Name: atom probe tomography analysis of exsolved mineral phases
Uploaded: 2019-10-25T12:30:00
Description: Watch this Scientific Journal Video about Atom Probe Tomography Analysis of Exsolved Mineral Phases at JoVE.com

This work was supported by funding from the National Science Foundation (NSF) through grants EAR-1560779 and EAR-1647012, the Office of the VP for Research and Economic Development, the College of Arts and Sciences, and the Department of Geological Sciences. Authors also acknowledge Chiara Cappelli, Rich Martens and Johnny Goodwin for technical assistance and the Montserrat Volcano Observatory for providing the ash samples.

1. Sourcing, selection, and preparation of mineral grains
NOTE: Samples were obtained from the catalogued collection at the Montserrat Volcano Observatory (MVO) and derived from falling deposits originating from a vigorous ash venting episode at Soufri&#232;re Hills Volcano that occurred on 5 October, 2009; this was one of 13 similar events over a course of three days14. This ash venting preceded a new phase of lava dome growth (phase 5) that commenced on 9 October. Previ...

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P., Kelly, T. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Local Electrode Atom Probe Tomography: A User&#8217;s Guide. , 318 (2013).</li><li>Devine, J. D., Rutherford, M. J., Norton, G. E., Young, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magma+storage+region+processes+inferred+from+geochemistry+of+Fe&#8211;Ti+oxides+in+andesitic+magma,+Soufriere+Hills+Volcano.">Magma storage region processes inferred from geochemistry of Fe&#8211;Ti oxides in andesitic magma, Soufriere Hills Volcano.</a> Journal of Petrology. 44, 1375-1400 (2003).</li><li>Jackson, M., Bowles, J. 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3D APT data reconstructions allow a precise measurement of the interlamellar spacing in the analyzed crystal at a resolution three orders of magnitude higher than those measured from conventional SEM images. This indicates that atomic variations in chemistry occur over a spatial extent three orders of magnitude smaller than optically observable mineralogical changes. Also, the measured interlamellar distances (29 nm and 14 nm), are consistent with the length scale for oxyexsolution as opposed to that for nucleation and g...

The study of chemical mineralogy has been a major source of information within the field of Earth Sciences for more than a century, as minerals actively record geological processes during and after their crystallization. Physio-chemical conditions of these processes, such as temperature changes during volcanism and metamorphism, are recorded during mineral nucleation and growth in the form of chemical zonation, striations, and lamellae, among others. Exsolution lamellae form when a phase unmixes into two separate phases in the solid state. The analysis of the orientation, size, morphology, and spacing of such exsolution lamellae can provide essential information to understand temperature and pressure changes during volcanism and metamorphism1,2,3 and the formation of ore mineral deposits4.
Traditionally, the study of exsolution lamellae was conducted with the observation of micrographs by simple scanning electron imaging5. More recently, this has been substituted by the use of energy-filtered transmission electron microscopy (TEM) providing detailed observations at the nanoscale level1,2,3. Nevertheless, in both cases, the observations are made in two dimensions (2D), which is not fully adequate for three dimensional (3D) structures represented by these exsolution lamellae. Nanotomography6 is emerging as a new technique for the 3D observation of nanoscale features inside minerals grains, yet there is insufficient information about the composition of these features. An alternative to these approaches is the use of atom probe tomography (APT), representing the highest spatial resolution analytical technique in existence for the characterization of materials7. The strength of the technique lies in the possibility of combining a 3D reconstruction of nanoscale features with their chemical composition at the atomic scale with a near part-per-million analytical sensitivity7. Previous applications of APT to the analysis of geological samples have provided excellent results8,9,10,11, particularly in the chemical characterization of element diffusion and concentrations9,12,13. Yet, this application has not been used for the study of exsolution lamellae, abundant in some minerals hosted in metamorphic and igneous rocks. Here, we explore the use of APT, and its limitations, for the analysis of the size and composition of exsolution lamellae, and interlamellar spacing in volcanic titanomagnetite crystals.

