Diffuse reflectance infrared fourier transform (DRIFT) spectroscopy in soil studies

Abstract

The diffuse reflectance spectroscopic technique provides a convenient means of obtaining mid-infrared spectra of soils, as an alternative to the pressed halide disc method. Advantages and drawbacks of the DRIFT technique are discussed and compared with those for the KBr pressed disc method for a range of Australian soils. Useful sample concentrations for DRIFT spectra range from 1-100%, i.e. much higher than for typical pressed halide discs. This high sample concentration leads to an apparent enhancement of relatively weak band intensities, providing increased information content for soil characterization. Some neat soils and soil minerals, however, show severe distortion of strongly absorbing bands at high sample concentrations, generally at frequencies below 1100 cm-1. This results in some bands having an 'inverted' appearance. Bands due to organic components are clearly visible in the range 3100-2800 cm-l. Mineral components of soils often show a group of broad, weak-medium intensity bands in the 2600-1650 cm-1 region due to overtone and combination vibrations. These bands, enhanced in DRIFT spectra, are useful for characterization purposes. For example, bands in the region near 2600-2500 cm-1 are diagnostic features for the identification of calcite and dolomite, while those in the region 2000-1650 cm-1 are characteristic of quartz and kaolinite.

Recent applications of vibrational mid-Infrared (IR) spectroscopy for studying soil components: a review

“…This technique was introduced by Nguyen, et al (1991) for studying soil chemical composition and was subsequently used to investigate SOM and the chemical composition of humic substances, as well as the effect of amendment practice on soil (Aguiar, et al, 2013;Calderon, et al, 2011aCalderon, et al, , 2011bDemyan, et al, 2012;Ellerbrock, et al, 2009;Ferrari, et al, 2011;Janik, et al, 2007a;Kaiser, et al, 2007;Leue, et al, 2010;Ludwig, et al, 2008;Minasny, et al, 2008;Reeves III and Smith, 2009). It has also been applied to study many other agricultural related aspects such as the composition of different coal ranks (Chen, et al, 2012;Li, et al, 2010) and their soluble SOM fraction (Gezic, et al, 2012;Ghosh, et al, 2009), the chemistry of waste and compost materials (Huber-Humer, et al, 2011;Salati, et al, 2013;Smidt and Meissl, 2007), the decomposition processes of forest litter (Duboc, et al, 2012;Nault, et al, 2009;Osono, et al, 2011;Tatzber, et al, 2010), the chemical structure of pyrogenic organic matter (OM) Nocentini, et al, 2010) and the behaviour of chemical compounds adsorbed on clays (Aochi and Farmer, 2011;Dorado, et al, 2010).…”

“…FTIR spectroscopy was used to identify primary (quartz, feldspars) and secondary (silicates, clays, aluminosilicates) soil minerals (Janik, et al, 2007a;Madejova, 2003;Nguyen, et al,1991;Viscarra-Rossel, et al, 2006). Table 1 reports the IR attributions and the integration limits used in some studies regarding the main bands of soil inorganic components.…”

“…In particular the FTIR spectra of clay minerals made it possible to distinguish clay minerals from each other through the bands assigned to OH and Si-O groups (Bishop, et al, 2008;Madejova, 2003). Clays or aluminosilicates show two sharp peaks at 3695 and 3622 cm -1 due to OH stretching (Janik, et al, 2007b;Madejova, 2003;Nguyen, et al, 1991). A broad band near 3400 cm -1 is due to OH stretching (H bonded water); the position and intensity of this band is affected by various exchangeable cations.…”

“…On the basis of a chemisorption study, it was concluded that the band at 1640-1610 cm -1 was due to physically adsorbed water while the one at 1380 cm -1 was due to coordinatively bound water (Aochi, et al, 2011). Weak bands at about 1980, 1870 and 1790 cm -1 are attributed to quartz overtone (Janik, et al, 2007b;Nguyen, et al, 1991). In addition, clay mineral spectra show an intense complex band at around 1048 cm -1 , related to the stretching vibrations of Si-O groups, while the bands at 525 and 468 (Bishop, et al, 2008;Spence and Kelleher, 2012).…”

“…At lower frequencies, the bands at around 712 cm -1 and 871 cm -1 result from in-plane and out-of-plane deformation vibrations of CO 3 2-, respectively. Demyan, et al (2012) ;Nguyen, et al (1991) ;Tatzber, et al (2010). Particular attention has been devoted to the bands at 2506 cm -1 and 875 cm -1 because they are suitable for quantification purposes (Tatzber, et al, 2007).…”