Using Spectrometric Colour Measurement for the Prediction of Soil PCBs in a Contaminated Site of Southern Italy

Soil contamination with polychlorinated biphenyls (PCBs) is one the most relevant environmental problem in the SIN (Site of National Interest) of Taranto (Apulia Region, Southern Italy) and the surrounding area. Evaluation of PCB contents and their spatial distribution is an essential pre-requisite for soil remediation. Conventional laboratory analyses, although useful and irreplaceable for a precise and detailed evaluation of these contaminants, are costly and time-consuming, thus not very suitable for investigation over large areas. Then, there is a need to develop/validate alternative, rapid and cost-effective techniques, to use as substitutive of integrative to conventional analytical approaches. In this study, the usefulness of soil colour, based on spectrometric measurements, coupled with regression analysis, was assessed. Until now, never an analogous investigation has been realised. Twenty-eight soil samples, previously collected within an area (the ex-MATRA) highly contaminated by the disposal of oil used as dielectric fluid, composed by a mixture of PCB congeners, were used in the investigation. Colour coordinates in different colour systems were calculated from spectroradiometric measurements over the soil samples. Eighteen PCB congeners (i.e. 12 dioxin-like PCBs and six non-dioxin-like "indicator" PCBs), their sum (PCBs₁₈) and the extractable organic halogen content (EOX)—which is an expression of the total content of halogen in organochlorine compounds, including the PCBs—were determined through conventional laboratory analysis. Simple linear regression analysis was carried out to predict the values of PCBs and EOX on the basis of colour variables. Excellent predictive models (R² > 0.80) for PCBs₁₈ and EOX, as well as for some of the individual PCB congener, resulted from the regression analysis. Thus, spectroscopic determination of soil colour can be considered as a promising tool for a rapid screening of PCBs in contaminated soils.

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