Hydrochemical characterization of the water resources in the coastal environments of the outer Río de la Plata estuary, Argentina

Hydrogeochemical processes affecting the chemical composition of groundwater and surface water in the coastal areas of the central and northern sectors of the outer Río de la Plata estuary in Argentina are evaluated. Results indicate hydrochemical differences between the three hydrological units analyzed. In shell ridges, groundwater is a low-salinity sodium bicarbonate type with a predominance of CO2(g) dissolution, carbonate dissolution and ion exchange. In the coastal plain, groundwater is a saline sodium chloride type and its chemical characteristics are related to the contribution of water from the estuary, the dissolution of gypsum and halite, and the oxidation of pyrite. Surface waters are a sodium chloride type and their composition shows the incidence of tidal water flowing into the continent. In this area a wetland occurs and it is regarded as a natural reserve that depends to a large extent on its hydrological characteristics. Knowledge of the processes regulating the hydrochemistry would constitute an essential tool in the management and preservation of the environmental characteristics of this system.

► Hydrological and geochemical processes determine the chemical composition of water. ► Three environments with different hydrochemical characteristics can be observed. ► The hydrology and hydrochemistry of the Samborombón Bay wetland define its dynamics.