species at the site (Table 3).
Fractionation of Solid-Phase Zinc and Lead
To assess the solid-phase distribution of Zn and Pb in soils, many studies have relied on sequential extractions, in which progressively stronger chemical reagents are employed to solubilize portions of the total metal pool in the soil. The derived fractions are typically interpreted to represent exchangeable, carbonate-bound, sesquioxide-bound, organicmatter–bound, or residual or structural (i.e., metal ions that are incorporated in silicate or primary mineral structures) (e.g., Tessier et al., 1979; Shuman, 1985). Although the specificity of the extracting solutions for a given metal form may never be certain (Beckett, 1989; Sheppard and Stephenson, 1997), a well-planned sequence of extractants can at least minimize solubilization of multiple phases in one extract, providing a basis for the comparison of one soil sample to others.
Sequential extraction of both undisturbed and mine spoil samples revealed that the highest concentrations of Zn and Pb were in the CBD-extractable and residual fractions (Table 5). The concentrations of both metals in the residual fraction of the mine spoil samples could reflect Zn and Pb in ore fragments that were not susceptible to decomposition by treatments intended to dissolve carbonates, sesquioxides, and organic matter. The abundance of Zn and Pb in the CBD-extractable fractions correlates well with the tendency and capacity of Fe, Mn, and Al oxides to sorb metal cations from solution (Schwertmann and Taylor, 1989; McKenzie, 1989; Hsu, 1989). Thus, the sequential extraction approach gave results generally consistent with those of spectroscopic and microscopic techniques that allow more certain identification of the dominant metal-bearing solid phases in contaminated soils, e.g., iron oxyhydroxides and smectites for Zn (Buatier et al., 2001) and pyromorphite, jarosite, cerrussite, or iron oxyhydroxides for Pb (Cotter-Howells et al., 1994; Morin et al., 1999; Buatier et al., 2001).
There was sufficient range in the concentrations of soil Zn fractions among the mine spoil samples to explore if the fractions were good predictors of plant uptake. In this tightly controlled data set, however, the Zn contents of the solid-phase fractions were strongly correlated with one another and with the total concentrations of Zn in the soils. Therefore, we could not assess the relative impact of each fraction on plant availability of the metals. As predictors of Zn uptake by the roots and shoots of aniseroot and black snakeroot, some of the sequentially extracted fractions compared favorably with DTPA-extractable Zn (compare the coefficients of determination, r2, in Table 6). Although the amounts were small, our data suggest that the initial Mg(NO3)-extractable Zn was as strongly correlated with plant uptake in roots as was DTPA-extractable Zn. A similar analysis for Pb was not possible with our data set because values for Pb in the soil fractions as well as in the plants tended to be strongly clustered at either the mine spoil sites or the undisturbed sites.
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Table 6. Linear regression expressions that describe the concentration of Zn in plant roots and shoots (y) as a function of extractable Zn fractions in the soil (x) (n = 7).
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Phosphorus and Metal Uptake
There has long been interest in understanding how plant uptake of both Zn and Pb may be influenced by P. For example, apparent Zn deficiencies (or higher Zn requirements) in crop plants have been reported where there are high levels of supplied P (Loneragan and Webb, 1993, among others). Potential mechanisms for the influence of P on plant uptake of Zn include (i) less Zn absorption due to a reduction in root infections by vesicular arbuscular mycorrizhae at high P levels and (ii) increased sorption of Zn to the solid-phase soil components where phosphate is abundant. For example, Agbenin (1998) reported experimental and modeling evidence that both surface complexation and precipitation of ZnHPO4 could account for enhanced retention of Zn in a P-treated soil.
Uptake of Pb could also be reduced when soil P levels are high. Thermodynamic equilibrium models predict that, where P is abundant, soluble Pb in contaminated soils should be controlled by sparingly soluble phosphates like pyromorphite. A number of workers (including Zhang et al., 1997; Laperche et al., 1997; Hettiarachchi et al., 2000, 2001; Manecki et al., 2000; Basta et al., 2001) have reported feasibility studies in which pyromorphite or pyromorphite-like minerals formed when phosphate sources such as apatite, rock phosphate, or fertilizer phosphate were mixed with Pb-bearing minerals or soil materials. The theme of these investigations is that the bioavailability of Pb might be limited if relatively insoluble phosphate minerals control its concentration in the soil solution.
The Galena dolomite beds from which Zn and Pb were mined at the Mines of Spain lie below phosphatic dolomites of the Upper Ordovician Maquoketa Group (Witzke and Heathcote, 1997). The basal Maquoketa phosphorite consists of small, millimeter-scale pellets of apatite and phosphatic fossil molds, and this material was mixed with the ore spoil during mining. As a result, the spoil materials at the Mines of Spain contained about twice as much total P as the undisturbed, loess-derived soil (Table 2).
