Mickey E. Gunter

Micro-spectroscopic investigation of selenium-bearing minerals from the Western US Phosphate Resource Area

Mining activities in the US Western Phosphate Resource Area (WPRA) have released Se into the environment. Selenium has several different oxidation states and species, each having varying degrees of solubility, reactivity, and bioavailability. In this study we are investigating the speciation of Se in mine-waste rocks. Selenium speciation was determined using bulk and micro-x-ray absorption spectroscopy (XAS), as well as micro-x-ray fluorescence mapping. Rocks used for bulk-XAS were ground into fine powders. Shale used for micro-XAS was broken along depositional planes to expose unweathered surfaces. The near edge region of the XAS spectra (XANES) for the bulk rock samples revealed multiple oxidation states, with peaks indicative of Se(-II), Se(IV), and Se(+VI) species. Micro-XANES analysis of the shale indicated that three unique Se-bearing species were present. Using the XANES data together with ab initio fitting of the extended x-ray absorption fine structure region of the micro-XAS data (micro-EXAFS) the three Se-bearing species were identified as dzharkenite, a di-selenide carbon compound, and Se-substituted pyrite. Results from this research will allow for a better understanding of the biogeochemical cycling of Se in the WPRA.

Composition, Fe3+/∑Fe, and crystal structure of non-asbestiform and asbestiform amphiboles from Libby, Montana, U.S.A.

Abstract Compositional data and Fe3+/ΣFe ratios obtained by electron microprobe and Mössbauer analyses are given for a suite of three amphibole and amphibole-asbestos samples collected from the former vermiculite mine near Libby, Montana. A crystal structure analysis, compositional data, and Fe3+/ΣFe values for two samples from a previous study are also reported. The results confirm the conclusion drawn in the previous study that these amphiboles are dominantly compositions ranging from winchite to richterite. Mössbauer spectroscopy yielded Fe3+/ΣFe ratios from 58% to 72% for the five samples. The crystal structure was determined for a single crystal selected from a bulk sample. Its formula (as determined by electron microprobe analysis and Mössbauer spectroscopy) is (K0.19 Na0.32)A(Na0.85 Ca1.12Mn0.03)B(Mn0.01Mg4.43Fe3+ 0.34Fe2+0.19Ti0.01Al0.02)(Al0.03Si7.97O22)(OH1.63F0.37). The refinement was carried out based on space group C2/m, with a = 9.879(2), b = 18.024(3), c = 5.288(1) Å, b = 104.377(3)° and using data collected at room temperature. Mg is partitioned among the M1, M2, and M3 sites. All of the Fe3+ occupies M2, while Fe2+ is split between M2 and M3; Ca and Na fill the M4 site, while Na and K occupy the partially filled A site. The A-site occupancy is calculated as 0.51 based on chemical data, but only 0.48 based on X-ray diffraction results. Minerals with the former values would be classified as richterite and those with the latter as winchite.

VIBRATIONAL SPECTROSCOPIC STUDIES OF ASBESTOS AND COMPARISON OF SUITABILITY FOR REMOTE ANALYSIS

Abstract Raman, mid-infrared (MIR) and near-infrared (NIR) spectroscopic methods have been applied to the analysis of fibrous (asbestos) and non-fibrous forms of serpentine and amphibole minerals. This paper describes the first application of NIR diffuse reflectance spectroscopy to the study of asbestos minerals. In addition, a more generally applicable Raman spectroscopic study, in terms of multiple excitation wavelengths and asbestos materials, than has previously been made is reported. Improvements in spectral quality (especially in the OH stretching region) over previously published MIR spectroscopic data are also reported. The results of this work indicate the NIR diffuse reflectance spectroscopy appears to be the preferred method for the remote analysis of asbestos due to the relatively simple spectra in the wavenumber range 7400-6900 cm −1 , the high signal-to-noise ratio and spectral contrast of the spectra, the capability of using silica fiber-optics cables, and the time required to perform the analysis relative to the other vibrational spectroscopic techniques.