<table>
	<tbody>
		<tr>
			<td>InTouchScope Secondary Electron Microscope (SEM)</td>
			<td>JEOL</td>
			<td>JSM-6010PLUS/LA</td>
			<td></td>
		</tr>
		<tr>
			<td>Focus Ion Beam (FIB) Secondary Electron Microscope (SEM)</td>
			<td>TESCAN</td>
			<td>LYRA XMU</td>
			<td></td>
		</tr>
		<tr>
			<td>Local Electrode Atom Probe (LEAP)</td>
			<td>CAMECA</td>
			<td>5000 XS</td>
			<td></td>
		</tr>
		<tr>
			<td>Integrated Visualization and Analysis Software (IVAS, version 3.6.12).</td>
			<td></td>
			<td></td>
			<td>processing software</td>
		</tr>
	</tbody>
</table>

atom probe tomography analysis of exsolved mineral phases

Element diffusion rates and temperature/pressure control a range of fundamental volcanic and metamorphic processes. Such processes are often recorded in lamellae exsolved from host mineral phases. Thus, the analysis of the orientation, size, morphology, composition and spacing of exsolution lamellae is an area of active research in the geosciences. The conventional study of these lamellae has been conducted by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and more recently with focused ion beam (FIB)-based nanotomography, yet with limited chemical information. Here, we explore the use of atom probe tomography (APT) for the nanoscale analysis of ilmenite exsolution lamellae in igneous titanomagnetite from ash deposits erupted from the active Soufri&#232;re Hills Volcano (Montserrat, British West Indies). APT allows the precise calculation of interlamellar spacings (14&#8211;29 &#177; 2 nm) and reveals smooth diffusion profiles with no sharp phase boundaries during the exchange of Fe and Ti/O between the exsolved lamellae and the host crystal. Our results suggest that this novel approach permits nanoscale measurements of lamellae composition and interlamellar spacing that may provide a means to estimate the lava dome temperatures necessary to model extrusion rates and lava dome failure, both of which play a key role in volcanic hazard mitigation efforts.

Like many titanomagnetite crystals from various stages of the Soufri&#232;re Hills Volcano (SHV) eruption, the crystal analyzed here contains exsolution lamellae &#60;10 &#181;m in thickness, visible in secondary SEM images (Figure 1d), which separate zones of Ti-rich magnetite, indicating a C2 stage of oxidation18. Based upon the SEM images, spacing between these lamellae ranges from 2 to 6 &#181;m (n = 15). Four titanomagnetite specimen tips, referred as 20...

Watch this Scientific Journal Video about Atom Probe Tomography Analysis of Exsolved Mineral Phases at JoVE.com

Atom Probe Tomography Analysis of Exsolved Mineral Phases

Analysis of the morphology, composition, and spacing of exsolution lamellae can provide essential information to understand geological processes related to volcanism and metamorphism. We present a novel application of APT for the characterization of such lamellae and compare this approach to the conventional use of electron microscopy and FIB-based nanotomography.

Element diffusion rates and temperature/pressure control a range of fundamental volcanic and metamorphic processes. Such processes are often recorded in ...

