Public awareness of environmental concerns are on the increase, and thus, safety standards have become more stringent, and far more analyses are required. Due to extensive oil exploitation, refining and transportation, oil pollution has become a major source of water and soil contamination. Although a number of standard proce- dures exist to quantify total petroleum hydrocarbons (TPHs) in soil, they all require time- and labor-intensive sample preparation, and most use per-halogenated solvents. Therefore, a feasibility study was undertaken to test the possibility of using near-infrared reflectance spectroscopy (NIRS) for direct determination of oil con- tamination in soil. Based on a set of no. 43 samples spiked with known and independently confirmed TPH contamination of 0.05 to 2.19 wt% (using liquid-solid extraction and US-EPA method 418.1) a chemometric model was developed. The regression model fulfilled the following criteria for the reference data: validation coefficient r2³0.929 and root-mean-square error of validation £0.177. A set of no. 26 field samples contami- nated with weathered crude oil (»0.1-5%) were analyzed by NIRS and conventional methods (i.e., extraction and US-EPA method 418.1). A correlation factor of r2³0.928 with a standard deviation of the absolute differ- ences between true and predicted values of £0.251 was obtained.
NIRS, quantification, soil, TPH
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