Mark P.S. Krekeler

MICROSCOPY STUDIES OF THE PALYGORSKITE-TO-SMECTITE TRANSFORMATION

The transformation process between palygorskite and smectite was studied by examining the morphological and structural relationships between these two minerals in an assemblage from the Meigs Member of the Hawthorne Formation, southern Georgia. Studied samples were related to an alteration horizon with a tan clay unit above and a blue clay unit below. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to study the mechanism of transformation.From AFM data, both clay units contain euhedral palygorskite fibers. Many fibers are found as parallel intergrowths joined along the [010] direction to form ‘raft-like’ bundles. Degraded fibers, which are common in the tan clay, have a distinctly segmented morphology, suggesting a dissolution texture. Many of the altered palygorskite fibers in the tan clay exhibit an oriented overgrowth of another mineral phase, presumably smectite, displaying a platy morphology. This latter mineral forms along the length of the palygorskite crystals with an interface parallel to {010} of the palygorskite. The resulting grain structures have an elongate ‘wing-like’ morphology.Imaging by TEM of tan clay material shows smectite lattice-fringe lines intergrown with 2:1 layer ribbon modules (polysomes) of the palygorskite. These features indicate an epitaxial overgrowth of smectite on palygorskite and illustrate the structural relationship between platy overgrowths on fibers observed in AFM data. The epitaxial relationship is described as {010} [001] palygorskite ‖ {010} [001] smectite.Energy dispersive spectroscopy indicates that the smectite is ferrian montmorillonite. Polysomes of palygorskite fibers involved in these textures commonly vary and polysome widths are consistent with double tetrahedral chains (10.4 Å), triple tetrahedral chains (14.8 Å), quadruple tetrahedral chains (21.7 Å) and quintuple tetrahedral chains (24.5 Å).The transformation of palygorskite to smectite and the resulting intergrowths will cause variations in bulk physical properties of palygorskite-rich clays. The observation of this transformation in natural samples suggests that this transformation mechanism may be responsible for the lower abundance of palygorskite in Mesozoic and older sediments.

A mineralogical and geochemical investigation of street sediment near a coal-fired power plant in Hamilton, Ohio: an example of complex pollution and cause for community health concerns.

The Hamilton Municipal Electric Plant is a 125 MW coal-fired power plant, owned and operated by the City of Hamilton in Butler County, Ohio. The plant is located within 110 m of 50 homes. Bulk chemical investigation of street sediment near these homes indicates average concentrations of 25 ppm Cr, 40 ppm Cu, 15 ppm Ni, 215 ppm Pb, and 500 ppm Zn. Lead and Zn have maximum concentrations of 1207 ppm and 1512 ppm, respectively. Scanning electron microscopy indicates coal ash spherules are present in the street sediment as well as a variety of Pb, Ni, Cr, W, and BaSO4 particulates. Transmission electron microscopy indicates heavy metals are sorbed onto clay particles with some preference for illite over chlorite. This investigation shows bulk chemistry and electron microscopy approaches are very effective tools to investigate particulate pollutants and identify contexts in complex urban settings involving coal pollution.

Sorption-desorption of carbamazepine by palygorskite-montmorillonite (PM) filter medium.

Palygorskite-montmorillonite (PM) was studied as a potential sewage treatment effluent filter material for carbamazepine. Batch sorption experiments were conducted as a function of granule size (0.3-0.6, 1.7-2.0 and 2.8mm) and different sewage effluent conditions (pH, ionic strength and temperature). Results showed PM had a mix of fibrous and plate-like morphologies. Sorption and desorption isotherms were fitted to the Freundlich model. Sorption is granule size-dependent and the medium granule size would be an appropriate size for optimizing both flow and carbamazepine retention. Highest and lowest sorption capacities corresponded to the smallest and the largest granule sizes, respectively. The lowest and the highest equilibrium aqueous (Ce) and sorbed (qe) carbamazepine concentrations were 0.4 mg L(-1) and 4.5 mg L(-1), and 0.6 mg kg(-1) and 411.8 mg kg(-1), respectively. Observed higher relative sorption at elevated concentrations with a Freundlich exponent greater than one, indicated cooperative sorption. The sorption-desorption hysteresis (isotherm non-singularity) indicated irreversible sorption. Higher sorption observed at higher rather than at lower ionic strength conditions is likely due to a salting-out effect. Negative free energy and the inverse sorption capacity-temperature relationship indicated the carbamazepine sorption process was favorable or spontaneous. Solution pH had little effect on sorption.

