Detection of the natural origin hydrocarbon contamination in carbonate aquifers (central Apennine, Italy)

The water-rock interaction is discussed in this study for some Central Apennine aquifers and their relative springs, where the geological and hydrogeological setting is potentially responsible for hydrocarbon contamination. The contamination is related to the presence of limestone formations with high organic content that are connected to the genesis of hydrocarbons in the Central-Southern Apennines. Thanks to a multidisciplinary approach based on a seasonal monitoring of hydrogeological, hydrogeochemical, organic chemical, and isotopic variables, and to a detailed geological analysis, it was possible to demonstrate that the bituminous schists within the bituminous dolomite formation (a Triassic Formation presents in the Gran Sasso acquifer), the bituminous intercalations within the Bolognano Formation (an Olocenic calcareous Formation in the Majella acquifer), and the petroleum-saturated rocks of the Bolognano Formation (in the Morrone acquifer) are all able to leach hydrocarbons into groundwater. The results suggest that more detailed studies are required for areas where lithologies with fossil organic components are present. Insights should further investigate the interaction between groundwater and rocks in terms of organic compounds as well as inorganic compounds. In particular, the study also suggests that the supplementary quantification of hydrocarbon compounds in bituminous rock and the leaching tests are analyses that provide reliable results. From the normative point of view, the results of the study can be useful when dealing with hydrocarbon contamination resulting from anthropogenic activities within catchments where formations with high concentration of organic matter are present. In these cases, it will possible to assess the natural background concentrations and review the threshold values upwards.