Application of NMR spectroscopy for determining functionality in humic substances
No abstract available.
Book chapter↗
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A review of spatially resolved techniques and applications of organic petrography in shale petroleum systems
This review examines new techniques and applications of organic petrography in source-rock reservoir petroleum systems that have occurred along with development of the global ‘shale revolution’ in energy resources. The review is limited to techniques and instrumentation that provide spatially resolved information, typically at or below microscales, for dispersed organic matter occurring in situ in samples of shale and mudrock. A brief summary of ion beam sample preparation is followed by discussion of the most common analytical techniques and applications. Advantages and limitations of each technique, including requisite sample preparation, types of information generated [e.g., molecular or elemental (isotopic) abundance], sensitivity, and resolution are discussed. In a few cases, techniques not yet applied to organic petrology of shale or mudrock are described (e.g., X-ray photoelectron spectroscopy imaging), in anticipation of near-term future application. The most common in situ techniques applied for characterization of organic matter in shale and mudrock include optical (including fluorescence) and electron microscopies, Raman, fluorescence, and infrared spectroscopies, and surficial measurements via force microscopy. Techniques that show growing application to organic petrography of shale include tip-enhanced photothermal infrared spectroscopy, mass spectrometry imaging, and synchrotron-based spectroscopies, among others. It is anticipated that the future of dispersed organic matter petrography will hold continued development of integrated instrument techniques (e.g., simultaneous or sequential correlative microscopies and/or spectroscopies of the same location), increased instrumental resolution, increased use of multiscale and multimodal organic petrography investigations, and three-dimensional imaging and chemical speciation mapping applications via multiple analytical approaches.
International Journal of Coal Geology↗
Multiscale hyperspectral imaging of the Orange Hill Porphyry Copper Deposit, Alaska, USA, with laboratory-, field-, and aircraft-based imaging spectrometers
In the past decade, use of hyperspectral imaging (imaging spectroscopy) for mineral exploration and mining operations has been increasing at different spatial scales. In this paper, we focus on recent trends in applying imaging spectrometer data to: 1) airborne imaging of high latitude deposits, 2) field-based imaging of outcrops, and 3) laboratory-level imaging of geologic samples. Comparing mineral information derived from imaging spectrometer data acquired at these three scales in Alaska in areas of exposed porphyry Cu-Au-Mo deposits, Orange Hill and Bond Creek, we find notable consistency in identifications of spectrally predominant minerals, including white mica, chlorite, clays, and gypsum. Variations in the wavelength position of white mica 2200 nm Al-OH absorption seen at the airborne level are echoed by finerscale field and laboratory imaging, with wavelength positions spanning the 2199 to 2207 nm range. The longerwavelength micas associated with porphyry formation are more phengitic in composition, and thus distinct from mica in plutonic and volcanic arc rocks not affected by magmatic-hydrothermal fluids. The hillside imagery, collected on a cloudy day that would have precluded aircraft survey, gave comparable result to airborne and laboratory data, indicating field-based imaging spectroscopy can be a feasible alternative to airborne survey for accessible targets. Direct spectral observation of molybdenite in rocks collected from the Orange Hill deposit demonstratesthat additional important mineral information can be revealed with laboratory level imaging spectroscopy that is difficult to obtain in coarser scale data, commonly due to low areal extent of target minerals. The spatial association of the clinochlore + white mica and long wavelength white mica spectral classes to multi-element Cu-Mo-Au anomalies from geochemical analyses of rocks and sediments support a causative relationship with magmatic-hydrothermal alteration. Mineral maps from the airborne data were used to guide field sampling that found additional CuMo-Au mineralized areas, which were previously unknown or unreported. The results from this study provide support for utilization of imaging spectroscopy for assisting mineral exploration in other portions of the state of Alaska as well as other areas at high latitudes. Imaging spectroscopy has the potential to provide targeting information for follow-up sampling and investigations, potentially reducing subsequent exploration costs.
