Rapid prediction of total petroleum hydrocarbons in soil using a hand-held mid-infrared field instrument

• We present a novel field technique for the rapid prediction of TPH.
• Accurate predictions of TPH were obtained.
• Technique tested across different soil types and TPH concentrations.
• Technique suitable for commercial use and number of applications.
• Results pave the way for using hand-held mid-infrared instruments in the field.

This manuscript reports on the performance of a hand-held diffuse reflectance (mid)-infrared Fourier transform (DRIFT) spectrometer for the prediction of total petroleum hydrocarbons (TPH) in three different diesel-contaminated soils. These soils include: a carbonate dominated clay, a kaolinite dominated clay and a loam from Padova Italy, north Western Australia and southern Nigeria, respectively. Soils were analysed for TPH concentration using a standard laboratory methods and scanned in DRIFT mode with the hand-held spectrometer to determine TPH calibration models. Successful partial least square regression (PLSR) predictions, with coefficient of determination (R2) ~0.99 and root mean square error (RMSE) <200 mg/kg, were obtained for the low range TPH concentrations of 0 to ~3,000 mg/kg. These predictions were carried out using a set of independent samples for each soil type. Prediction models were also tested for the full concentration range (0–60,000 mg/kg) for each soil type model with R2 and RMSE values of ~0.99 and <1,255 mg/kg, respectively. Furthermore, a number of intermediate concentration range models were also generated for each soil type with similar R2 values of ~0.99 and RMSE values <800 mg/kg. This study shows the capability of using a portable mid-infrared (MIR) DRIFT spectrometer for predicting TPH in a variety of soil types and the potential for being a rapid in-field screening method for TPH concentration levels at common regulatory thresholds.A novel hand-held mid-infrared instrument can accurately detect TPH across different soil types and concentrations, which paves the way for a variety of applications in the field.

Figure optionsDownload as PowerPoint slide