Micro-X-ray absorption spectroscopy

Bertsch, P. M., Hunter, D. B., Sutton, S. R., Bajt, S. Rivers, M. L. 1994. In situ chemical speciation of uranium in soils and sediments by micro x-ray absorption spectroscopy. Environmental Science and Technology, 28, 980-984. 

Techniques of microscopic XRF ( j,-XRF) developed in the last 20 years provide 2D images and elemental maps of each element present in the target material. Portable/in situ p-XRF, j,-XRF spectrometers synchrotron-based ( -SRXRF) and micro-x-ray absorption spectroscopy/micro-x-ray absorption near-edge structure spectroscopy (XAS/ J,-XANES) have improved the mineralogical characterization, as well as the elemental and chemical imaging of samples at the submicrometer scale [61]. 

Bertsch PM, Hunter DB, Sutton SR, Bajt S, Rivers ML (1994) In situ chemical speciation of uranium in soils and sediments by micro X-ray absorption spectroscopy. Environ Sci Technol 28 980-984 Bertsch PM and Seaman JC (1999) Characterization of complex mineral assemblages Implications for contaminant transport and environmental remediation. Proc Nat Acad Sci USA 96 3350-3357 Beyersmann D, Koester A, Buttner B, Flessel P (1984) Model reactions of chromium compounds with mammalian and bacterial cells. Toxicol Environ Chem 8 279-286 Bhattachaiya P, Chatterjee D, Jacks G (1997) Occurrence of arsenic contaminated groundwater in alluvial aquifers from Delta Plains, Eastern India Options for safe drinking water supply. Int Jour Water Resources Management 13 79-92... 

U-XRF spectrometry synchrotron-based micro-x-ray absorption near-edge stmcture spectroscopy multiple collector inductively coupled plasma mass spectrometry... 

Photons/X-rays Electron-Probe Micro-Analysis, Electron-Spin Resonance, Laser Micro-Probe, Photo-Desorption, Photoelectron Spectroscopy, y-Ray Absorption Spectroscopy, X-Ray Fluorescence, and Other (IR, NMR, UV, Visible, y-Ray, and X-Ray Absorption Spectroscopy). 

Hunter, D.B. and Bertsch, P.M., In situ examination of uranium contaminated soil particles by micro-x-ray absorption and micro-fluorescence spectroscopies, J. Radio-anal. Nucl. Chem., 234, 237, 1998. 

Hunter DB, Bertsch PM (1998) In situ examination of uranium contaminated soil particles by micro-X-ray absorption and micro-fluorescence spectroscopies. J Radioanal Nucl Chem 234 237-242 Hunter DB, Bertsch PM, Kemner KM, Clark SB (1997) Distribution and chemical speciation of metals and metalloids in biota collected from contaminated environments by spatially resolved XRF, XANES, and EXAFS. JPhys IV 7 (Colloque C2, X-Ray Absorption Fine Structure, Vol. 2) 767-771 Hunter KA (1980) Microelectrophoretic properties of natural surface-active organic matter in coastal seawater. Limnology and Oceanography 25 807-822... 

In this chapter we first provide an overview of eommonly applied synchrotron radiation-based X-ray techniques for determining metal speciation in powdered samples, including X-ray absorption spectroscopy, micro X-ray fluorescence, and micro X-ray diffraction (XRD). The seeond part of this ehapter will provide an example of the application of these teehniques to an investigation of lead (Pb) speciation in a house dust sample, characterized by elevated total and bioaccessible Pb concentrations. 

It could be concluded that, elements that can be hyperaccumulated include As (>0.1 %), Cd (>0.01 %), Co (>0.1 %), Cu (>0.1 %), Pb (>0.1 %), Mn (>1 %), Ni (>0.1 %), Se (>0.1 %) and Zn (>1 %). It could be also mentioned that, the element levels accumulated in these plants would be lethal to other organisms, yet cause no toxicity in hyperaccnmulators. The Se-tolerance mechanism of hyperaccumulators can be followed by nsing microfocused X-ray fluorescence (pXRF) mapping and micro-X-ray absorption near edge structure (pXANES) spectroscopy, which revealed a stark contrast in spatial distribution and chemical speciation of Se between hyperaccnmnlators and nonaccumulators. 

Although a number of secondary minerals have been predicted to form in weathered CCB materials, few have been positively identified by physical characterization methods. Secondary phases in CCB materials may be difficult or impossible to characterize due to their low abundance and small particle size. Conventional mineral identification methods such as X-ray diffraction (XRD) analysis fail to identify secondary phases that are less than 1-5% by weight of the CCB or are X-ray amorphous. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM), coupled with energy dispersive spectroscopy (EDS), can often identify phases not seen by XRD. Additional analytical methods used to characterize trace secondary phases include infrared (IR) spectroscopy, electron microprobe (EMP) analysis, differential thermal analysis (DTA), and various synchrotron radiation techniques (e.g., micro-XRD, X-ray absorption near-eidge spectroscopy [XANES], X-ray absorption fine-structure [XAFSJ). 

X-ray absorption near edge structure(XANES) and electron energy loss near edge structure(ELNES) show similar spectra, thus almost the same theoretical analysis is valid both for these spectroscopies. The careful analysis including higher excited atomic orbitals in the basis set reproduce very well the spectral structure even in details. The core-hole effects are sometimes very important in the excited state electronic state. The theoretical analysis by the cluster model calculation provides very useful information on the local electronic property and the micro structure. 

Neal RH, Sposito G (1989) Selenate adsorption on alluvial soils. Soil Sci Soc Am J 53 70-74 Newville M, Sutton S, Rivers M, Eng P (1999) Micro-beam X-ray absorption and fluorescence spectroscopies at GSECARS APS beamline 13 . J Synchrotron Rad 6 353-355 Nier AO, Schlutter DJ (1993) The thermal history of interplanetary dust particles collected in the Earth s stratosphere. Meteoritics 28 675-681... 

Near-edge X-ray absorption flne structure spectroscopy (STXM/NEXAFS) and optical spectroscopy coupled with micro-FTIR have been used to detect the presence of an equilibrium between malonic acid and its enol form on deliquesced micrometer particles [45]. The amount of enol increases with the amount of water that is present (Figure 3.34). 

Also in the literature, there is little discussion of the accuracy or reproducibility of the analytical technique used for determining the corresponding matrix and particle composition [37, 38], Various analytical methods that have been used to determine the particle concentration in the deposit include gravimetric analysis [29, 31, 39], x-ray fluorescence [5], atomic absorption spectroscopy [33, 40, 41-43], and micro-... 

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