Hydrogeological Behaviour and Geochemical Features of Waters in Evaporite-Bearing Low-Permeability Successions: A Case Study in Southern Sicily, Italy

Abstract

Knowledge about the hydrogeological behaviour of heterogeneous low-permeability media is an important tool when designing anthropogenic works (e.g., landfills) that could potentially have negative impacts on the environment and on people’s health. The knowledge about the biogeochemical processes in these media could prevent “false positives” when studying groundwater quality and possible contamination caused by anthropogenic activities. In this research, we firstly refined knowledge about the groundwater flow field at a representative site where the groundwater flows within an evaporite-bearing low-permeability succession. Hydraulic measurements and tritium analyses demonstrated the coexistence of relatively brief to very prolonged groundwater pathways. The groundwater is recharged by local precipitation, as demonstrated by stable isotopes investigations. However, relatively deep groundwater is clearly linked to very high tritium content rainwater precipitated during the 1950s and 1960s. The deuterium content of some groundwater samples showed unusual values, explained by the interactions between the groundwater and certain gases (H2S and CH4), the presences of which are linked to sulfate-reducing bacteria and methanogenic archaea detected within the saturated medium through biomolecular investigations in the shallow organic reach clayey deposits. In a wider, methodological context, the present study demonstrates that interdisciplinary approaches provide better knowledge about the behaviour of heterogeneous low-permeability media and the meaning of each data type.

How do turbidite systems behave from the hydrogeological point of view? New insights and open questions coming from an interdisciplinary work in southern Italy

“…Tritium content detected during the recession (with no influence related to possible rapid recharge) ranged between 2.5 ± 0.6 and 3.9 ± 0.7 TU (Table 4), suggesting the coexistence of both more (e.g., 2.5 ± 0.6 TU in P002-waters) and less prolonged groundwater pathways (e.g., 3.9 ± 0.7 TU in S90-waters) within the studied system. When compared with the tritium content recently detected in rainwater collected in southern Italy (4.5 TU in [8]; 5.0 TU in [20]; 6.2 to 10.8 TU in [47]), they indicate approximately 2.5-24.5 years of ground residence. In detail, no significant differences were observed among the whole range of spring (2.5 ± 0.6 to 3.9 ± 0.7 TU) and stream waters (2.6 ± 0.6 to 3.8 ± 0.7 TU), indicating that the streams were mostly recharged by the springs, at least in the sampling period.…”

“…As per the microbiological features of spring waters, according to findings in other hydrogeological settings [47], the detection of fecal bacteria demonstrates the hydraulic interconnection between the topsoil and the springs, suggesting the existence of a pore/fracture network (within the low-permeability rocks) whose size is greater than that of bacterial cells (in the PLOS ONE order of one to several microns), and the absence of significant mechanical filtration (e.g., [51][52][53]). Methodologically, these findings further support the effectiveness of microbial communities as natural tracers in hydrogeological studies [54], even when studying migration in lowpermeability heterogenous media (e.g., [23]).…”

Investigating the activity of indigenous microbial communities from Italian depleted gas reservoirs and their possible impact on underground hydrogen storage

“…Along with AB and HM, several studies report the presence of SRBs in different geological formations such as oil fields, sulfate and CH4-rich groundwater from deep boreholes, marine sediments, aquifers and salt mines ( Martini et al, 2005 ; Mochimaru et al, 2007 ; Morozova et al, 2011 ; Bomberg et al, 2015 ; Varjani and Gnansounou, 2017 ; Rusmanis et al, 2019 ; Rizzo et al, 2020 ; Briones-Gallardo et al, 2022 ). Although initially believed to rely only on H 2 for sulfur reduction, different studies characterized SRBs as capable of generating electrons from the oxidation of organic compounds including sugars, organic acids (i.e., scVFAs, acetate) and amino acids.…”

The Importance of Physiochemical Processes in Decarbonisation Technology Applications Utilizing the Subsurface: A Review

“…Even though there has been over 20 years of intense research on the permeability and flow behaviour of salt rocks (e.g., Beauheim and Roberts, 2000;Hovland et al, 2008;Smith et al, 2013;Bertoni and Cartwright, 2015;Ghanbarzadeh et al, 2015;Rizzo et al, 2020), many uncertainties still exist in this field. Does salt become permeable at greater depth?…”