A multidisciplinary monitoring approach involving radioactivity, greenhouse gas emissions, stratigraphy and rock magnetism

Mud volcanoes (MV), classified as "sedimentary volcanism", represent the surface expression of underground processes characterized by movements of large masses of fluids (water and gas) and sediments. Some MVs can represent a serious source of geohazards, mainly related to paroxysmal events with flooding of huge amounts of mud that can damage structures and seriously injure people in their vicinity. Although MVs constitute a source of geohazard, albeit limited to their proximity, monitoring protocols for their surveillance have never been employed. Gas released from mud volcanoes consists mainly of CH₄ and minor components N₂, O₂, CO₂ and light hydrocarbons, but radon emission rate has been poorly studied. With the aim of filling this knowledge gap, the present work proposes a multidisciplinary approach to the study of MVs, with the final goal of identifying reliable indicators of their state of activity that could be used as precursors of paroxysmal events and their dangerousness for the population. The multidisciplinary monitoring method used to study the Salse di Nirano MVs is based on radioactivity and greenhouse gas emissions, stratigraphy and magnetism of the rocks in order to develop a model of the space-time evolution of their activity and identify any variations. To estimate the amount of gas released, some surveys of flux measurements (CO₂, CH₄) and gas content (CO₂, CH₄, ²²²Rn, ²²⁰Rn) were conducted.

Furthermore, with the aim of identifying a correlation between methane emissions and radon activity, a series of laboratory tests were performed in a controlled system.

Salse di Nirano are within a natural reserve, visited by many people every year, so the definition of the natural gas hazard estimation is essential for the protection of the population and extremely useful for the local authorities. Our objective is to acquire a better understanding of the processes happening in the eruption conduit, the activity (speed and intensity of gas migration) of the seepage system connected to the feeding reservoir, and the interaction between faults and deep and/or shallow reservoirs. The results can also be exported to other areas characterized by the presence of sedimentary volcanism.