Alaska↗
Composition of dust deposited to snow cover in the Wasatch Range (Utah, USA): Controls on radiative properties of snow cover and comparison to some dust-source sediments
Dust layers deposited to snow cover of the Wasatch Range (northern Utah) in 2009 and 2010 provide rare samples to determine the relations between their compositions and radiative properties. These studies are required to comprehend and model how such dust-on-snow (DOS) layers affect rates of snow melt through changes in the albedo of snow surfaces. We evaluated several constituents as potential contributors to the absorption of solar radiation indicated by values of absolute reflectance determined from bi-conical reflectance spectroscopy. Ferric oxide minerals and carbonaceous matter appear to be the primary influences on lowering snow-cover albedo. Techniques of reflectance and Mössbauer spectroscopy as well as rock magnetism provide information about the types, amounts, and grain sizes of ferric oxide minerals. Relatively high amounts of ferric oxide, indicated by hard isothermal remanent magnetization (HIRM), are associated with relatively low average reflectance (<0.25) across the visible wavelengths of the electromagnetic spectrum. Mössbauer spectroscopy indicates roughly equal amounts of hematite and goethite, representing about 35% of the total Fe-bearing phases. Nevertheless, goethite (α-FeOOH) is the dominant ferric oxide found by reflectance spectroscopy and thus appears to be the main iron oxide control on absorption of solar radiation. At least some goethite occurs as nano-phase grain coatings less than about 50 nm thick. Relatively high amounts of organic carbon, indicating as much as about 10% organic matter, are also associated with lower reflectance values. The organic matter, although not fully characterized by type, correlates strongly with metals (e.g., Cu, Pb, As, Cd, Mo, Zn) derived from distal urban and industrial settings, probably including mining and smelting sites. This relation suggests anthropogenic sources for at least some of the carbonaceous matter, such as emissions from transportation and industrial activities. The composition of the DOS samples can be compared with sediments in a likely dust-source setting at the Milford Flat Fire (MFF) area about 225 km southwest of Salt Lake City. The MFF area represents geologically and physiographically similar and widespread dust sources west-southwest of the Wasatch Range and heavily populated Wasatch Front. The DOS layers and MFF sediments are similar in some textural, chemical, and magnetic properties, as well as in the common presence of goethite, hematite, magnetite-bearing basalt fragments, quartz, plagioclase, illite, and kaolinite. Textural and some chemical differences among these deposits can be explained by atmospheric sorting as well as by inputs from other settings, such as salt-crusted playas and contaminant sources.
Utah↗
Progressive oxidation of pyrite in five bituminous coal samples: An As XANES and 57 Fe Mössbauer spectroscopic study
Naturally occurring pyrite commonly contains minor substituted metals and metalloids (As, Se, Hg, Cu, Ni, etc.) that can be released to the environment as a result of its weathering. Arsenic, often the most abundant minor constituent in pyrite, is a sensitive monitor of progressive pyrite oxidation in coal. To test the effect of pyrite composition and environmental parameters on the rate and extent of pyrite oxidation in coal, splits of five bituminous coal samples having differing amounts of pyrite and extents of As substitution in the pyrite, were exposed to a range of simulated weathering conditions over a period of 17 months. Samples investigated include a Springfield coal from Indiana (whole coal pyritic S = 2.13 wt.%; As in pyrite = detection limit (d.l.) to 0.06 wt.%), two Pittsburgh coal samples from West Virginia (pyritic S = 1.32–1.58 wt.%; As in pyrite = d.l. to 0.34 wt.%), and two samples from the Warrior Basin, Alabama (pyritic S = 0.26–0.27 wt.%; As in pyrite = d.l. to 2.72 wt.%). Samples were collected from active mine faces, and expected differences in the concentration of As in pyrite were confirmed by electron microprobe analysis. Experimental weathering conditions in test chambers were maintained as follows: (1) dry Ar atmosphere; (2) dry O 2 atmosphere; (3) room atmosphere (relative humidity ∼20–60%); and (4) room atmosphere with samples wetted periodically with double-distilled water. Sample splits were removed after one month, nine months, and 17 months to monitor the extent of As and Fe oxidation using As X-ray absorption near-edge structure (XANES) spectroscopy and 57 Fe Mössbauer spectroscopy, respectively. Arsenic XANES spectroscopy shows progressive oxidation of pyritic As to arsenate, with wetted samples showing the most rapid oxidation. 57 Fe Mössbauer spectroscopy also shows a much greater proportion of Fe 3+ forms (jarosite, Fe 3+ sulfate, FeOOH) for samples stored under wet conditions, but much less difference among samples stored under dry conditions in different atmospheres. The air-wet experiments show evidence of pyrite re-precipitation from soluble ferric sulfates, with As retention in the jarosite phase. Extents of As and Fe oxidation were similar for samples having differing As substitution in pyrite, suggesting that environmental conditions outweigh the composition and amount of pyrite as factors influencing the oxidation rate of Fe sulfides in coal.