The atomic arrangement of merrillite from the Fra Mauro Formation, Apollo 14 lunar mission: The first structure of merrillite from the Moon

Abstract The atomic arrangement of lunar merrillite has been refined to R = 0.0452 in R3c using X-ray diffraction data recorded on a CCD detector; previous attempts at structure solution using a point detector were not successful because of the poorly crystallized nature of the lunar material. The atomic arrangement of merrillite has a structural unit of [(Mg,Fe)(PO4)6]216- that forms a “bracelet-and-pinwheel„ unit that is common in hexagonal-closest-packed layers. The individual structural units are not polymerized and exist in layers at z = 1/6, 1/3, 1/2, 2/3, and 5/6. In lunar merrillite, the [(Mg,Fe)(PO4)6]216- structural units are linked by a [(Ca,REE)18Na2(PO4)2]32+ interstitial complex, formed of Ca1O8, Ca2O8, Ca3O8, NaO6, and P1O4 polyhedra. There has long been speculation regarding the relationship between merrillite and terrestrial whitlockite, and the solution of the Fra Mauro merrillite atomic arrangement allows the characterization of the lunar phase. Lunar merrillite and terrestrial whitlockite have largely similar atomic arrangements, but the phases differ due to the presence or absence of hydrogen. In whitlockite, H is an essential element and allows the charge balance. Hydrogen is incorporated into the whitlockite atomic arrangement by disordering one of the phosphate tetrahedra and forming a PO3(OH) group. Lunar merrillite is devoid of hydrogen, and thus no disordered tetrahedral groups exist. Charge balance for substituents Y and REE (for Ca) is maintained by Si ↔ P tetrahedral substitution and □ ↔ Na at the Na site. The structure solution demonstrates the effectiveness of the CCD detector in unraveling previously intractable diffraction data and urges that previously analyzed lunar material be reexamined using this instrumentation.

A review of scientific literature examining the mining history, geology, mineralogy, and amphibole asbestos health effects of the Rainy Creek igneous complex, Libby, Montana, USA.

This article reviews the past 90 yr of scientific research directed on multiple aspects of the unique geology and environmental health issues surrounding the vermiculite deposit found at Libby, MT. Hydrothermal alteration and extensive weathering of the ultramafic units resulted in the formation of a rich deposit of vermiculite that was mined for 67 yr and used in numerous consumer products in its expanded form. Later intrusions of alkaline units caused hydrothermal alteration of the pyroxenes, resulting in formation of amphiboles. Some of these amphiboles occur in the asbestiform habit and have been associated with pulmonary disease in former miners and mill workers. Identification of these amphibole asbestos minerals has received little attention in the past, but recent work shows that the majority of the amphibole mineral species present may not be any of the amphibole species currently regulated by government agencies. Epidemiological studies on former miners have, nevertheless, shown that the amphibole asbestos from the Rainy Creek igneous complex is harmful; also, a recent study by the Agency for Toxic Substances and Disease Registry shows that residents of Libby who had not been employed in the vermiculite mining or milling operations also appear to have developed asbestos-related pulmonary diseases at a higher rate than the general public elsewhere. Since November 1999, the U.S. Environmental Protection Agency has been involved in the cleanup of asbestos-contaminated sites in and around Libby associated with the mining and processing of vermiculite.

Na, K, Rb, and Cs exchange in heulandite single crystals: Diffusion kinetics

Abstract Diffusion-exchange kinetics were determined at temperatures between 320 and 425 K for Na+ in single crystals of natural heulandite, Na0.96Ca3.54K0.09(Al8.62Si27.51O72)·nH2O, and K+, Rb+, and Cs+ for Na+ in Na-exchanged heulandite. Cation diffusion was measured on (010) cleavage plates with the aid of a polarizing microscope. This is possible because the optical properties, in particular the extinction angle, vary with the chemical composition of the channel occupants. This optical method is restricted to platy zeolites of monoclinic or triclinic symmetry where the channels are parallel to the crystal plate. Unlike conventional measurements, this method does not require the determination of the surface area of the zeolite. No indication of anisotropic diffusion was observed on (010) plates for any of the exchanged cation pails. Diffiision coefficients (D) show that the diffusion rate of Na+ → Ca2+ is much slower than those of K+ → Na+, Rb+ → Na+, and Cs+ → Na+, because of the strong Coulonibic interaction of Ca2+ with the tetrahedral framework compared with an exchange of monovalent species. The activation energy (Ea) and the pre-exponential factor (D0) were calculated from the variation of D with temperature for each diffusing cation. Comparable values of Ea for K+ → Na+ and Rb+ → Na+ suggest a similar diffusion process, while the lower value of Ea. combined with relatively low diffusion rates for Cs+ → Na+ implies a different diffusion mechanism for Cs+.

