Analisi del meccanismo di contaminazione delle acque sotterranee da cromo esavalente in un sito industriale dismesso in provincia di Vicenza

Analysis of the groundwater contamination by hexavalent chromium in an industrial site in the Vicenza province The present thesis work, consists in the study of mechanisms able to mobilize a pollutant in a site on the higher plain of Veneto. Specifically, considering the contaminated site by hexavalent chromium in the "Galvanica pm" a dismantled factory in the municipality of Tezze sul Brenta (province of Vicenza), we wanted to distinguish the contribution of groundwater table raising from the infiltrated rainfall on mobilization of hexavalent chromium from contaminated soil to groundwater. The processing of historical monitoring data, allowed to build the trends of piezometric level, rainfall intensity and infiltration rate, the concentrations of hexavalent chromium in groundwater and pumping rates for contaminant plume capture. The analysis of these data sets are fundamental to reconstruct the quantity (mass) of hexavalent chromium extracted from 2008 to 2014, highlighting the crucial role of rainfall in the transport of the pollutant in groundwater. The analysis of historical data has allowed to distinguish different mechanisms leading to the release of contaminants in groundwater and their weight. In detail, the study showed that in periods, in which there is the effect of the infiltration of rainwater, in groundwater we registered long-lasting contamination events, with concentrations of chrome in the order of hundreds of ug/l. Meanwhile, with the raising of the piezometric level above a threshold limit, the hexavalent chromium values reach values of a few thousand mg/l for short time periods. Finally, it was found that the combined action of abundant rainfall and the groundwater table raising, originates a mobilization mechanism that leads to have intermediate concentration values compared to those previously described, but for long time periods.