Applied Geochemistry↗
Iron- and 4-hydroxy-2-alkylquinoline-containing periplasmic inclusion bodies of Pseudomonas aeruginosa: A chemical analysis
Dark aggregated particles were seen on pellets of iron-rich, mid-logarithmic phase Pseudomonas aeruginosa. Transmission electron microscopy of these cells showed inclusion bodies in periplasmic vacuoles. Aggregated particles isolated from the spent medium of these cells contained iron as indicated by atomic absorption spectroscopy and by electron paramagnetic resonance spectroscopy that revealed Fe3+. Scanning electron microscopy/energy dispersive X-ray analysis of whole cells revealed the presence of iron-containing particles beneath the surface of the cell, indicating that the isolated aggregates were the intracellular inclusion bodies. Collectively, mass spectroscopy and nuclear magnetic resonance spectroscopy of the isolated inclusion bodies revealed the presence of 3,4-dihydroxy-2-heptylquinoline which is the Pseudomonas quinolone signaling compound (PQS) and an iron chelator; 4-hydroxy-2-heptylquinoline (pseudan VII), which is an iron chelator, antibacterial compound and precursor of PQS; 4-hydroxy-2-nonylquinoline (pseudan IX) which is an iron chelator and antibacterial compound; 4-hydroxy-2-methylquinoline (pseudan I), and 4-hydroxy-2-nonylquinoline N-oxide. ?? 2006 Elsevier Inc. All rights reserved.
Bioorganic Chemistry↗
A possible link between Balkan endemic nephropathy and the leaching of toxic organic compounds from Pliocene lignite by groundwater: Preliminary investigation
Balkan endemic nephropathy (BEN) is a fatal kidney disease that is known to occur only in clusters of villages in alluvial valleys of tributaries of the Danube River in Bulgaria, Romania, Yugoslavia, Bosnia, and Croatia. The confinement of this disease to a specific geographic area has led to speculation that an environmental factor may be involved in the etiology of BEN. Numerous environmental factors have been suggested as causative agents for producing BEN, including toxic metals in drinking water, metal deficiency in soils of BEN areas, and environmental mycotoxins to name a few. These hypotheses have either been disproved or have failed to conclusively demonstrate a connection to the etiology of BEN, or the clustering of BEN villages. In previous work, we observed a distinct geographic relationship between the distribution of Pliocene lignites in the Balkans and BEN villages. We hypothesized that the long-term consumption of well water containing toxic organic compounds derived from the leaching of nearby Pliocene lignites by groundwater was a primary factor in the etiology of BEN. In our current work, chemical analysis using 13C nuclear magnetic resonance (13CNMR) spectroscopy indicated a high degree of organic functionality in Pliocene lignite from the Balkans, and suggested that groundwater can readily leach organic matter from these coal beds. Semi-quantitative gas chromatography/mass spectroscopy analysis of solvent extracts of groundwater from shallow wells in BEN villages indicated the presence of potentially toxic aromatic compounds, such as napthalene, fluorene, phenanthrene, and pyrene at concentrations in the ppb range. Laboratory leaching of Balkan Pliocene lignites with distilled water yielded soluble organic matter (> 500 MW) containing large amounts of aromatic structures similar to the simple/discrete aromatic compounds detected in well water from BEN villages. These preliminary results are permissive of our hypothesis and suggest that further work on the possible relationship between the etiology of BEN and toxic aromatic substances leached from Pliocene lignites in well water is warranted.A distinct geographic relationship between the distribution of Pliocene lignites in the Balkans and villages where Balkan endemic nephropathy (BEN) occurs has been observed, indicating a possible link between BEN and the long-term consumption of well water containing toxic organic compounds derived from the leaching of nearby Pliocene lignites. Preliminary investigations by NMR spectroscopy, gas chromatography/mass spectroscopy and leaching experiments show a high degree of organic functionality in the Pliocene lignites, high-leachability by groundwater of organic matter from these beds, and the presence of toxic aromatic compounds.
