Analysis of Diesel Fuel Contamination in Soils by Near-Infrared Reflectance Spectrometry and Solid Phase Microextraction-Gas Chromatography

A feasibility study was undertaken to determine whether the rapid, nondestructive analytical technology, near-infrared reflectance spectrometry (NIRS) could be used to predict total petroleum hydrocarbon (TPH) in contaminated soil. Hydrocarbon concentrations were determined on samples of diesel-contaminated soils by the solid phase microextraction-gas chromatography (SPME-GC) method. The same samples were then scanned for near-infrared reflectance spectrometry over the wavelength range 1100 to 2498 nm. Calibrations were developed between the NIR spectral data and the reference SPME-GC chemical data using stepwise multiple linear regression. Linear regression relationships between NIR-predicted TPH concentrations and reference data had r² of 0.68 and 0.72. These results indicate that the combination of NIRS and SPME-GC shows promise as a method for rapid estimation of TPH in soil. A major hurdle in the evaluation of methodology for hydrocarbons residues in soil is the challenge posed by the weathering of such residues.