Examining variations in mineral chemistry can shed light on changes in volcanic activity, and allow researchers to obtain timescales of volcanic processes to better understand any potential hazards. Atom probe tomography allows an unprecedented 3D visualization of mineral exsolved phases while measuring their chemical composition at atomic scale. We are currently applying the technique to the characterization of pathological mineralization, for example, in the case of kidney stones.This method can be applied to volcanic systems where eruption transitions can occur over small timescales. These transitions are recorded in the minerals over very small spatial scales. Begin by pouring one gram of the sample into a 10-centimeter glass Petri dish and wrap a three by three-centimeter sheet of weight paper around a 10-gauss magnet.Use the magnet to pull magnetite-rich grains between 100 and 500 micrometers in diameter from the ash sample and place the grains in a 32-micrometer pore, 8-centimeter diameter stainless steel sieve. Use a squeeze bottle of deionized water to flush the smaller adhering ash particles through the sieve for 20 to 30 seconds and allow the grains to air dry for 24 hours. The next day, affix any clean and dry ash particles to sample mounts suitable for a secondary scanning electron microscope and image the particles in secondary electron mode at a 15 to 20-kilovolt accelerating voltage and at a working distance of 10 millimeters to select the five to 10 best candidates for further analysis.The selected grains should be predominantly magnetite. Affix the selected ash grains to a piece of clear tape and surround the samples with a one-inch diameter hollow mold that has been internally coated with vacuum grease, then fill the mold with epoxy resin mold. Once the epoxy is cured, remove the sample from the mold and peel tape from the bottom.The ash grains should be partially exposed. Polish the epoxy-cast ash grains with silicon carbide grinding paper of five different grit sizes, from the highest to lowest grit size in a figure eight motion for at least 10 minutes per grinding paper. In between grit sizes, sonicate the sample in a bath of deionized water for 10 minutes.After each last polish, check the sample under a microscope to ensure that no polishing grit is present and that the sample surface is free from scratches. Next use polishing cloths to polish the epoxy-cast ash grains with consecutive one and 0.3-micrometer alumina polishing suspensions in a figure eight motion for at least 10 minutes, sonicating the sample in deionized water for 10 minutes between suspension sizes. After the second suspension polish, check the sample under the microscope to ensure that no suspension is present and that the sample surface is free of scratches.At the end of the polishing procedure, the epoxy surface should be smooth and the ash grains should be flat and well exposed. Using an available sputter coating device, coat the sample surface with an approximately 10-nanometer thick carbon-conducting coat and obtain backscattered electron images of the ash grains with the electron microscope at a 15 to 20-kilovolt accelerating voltage and a working distance of 10 millimeters to determine the location of exsolution lamellae in the magnetite. Before beginning the focused ion beam procedure, sputter coat the sample surface with a 15-nanometer layer of copper to avoid electron charging and sample drifting.Next use a focused gallium-ion beam in a dual-beam scanning electron microscope on the polished section of interest containing the lamellae over a 1.5 by 20-micrometer region at 30 kilovolts and seven pascals. Use the ion beam to mill three wedges of material below three sides of the platinum rectangle and insert the gas-injection system to weld the wedge to an in situ nanomanipulator using gas-injection system-deposited platinum before cutting the final edge free. Using the gallium-ion beam, cut 10 one to two micrometer-wide segments from the wedge and sequentially affix the wedges with platinum to the tops of silicon posts of a microtip array coupon.Shape and sharpen each specimen tip using annular milling patterns of increasingly smaller inner and outer diameters, starting at 30 kilovolts to produce the specimen geometry necessary for atom probe tomography and finishing at an accelerating voltage of five kilovolts to reduce the gallium implantation and to obtain a consistent tip-to-tip shape. For atom probe tomography acquisition, mount the micro coupon with the sharpened tips welded to the silicon posts onto a specimen puck and load the puck into a carousel for placement inside the local electrode atom probe. Insert the carousel inside the buffer chamber of a local electrode atom probe equipped with a picosecond 355-nanometer ultraviolet laser and turn the head of the laser.After calibration, achieve a vacuum in the analysis chamber at or below six by 10 to the negative 11 torr and use a transfer rod to insert the puck specimen into the main analysis chamber. Then move the specimen puck to align the micro coupon with the local electrode to select the tip and update the database to indicate the tip number. In this analysis, four titanomagnetite specimen tips were successfully extracted from the single crystal and analyzed by atom probe tomography.Two of the specimens demonstrated homogenous concentrations of both iron and titanium throughout, indicating that lamellae were not intersected. The other two specimens exhibited zones with variable concentrations in iron, oxygen, and titanium. 3D reconstructions of the atom probe tomography data permit a precise measurement of the intralamellar spacing and provide length scales that average between 14 to 29 nanometers with a one-sigma value of two nanometers for both specimens.In addition to these measurements, atom probe tomography permits the extraction of chemical information across these lamellae at a high spatial resolution through the analysis of proxigrams using the point zero as the intersection between the lamella and the host mineral. Atomic concentrations of titanium in the crystal confirmed that the fragment is indeed a titanomagnetite and are consistent with previous petrologic analyses of Soufriere Hills Volcano eruptive products. These proxigrams also confirm that the composition of the lamella matches that of ilmenite.Preparing the wedges to capture the lamellae is critical to the FIB SEM sample preparation as well as sharpening the tips to the correct dimension. Transmission electro microscopy can also be performed to verify the lamellae dimensions and the interlamellar spacing. This technique could allow vulcanologists to calculate the timescales of eruptive activity to better understand the potential hazards of active volcanoes.

