In-Situ Measurements of Carbon Stable Isotopes Ratio in Karstic Caves by FTIR Spectroscopy

Abstract

Carbon stable isotope ratios measurement serves as an important implement for environmental geochemical processes study. While Mass spectrometry is commonly used for the task, FTIR (Fourier Transform Infra-Red) spectroscopy has the potential for determining these isotopic ratios with the advantage of simple in-situ measurements. Online analysis enables continuous processes monitoring and decreases sampling errors, caused by the sampling and the laboratory analysis procedures (e.g. for measurement in the mass spectrometer). Variance in carbon stable isotope ratios are results of waterrock interactions, phase transitions, changes in ambient temperature and humidity, biochemical reactions and more. In this study carbon isotope ratios were measured using FTIR spectrophotometer in both field and in laboratory conditions and corroboration of the analysis validity was done by Mass spectrometer measurements. The research results suggest that: Carbon isotope ratio (13 C/ 12 C) may be determined by FTIR spectroscopy of the CO 2 released from water samples under acidic conditions. As a case-study, FTIR analysis was used for characterizing phase transitions and water-rock interactions of runoff infiltrating a cave. By profiling the stable isotope systems, we have found that the 13 C values, which were calculated using FTIR showed sufficient agreement to those of the Mass Spectrometer measurements. A case study analyzing water samples from karstic cave (Sif cave, Israel), verified that: (a) On line determination of water 13 C/ 12 C ratio can be carried out with the portable FTIR spectrometer, hence can be taken to field measurements as preformed in the Sif cave. (b) The C concentration sensitivity achieved was 7‰ in δ values, which is applicable for most carbon stable isotopes applications.

An Eco-Friendly Modification of a Walnut Shell Biosorbent for Increased Efficiency in Wastewater Treatment

“…However, all spectra presented the characteristic doublet (2359 and 2337 cm −1 for WS, 2372 and 2340 cm −1 for WS H2O, 2372 and 2341 cm −1 for WS NaOH ) for R-branch and P-branch of the 12 CO 2 absorption from atmospheric air. Moreover, a small absorption band located around 2279 cm −1 (most visible in WS H2O spectra) appears due to the P-branch of the 13 CO 2 absorption, while the corresponding R-branch is superimposed with the Pbranch of the 12 CO 2 absorption band [33]. It can be mentioned that the increased intensity of these adsorption bands for the modified walnut shells, as compared with raw WS, can be correlated with their morphological porous structure.…”

“…However, all spectra presented the characteristic doublet (2359 and 2337 cm −1 for WS, 2372 and 2340 cm −1 for WSH2O, 2372 and 2341 cm −1 for WSNaOH) for R-branch and P-branch of the 12 CO2 absorption from atmospheric air. Moreover, a small absorption band located around 2279 cm −1 (most visible in WSH2O spectra) appears due to the P-branch of the 13 CO2 absorption, while the corresponding R-branch is superimposed with the P-branch of the 12 CO2 absorption band [33]. It can be mentioned that the increased intensity of these The unmodified WS spectrum typically shows absorption bands, as follows: a broad band centered at 3431 cm −1 is due the stretching vibrations for O-H functional groups in cellulose, lignin, hemicellulose and from the adsorbed water; the band at 2924 cm −1 (with a shoulder at 2856 cm −1 ) appears as a result of C-H stretching vibrations in methyl and methylene groups; the absorption at 1741 cm −1 corresponds to the C=O group of acetyl and esters in hemicellulose and to the ester linkages of the hydroxycinnamic acids' carboxylic groups that bind lignin and hemicellulose [27]; the band at 1619 cm −1 is attributed to the C=O stretching vibrations from the aromatics skeletal of hemicellulose and lignin, superimposed on C=C stretching vibrations; the C=C from the aromatic rings in lignin is also found at 1514 cm −1 and 1446 cm −1 [29]; in-plane C-H bending vibration from lignin metoxy groups gives the 1377 cm −1 absorption band, while C-C aromatic bonds are found at 1323 cm −1 ; the C-O, C-O-C, and O-H groups from anhydrides, ethers, esters, phenols, carboxylic acids and derivatives are found at 1259 cm −1 and 1158 cm −1 ; the broad band centered at 1052 cm −1 is attributed to the secondary and primary C-O, C-O-C, R-O-R and R-O-H bonds (lignin, hemicellulose, polysaccharides); stretching vibrations of C-O-C glycosidic linkage is found at 896 cm −1 and the absorption band corresponding to aromatic sp 2 bending of (C-H) from lignin is found at 803 cm −1 [30]; and the presence of α-branched aliphatic monocarboxylic acids is evidenced by the three bands characteristic for the O-C-O in-plane deformation are found at 667, 636 (shoulder), and 614 cm −1 , and C-C-O in plane deformation vibrations (around 520 cm −1 ) [31].…”

Electrical Detection of Molecular Transformations Associated with Chemical Reactions Using Graphene Devices

“…The structure and bond changes in the molecules are generally analyzed by spectroscopy. This includes Fourier transform infrared (FTIR) spectroscopy, , nuclear magnetic resonance (NMR), − and mass spectrometry (MS). − FTIR spectroscopy analyzes the molecular structure and the state of the molecule from the infrared absorption spectrum, which is specific to the bonding vibrations. NMR analyzes and identifies the substances from the chemical shift by the absorption of the electromagnetic waves that occurs when an external magnetic field is applied.…”