At our study sites, Zn and Pb were taken up by plants growing in the P-rich mine spoil more than 100 yr after the spoil was exposed at the land surface; thus neither Zn nor Pb were completely immobilized by the presence of apatite nor by soil pH values of 7.3 to 7.4. It is possible that the rate at which apatite was solubilized or the rates at which the metals could be precipitated with phosphate anions were slow enough that free, soluble metal ions continued to be available for uptake by aniseroot and black snakeroot. Alternatively, complexation of Zn and Pb by soluble organic compounds may have precluded metal phosphate precipitation and still maintained the metals in a form that could be taken up by roots. A third possible mechanism of uptake could involve direct contact between roots and metal ions sorbed on the solid phase of the soil. Our data do not allow us to identify the most likely of these mechanisms, but they all deserve further investigation.
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CONCLUSION
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Spoil materials that remain from mining during the 19th century at the Mines of Spain, Iowa, exhibited elevated Zn and Pb concentrations compared with nearby undisturbed soil. We found that two native understory species, aniseroot and black snakeroot, grew well on the mine spoil and took up Zn and Pb from it. Much of the Zn and Pb in the spoil remained in sparingly soluble or poorly extractable solid phases. Outside of the residual fraction, Zn and Pb were primarily associated with sesquioxide minerals. Even though the roughly century-old spoil contained significant levels of a phosphate-bearing mineral and had a relatively high pH, Zn and Pb were available for uptake by plants growing at the site in amounts proportional to Zn and Pb concentrations in the soil and spoil materials.
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ACKNOWLEDGMENTS
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We thank L. Schultz, Y. Sui, P. Fleming, and D. Laird for assistance in laboratory analyses; D. Lewis for assistance in identifying plants; P. Dixon for advice on statistical analyses; J. Hutchison for assistance with the figure; and L. Hundal for helpful comments on the manuscript. We also thank the Iowa Department of Natural Resources and its Rangers W. Buchholtz and L. Zirkelbach for access and assistance in locating the study sites. We gratefully acknowledge the Iowa Agriculture and Home Economics Experiment Station for funding the research.
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REFERENCES
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- Agbenin, J.O. 1998. Phosphate-induced zinc retention in a tropical semi-arid soil. Eur. J. Soil Sci. 49:693–700.
- Baker, A.J.M. 1981. Accumulators and excluders: Strategies in the response of plants to heavy metals. J. Plant Nutr. 3:643–654.[Web of Science]
- Barber, S.A. 1995. Soil nutrient bioavailability. A mechanistic approach. 2nd ed. John Wiley & Sons, New York.
- Basta, N.T., R. Gradwohl, K.L. Snethen, and J.L. Schroder. 2001. Chemical stabilization of lead, zinc, and cadmium in smelter-contaminated soils using biosolids and rock phosphate. J. Environ. Qual. 30:1222–1230.[Abstract/Free Full Text]
- Beckett, P.H.T. 1989. The use of extractants in studies on trace metals in soils, sewage sludges, and sludge-treated soils. Adv. Soil Sci. 9:143–176.
- Blake, G.R., and K.H. Hartge. 1986. Bulk density. p. 363–375. In A. Klute (ed.) Methods of soil analysis. Part 1. 2nd ed. Agron. Monogr. 9. SSSA, Madison, WI.
- Boeckman, L. 1983. Soil survey of Dubuque County, Iowa. USDA-SCS, Washington, DC.
- Buatier, M.D., S. Sobanska, and F. Elsass. 2001. TEM-EDX investigation on Zn- and Pb-contaminated soils. Appl. Geochem. 16:1165–1177.
- Brennan, R.F., J.D. Armour, and D.J. Reuter. 1993. Diagnosis of zinc deficiency. p. 167–181. In A.D. Robson (ed.) Zinc in soils and plants. Vol. 55. Developments in plant and soil sciences. Kluwer Academic Publ., Boston.
- Cotter-Howells, J.D., P.E. Chapness, J.M. Charnock, and R.A.D. Pattrick. 1994. Identification of pyromorphite in mine-waste contaminated soils by ATEM and EXAFS. Eur. J. Soil Sci. 45:393–402.
- Dahmani-Muller, H., F. van Oort, B. Gélie, and M. Balabane. 2000. Strategies of heavy metal uptake by three plant species growing near a metal smelter. Environ. Pollut. 109:231–238.[Medline]
- Gee, G.W., and J.W. Bauder. 1986. Particle size analysis. p. 383–412. In A. Klute (ed.) Methods of soil analysis. Part 1. 2nd ed. Agron. Monogr. 9. SSSA, Madison, WI.
- Hettiarachchi, G., G.M. Pierzynski, and M.D. Ransom. 2000. In situ stabilization of soil lead using phosphorus and manganese oxide. Environ. Sci. Technol. 34:4614–4619.
- Hettiarachchi, G., G.M. Pierzynski, and M.D. Ransom. 2001. In situ stabilization of soil lead using phosphorus. J. Environ. Qual. 30:1214–1221.[Abstract/Free Full Text]
- Holmgren, G.C.S., M.W. Meyer, R.L. Chaney, and R.B. Daniels. 1993. Cadmium, lead, zinc, copper, and nickel in agricultural soils of the United States of America. J. Environ. Qual. 22:335–348.[Abstract/Free Full Text]
- Hsu, P.H. 1989. Aluminum oxides and oxyhydroxides. p. 331–378. In J.B. Dixon and S.B. Weed (ed.) Minerals in soil environments. 2nd ed. SSSA Book Ser. 1. SSSA, Madison, WI.
