Quantitative analysis of total hydrocarbons and water in oil‐contaminated soils with attenuated total reflection infrared spectroscopy

Abstract

The feasibility of direct (ie, without sample preparation) quantitative analysis of total hydrocarbons and water in oil-contaminated soils using mid-infrared spectroscopy and an attenuated total reflection (ATR) probe has been investigated. Spectral characteristics of unpolluted and oil-contaminated soils composed of sand, clay, dolomite, and humus have been studied over the full mid-infrared range (4000-400 cm). Spectra of 25 typical soil samples containing varying levels of oil and water have been analyzed using a chalcogenide infrared fiber-based probe with a ZrO 2 crystal as an ATR element. The spectral data were used to build calibration models for the analysis of hydrocarbon contamination as well as moisture content of soil samples. The low quality of ATR spectra of drier samples and variable spectral intensity inherent in the ATR measurement of solids has been overcome by suitable data processing. Further improvement of the model performance has been achieved using a variable selection based on the modified genetic algorithm. Our proposed method allows the determination of oil and moisture content in soils with accuracies of 1.1% and 0.6%, respectively, which is sufficient for a number of practical applications. The reported results may be used to develop portable devices for measuring petroleum and water content of soils.

Determination of Total Hydrocarbons in Contaminated Soil with “Thin Layer Sorptive Extraction Coupled with Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy”

“…In the 3000 cm −1 region, hydrocarbons have characteristic peaks at 2954, 2872, and 2926 cm −1 related to the stretching vibrations of methyl and methylene groups of hydrocarbons. 35 In terms of the quantitative analysis of THC in soils, these are the most relevant responses. As for previous methods using now banned IR-transparent solvents (CCl 4 , freon-113), the integration of absorption bands in the region 2850 and 2960 cm −1 has been widely used to quantify THC.…”

“…Thanks to the interactive subtraction of the spectrum of blank samples (PDMS only) from the sample spectrum (after exposition to THC), the infrared spectrum of hydrocarbons was obtained without PDMS interference. In the 3000 cm -1 region, hydrocarbons have characteristic peaks at 2954, 2872, and 2926 cm −1 related to the stretching vibrations of methyl and methylene groups of hydrocarbons 35 .…”

“…Figure 3 : Overlayed spectroscopic patterns of different hydrocarbons found in a thin layer of PDMSIR spectra of hydrocarbon derivatives originate mainly from combinations or overtones of C-H stretching modes of saturated CH 2 and terminal -CH 3 or aromatic C-H functional groups. In the 3000 cm -1 region, hydrocarbons have characteristic peaks at 2954, 2872, and 2926 cm −1 related to the stretching vibrations of methyl and methylene groups of hydrocarbons35 .…”

Fiber Probe for Simultaneous Mid-Infrared and Fluorescence Spectroscopic Analysis

“…Modern applications of fiber-probe optical spectroscopy include in-line control of industrial processes, field analysis in agriculture, ecological monitoring, , and medical diagnostics. − Considerable progress in this area is associated with the advent of new optical fiber materials on the basis of chalcogenide glasses and polycrystalline silver halides , having sufficiently high transmittance in different intervals of the mid-infrared (IR) spectral region (4000–400 cm –1 ). The modern optical fiber probes together cover the entire practical range of the optical spectroscopic analysis, thereby extending the applicability of ultraviolet, visible, near and mid-IR spectroscopy.…”

“…Fiber optics and probes on its basis enable sampling-free measurements in situ, thereby essentially expanding the scope of optical analysis compared to the traditional lab spectroscopy. 1 Modern applications of fiber-probe optical spectroscopy include in-line control of industrial processes, 2 field analysis in agriculture, 3 ecological monitoring, 4,5 and medical diagnostics. 6−8 Considerable progress in this area is associated with the advent of new optical fiber materials on the basis of chalcogenide glasses and polycrystalline silver halides 1,9 having sufficiently high transmittance in different intervals of the midinfrared (IR) spectral region (4000−400 cm −1 ).…”