atom-probe-tomography-analysis-of-exsolved-mineral-phases

Research

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Environment

Measuring Fluxes of Mineral Nutrients and Toxicants in Plants with Radioactive Tracers

Unidirectional influx and efflux of nutrients and toxicants, and their resultant net fluxes, are central to the nutrition and toxicology of plants. Radioisotope tracing is a major technique used to measure such fluxes, both within plants, and between plants and their environments. Flux data obtained with radiotracer protocols can help elucidate the capacity, mechanism, regulation, and energetics of transport systems for specific mineral nutrients or toxicants, and can provide insight into compartmentation and turnover rates of subcellular mineral and metabolite pools. Here, we describe two major radioisotope protocols used in plant biology: direct influx (DI) and compartmental analysis by tracer efflux (CATE). We focus on flux measurement of potassium (K+) as a nutrient, and ammonia/ammonium (NH3/NH4+) as a toxicant, in intact seedlings of the model species barley (Hordeum vulgare L.). These protocols can be readily adapted to other experimental systems (e.g., different species, excised plant material, and other nutrients/toxicants). Advantages and limitations of these protocols are discussed.

In planta measurement of nutrient and toxicant fluxes is essential to the study of plant nutrition and toxicity. Here, we cover radiotracer protocols for influx and efflux determination in intact plant roots, using potassium (K+) and ammonia/ammonium (NH3/NH4+) fluxes as examples. Advantages and limitations of such techniques are discussed.

Unidirectional influx and efflux of nutrients and toxicants, and their resultant net fluxes, are central to the nutrition and toxicology of plants. ...

Use of Chironomidae (Diptera) Surface-Floating Pupal Exuviae as a Rapid Bioassessment Protocol for Water Bodies

Rapid bioassessment protocols using benthic macroinvertebrate assemblages have been successfully used to assess human impacts on water quality. Unfortunately, traditional benthic larval sampling methods, such as the dip-net, can be time-consuming and expensive. An alternative protocol involves collection of Chironomidae surface-floating pupal exuviae (SFPE). Chironomidae is a species-rich family of flies (Diptera) whose immature stages typically occur in aquatic habitats. Adult chironomids emerge from the water, leaving their pupal skins, or exuviae, floating on the water&#8217;s surface. Exuviae often accumulate along banks or behind obstructions by action of the wind or water current, where they can be collected to assess chironomid diversity and richness. Chironomids can be used as important biological indicators, since some species are more tolerant to pollution than others. Therefore, the relative abundance and species composition of collected SFPE reflect changes in water quality. Here, methods associated with field collection, laboratory processing, slide mounting, and identification of chironomid SFPE are described in detail. Advantages of the SFPE method include minimal disturbance at a sampling area, efficient and economical sample collection and laboratory processing, ease of identification, applicability in nearly all aquatic environments, and a potentially more sensitive measure of ecosystem stress. Limitations include the inability to determine larval microhabitat use and inability to identify pupal exuviae to species if they have not been associated with adult males.

Use of Chironomidae Diptera Surface-Floating Pupal Exuviae as a Rapid Bioassessment Protocol for Water Bodies

Rapid bioassessment protocols using benthic macroinvertebrates are often used to monitor and assess water quality. An efficient protocol involves collections of Chironomidae surface-floating pupal exuviae (SFPE). Here, techniques for field collection, laboratory processing, slide mounting, and identification of Chironomidae SFPE are described.

Rapid bioassessment protocols using benthic macroinvertebrate assemblages have been successfully used to assess human impacts on water quality. ...

