Environmental Radioactivity and Plants Adaptations in the Maccalube Nature Reserve (Ag): Insights and Implications for the sedimentary volcanic source

This research focuses on the Maccalube di Aragona Nature Reserve (Agrigento, Italy), studying environmental radioactivity and plant activity in the context of mud volcano dynamics. The Reserve contains several gryphons and pools emitting methane, hydrocarbons, and highly saline water. Occasionally, these volcanoes experience explosive events, such as a fatal explosion in 2014. The research is part of the Promud project- INGV (https://progetti.ingv.it/it/promud), which aims to assess the Reserve’s geophysical, seismological, geodetic, and biodiversity characteristics for civil protection purposes.

Two field surveys were conducted to measure environmental radioactivity, focusing on ²²²Rn and ²²⁰Rn emissions from soil gas by means of specific accessorized equipment (RAD7). The main aim was to acquire more data to support the identification of the source location in a compact clay layer. Results showed a high concentration of ²²²Rn only in correspondence with the active emitting centers, whereas concentrations below the instrumentation sensitivity were revealed elsewhere. Moreover, the radioactive contents were determined in muds, soils, and parts of the plants (especially leaves) taken in the surroundings. Particularly, ²²⁶Ra, ²³²Th, ⁴⁰K, and ¹³⁷Cs were measured by using gamma spectrometry. Very homogeneous concentrations of previous radionuclides were found, except for ⁴⁰K measured in the dried plants suggesting a possible link between that radionuclide and the plant’s activity.

Studying plants that thrive in extreme environments could provide valuable insights into the relationship between soil properties and reservoirs. For this study, the halophytic species Suaeda vera, collected from the Maccalube Reserve, was used as a model. Samples were also collected from a mountainous habitat to compare its metabolism under stressed and stress-free conditions. An untargeted metabolomic analysis of hydroalcoholic extracts of aerial parts of S. vera, performed using HR-LC-MS, revealed a diverse and rich phytochemical profile. This analysis identified a wide range of specialized metabolites. Plants from the Maccalube region have an interesting phytochemical profile, producing sulphated metabolites, particularly flavonoids, which are rare and often associated with survival in harsh environments. This secondary metabolism suggests a local biochemical adaptation of the Maccalube population. It may be influenced by the harsh environmental conditions of the region.