A hydrochemical and stable oxygen and hydrogen isotope analysis in combination with a study of the paleo- hydrology provides insight in to the current hydrochemistry of the coastal aquifer near Ravenna Italy, with emphasis on the cause of the high salinity present all throughout the aquifer. Two hundred and twenty nine samples of ground and surface water were analyzed for major cat ions, anions and stable oxygen and hydrogen isotopes. The samples were grouped according to sampling environment to see if waters coming from the same background (new or old dunes, lagoons, agricultural fields, quarries, and rivers) showed the same hydrochemistry. The most occurring water type based on the classification of Stuyfzand (1989) is the brackish to saline NaCl type. Calcium rich water is found only in the rivers, in the irrigation channels and in a few wells. The stable isotope analysis and the analysis of tracers such as SO4/Cl- and 18O versus Cl show that most ground water samples are a mix between fresh water similar to rain or irrigation, river or fresh dune water and water that is similar to current Adriatic Sea water. Two groups of samples have an anomalous chemical and isotope signature that does not reflect pure mixing of fresh with seawater: One group is chemically very similar to waters that are trapped in sediments of the North Sea marshes during the Holocene transgression while the other group of samples is derived in and around current lagoons. Analysis of the paleo-hydrology shows that our coastal aquifer was formed during the Holocene transgression. As the sea regressed fresh water infiltrated into the sandy deposits but because recharge areas were small and the amount was reduced by evapotranspiration of pine trees since Roman times, there was not enough infiltration to flush the aquifer completely.
HYDROCHEMISTRY, STABLE ISOTOPES AND PALEOHYDROLOGY OF THE COASTAL AQUIFER NEAR RAVENNA (ITALY)
MOLLEMA, PAULINE NELLA;ANTONELLINI, MARCO;DINELLI, ENRICO;GABBIANELLI, GIOVANNI;GREGGIO, NICOLAS;
2012
Abstract
A hydrochemical and stable oxygen and hydrogen isotope analysis in combination with a study of the paleo- hydrology provides insight in to the current hydrochemistry of the coastal aquifer near Ravenna Italy, with emphasis on the cause of the high salinity present all throughout the aquifer. Two hundred and twenty nine samples of ground and surface water were analyzed for major cat ions, anions and stable oxygen and hydrogen isotopes. The samples were grouped according to sampling environment to see if waters coming from the same background (new or old dunes, lagoons, agricultural fields, quarries, and rivers) showed the same hydrochemistry. The most occurring water type based on the classification of Stuyfzand (1989) is the brackish to saline NaCl type. Calcium rich water is found only in the rivers, in the irrigation channels and in a few wells. The stable isotope analysis and the analysis of tracers such as SO4/Cl- and 18O versus Cl show that most ground water samples are a mix between fresh water similar to rain or irrigation, river or fresh dune water and water that is similar to current Adriatic Sea water. Two groups of samples have an anomalous chemical and isotope signature that does not reflect pure mixing of fresh with seawater: One group is chemically very similar to waters that are trapped in sediments of the North Sea marshes during the Holocene transgression while the other group of samples is derived in and around current lagoons. Analysis of the paleo-hydrology shows that our coastal aquifer was formed during the Holocene transgression. As the sea regressed fresh water infiltrated into the sandy deposits but because recharge areas were small and the amount was reduced by evapotranspiration of pine trees since Roman times, there was not enough infiltration to flush the aquifer completely.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
