Caratterizzazione idrogeochimica e analisi di rischio delle acque sotterranee nell’Altopiano di Poirino

The subject of the Thesis was the risk analysis applied to groundwater in the Poirino Plateau. Such area, particularly in the northernmost part between the towns of Riva presso Chieri, Chieri, the Marocchi district, Poirino and Villanova d'Asti, represents an area with a widespread state of contamination of the surface water table, by nitrates and hexavalent chromium. Widespread nitrate pollution in groundwater is considered one of the main causes of water quality degradation in this area, where the use of synthetic nitrogen fertilizers and organic manure is a common practice and locally there is a lack of connection to sewage services. Highly developed livestock farming also contributes to the deterioration of groundwater. Another contaminant of particular concern is chromium in its hexavalent form, which has been found in monitoring campaigns since the late 1980s. The work of this Thesis focused on forward mode risk analysis, a technique that estimates the consequences on human health of a potentially harmful event, in terms of the probability of the same consequences occurring through ingestion and dermal contact of surface groundwater. The population was divided into residential (children, adolescents, adults and the elderly) and commercial (workers). Sampling of 18 wells and chemical analyses of the samples were carried out: acid-base titrations, ion chromatography analysis with chemical suppression and plasma spectrometry coupled with mass spectrometry were fundamental techniques for the identification of anions, cations and metals in solution. In particular, the close correlation between chlorides, sulphates and nitrates was noted through the use of various diagrams, which, in this area, is an indication of pollution due to anthropic activity (use of fertilizers, sewage, spreading of NaCl as antifreeze, use of ammonium chloride and sulphate in agriculture). The Risk-net 3.1.1 Pro software was used to calculate the risk through ingestion, while for dermal contact it was necessary to use the formulae developed by the U.S. EPA in 2004. The Hazard Index for non-carcinogenic substances and the Risk for carcinogenic substances were thus calculated; the calculations carried out showed that the maximum values laid down in the regulations were exceeded - even very significantly - at almost all the points sampled (apart from the commercial area). These exceedances were also found for water samples that were formally unpolluted according to the CSC (Contamination Threshold Concentration) tables of Regulation 152/06. The most exposed population category was children and adolescents. The groundwater of the surface aquifer in the study area, according to the risk analysis methods applied, revealed extremely poor quality.