International Journal of Coal Geology↗
Crystal chemistry of thallium in marine ferromanganese deposits
Our understanding of the up to 7 orders of magnitude partitioning of thallium (Tl) between seawater and ferromanganese (FeMn) deposits rests upon two foundations: (1) being able to quantify the Tl(I)/Tl(III) ratio that reflects the extent of the oxidative scavenging of Tl by vernadite (δ-MnO 2 ), the principle manganate mineral in oxic and suboxic environments, and (2) being able to determine the sorption sites and bonding environments of the Tl(I) and Tl(III) complexes on vernadite. We investigated these foundations by determining the oxidation state and chemical form of Tl in FeMn crusts and nodules from the global oceans at a Tl concentration ranging from several hundred ppm (mg/kg) down to the low ppm level. Seventeen hydrogenetic crusts and eleven nodules from the Pacific, Atlantic, Arctic, and Indian Oceans and Baltic Sea were characterized by chemical analysis, X-ray diffraction, Raman spectroscopy, Mn K-edge X-ray absorption near-edge structure (XANES) spectroscopy, Tl L 3 -edge high energy-resolution XANES (HR-XANES) spectroscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The Tl concentration increases linearly from 1.5 to 319 ppm with the Mn/Fe ratio in Fe-vernadite from hydrogenetic crusts, whereas the percentage of Tl(III) to total Tl varies between 62 and 100% independent of both the Mn/Fe and Mn(III)/Mn(IV) ratios. The data, complemented by molecular modeling of the Tl(III) coordination and by XANES calculations, suggest that the enrichment of Tl in Fe-vernadite is driven by (1) the oxidative uptake of octahedrally coordinated Tl(III) above the vacant Mn(IV) sites and on the layer edges of the vernadite layers, and (2) the sorption of Tl(I) on the crystallographic site of Ba at the surface of the vernadite layers, which is an analogue to the surface site of K. Thus, Tl has a high affinity for vernadite regardless of its oxidation state, and the lack of correlation between Tl(III) and the Mn/Fe ratio in FeMn crusts is explained by the affinity of Tl(I) for the Ba site. The Tl concentration varies between 2 and 112 ppm in surface and buried nodules independent of the Mn/Fe ratio, and the percentage of Tl(III) varies between 0 and 100%. Nodules subjected to sediment diagenesis with replacement of layered vernadite by tunneled todorokite are depleted in Tl and have more reduced thallium. Knowledge of the complex interplay of mineralogy, surface chemical processes, and crystallographic siting is required to understand the variability of Tl concentrations, redox state, and acquisition processes by marine FeMn deposits.
ACS Earth and Space Chemistry↗
Integrating airborne remote sensing and field campaigns for ecology and Earth system science
In recent years, the availability of airborne imaging spectroscopy (hyperspectral) data has expanded dramatically. The high spatial and spectral resolution of these data uniquely enable spatially explicit ecological studies including species mapping, assessment of drought mortality and foliar trait distributions. However, we have barely begun to unlock the potential of these data to use direct mapping of vegetation characteristics to infer subsurface properties of the critical zone. To assess their utility for Earth systems research, imaging spectroscopy data acquisitions require integration with large, coincident ground‐based datasets collected by experts in ecology and environmental and Earth science. Without coordinated, well‐planned field campaigns, potential knowledge leveraged from advanced airborne data collections could be lost. Despite the growing importance of this field, documented methods to couple such a wide variety of disciplines remain sparse. We coordinated the first National Ecological Observatory Network Airborne Observation Platform (AOP) survey performed outside of their core sites, which took place in the Upper East River watershed, Colorado. Extensive planning for sample tracking and organization allowed field and flight teams to update the ground‐based sampling strategy daily. This enabled collection of an extensive set of physical samples to support a wide range of ecological, microbiological, biogeochemical and hydrological studies. We present a framework for integrating airborne and field campaigns to obtain high‐quality data for foliar trait prediction and document an archive of coincident physical samples collected to support a systems approach to ecological research in the critical zone. This detailed methodological account provides an example of how a multi‐disciplinary and multi‐institutional team can coordinate to maximize knowledge gained from an airborne survey, an approach that could be extended to other studies. The coordination of imaging spectroscopy surveys with appropriately timed and extensive field surveys, along with high‐quality processing of these data, presents a unique opportunity to reveal new insights into the structure and dynamics of the critical zone. To our knowledge, this level of co‐aligned sampling has never been undertaken in tandem with AOP surveys and subsequent studies utilizing this archive will shed considerable light on the breadth of applications for which imaging spectroscopy data can be leveraged.
