Hydrogeochemical analyses were carried out to identify geochemical processes occurring in the low-lying coastal aquifer of Ravenna, North Adriatic Sea (Italy). The area is characterized by a complex coexistence of several environments: coastal dunes, paleodunes, pine forests, freshwater wetlands, rivers, brackish lagoons, gravel pit lakes, reclaimed lands, agricultural fields and industrial areas. Water quality is of primary importance for the sustainability of these, areas and a full understanding of geochemical processing is fundamental for their management. A total of 104 water samples was collected from groundwater wells and surface water bodies, and analyzed for the major and trace elements (TEs). Field measurements of chemical-physical parameters were carried out by a multiparameter device XS PCD650; major elements were analyzed following the Italian National Environmental Agency standards (APAT-IRSA 2003), while TEs were analyzed by ICP-AES/ICP-MS. The major findings include: organic matter degradation in salinized and anoxic conditions; TEs concentrations related to water–sediment interactions, i.e., adsorption, ion exchange, redox reactions, mineral dissolution and precipitation; anthropogenic contamination from pesticides and fertilizers use; pollution from industrial district; TEs enrichments and depletion due to groundwater salinization and water management practices; comparison of TEs concentrations with respect to national and international thresholds. The findings can provide water managers and local authorities with a comprehensive framework of the coastal water hydrochemistry, allowing a better understanding of the effects of current management practices and the design of mitigation measures to reduce water resource deterioration in the studied coastal area.

Flow‐through brackish gravel pit lakes near the Adriatic Coast of Emilia Romagna (Italy) in the Mediterranean have a large influence on the hydrologic budget of the watershed. Strong evaporation in combination with intense drainage of the low lying basins enhances groundwater inflow into the lake. Precipitation falling on the lakes is mixed with brackish/saline lake water causing the loss of freshwater. The gravel pit lakes are characterized by a high salinity (TDS = 4.6–12.3 g L⁻¹) and high pH (8.5). Stable isotope data show that gravel pit lake water is fed by groundwater which is a mix of Apennine River water and (Holocene) Adriatic Seawater, subsequently enriched by evaporation. The slope of the local evaporation line is 5.4. Conservative tracer and water budget modeling shows that the final Cl concentration depends strongly on the ratio of evaporation to total inflow. Increasing drainage to compensate for sea level rise, subsidence or intense precipitation would enhance ground water flow into the lake and decrease Cl concentration while increasing evaporation would increase Cl concentration. Groundwater rich in dissolved trace elements flows into the gravel pit lakes that contains water with a higher pH and dissolved oxygen. Pit lake water remains enriched in some elements (e.g., Ba, Mo, Sb) and depleted in others (e.g., Fe, Ca, Zn, SO4) with respect to groundwater composition. The gravel pit lakes show limited eutrophication but the water quality should be monitored for trace elements (e.g., As) if they are to be used for recreational purposes.