Extracting Metrics for Three-dimensional Root Systems: Volume and Surface Analysis from In-soil X-ray Computed Tomography Data

Plant roots play a critical role in plant-soil-microbe interactions that occur in the rhizosphere, as well as processes with important implications to climate change and crop management. Quantitative size information on roots in their native environment is invaluable for studying root growth and environmental processes involving plants. X-ray computed tomography (XCT) has been demonstrated to be an effective tool for in situ root scanning and analysis. We aimed to develop a costless and efficient tool that approximates the surface and volume of the root regardless of its shape from three-dimensional (3D) tomography data. The root structure of a Prairie dropseed (Sporobolus heterolepis) specimen was imaged using XCT. The root was reconstructed, and the primary root structure was extracted from the data using a combination of licensed and open-source software. An isosurface polygonal mesh was then created for ease of analysis. We have developed the standalone application imeshJ, generated in MATLAB1, to calculate root volume and surface area from the mesh. The outputs of imeshJ are surface area (in mm2) and the volume (in mm3). The process, utilizing a unique combination of tools from imaging to quantitative root analysis, is described. A combination of XCT and open-source software proved to be a powerful combination to noninvasively image plant root samples, segment root data, and extract quantitative information from the 3D data. This methodology of processing 3D data should be applicable to other material/sample systems where there is connectivity between components of similar X-ray attenuation and difficulties arise with segmentation.

A methodology for obtaining visual and quantitative root structure information from X-ray computed tomography data acquired in-soil is presented.

Plant roots play a critical role in plant-soil-microbe interactions that occur in the rhizosphere, as well as processes with important implications to ...

Modification and Application of a Leaf Blower-vac for Field Sampling of Arthropods

Rice fields host a large diversity of arthropods, but investigating their population dynamics and interactions is challenging. Here we describe the modification and application of a leaf blower-vac for suction sampling of arthropod populations in rice. When used in combination with an enclosure, application of this sampling device provides absolute estimates of the populations of arthropods as numbers per standardized sampling area. The sampling efficiency depends critically on the sampling duration. In a mature rice crop, a two-minute sampling in an enclosure of 0.13 m2 yields more than 90% of the arthropod population. The device also allows sampling of arthropods dwelling on the water surface or the soil in rice paddies, but it is not suitable for sampling fast flying insects, such as predatory Odonata or larger hymenopterous parasitoids. The modified blower-vac is simple to construct, and cheaper and easier to handle than traditional suction sampling devices, such as D-vac. The low cost makes the modified blower-vac also accessible to researchers in developing countries.

Assessment of arthropod abundance in crops is critical for investigating population dynamics and species interactions. Here we describe the modification and application of a leaf blower-vac for suction sampling of arthropods in rice.

Rice fields host a large diversity of arthropods, but investigating their population dynamics and interactions is challenging. Here we describe the ...

Dispersion of Nanomaterials in Aqueous Media: Towards Protocol Optimization

The sonication process is commonly used for de-agglomerating and dispersing nanomaterials in aqueous based media, necessary to improve homogeneity and stability of the suspension. In this study, a systematic step-wise approach is carried out to identify optimal sonication conditions in order to achieve a stable dispersion. This approach has been adopted and shown to be suitable for several nanomaterials (cerium oxide, zinc oxide, and carbon nanotubes) dispersed in deionized (DI) water. However, with any change in either the nanomaterial type or dispersing medium, there needs to be optimization of the basic protocol by adjusting various factors such as sonication time, power, and sonicator type as well as temperature rise during the process. The approach records the dispersion process in detail. This is necessary to identify the time points as well as other above-mentioned conditions during the sonication process in which there may be undesirable changes, such as damage to the particle surface thus affecting surface properties. Our goal is to offer a harmonized approach that can control the quality of the final, produced dispersion. Such a guideline is instrumental in ensuring dispersion quality repeatability in the nanoscience community, particularly in the field of nanotoxicology.

Here, we present a step-wise protocol for the dispersion of nanomaterials in aqueous media with real-time characterization to identify the optimal sonication conditions, intensity, and duration for improved stability and uniformity of nanoparticle dispersions without impacting the sample integrity.

The sonication process is commonly used for de-agglomerating and dispersing nanomaterials in aqueous based media, necessary to improve homogeneity and ...

