Freshwater lenses constitute one of the most vulnerable aquifer systems in the world, especially in coastal wetland areas. The objectives of this work are to determine the hydrogeochemical processes that regulate the quality of the freshwater lenses in a sector of the Samborombón Bay wetland, and to assess their sustainability as regards the development of mining activities. A hydrochemical evaluation of groundwater was undertaken on the basis of major ion, trace and environmental isotope data. The deterioration in time of the freshwater lenses in relation to mining was studied on the basis of the analysis of topographic charts, aerial photography and satellite imaging. The results obtained show that the CO 2(g) that dissolves in the rainwater infiltrating and recharging the lenses is converted to HCO 3 − , which dissolves the carbonate facies of the sediment. The exchange of Ca 2+ for Na + , the incongruent dissolution of basic plagioclase and the reprecipitation of carbonate produce a change of the Ca-HCO 3 facies

The coastal plain of the middle estuary of the Río de la Plata is a highly industrialized area and is densely populated by sectors. The main human activity in the sector encompassed between the cities of Ensenada and Berisso is associated with the petrochemical industry. In this work, hydrogeochemical and isotopic characteristics of surface and groundwater in the impacted area are analyzed and the results are contrasted with those obtained in an undisturbed protected area. Major and trace elements were determined using standardized methods while the stable isotopes δO y δH were analyzed by mass spectroscopy. Human impact is evidenced by the occurrence of large variations in the major chemical composition of water, and also by the elevated concentrations of some trace elements that are not contributed from natural sources. These results may contribute to the understanding of chemical processes and pollutants distribution in highly industrialized coastal plain areas.

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