- Jackson, M.L., C.H. Lim, and L.W. Zelazny. 1986. Oxides, hydroxides, and aluminosilicates. p. 101–150. In A. Klute (ed.) Methods of soil analysis. Part 1. 2nd ed. Agron. Monogr. 9. SSSA, Madison, WI.
- Kabata-Pendias, A., and H. Pendias. 2001. Trace elements in soils and plants. 3rd ed. CRC Press, Boca Raton, FL.
- Laperche, V., T.J. Logan, P. Gaddam, and S.J. Traina. 1997. Effect of apatite amendments on plant uptake from contaminated soil. Environ. Sci. Technol. 31:2745–2753.
- Lindsay, W.L., and W.A. Norvell. 1978. Development of a DTPA soil test for Zn, Fe, Mn, and Cu. Soil Sci. Soc. Am. J. 42:421–428.
- Loneragan, J., and M.J. Webb. 1993. Interactions between zinc and other nutrients affecting the growth of plants. p. 119–134. In A.D. Robson (ed.) Zinc in soils and plants. Vol. 55. Developments in plant and soil sciences. Kluwer Academic Publ., Boston.
- Ludvigson, G.A., and J.A. Dockal. 1984. Lead and zinc mines in the Dubuque area. Iowa Geology no. 9. Iowa Dep. of Natural Resources, Iowa Geological Survey, Iowa City.
- Manecki, M., P.A. Maurice, and S.J. Traina. 2000. Kinetics of aqueous Pb reaction with apatites. Soil Sci. 165:920–933.
- Mbila, M.O. 2000. Mobility and bioavailability of heavy metals in selected soils from Nigeria and Iowa. Ph.D. diss. Iowa State Univ., Ames, IA.
- McKenzie, R.M. 1989. Manganese oxides and hydroxides. p. 439–466. In J.B. Dixon and S.B. Weed (ed.) Minerals in soil environments. 2nd ed. SSSA Book Ser. 1. SSSA, Madison, WI.
- Miller, W.P., and W.W. McFee. 1983. Distribution of Cd, Zn, Cu, and Pb in soils of industrial northwestern Indiana. J. Environ. Qual. 12:29–33.
- Morin, G., J.D. Ostergren, F. Juillot, P. Ildefonse, G. Calas, and G.E. Brown, Jr. 1999. XAFS determination of the chemical form of lead in smelter-contaminated soils and mine tailings: Importance of adsorption processes. Am. Mineral. 84:420–434.[Abstract]
- Nelson, D.W., and L.E. Sommers. 1996. Total carbon, organic carbon and organic matter. p. 961–1010. In D.L. Sparks et al. (ed.) Methods of soil analysis. Part 3. SSSA Book Ser. 5. SSSA, Madison, WI.
- Sauvé, S., M. McBride, and W. Hendershot. 1998. Lead phosphate solubility in water and soil suspensions. Environ. Sci. Technol. 32:388–393.
- Schwertmann, U., and R.M. Taylor. 1989. Iron oxides. p. 379–438. In J.B. Dixon and S.B. Weed (ed.) Minerals in soil environments. 2nd ed. SSSA Book Ser. 1. SSSA, Madison, WI.
- Sheppard, M.I., and M. Stephenson. 1997. Critical evaluation of selective extraction methods for soils and sediments. p. 69–100. In R. Prost ed. Third Int. Conf. on Biogeochemistry of Trace Elements: Contaminated Soils, Paris, France. 15–19 May 1995. INRA Editions, Versailles, France.
- Shuman, L.M. 1985. Fractionation method for soil microelements. Soil Sci. 140:11–23.
- Sinaj, S., F. Mächler, and E. Frossard. 1999. Assessment of isotopically exchangeable zinc in polluted and nonpolluted soils. Soil Sci. Soc. Am. J. 63:1618–1625.[Abstract/Free Full Text]
- Tessier, A., P.G.C. Campbell, and M. Bisson. 1979. Sequential extraction procedure for the speciation of particulate trace metals. Anal. Chem. 51:844–850.
- Traina, S.J., and V. Laperche. 1999. Contaminant bioavailability in soils, sediments, and aquatic environments. Proc. Natl. Acad. Sci. USA 96:3365–3371.[Abstract/Free Full Text]
- Turpeinen, R., J. Salminen, and T. Kairesalo. 2000. Mobility and bioavailability of lead in contaminated boreal forest soil. Environ. Sci. Technol. 34:5152–5156.
- Witzke, B.J., and R.C. Heathcote. 1997. Lower Maquoketa phosphatic and organic-rich facies, Upper Ordovician, Dubuque County. p. 25–37. In B. Witzke et al. (ed.) Geology of the Dubuque area. Guidebook 63. Iowa Geological Soc., Iowa City, IA.
- Zhang, P., J.A. Ryan, and L.T. Bryndzia. 1997. Pyromorphite formation from goethite adsorbed lead. Environ. Sci. Technol. 31:2673–2678.
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ABSTRACT
INTRODUCTION
