Hydrochemical and Isotopic Characterization of Groundwater in the Metaponto Coastal Aquifer, Italy

The increasing reliance on groundwater resources and the widespread occurrence of seawater intrusion in coastal regions demand an integrated approach to characterize and manage these aquifers. In this study, a multi-tracer methodology combined with hydrochemical modeling was employed to investigate the hydrogeological dynamics of the Metaponto coastal aquifer in southern Italy. Groundwater age dating was achieved using tritium (³H) and radiocarbon (¹⁴C) isotopes, complemented by stable isotope signatures (δ¹⁸O and δ²H) to trace recharge processes, flow paths, and mixing dynamics.

Hydrogeochemical analyses, including major ions (Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl⁻, SO₄²⁻, NO₃⁻) and minor constituents (e.g., Al, As, B, Ba, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Sr, U, Zn), were conducted to characterize the aquifer's chemical signature and identify processes such as seawater intrusion, cation exchange, and anthropogenic influence. Environmental isotopes of hydrogen (δ²H), oxygen (δ¹⁸O), and carbon (δ¹³C) were also utilized to trace groundwater origin, evaluate recharge mechanisms, and identify geochemical reactions. To simulate groundwater flow and assess the impact of density-driven processes, the MODFLOW/SEAWAT code was utilized. This coupled flow and transport model provided insights into the movement of freshwater and saltwater within the aquifer system, enabling the refinement of the conceptual hydrogeological model.

The results reveal the complex interplay between freshwater recharge and seawater intrusion, emphasizing the role of geochemical interactions and flow dynamics in shaping the aquifer's characteristics. This integrated approach has proven effective in enhancing the understanding of coastal aquifers and highlights the critical need for such methodologies in managing groundwater resources under increasing anthropogenic and climate pressures.

This work was supported by the ENI-CNR joint Research Center “Water - Hypatia of Alexandria” (Metaponto, Italy).

 

Keywords: Coastal aquifer, Seawater intrusion, Multi-tracer approach, Hydrochemical analysis, Environmental isotopes