Distribution and health risk assessment of some organic and inorganic substances in a petroleum facility in central Mexico

An oil distribution and storage station was subjected to an Environmental Auditory and results showed soil contamination in part of the surface. An assessment of the site was required in order to fulfill a complete characterization of the contaminants present in soil and groundwater, as well as to establish the probable sources of contamination. Besides, a health risk assessment was performed to set remediation goals. The aim of this work is to show how the entire characterization and risk assessment process performed in this storage station from central Mexico, regarding to subsoil and groundwater. Thirty sample points were examined. Total petroleum hydrocarbons concentrations in soil were in a very low range (20-268 mg/kg). Ethylbenzene, methyl tert-butyl ether, tert-amyl methyl ether, and lead were identified in one sampling point. Iron and zinc were found in all soil samples. There was no correlation between total petroleum hydrocarbons and any of the metals or between both metals. Only two out of four monitoring wells showed total petroleum hydrocarbons levels (1.4 and 66 mg/L, respectively). Regarding lead, all four monitored wells showed lead concentrations (0.043-0.15 mg/L). Results suggested that metal concentrations were not associated to petroleum contamination, but to iron scrap deposits placed over the soil; nevertheless more data is needed to make a clear conclusion. Health risk assessment showed that none of the evaluated contaminants represented a risk either for the on-site or the off-site receptors, since the hazardous quotients estimated did not exceed the acceptable values.