Colorado↗
Chemical analysis of archived stream-sediment samples, Alaska
Geochemical data are presented for more than 1,500 archived stream-sediment samples and accompanying quality control samples. The archived sediments were reanalyzed to improve the stream geochemical dataset for Alaska and to support ongoing U.S. Geological Survey (USGS) studies. Sediment samples were primarily from the USGS Mineral Resources Program’s sample archive in Denver, Colorado, but a few were from the Alaska Geological & Geophysical Surveys’ Geologic Materials Center in Anchorage, Alaska. All samples were submitted to the USGS contract laboratory, AGAT Laboratories, for analysis. All samples were analyzed using a 60-element analytical method involving fusion of the sample by sodium peroxide, dissolution of the fusion cake by nitric acid, and elemental analysis by inductively coupled plasma-optical emission spectroscopy and inductively coupled plasma-mass spectroscopy. Additionally, 106 samples from the Nixon Fork area were analyzed by a second multi-element method involving decomposition by a mixture of hydrochloric, nitric, perchloric, and hydrofluoric acids and the elemental analysis of the resulting solution by inductively coupled plasma-optical emission spectroscopy and inductively coupled plasma-mass spectroscopy. The latter method was used because the detection limit is lower for several elements including As, Cd, Pb, and Sb. Mercury concentrations in 296 samples from southeast Alaska were determined using a cold-vapor atomic absorption spectrometry method. The concentration data from the archived samples are presented along with concentration data from the standard reference material that was submitted with the samples.
Alaska↗
Presence and potential significance of aromatic-ketone groups in aquatic humic substances
Aquatic humic- and fulvic-acid standards of the International Humic Substances Society were characterized, with emphasis on carbonyl-group nature and content, by carbon-13 nuclear-magnetic-resonance spectroscopy, proton nuclear-magnetic-resonance spectroscopy, and infrared spectroscopy. After comparing spectral results of underivatized humic and fulvic acids with spectral results of chemically modified derivatives, that allow improved observation of the carbonyl group, the data clearly indicated that aromatic ketone groups comprised the majority of the carbonyl-group content. About one ketone group per monocyclic aromatic ring was determined for both humic and fulvic acids. Aromatic-ketone groups were hypothesized to form by photolytic rearrangements and oxidation of phenolic ester and hydrocarbon precursors; these groups have potential significance regarding haloform formation in water, reactivity resulting from active hydrogen of the methyl and methylene adjacent to the ketone groups, and formation of hemiketal and lactol structures. Aromatic-ketone groups also may be the point of attachment between aliphatic and aromatic moieties of aquatic humic-substance structure.
Georgia↗
Iron oxide minerals in dust of the Red Dawn event in eastern Australia, September 2009
Iron oxide minerals typically compose only a few weight percent of bulk atmospheric dust but are important for potential roles in forcing climate, affecting cloud properties, influencing rates of snow and ice melt, and fertilizing marine phytoplankton. Dust samples collected from locations across eastern Australia (Lake Cowal, Orange, Hornsby, and Sydney) following the spectacular “Red Dawn” dust storm on 23 September 2009 enabled study of the dust iron oxide assemblage using a combination of magnetic measurements, Mössbauer spectroscopy, reflectance spectroscopy, and scanning electron microscopy. Red Dawn was the worst dust storm to have hit the city of Sydney in more than 60 years, and it also deposited dust into the Tasman Sea and onto snow cover in New Zealand. Magnetization measurements from 20 to 400 K reveal that hematite, goethite, and trace amounts of magnetite are present in all samples. Magnetite concentrations (as much as 0.29 wt%) were much higher in eastern, urban sites than in western, agricultural sites in central New South Wales (0.01 wt%), strongly suggesting addition of magnetite from local urban sources. Variable temperature Mössbauer spectroscopy (300 and 4.2 K) indicates that goethite and hematite compose approximately 25–45% of the Fe-bearing phases in samples from the inland sites of Orange and Lake Cowal. Hematite was observed at both temperatures but goethite only at 4.2 K, thereby revealing the presence of nanogoethite (less than about 20 nm). Similarly, hematite particulate matter is very small (some of it d < 100 nm) on the basis of magnetic results and Mössbauer spectra. The degree to which ferric oxide in these samples might absorb solar radiation is estimated by comparing reflectance values with a magnetic parameter (hard isothermal remanent magnetization, HIRM) for ferric oxide abundance. Average visible reflectance and HIRM are correlated as a group ( r 2 = 0.24), indicating that Red Dawn ferric oxides have capacity to absorb solar radiation. Much of this ferric oxide occurs as nanohematite and nanogoethite particles on surfaces of other particulate matter, thereby providing high surface area to enhance absorption of solar radiation. Leaching of the sample from Orange in simulated human-lung fluid revealed low bioaccessibility for most metals.
