Abstract:

In this contribution we present some preliminary findings on the chemical quality of groundwaters of the deltaic plain of R. Pinios (Thessaly), as part of the implementation of the project THALISDAPHNE. Samples were obtained from 13 groundwater drillings on a seasonal basis during the hydrological year 2012 - 2013 and analyzed for major ions, nutrients, dissolved organic carbon and trace metals. Temperature, pH, conductivity and salinity were measured in situ. In order to evaluate the groundwater quality, we compare the data obtained against the Hellenic legislation threshold values and FAO guidelines for irrigation waters. Conductivity ranged from 230 to 9180 μS/cm. Exceedance of the 700 μS/cm threshold (Type I water FAO) in 71% of the samples suggests slight to moderate restrictions in irrigation. In two drillings (No 10, 13) maximum permissible limits of conductivity, sodium and chloride concentrations were exceeded particularly in summer and autumn. Some exceedances of guidelines were also identified for nitrates and ammonium. Concentrations of dissolved trace metals, were generally below the limits, with the exception of Zn, however some concern has been raised in terms of increased levels of total dissolved Cr in drilling No. 15 (8.3 - 37.9 μg/L). On the basis of our results degradation of groundwater quality was identified together with seasonal salinization; these two factors corroborate to the need for sustainable groundwater use especially in months with increased demands for water supplies.