Mechanisms of oxidative stress and alterations in gene expression by Libby six-mix in human mesothelial cells

BackgroundExposures to an amphibole fiber in Libby, Montana cause increases in malignant mesothelioma (MM), a tumor of the pleural and peritoneal cavities with a poor prognosis. Affymetrix microarray/GeneSifter analysis was used to determine alterations in gene expression of a human mesothelial cell line (LP9/TERT-1) by a non-toxic concentration (15×106 μm2/cm2) of unprocessed Libby six-mix and negative (glass beads) and positive (crocidolite asbestos) controls. Because manganese superoxide dismutase (MnSOD; SOD2) was the only gene upregulated significantly (p < 0.05) at both 8 and 24 h, we measured SOD protein and activity, oxidative stress and glutathione (GSH) levels to better understand oxidative events after exposure to non-toxic (15×106 μm2/cm2) and toxic concentrations (75×106 μm2/cm2) of Libby six-mix.ResultsExposure to 15×106 μm2/cm2 Libby six-mix elicited significant (p < 0.05) upregulation of one gene (SOD2; 4-fold) at 8 h and 111 gene changes at 24 h, including a 5-fold increase in SOD2. Increased levels of SOD2 mRNA at 24 h were also confirmed in HKNM-2 normal human pleural mesothelial cells by qRT-PCR. SOD2 protein levels were increased at toxic concentrations (75×106 μm2/cm2) of Libby six-mix at 24 h. In addition, levels of copper-zinc superoxide dismutase (Cu/ZnSOD; SOD1) protein were increased at 24 h in all mineral groups. A dose-related increase in SOD2 activity was observed, although total SOD activity remained unchanged. Dichlorodihydrofluorescein diacetate (DCFDA) fluorescence staining and flow cytometry revealed a dose- and time-dependent increase in reactive oxygen species (ROS) production by LP9/TERT-1 cells exposed to Libby six-mix. Both Libby six-mix and crocidolite asbestos at 75×106 μm2/cm2 caused transient decreases (p < 0.05) in GSH for up to 24 h and increases in gene expression of heme oxygenase 1 (HO-1) in LP9/TERT-1 and HKNM-2 cells.ConclusionsLibby six-mix causes multiple gene expression changes in LP9/TERT-1 human mesothelial cells, as well as increases in SOD2, increased production of oxidants, and transient decreases in intracellular GSH. These events are not observed at equal surface area concentrations of nontoxic glass beads. Results support a mechanistic basis for the importance of SOD2 in proliferation and apoptosis of mesothelial cells and its potential use as a biomarker of early responses to mesotheliomagenic minerals.

Na- and Cs-exchange in a clinoptilolite-rich rock: Analysis of the outgoing cations in solution

