Implementation of a hydrogeochemical monitoring network following a multi-risk vision: the Strait of Messina (Italy) case.

The Strait of Messina, separating Sicily from continental Italy, is an area prone to different, high-grade, geological hazards. Here, many of the most devastating earthquakes of Italy have occurred, including the M 7.1 Messina-Reggio Calabria earthquake of 28 December 1908, the most intense event recorded in southern Europe in the instrumental epoch. The strait, on both sides, is surmounted by a mountain chain, directly degrading on a narrow, densely urbanized, coastal belt. Its steep slopes, composed of geological terrains with poor geotechnical characteristics, are affected by diffuse mass movements, as the 1 October 2009 landslide, triggered by an intense rainfall, which destroyed several little villages immediately southward of Messina, causing 37 causalities. The Peloro Cape area, the north-eastern termination of Sicily, hosts a lacunar environmental system, protected by the Ramsar Convention but also of economic interest, because exploited for shellfish livestock; these lagoons are extremely sensible to changes in sea level and temperature, which can pose serious threats to its ecological stability. This complex scenario exhibits a further criticality: the planned bridge for linking Sicily and continental Italy that, if realized, will be the longest single span bridge of the world.This complex natural-built environment needs a multidisciplinary monitoring network for mitigating the multiple risks that affect both its natural and anthropic components. Its implementation is the aim of the Work Package 5 “NEMESI” of the Italian PNRR project MEET, the post-Covid 19 pandemic national plan for recovery and resilience, financed in the framework of the European Next Generation EU initiative.Part of this multidisciplinary monitoring system will consist of a hydrogeochemical network, composed of 11 stations measuring, acquiring in a local logger and transmitting to the INGV data centre, data of temperature, level, electric conductivity, turbidity and dissolved O2 and CO2.The main challenge in the implementation of the Strait of Messina hydrogeochemical network is the correct selection of the monitoring sites, which will be based in underground and surface water bodies, whose physic-chemical characteristics should contemporary work as indicators of very different processes: changes in electrical conductivity due to sea level rise, variations of temperature and piezometric levels induced by permeability changes driven by seismic and aseismic deformations, changes in oxygenation, turbidity and dissolved CO2, which can be controlled by both eutrophication and mixing with deep volatiles, whose flux is driven by neotectonic activity.For accomplishing this mission, and producing open access data of interest for the different stakeholders, spanning from the scientific community to the shellfish food industry, it will be mandatory a real multidisciplinary approach, embracing geological, geophysical, geodetic, geochemical, eco-hydrological and socio-economic data.