Preliminary assessment of soil contamination by hydrocarbon storage activities: Main site investigation selection

• Large soil areas may be potentially affected by hydrocarbon storage and supply.
• The selection of potentially contaminated sites in a cost efficient way is proposed.
• Preliminary investigation reduces the number of studied sites around 90%.
• The samples above the screening level are divided into TPH fractions.

Soil contamination is a serious environmental problem that must be properly managed. The study of wide territories is focused on the potentially dangerous activities; iterating, identifying, quantifying and evaluating the potential hazard through three stages: preliminary, exploratory and main site investigation. Petroleum hydrocarbons are widespread environmental pollutants, causing risks for humans and the environment. Many activities regarding hydrocarbon storage and supply are located in all Spanish regions, therefore the Cantabria region is chosen as a case study. The preliminary investigation was conducted through a Source–Pathway–Receptor (S–P–R) approach. The potential hazard of the source is established by means of a mixed additive and multiplicative algorithm. From the 165 activities located in Cantabria, the preliminary risk assessment model enables a selection of 14 activities posing high potential for contamination. On the other hand, the later environmental vulnerability evaluation leads to eight sites for further investigation. A reduction of about 90% of the sites from the source evaluation, and around 50% from the receptor evaluation, has been achieved. Subsequently, several soil and water samples were collected and analysed in terms of total petroleum hydrocarbon content. From the 56 measured samples collected from the eight sites, 14 of them were above the Spanish regulatory screening level of 50 mg/kg. Concentrations above this trigger value were divided into four fractions, C10–12, C12–16, C16–21 and C21–40, determining only one site showing high environmental risks, where a main site investigation is necessary.