Study of Sicilian Surface Freshwater Catchments for Environmental and Peoples Risk Assessment

Abstract

Due to the population growth, urbanization and economic development, demand for freshwater in urban areas is increasing throughout Europe. At the same time, climate change and pollution are also affecting the availability of water supplies. Sicily, a southern island of Italy, suffers from a growing strong water scarcity and drought. The freshwater basins of Sicily are not well characterized and classified. In last decades, in Sicilian freshwater surface reservoirs several Planktothrix rubescens and Microcystis aeruginosa blooms have reported. A further actual worldwide problem for all surface freshwaters basins is the increasing of heavy metals concentrations in their waters. Aims of this research doctoral project were: a) perform a census of Sicilian natural and artificial freshwater basins and identify which of these are suitable for use for drinking purposes; b) carry out a risk assessment related to presence of Microcystins and heavy metals (As, Pb, V, Cd, Al); c) evaluate the waters toxicity through ecotoxicological bioassays and verify if they would be sensitive and reliable to investigate on toxicity of mixtures of heavy metals and Microcystins. It was carried out the monitoring of 15 surface basins, among the 30 existing in Sicilian territory, through seasonal chemical, physical and microbiological analysis of the waters such as required by Italian law, the Legislative Decree 152/2006. Moreover, it was performed speciation of cyanobacteria community, cell counting, and PCR analysis. Finally, it was carried out acute (V. fischeri), subacute (T. platyurus) and chronic (D. magna) ecotoxicological assays. There is much reassurance about quality chemical status of basins. In fact, there are no heavy metals above the reference values. Only Aluminum and Iron are present often in large concentration. The high levels of total nitrogen and phosphorus give information about the inflow of partially or completely untreated urban and rural wastewater in all basins. However, in 50% of examined dams, there were the presence of several cyanobacteria species. In particular, it was detected cyanobacteria bloom in Disueri in period between July and September 2017. Microcystis sp. and Cylindrospermopsis raciborskii were detected (108 and 107 cell/L, respectively) and by mid-August were replaced by Anabaenopsis sp. and Plankthotrix rubescens, still growing in mid-September (107 and 106 cell/L, respectively). MCs concentrations in every samples were low, in agreement with the lack of qualitative amplification of the mcyE gene. The distance biplot of PCA showed that Disueri, Pozzillo, Trinità and Arancio dams are located near together and are strongly influenced by N, Fe, Al, V, Mn, F, Mn, Cl, pH, Ca and Nitrite. In recent past, all these dams were currently affected by harmful algal bloom. V. fischeri and D. magna assays seem to respond to the number of cyanobacteria cells rather than toxins concentrations. Instead, T. platyurus assay show a significant positive relationship between MCs concentrations measured by ELISA test. In conclusion, the chemical quality of Sicilian surface freshwaters catchments is good and it could be improved it with a better treatment and management of wastewaters got into the surface waters. Concerning the Microcystins contamination, since in every analyzed sample the concentration was below the WHO reference value for drinking waters (1 ug/L) it seems not to be a high and worrying risk for human and environmental health in the brief time. The simultaneous execution of V. fischeri and T. platyurus bioassays could favor the monitoring of waters both economically and technically. PCA analysis seems to be reliable to be used as predictive models for cyanobacteria growth. Finally, respecting these describes condition, it would be possible the use of waters of all monitored basins as drinking after an adequate treatment according to Italian Legislative Decree 152/2006.