Aeolian Research↗
Reactivity of As and U co-occurring in mine wastes in northeastern Arizona
The reactivity of co-occurring arsenic (As) and uranium (U) in mine wastes was investigated using batch reactors, microscopy, spectroscopy, and aqueous chemistry. Analyses of field samples collected in proximity to mine wastes in northeastern Arizona confirm the presence of As and U in soils and surrounding waters, as reported in a previous study from our research group. In this study, we measured As (<0.500 to 7.77 μg/L) and U (0.950 to 165 μg/L) in waters, as well as mine wastes (<20.0 to 40.0 mg/kg As and <60.0 to 110 mg/kg U) and background solids (<20.0 mg/kg As and <60.0 mg/kg U). Analysis with X-ray fluorescence (XRF) and electron microprobe show the co-occurrence of As and U with iron (Fe) and vanadium (V). These field conditions served as a foundation for additional laboratory experiments to assess the reactivity of metals in these mine wastes. Results from laboratory experiments indicate that labile and exchangeable As(V) was released to solution when solids were sequentially reacted with water and magnesium chloride (MgCl 2 ), while limited U was released to solution with the same reactants. The predominance of As(V) in mine waste solids was confirmed by X-ray absorption near edge (XANES) analysis. Both As and U were released to solution after reaction of solids in batch experiments with HCO 3 − . Both X-ray photoelectron spectroscopy (XPS) and XANES analysis determined the predominance of Fe(III) in the solids. Mössbauer spectroscopy detected the presence of nano-crystalline goethite, Fe(II) and Fe(III) in (phyllo)silicates, and an unidentified mineral with parameters consistent with arsenopyrite or jarosite in the mine waste solids. Our results suggest that As and U can be released under environmentally relevant conditions in mine waste, which is applicable to risk and exposure assessment.
Arizona↗
Characterization of bituminite in Kimmeridge Clay by confocal laser scanning and atomic force microscopy
This work investigates bituminite (amorphous sedimentary organic matter) in Upper Jurassic Kimmeridge Clay source rock via confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM). These petrographic tools were used to provide better understanding of the nature of bituminite, which has been historically difficult to identify and differentiate from similar organic matter types in source rocks. As part of an International Committee for Coal and Organic Petrology (ICCP) working group, an immature (0.42% vitrinite reflectance), organic-rich (44.1 wt% total organic carbon content) sample of Kimmeridge Clay was distributed to multiple laboratories for CLSM characterization. The primary observations from CLSM imaging and spectroscopy include: 1) the interpreted presence of Botryococcus algae as a contributor to bituminite precursors; 2) color red-shift of sulfide reflectance and bituminite auto-fluorescence from below the sample surface; 3) positive alteration of bituminite from laser-induced photo-oxidation of the sample surface, including fluorescence blue-shift; 4) fluorescence blue-shift associated to higher fluorescence intensity regions in bituminite indicative of compositional (fluorophore) differences; 5) the need for fluorescence spectroscopy standardization as applied via CLSM; and 6) the suitability of CLSM fluorescence spectroscopy to predict solid bitumen reflectance from bituminite spectral emission via calibration to an extant dataset. Secondary CLSM observations include detection of reflected laser light from highly reflective inclusions in bituminite, including sulfides and fusinite, and radiolytic alteration of bituminite caused by substitution of U for Fe in sulfides. Findings from AFM include the observation that surface roughening or surface flattening of bituminite are induced by differential broad ion beam (BIB) milling and are dependent on the location and scale of AFM topology measurement. This result highlights our still limited understanding of the effects of BIB milling on sedimentary organic matter and indicates the need for further research before this technique can be advanced as a standard practice in petrographic sample preparation. Collectively, the results of this study illustrate the general applicability and versatility of AFM and CLSM as tools for organic petrology research, specifically for better understanding of the nature and properties of the bituminite maceral.
