Investigation of the origin of salt in coastal aquifers and assessment of metals in the aquatic environment : River Drin and River Vjosa, Albania
Sammanfattning: The preservation of freshwater aquifers is one important task of managing natural resources today. Intrusion of saltwater from the sea into the groundwater might occur in coastal-near areas and can affect the freshwater quality negatively. One such risk area is the Adriatic coast line of Albania, a country predominantly rich in freshwater resources due to the numerous rivers flowing from the mountains in the east towards the sea. The coastal areas are mainly used for agricultural activities were groundwater is an important resource for irrigation purposes. This study was therefore partly conducted in Albania where samples of groundwater and river waters were collected from the river deltas of Drin and Vjosa in order to investigate the origin of the salt and to assess the bioavailable metal concentrations of nickel and zinc. Both on-site tests and off-site tests, in laboratories, were conducted. In the laboratory, the samples were analysed for oxygen and deuterium isotope data. The results were used to assess the origin of the oxygen content as the method of investigating the origin of the salt uses the oxygen isotope as a tracer. Anion and cation concentrations were analysed as well as the concentrations of metals. These were used as input data to Visual Minteq, a model used to calculate the metal speciation of waters, and a Biotic Ligand Model used to calculate the bioavailable concentrations and the HC5 concentrations. The isotope analysis yielded results similar to previous studies conducted in the nearby area indicating that the salt does not have oceanic origin but meteorological. The bioavailable concentrations were in most sample sites lower than the calculated HC5 concentrations indicating that there is a sufficient buffering system present even though there are several mining activities upstream of the sample sites that could have affected the water quality. This study concludes that the origin of salt is of meteoric origin and not from seawater intrusion. The bioavailable concentrations do not pose a threat as the concentrations are under the HC5 concentrations for all sites but one. In order to deepen the understanding and knowledge of the water qualities in these areas, future studies should focus on a continuous measuring period lasting for example over the whole year minimizing any seasonal variations of the sampled data. Other methods such as geophysical measures could also contribute to a wider analysis of the groundwater condition.
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