Stress Distribution During Cold Compression of Rocks and Mineral Aggregates Using Synchrotron-based X-Ray Diffraction

We report detailed procedures for performing compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus (D-DIA) coupled with synchrotron X-radiation. A cube-shaped sample assembly is prepared and compressed, at room temperature, by a set of four X-ray transparent sintered diamond anvils and two tungsten carbide anvils, in the lateral and the vertical planes, respectively. All six anvils are housed within a 250-ton hydraulic press and driven inward simultaneously by two wedged guide blocks. A horizontal energy dispersive X-ray beam is projected through and diffracted by the sample assembly. The beam is commonly in the mode of either white or monochromatic X-ray. In the case of white X-ray, the diffracted X-rays are detected by a solid-state detector array that collects the resulting energy dispersive diffraction pattern. In the case of monochromatic X-ray, the diffracted pattern is recorded using a two-dimensional (2-D) detector, such as an imaging plate or a charge-coupled device (CCD) detector. The 2-D diffraction patterns are analyzed to derive lattice spacings. The elastic strains of the sample are derived from the atomic lattice spacing within grains. The stress is then calculated using the predetermined elastic modulus and the elastic strain. Furthermore, the stress distribution in two-dimensions allow for understanding how stress is distributed in different orientations. In addition, a scintillator in the X-ray path yields a visible light image of the sample environment, which allows for the precise measurement of sample length changes during the experiment, yielding a direct measurement of volume strain on the sample. This type of experiment can quantify the stress distribution within geomaterials, which can ultimately shed light on the mechanism responsible for compaction. Such knowledge has the potential to significantly improve our understanding of key processes in rock mechanics, geotechnical engineering, mineral physics, and material science applications where compactive processes are important.

We report detailed procedures for compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus coupled with synchrotron X-radiation. Such experiments allow quantification of the stress distribution within samples, that ultimately sheds light on compaction processes in geomaterials.

We report detailed procedures for performing compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus (D-DIA) ...

An Experimental Protocol for Studying Mineral Effects on Organic Hydrothermal Transformations

Organic-mineral interactions are widely occurring in hydrothermal environments, such as hot springs, geysers on land, and the hydrothermal vents in the deep ocean. Roles of minerals are critical in many hydrothermal organic geochemical processes. Traditional hydrothermal methodology, which includes using reactors made of gold, titanium, platinum, or stainless-steel, is usually associated with the high cost or undesired metal catalytic effects. Recently, there is a growing tendency for using the cost-effective and inert quartz or fused silica glass tubes in hydrothermal experiments. Here, we provide a protocol for carrying out organic-mineral hydrothermal experiments in silica tubes, and we describe the essential steps in the sample preparation, experimental setup, products separation, and quantitative analysis. We also demonstrate an experiment using a model organic compound, nitrobenzene, to show the effect of an iron-containing mineral, magnetite, on its degradation under a specific hydrothermal condition. This technique can be applied to study complex organic-mineral hydrothermal interactions in a relatively simple laboratory system.

Earth-abundant minerals play important roles in the natural hydrothermal systems. Here, we describe a reliable and cost-effective method for the experimental investigation of organic-mineral interactions under hydrothermal conditions.

Organic-mineral interactions are widely occurring in hydrothermal environments, such as hot springs, geysers on land, and the hydrothermal vents in the ...

Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions

Combined size and density fractionation (CSDF) is a method used to physically separate soil into fractions differing in particle size and mineralogy. CSDF relies on sequential density separation and sedimentation steps to isolate (1) the free light fraction (uncomplexed organic matter), (2) the occluded light fraction (uncomplexed organic matter trapped in soil aggregates) and (3) a variable number of heavy fractions (soil minerals and their associated organic matter) differing in composition. Provided that the parameters of the CSDF (dispersion energy, density cut-offs, sedimentation time) are properly selected, the method yields heavy fractions of relatively homogeneous mineral composition. Each of these fractions is expected to have a different complexing ability towards organic matter, rendering this a useful method to isolate and study the nature of organo-mineral interactions. Combining density and particle size separation brings an improved resolution compared to simple size or density fractionation methods, allowing the separation of heavy components according to both mineralogy and size (related to surface area) criteria. As is the case for all physical fractionation methods, it may be considered as less disruptive or aggressive than chemically-based extraction methods. However, CSDF is a time-consuming method and furthermore, the quantity of material obtained in some fractions can be limiting for subsequent analysis. Following CSDF, the fractions may be analyzed for mineralogical composition, soil organic carbon concentration and organic matter chemistry. The method provides quantitative information about organic carbon distribution within a soil sample and brings light to the sorptive capacity of the different, naturally-occurring mineral phases, thus providing mechanistic information about the preferential nature of organo-mineral interactions in soils (i.e., which minerals, what type of organic matter).