Kimmeridge↗
Relating systematic molecular and textural properties of graptolite pyrolyzed via gold tube hydrous pyrolysis: Implications for thermal proxies in lower Paleozoic marine shales
A series of gold tube pyrolysis experiments (72 h, 300–550 °C, 50 MPa) conducted on a graptolite-rich lower Paleozoic marine shale generated pyrolysis residues for a comprehensive evaluation of the molecular and structural variability of three types of graptolite periderm. Organic petrology, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM) with energy dispersive spectroscopy (EDS) were combined to evaluate the thermal evolution process. The three types of graptolite periderm, namely granular, non-granular, and nodular graptolite, were analyzed by Raman spectroscopy wherein point measurements were obtained after the maceral was identified and the location verified by organic petrology. Distinct thermal evolution pathways among non-granular, granular, and nodular graptolite periderms were recorded. The evolution patterns of the Raman parameters, particularly D1 and G bands, highlight the differences in geochemical composition of the graptolite periderm types and the alteration of molecular structure with increasing thermal maturity. Raman parameters D1 (position of the D1 peak), G-FWHM (full width at half maximum of the G peak), and ratios D1-FWHM/G-FWHM (full width at half maximum of the D1 peak ratioed to G-FWHM) and A D1 /A G (ratio of D1 and G peak intensities) showed effectiveness in assessing thermal maturity. Bireflectance with increasing gold tube pyrolysis temperature followed a hierarchy: non-granular > granular > nodular, reflecting different molecular alignment intensities. Qualitative FE-SEM evaluation showed that fine-grained mineral inclusions (primarily Fe-sulfide as determined via EDS) were associated with the graptolite populations, with granular graptolite containing greater amounts of coarser-grained (e.g., ∼300–1400 nm) mineral inclusions relative to non-granular and nodular graptolite, which contain finer-grained (e.g., ∼100–200 nm) inclusions difficult to resolve with optical microscopy. These findings are investigated to highlight the mechanisms that drive organic matter evolution within graptolite during thermal maturation, as well as to explore some of the limitations of using spectroscopic parameters as thermal maturity proxies.
International Journal of Coal Geology↗
EXAFS study of mercury(II) sorption to Fe- and Al-(hydr)oxides: I. Effects of pH
The study of mercury sorption products in model systems using appropriate in situ molecular-scale probes can provide detailed information on the modes of sorption at mineral/water interfaces. Such studies are essential for assessing the influence of sorption processes on the transport of Hg in contaminated natural systems. Macroscopic uptake of Hg(II) on goethite (??-FeOOH), ??-alumina (??-Al2O3), and bayerite (??-Al(OH)3) as a function of pH has been combined with Hg L III-edge EXAFS spectroscopy, FTIR spectroscopy, and bond valence analysis of possible sorption products to provide this type of information. Macroscopic uptake measurements show that Hg(II) sorbs strongly to fine-grained powders of synthetic goethite (Hg sorption density ??=0.39-0.42 ??mol/m2) and bayerite (??=0.39-0.44 ??mol/m2), while sorbing more weakly to ??-alumina (??=0.04-0.13 ??mol/m 2). EXAFS spectroscopy on the sorption samples shows that the dominant mode of Hg sorption on these phases is as monodentate and bidentate inner-sphere complexes. The mode of Hg(II) sorption to goethite was similar over the pH range 4.3-7.4, as were those of Hg(II) sorption to bayerite over the pH range 5.1-7.9. Conversion of the ??-Al2O3 sorbent to a bayerite-like phase in addition to the apparent reduction of Hg(II) to Hg(I), possibly by photoreduction during EXAFS data collection, resulted in enhanced Hg uptake from pH 5.2-7.8 and changes in the modes of sorption that correlate with the formation of the bayerite-like phase. Bond valence calculations are consistent with the sorption modes proposed from EXAFS analysis. EXAFS analysis of Hg(II) sorption products on a natural Fe oxyhydroxide precipitate and Al/Si-bearing flocculent material showed sorption products and modes of surface attachment similar to those for the model substrates, indicating that the model substrates are useful surrogates for the natural sediments. ?? 2003 Elsevier Inc. All rights reserved.
