Mapping polycyclic aromatic hydrocarbons and total toxicity equivalent soil concentrations for hazard assessment by visible and near infrared spectroscopy

In a previous study, we have shown that spectroscopic models based on visible and nearinfrared (vis-NIR) spectroscopy (350–2500 nm) predicts polycyclic aromatic hydrocarbons (PAHs) in tropical rainforest soils with reasonable accuracy. In this study, we used these models to develop soil maps of PAHs and total toxicity equivalent soil concentrations (TTEC) of the PAH mixture. We used the soil maps of TTEC for hazard assessment of three petroleum release sites in Ogoniland in the Niger Delta province of Nigeria from where the soils were collected. Inverse distance weighting soil maps show a near-perfect match of high and low PAH and TTEC zones between measured and predicted maps. There were nonsignificant (p<0.05) differences between measured and predicted soil maps as the ANOVA revealed. Hazard assessment results showed that the degree of action for site-specific risk assessment and/or remediation differs among the different management zones. Only one zone, covering some 20 m in site C, showed very high levels of PAH with significant and unacceptable risk to specified targets. These results are indications that vis-NIR spectroscopy has the potential for mapping PAH and TTEC of the PAH mixture for hazard assessment of petroleum release sites in the Niger Delta province of Nigeria.