Hydrogeochemical characterization of small coastal wetlands and forests in the Southern Po plain (Northern Italy)

Abstract

This study is aimed to characterize the shallow groundwater system in the coastal area between the Uniti and Bevano rivers (southern part of the Po plain), where salinization is threatening the coastal ecosystems and posing a major environmental issue for the phreatic water management in the coast. A thin rainwater lens is present at the top of the aquifer in the backshore area and its extent has a seasonal variability. These few centimetres of freshwater represent a thin interface between sea water and the delicate coastal ecosystems, such as those of dunes and wetlands. To have a better understanding of the changes in groundwater chemistry, we performed a seasonal monitoring of the water quality at the top of the aquifer. Effective concentrations of chemicals and actual values of physical-chemical parameters in the rainwater lens could be measured by means of auger holes. The analysis of the cation-exchange process in the aquifer was made through the application of the Base Exchange index (BEX index) of Stuyfzand (2008), an indicator of salinization or freshening of waters. The results pointed out that a salinization process is taking place in the largest part of the aquifer. Extension and chemical composition of the rainwater lens are strongly influenced by anthropogenic factors such as drainage and land use. The surface water bodies are all brackish to salty and characterized by anoxic and reducing conditions. At present, only halophytes are present around the dune slacks, which have turned into brackish to hypersaline lakes.

Climate and water budget change of a Mediterranean coastal watershed, Ravenna, Italy

“…The phreatic groundwater salinity measurements done by Marconi et al (2011) show that during the summer the freshwater lenses are larger and thicker than in the winter, and this is very likely due to recharge from irrigation water.…”

“…The remaining freshwater consists mostly of lenses floating on top of the salt water ) that may change shape and size over short periods of time (Marconi et al 2011). To better understand the behavior of these freshwater lenses, it is important to know how much freshwater infiltrates into the underlying aquifer.…”

Ecohydrology on the edge: interactions across the interfaces of wetland, riparian and groundwater‐based ecosystems

“…The threats to coastal ecosystems and water resources associated with salinization of a shallow groundwater water system in the coastal area of the southern plain of the River Po in Italy are highlighted by Marconi et al (2011). Their study focuses on the hydro-chemistry of the predominately brackish groundwater aquifer and a seasonally variable freshwater lens in the upper layers of the aquifer which has been found to represent a thin but important interface between seawater and vulnerable coastal ecosystems.…”

Saltwater Intrusion in Coastal Aquifers: A Primary Case Study along the Adriatic Coast Investigated within a Probabilistic Framework

“…These impacts have been attributed to groundwater salinity, shallow water tables, drought, and air pollution [14,15]. The trend in groundwater salinization underneath the coastal pine forest is a process that is progressing in time, as recent studies have demonstrated [16].…”