Reflectance spectra of crude oils and refined petroleum products on a variety of common substrates

A variety of crude oils and refined petroleum products were applied to ten common terrestrial substrates with the goal of developing a set of representative reflectance spectra for hydrocarbon-substrate combinations. Similar to previous studies, each hydrocarbon darkened the substrates and produced hydrocarbon absorption features near 1200, 1690-1770, and 2270-2400 nm, along with a host of other minor features in the VIS/NIR/SWIR portion of the spectrum. Some substrate absorption features interfered with hydrocarbon absorptions, complicating spectral signatures. The reflectance spectra varied directly with the amount of liquid on the substrate. Liquid-saturated samples were left to age and regularly re-measured, establishing a relationship between evaporative loss for volatile and semivolatile products and sample reflectance. The results outline temporal windows of opportunity and minimum detection thresholds for volatiles. They also provide a means for remotely distinguishing 1) water from petroleum products on some substrates and 2) some similar hydrocarbons from one another based on their volatility.

Metal pollution investigation of Goldman Park, Middletown Ohio: Evidence for steel and coal pollution in a high child use setting

A geochemical investigation of both ballfield sediment and street sediment in a park adjacent to a major steel manufacturing site in Middletown, Ohio revealed Pb, Cu, Cr and Zn exceeded background levels, but in heterogeneous ways and in varying levels of health concern. Pb, Sn, and Zn had geoaccumulation values>2 (moderate to heavy pollutants) in street sediment samples. Cr had a geoaccumulation value>1, while Ni, W, Fe and Mn had geoaccumulation values between 1 and 0 in street sediment. Street sediment contamination factors for respective elements are Zn (10.41), Sn (5.45), Pb (4.70), Sb (3.45), Cr (3.19), W (2.59), and Mn (2.43). The notable elements with the highest factors for ball fields are Zn (1.72), Pb (1.36), Cr (0.99), V (0.95), and Mn (1.00). High correlation coefficients of known constituents of steel, such as Fe and Mo, Ni and Cr, W and Co, W and V, as well as particulate steel and coal spherule fragments found by SEM suggest probable sourcing of some of the metals from the AK Steel facility directly adjacent to the park. However, overall extensive heterogeneity of metal pollutants in the area points to the difficulties in sourcing pollutant metals, with many outside sources likely contributing as well. This study demonstrates that different sediment media can be impacted by significantly different metal pollutants even when in very close proximity to a single source and points to unrecognized complexity in urban pollution processes in the region. This study pertains to large-scale regional importance, as Middletown, Ohio is indicative of a typical post-industrial Midwestern U.S. city where limited investigation has been conducted regarding urban pollution and sourcing of materials.

New insights into rare earth element (REE) particulate generated by cigarette lighters: an electron microscopy and materials science investigation of a poorly understood indoor air pollutant and constraints for urban geochemistry

AbstractCigarette smoking is a well-recognized cause of lung cancer and other diseases and is a major contributor to indoor air pollution in numerous settings worldwide. Most cigarette lighters use rare earth element (REE) mischmetal in their flints in order to aid ignition, and these lighters thus have pyrophoric properties. REE particulate emitted from these lighters presents a complexity in the role of health of smokers that has yet to be explored fully. Furthermore, these particles are likely present in numerous urban settings and contribute to the complexities of urban geochemistry. Details of the material properties of rare earth element (REE) particulate derived from smoking lighters are determined first the first time. Particulate was investigated using back-scatter detection scanning electron microscopy techniques and transmission electron microscopy techniques. Several particle types were observed and demonstrate a diverse range of size and textures, many of which are previously not documented and are much smaller than previous basic scanning electron microscopy investigations. These include irregularly shaped fragments of mischmetal, micrometer-scale spherules, aggregates of nanospherules, and platy sponge-like nanoparticles. All of these particles have significant REE content, and most are of a particle size that can be deposited deep in the lung. The available literature regarding toxicity of REEs and the material science data presented here argues very strongly for cause for concern.

