Monitoraggio chimico, isotopico e delle comunità microbiche delle acque sotterranee: strategie per una migliore comprensione dei processi naturali e antropici

In industrial areas, the alteration of groundwater quality is generally attributed to human activities, while the role of natural geogenic background levels is largely disregarded. Owing to the migration of leachate and various contaminants, the municipal landfi lls are one of the main threats for aquifers. Th e current regulatory framework is limited to indicating generic concentration thresholds for contaminants, after which it is assumed that the protection systems have failed, without relying on the comparison with the site's conceptual hydrogeological model. Th rough a series of studies conducted in diff erent sites in Latium, we attempted to defi ne an integrated methodological approach suitable to distinguish the anthropogenic impacts from the natural geochemical background, through a synoptic analysis of the hydrogeochemical characteristics, isotopic and microbiological groundwater. Th is paper describes one of the case studies, where key inorganic contaminants (i.e., As, Fe, and Mn) exceeded the local threshold values in most of the sampling points, while hazardous organic contaminants were generally very low. Tritium values and d13C were helpful to single out the possibly impacted groundwater within the study area, where a moderate impact was apparent and the inorganic levels seemed altered. Th e groundwater microbial community was characterized by fl ow cytometry, BIOLOG MicroPlates assay, and faecal indicators providing further supportive information on the landfi ll-induced alterations. Finally, a multivariate statistical approach facilitated the integrated elaboration of the diff erent inorganic, organic, isotope and microbiological parameters. Th e high levels of inorganic compounds were attributed to the natural water-rock interaction with the thick lacustrine sequence rich in geogenic organic matter and residual volcanic products in anoxic conditions. Th e presence of faecal contamination and the heterogenic microbiological properties showed that aquifer alterations involved the microbial community structure and the functional profi les related to organic carbon utilization. In conclusion, this integrated multiparametric approach was suitable to distinguish geogenic and anthropogenic impacts, thus suggesting appropriate strategies for groundwater management in landfi lls.