Near infrared spectroscopic analysis of hydrocarbon contaminants in soil with a hand-held spectrometer

The contamination of soil with hydrocarbons due to accidents or leakages is a wide-spread phenomenon with potential health risks. So far, no technique has been available for fast on-site identification and quantitative determination of the contaminant. This information, however, would be necessary for the assessment of decontamination measures to be taken for the area under consideration either by excavation or a biotechnical approach. All methods in current practice require a time-consuming retrieval and transportation of contaminated soil samples to the laboratory for further qualitative and quantitative analysis. Based on diffuse reflection measurements with a hand-held NIR spectrometer, in the present communication, results on the qualitative discrimination and on the quantitative determination of hydrocarbon contaminants (gasoline, diesel and oil) with standard errors of cross validation between 0.3% to 0.5% (w/w) in different types of soil are reported. The presented approach can serve as proof of concept to replace conventional methods in the case of hazardous incidents with high contamination concentrations by on-site investigations for a fast assessment of decontamination measures and an effective monitoring of their success. Furthermore, the method is not limited only to the characterisation of areal pollution, but can also be easily extended to depth-profiling measurements.