Combined size and density fractionation (CSDF) is a method to physically separate soil into fractions differing in texture (particle size) and mineralogy (density). The purpose is to isolate fractions with different reactivities towards soil organic matter (SOM), in order to better understand organo-mineral interactions and SOM dynamics.

Combined size and density fractionation (CSDF) is a method used to physically separate soil into fractions differing in particle size and mineralogy. CSDF ...

Automated 3D Optical Coherence Tomography to Elucidate Biofilm Morphogenesis Over Large Spatial Scales

Biofilms are a most successful microbial lifestyle and prevail in a multitude of environmental and engineered settings. Understanding biofilm morphogenesis, that is the structural diversification of biofilms during community assembly, represents a remarkable challenge across spatial and temporal scales. Here, we present an automated biofilm imaging system based on optical coherence tomography (OCT). OCT is an emerging imaging technique in biofilm research. However, the amount of data that currently can be acquired and processed hampers the statistical inference of large scale patterns in biofilm morphology. The automated OCT imaging system allows covering large spatial and extended temporal scales of biofilm growth. It combines a commercially available OCT system with a robotic positioning platform and a suite of software solutions to control the positioning of the OCT scanning probe, as well as the acquisition and processing of 3D biofilm imaging datasets. This setup allows the in situ and non-invasive automated&#160;monitoring of biofilm development and may be further developed to couple OCT imaging with macrophotography and microsensor profiling.

Microbial biofilms form complex architectures at interphases and develop into highly scale-dependent spatial patterns. Here, we introduce an experimental system (hard- and software) for the automated acquisition of 3D optical coherence tomography (OCT) datasets. This toolset allows the non-invasive and multi-scale characterization of biofilm morphogenesis in space and time.

Biofilms are a most successful microbial lifestyle and prevail in a multitude of environmental and engineered settings. Understanding biofilm ...

Laser-Induced Fluorescence Emission (L.I.F.E.) as Novel Non-Invasive Tool for In-Situ Measurements of Biomarkers in Cryospheric Habitats

Global warming affects microbial communities in a variety of ecosystems, especially cryospheric habitats. However, little is known about microbial-mediated carbon fluxes in extreme environments. Hence, the methodology of sample acquisition described in the very few studies available implies two major problems: A) high resolution data require a large number of samples, which is difficult to obtain in remote areas; B) unavoidable sample manipulation such as cutting, sawing, and melting of ice cores that leads to a misunderstanding of in situ conditions. In this study, a prototype device that requires neither sample preparation nor sample destruction is presented. The device can be used for in situ measurements with a high spectral and spatial resolution in terrestrial and ice ecosystems and is based on the Laser-Induced Fluorescence Emission (L.I.F.E.) technique. Photoautotrophic supraglacial communities can be identified by the detection of L.I.F.E. signatures in photopigments. The L.I.F.E. instrument calibration for the porphyrin derivates chlorophylla (chla) (405 nm laser excitation) and B-phycoerythrin (B-PE) (532 nm laser excitation) is demonstrated. For the validation of this methodology, L.I.F.E. data were ratified by a conventional method for chla quantification that involved pigment extraction and subsequent absorption spectroscopy. The prototype applicability in the field was proven in extreme polar environments. Further testing on terrestrial habitats took place during Mars analog simulations in the Moroccan dessert and on an Austrian rock glacier. The L.I.F.E. instrument enables high resolution scans of large areas with acceptable operation logistics and contributes to a better understanding of the ecological potential of supraglacial communities in the context of global change.

Laser-Induced Fluorescence Emission L.I.F.E. as Novel Non-Invasive Tool for In-Situ Measurements of Biomarkers in Cryospheric Habitats

Carbon fluxes in the cryosphere are hardly assessed yet but are crucial regarding climate change. Here we show a novel prototype device that captures the phototrophic potential in supraglacial environments based on laser-induced fluorescence emission (L.I.F.E.) technology offering high spectral and spatial resolution data under in situ conditions.