Morphologic Evidence of In-Situ Gold Deposition in Lateritic Placer Deposits from Guyana Shield of Venezuela

Recent studies have shown that gold can crystalize in-situ during diagenetic processes in fluvial or soil environments. In near surface environments gold is relatively insoluble, however, organic ligands such as humic acids can complex with gold and increase its solubility, providing a mechanism for gold precipitation in laterite (highly weathered soil) environments [1]. Electron microscopy is critical for observing micro-surface topology to identify unique textures and morphologies that suggest in-situ gold growth. A sample consisting of a gold nugget embedded in a laterite matrix from the Guyana shield of Venezuela was investigated to determine whether gold formed in-situ or by detrital processes. Scanning electron microscopy (SEM) shows gold textures within the laterite matrix that are commonly seen in organic rich soils at near surface conditions which suggest in-situ formation. Gold precipitation in porous regions found in the laterite show wire and fungoid-like morphologies, suggestive of biological precipitation (figure 1) [2,3]. Micro-surface topology of gold samples exhibits isolated nanometer to micrometer sized particles, agglomerated gold masses, and new gold layer growth, further suggesting insitu precipitation (figure 2).

An environmental investigation of the mineralogical, geotechnical, hydrogeologic and botanical properties of subsurface flow constructed wetlands in Akumal Mexico

Akumal is one of the few locations where subsurface flow constructed wetland systems can be compared directly without major differences in environmental setting. These systems in Akumal have highly variable geotechnical properties and performance and most systems are not well functioning. A basic water quality survey indicates SFCW effluent in no case meets UNEP or USEPA guidelines for ammonia or phosphate for sensitive waters. Systems are undersized and many are planted with less than optimal vegetation. Aggregate is generally too coarse and pores are commonly occluded with organic matter. The mineralogy of the locally sourced aggregate used in the systems is dominated by calcite, aragonite, quartz, boehmite and chlorite and is generally beneficial for improving the water quality of the systems; however, dissolution is observed and is of some concern. Major systematic retrofit efforts to improve these systems are warranted and should focus on better vegetation choices, use of locally sourced smaller and less soluble aggregate, exclusive use of the local limestone source containing boehmite, more frequent exchange of the aggregate, and an increase of overall cell size. The systems in Akumal are a classic example of a technological solution to an environmental problem caused by human development that has outpaced the designed capacity for wastewater treatment. This investigation serves as a baseline for numerous future interdisciplinary investigations and outlines challenges facing coastal communities attempting to use subsurface flow constructed wetlands.

Crude oil, petroleum product, and water discrimination on terrestrial substrates with airborne imaging spectroscopy

The Deepwater Horizon explosion and subsequent sinking produced the largest oil spill in U.S. history. One of the most prominent portions of the response is mapping the extent to which oil has reached thousands of miles of shoreline. The most common method of detecting oil remains visual spotting from airframes, supplemented by panchromatic / multispectral aerial photography and satellite imagery. While this imagery provides a synoptic view, it is often ambiguous in its ability to discriminate water from hydrocarbon materials. By employing spectral libraries for material identification and discrimination, imaging spectroscopy supplements traditional imaging techniques by providing specific criteria for more accurate petroleum detection and discrimination from water on terrestrial backgrounds. This paper applies a new hydrocarbon-substrate spectral library to SpecTIR HST-3 airborne imaging spectroscopy data from the Hurricane Katrina disaster in 2005. Using common material identification algorithms, this preliminary analysis demonstrates the applicability and limitations of hyperspectral data to petroleum/water discrimination in certain conditions. The current work is also the first application of the petroleum-substrate library to imaging spectroscopy data and shows potential for monitoring long term impacts of Deepwater Horizon.