Journal of Colloid and Interface Science↗
Guidelines for sample collecting and analytical methods used in the U.S. Geological Survey for determining chemical composition of coal
This report is intended to meet the many requests for information on current U.S. Geological Survey procedures in handling coal samples. In general, the exact type and number of samples of coal and associated rock to be collected are left to the best judgment of the geologist. Samples should be of unweathered coal or rock and representative of the bed or beds sampled; it is recommended that two channel samples, separated by 10 to 100 yards (10 to 100 metres) and weighing 4 to 5 pounds ( 1.8 to 2.3 kilograms) each, be collected of each 5 feet ( 1.5 metres) of vertical section. Care must be taken to avoid any sample contamination, and to record the exact locality, thickness, and stratigraphic information for each sample. Analytical methods are described for the determination of major, minor, and trace elements in coal. Hg, As, Sb, F, Se, U, and Th are determined in the raw coal, and the following 34 elements are determined after ashing the coal: Si, Al, Ca, Mg, Na, K, Fe (total), Cl, Ti, Mn, P, S (total), Cd, Li, Cu, Zn, Pb, B, Ba, Be, Co, Cr, Ga, La, Mo, Nb, Ni, Sc, Sr, Ti, V, Y, Yb, and Zr. The methods used to determine these elements include atomic absorption spectroscopy, X-ray fluorescence spectroscopy, optical emission spectroscopy, spectrophotometry, selective-ion electrode, and neutron activation analysis. A split of representative coal samples is submitted to the U.S. Bureau of Mines for proximate, ultimate, forms of sulfur, and Btu determinations.
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USGS Digital Spectral Library splib06a
Introduction We have assembled a digital reflectance spectral library that covers the wavelength range from the ultraviolet to far infrared along with sample documentation. The library includes samples of minerals, rocks, soils, physically constructed as well as mathematically computed mixtures, plants, vegetation communities, microorganisms, and man-made materials. The samples and spectra collected were assembled for the purpose of using spectral features for the remote detection of these and similar materials. Analysis of spectroscopic data from laboratory, aircraft, and spacecraft instrumentation requires a knowledge base. The spectral library discussed here forms a knowledge base for the spectroscopy of minerals and related materials of importance to a variety of research programs being conducted at the U.S. Geological Survey. Much of this library grew out of the need for spectra to support imaging spectroscopy studies of the Earth and planets. Imaging spectrometers, such as the National Aeronautics and Space Administration (NASA) Airborne Visible/Infra Red Imaging Spectrometer (AVIRIS) or the NASA Cassini Visual and Infrared Mapping Spectrometer (VIMS) which is currently orbiting Saturn, have narrow bandwidths in many contiguous spectral channels that permit accurate definition of absorption features in spectra from a variety of materials. Identification of materials from such data requires a comprehensive spectral library of minerals, vegetation, man-made materials, and other subjects in the scene. Our research involves the use of the spectral library to identify the components in a spectrum of an unknown. Therefore, the quality of the library must be very good. However, the quality required in a spectral library to successfully perform an investigation depends on the scientific questions to be answered and the type of algorithms to be used. For example, to map a mineral using imaging spectroscopy and the mapping algorithm of Clark and others (1990a, 2003b), one simply needs a diagnostic absorption band. The mapping system uses continuum-removed reference spectral features fitted to features in observed spectra. Spectral features for such algorithms can be obtained from a spectrum of a sample containing large amounts of contaminants, including those that add other spectral features, as long as the shape of the diagnostic feature of interest is not modified. If, however, the data are needed for radiative transfer models to derive mineral abundances from reflectance spectra, then completely uncontaminated spectra are required. This library contains spectra that span a range of quality, with purity indicators to flag spectra for (or against) particular uses. Acquiring spectral measurements and performing sample characterizations for this library has taken about 15 person-years of effort. Software to manage the library and provide scientific analysis capability is provided (Clark, 1980, 1993). A personal computer (PC) reader for the library is also available (Livo and others, 1993). The program reads specpr binary files (Clark, 1980, 1993) and plots spectra. Another program that reads the specpr format is written in IDL (Kokaly, 2005). In our view, an ideal spectral library consists of samples covering a very wide range of materials, has large wavelength range with very high precision, and has enough sample analyses and documentation to establish the quality of the spectra. Time and available resources limit what can be achieved. Ideally, for each mineral, the sample analysis would include X-ray diffraction (XRD), electron microprobe (EM) or X-ray fluorescence (XRF), and petrographic microscopic analyses. For some minerals, such as iron oxides, additional analyses such as Mossbauer would be helpful. We have found that to make the basic spectral measurements, provide XRD, EM or XRF analyses, and microscopic analyses, document the results, and complete an entry of one spectral library sample, all takes about
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