Spatial and seasonal trends of natural radioactivity and heavy metals in river waters of Epirus, Macedonia and Thessalia

Physicochemical parameters, natural radioactivity and heavy metals on the surface waters of rivers in Epirus (Aoos, Kalamas, Louros), Macedonia (Aliakmonas) and Thessalia (Pinios) were measured during the period May 2004–May 2006 in three sampling sites of each river. All the determined metal concentration values were lower than the ones usually found in polluted areas while each individual element displayed a wide variation in its concentration. Gross-alpha and -beta activities in the five Greek rivers were within the range usually observed in other European and world rivers. All 226Ra concentrations were lower than the world mean of 0.015 Bq L!1. Statistical analysis of variance and correlation analysis of the measured metals showed limited significant differences between sampling sites or periods, suggesting influence from geologic factors rather than from point sources. Significant differences between the three studied sites of Aliakmonas river were observed for gross-alpha and 226Ra activities and this result was attributed to the influence of the coal mines in the region and/or the runoff of fertilizers from agricultural activities in this area.

The current concerns with trace metals and radioactivity and their influence on a broad range of aquatic organisms and humans along with possible harmful effects, have renewed interest in environmental monitoring. The need for continuous scientific research to assess the potential risk posed by these elements in our environment seems inevitable. In this study, a trend of decreasing elements concentration of the order Aliakmonas ≥ Pinios > Louros ≥ Kalamas > Aoos was observed. Significant site differences in the concentration of 226Ra in the Aliakmonas River were attributed to the run-off of phosphate fertilizers or to the operation of the coal mines in the region, whereas the seasonal variations are mainly due to flow and dilution reduction. In contrast, the elevated amount of radium in the estuaries of Pinios River was rather due to mixing of river and seawaters and increase of the salinity. In general, dissolved metal concentrations at all sampling sites were low with a wide variation in elemental concentration as reflected by the large standard deviation values. Due to these variations, statistical analysis of variance and correlation analysis of the measured metals showed limited significant differences between sampling sites or periods, suggesting influence from geologic factors rather than from point sources. Since a large number of river data have resulted during the measurements campaigns, the analysis will be continued with the inclusion of sediments data and application of cluster and principal component analyses.