Abstract Batch cation-exchange experiments were performed by placing 4 g of clinoptilolite-rich rock into 100 mL of 1 M concentrations of NaCl or CsCl solution for differing times and temperatures. The solutions were analyzed for the outgoing cations Na, K, Ca, and Mg by ICP-AES. The goal of these experiments was to determine the behavior (i.e., effect of temperature, release rate, and time) of Na, K, Ca, and Mg exchanging out of the solid and into the liquid in either NaCl or CsCl solutions. For the Na-exchanged samples, the concentration of the outgoing divalent cations increased with time and increased temperature, with the majority of the exchange occurring in the first 10 h. Potassium behaved in a different manner, with approximately 20% exchange occurring within 0.5 h. With increased exchange time, K concentrations actually decreased slightly, indicating some reexchange back into the solid from the liquid. After 24 h, samples in the four storage conditions averaged approximately 20% K, 80% Ca, and 50% Mg exchange out of the sample and into the liquid. For the Cs-exchanged samples, the concentration of the outgoing divalent cations increased with time and increased temperature, with the majority of the exchange occurring in the first 10 h. The outgoing monovalent cations behaved in a different, and somewhat unpredictable, manner. The majority of the exchange for both Na and K occurred within the first 0.5 h. Increased time had little effect on exchange; in fact, both exhibited some re-exchange back into the liquid. Also, more exchange occurred at lower than higher temperatures. With increased exchange time, K concentrations decreased slightly, indicating some re-exchange back into the solid from the liquid. After 24 h, samples in the four storage conditions averaged approximately 85% Na, 50% K, 80% Ca, and 40% Mg exchange out of the sample and into the liquid.

The effects of time, temperature, and concentration on Sr2+ exchange in clinoptilolite in aqueous solutions

Abstract Four grams of a clinoptilolite-rich rock, crushed to -180 mesh, were exchanged in deionized water (DI), and in 0.1, 0.01, and 0.001 M solutions of SrCl2·6H2O at 5, 21, 50, and 90 °C for 0.5, 5, 24, and 240 h yielding 64 sample solutions, which were vacuum-filtered to remove solids. The solutions were analyzed by ICP-AES for the outgoing cations (i.e., Na+, K+, Ca2+, and Mg2+). The higher molarity solutions were expected to contain greater concentrations of the outgoing cations than the DI or lower molarity concentration solutions. This trend was exhibited by the monovalent and divalent cations in samples of all concentrations. Outgoing monovalent cations exchanged to greater extents with increasing time and temperature. Outgoing divalent cations of 0.01 and 0.001 M concentrations exchanged at low temperatures contained greater concentrations of outgoing divalent cations than solutions exchanged at high temperatures. The concentrations of the monovalent cations were slightly greater in the 0.001 M sample than in DI, whereas divalent cations had a similar concentration between the 0.001 M and DI treatments. Overall exchange of cations out of the clinoptilolite was favored at higher temperatures.

Relationships between respiratory diseases and quartz-rich dust in Idaho, U.S.A.

Abstract Quartz-one of the most abundant minerals in the Earth’s crust-has been deemed a human carcinogen by the International Agency for Research on Cancer (IARC), with the main threat to humans being lung cancer through inhalation of dust particles. Currently, the United States Environmental Protection Agency (EPA) has required communities to monitor PM10 (particulate matter less than 10 micrometers in diameter) levels, with the concern that higher levels of PM10 have been linked to increased respiratory disease rates. This hypothesis can be tested by an analysis of mortality data for groups that have received high lifelong exposures to quartz-rich PM10 (e.g., farmers). Idaho is a very dusty state with a large agricultural community and can serve as a model to test this hypothesis. A database was constructed of PM10 levels statewide and of all the deaths attributed to respiratory diseases in Idaho from 1969 to 1994. For the Moscow, Idaho, PM samples, quartz composed approximately 10% of the PM10, with the remainder being 30% feldspar and 60% Mount St. Helens volcanic ash. The PM2.5 samples contained no detectable mineral matter. Statewide, the quartz component for the PM10 samples ranged from 7 to 16%. Analysis of the database indicates that Idaho residents, in general, have below-average lung cancer rates when compared to the U.S. population and that Idaho farmers are at no greater risk of dying from lung cancer than non-farmers. These conclusions are based upon age- and smoking-adjusted standard mortality ratios (SMRs). No correlations or trends between PM10 levels and respiratory diseases could be found in the general population. Data for chronic obstructive pulmonary diseases (COPDs) are more difficult to interpret because of fewer deaths and the inability to compensate for the effect of smoking in the induction of these diseases; however, it appears that Idaho has a higher rate of COPDs when compared to the U.S. populations and that farmers have a higher rate of COPDs than non-farmers.