Application of attenuated total reflectance Fourier transform infrared spectroscopy in the mineralogical study of a landslide area, Hungary

This study demonstrates that the unpolarized attenuated total reflectance Fourier transform infrared spectroscopy (ATR FTIR) is a practical and quick tool to distinguish different types of sediments in landslide-affected areas, and potentially other types of physical environments too. Identification and quantification of minerals by ATR FTIR is implemented on a set of powdered natural sediments from a loess landslide (Kulcs, Hungary). A protocol including sample preparation, analytical conditions and evaluation of sediment ATR spectra is outlined in order to identify and estimate major minerals in sediments. The comparison of the defined FTIR parameters against qualitative and quantitative results of X-ray diffraction and thermal analysis was used to validate the use of ATR FTIR spectroscopy for the considered sediments. The infrared band areas and their ratios (water/carbonates; silicates/carbonates; kaolinite) appear to be the most sensitive parameters to identify strongly weathered sediments such as paleosols and red clays which most likely facilitate sliding and could form sliding zones. The effect of grain size and orientation of anisotropic minerals on the wave number and intensity of some major absorption bands is also discussed

A 137CS kimutathatósága Pest megyei talajmintákban

Pest megye területére vonatkozó gammaspektroszkópiai vizsgálatokon alapuló radontérkép adatbázisának feldolgozása közben - amely 31 talajfúrás alapján készül - figyeltünk fel arra, hogy néhány talajszelvény felső rétegeiben megtalálható a cézium 137-es tömegszámú izotópja. E radioaktív izotóp az 1945 és 1980 között zajló légköri atomfegyver kísérletekből illetve az 1986. április 26-án az ukrajnai Csernobil és Pripjaty városok melletti atomerőmű-balesetből származhat, ahogyan azt számos, más területen (pl. Fehéroroszország, Skandinávia, Ausztria, Svájc) (Ivanova et al., 1997, Riesen, 1998, Dubois and Bossew, 2003, Almgren and Isaksson, 2006, Persson, 2008,) történt vizsgálat megállapította. Ennek oka, hogy a baleset és a robbantások következményeként az aeroszolokra és a csapadékra kiülepedő radioaktív izotópok – köztük az emberre nézve veszélyes, hosszú élettartamú radionuklidok (pl. 137Cs és 90Sr) – a légkörben vándoroltak és kiülepedtek. Dolgozatunkban a 30 év felezési idejű 137Cs izotóp pest megyei eloszlását összesítettük 1992-ben gyűjtött talajfúrások felső rétegeinek (általában 30 cm és 60 cm) gammaspektroszkópiai elemzése alapján. A feldolgozás során két talajfúrás felső rétegében (30 cm) az átlagos 2-3 Bq/kg értékhez képest nagyobb - 12-32 Bq/kg - aktivitást mértünk a Budai-hegység DNy-i lábánál. E fúrások környezetében egy új fúrást mélyítettünk. Az itt gyűjtött nagyobb mennyiségű minta lehetővé tette, hogy részletes talajtani, fizikai és geokémiai vizsgálatokat végezzünk. Célunk a külföldi tapasztalatokhoz hasonló (Zygmunt et al., 1997, Filep, 1999) összefüggést keresni a cézium mélység szerinti eloszlása és a talajtani jellemzők (agyagásvány-, szervesanyagtartalom, szemcseméret) között

Geochemical reactions of Na-montmorillonite in dissolved scCO2 in relevance of modeling caprock behavior in CO2 geological storage

One of the challenges of the present century is to limit the greenhouse gas emissions for the mitigation of climate change which is possible for example by a transitional technology, CO2 geological storage. Clay minerals are considered to be responsible for the low permeability and sealing capacity of caprocks sealing off stored CO2. However, their reactions are not well understood for complex simulations. This work aims to create a kinetic geochemical model of Na-montmorillonite standard SWy-2 supported by solution and mineral composition results from batch experiments. Such experimentally validated numerical models are scarce. Four 70-hours experiments have been carried out at atmospheric conditions, and with CO2 supercritical phase at 100 bar and 80 °C. Solution samples have been taken during and after experiments and their compositions were measured by ICP-OES. The treated solid phase has been analyzed by XRD and ATR-FTIR and compared to in-parallel measured references (dried SWy-2). Kinetic geochemical modelling of the experimental conditions has been performed by software PHREEQC. Experiments and models show fast reactions under the studied conditions and increased reactivity in presence of scCO2. Solution composition results cannot be described by the change of the uncertain reactive surface area of mineral phases. By considering the clay standard’s cation exchange capacity divided proportionally among interlayer cations of Na-montmorillonite, the measured variation can be described on an order of magnitude level. It is furthermore indicated that not only the interlayer cations take part in this process but a minor proportion of other, structural ions as well, differently in the reference and scCO2 environments

An experimental study of water in nominally anhydrous minerals in the upper mantle near the water-saturated solidus

The incorporation of water in olivine and pyroxenes interlayered within fertile lherzolite compositions was explored experimentally near the wet solidus of lherzolite at 2·5 and 4 GPa. The concentrations and activities of water were varied to establish

Effects of Particle Size on the Attenuated Total Reflection Spectrum of Minerals

This study focuses on particle size effect on monomineralic powders recorded using attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. Six particle size fractions of quartz, feldspar, calcite, and dolomite were prepared (<2, 2–4, 4–8, 8–16, 16–32, and 32–63 mm). It is found that the width, intensity, and area of bands in the ATR FTIR spectra of minerals have explicit dependence on the particle size. As particle size increases, the intensity and area of IR bands usually decrease while the width of bands increases. The band positions usually shifted to higher wavenumbers with decreasing particle size. Infrared spectra of minerals are the most intensive in the particle size fraction of 2–4 mm. However, if the particle size is very small (<2 mm), due to the wavelength and penetration depth of the IR light, intensity decreases. Therefore, the quantity of very fine-grained minerals may be underestimated compared to the coarser phases. A nonlinear regression analysis of the data indicated that the average coefficients and indices of the power trend line equation imply a very simplistic relationship between median particle diameter and absorbance at a given wavenumber. It is concluded that when powder samples with substantially different particle size are compared, as in regression analysis for modal predictions using ATR FT-IR, it is also important to report the grain size distribution or surface area of samples. The band area of water (3000–3620 cm–1) is similar in each mineral fraction, except for the particles below 2 mm. It indicates that the finest particles could have disproportionately more water adsorbed on their larger surface area. Thus, these higher wavenumbers of the ATR FT-IR spectra may be more sensitive to this spectral interference if the number of particles below 2 mm is considerable. It is also concluded that at least a proportion of the moisture could be very adhesive to the particles due to the band shift towards lower wavenumbers in the IR range of 3000–3620 cm–1