Torquato Nanni

A DNA tracer used in column tests for hydrogeology applications

Tracing techniques are commonly used to investigate groundwater quality and dynamics, as well as to measure the hydrogeological parameters of aquifers. The last decade has seen a growing interest in environmentally friendly tracers, including single-stranded DNA molecules. In this study, an electrolytic tracer and a synthetic DNA tracer are comparatively evaluated in laboratory scale tests to assess their potential application in field studies aimed at investigating groundwater environments. A real-time quantitative Polymerase Chain Reaction assay was developed and optimized to detect and quantify the DNA tracer, while tracer column tests were performed to investigate the DNA tracer behavior and to compare it to the electrolytic tracer. The results show that the DNA tracer has an almost pure convective flow, while the KCl tracer experiences dispersive behavior. The tracing method proposed can be applied in hydrogeological field studies involving calcareous fractured rock systems, with the DNA tracer particularly suitable in tracing karst systems, which are often characterized by several conduits of flow. To test the DNA tracer in operation, a preliminary test was conducted in the field.

Hydrogeological mapping of the highly anthropogenically influenced Peligna Valley intramontane basin (Central Italy)

This paper presents hydrogeological mapping of the Peligna Valley (Central Italy) intramontane basin. The basin is hydrogeologically complex due to the significant surface and underground water resources which are extensively used for potable, industrial, agricultural and healing purposes. The basin history is characterised by significant fluvio-lacustrine deposition whose thickness can reach as much as 500 m. The depositional environment is completely surrounded by calcareous mountains. These represent extensive aquifers which feed large regional point and linear springs with total discharges of 16 m3/s. The highly complex hydrogeology of the study area and the varied use of water resources required extensive data collation and geological and hydrogeological assessments. Two years worth of hydrodynamic and hydrochemical monitoring of wells, springs, rivers and particularly artificial channels that convey water for industrial, hydroelectric and irrigational purposes were also undertaken. The construction of an accurate spatial-temporal database allowed the assessment and mapping of complex relationships between superficial water and groundwater. These relationships are shown in the 1:25,000 scale map. The map has been compiled using a detailed descriptive legend, various hydrogeological sections, schematics of anthropogenic activities, diagrams and tables and, finally, four schematics at 1:150,000 scale showing risk of contamination. It is hoped that this layout will assist in reading the map independently from any other supporting material.

The Mt Conero limestone ridge: the contribution of stable isotopes to the identification of the recharge area of aquifers

The recharge settings of aquifers (as those of the carbonate ridges in central Apennines) is strongly dependent on hydrogeological and geo-structural complexity; in fact, geochemical data, hydrographs interpretation, hydrogeological and geo-structural surveys, tracer and isotope data are usually not so developed and quite difficult to put into relation each other. In this paper, the importance of relating isotope techniques to hydrogeological survey on the recharge area evaluation is demonstrated by studying the system of the Mt Conero limestone ridge, located in central Italy close to the Adriatic sea. A closed system, at a pilot scale, with sufficiently well defined outcropping areas of aquifer, which is offering a contribution to the aquifer recharge area evaluation. In this study a hydrogeological investigation was performed to identify the infiltration areas in the aquifer, analysing the entire geological formation divided into several members, each of them showing different hydrogeological behaviour. In addition, periodic sampling of groundwater and of precipitation at different elevations were carried out to study the isotopic composition over a period of about 4 years. Weighted mean and arithmetic mean of isotopes were used in the gradient calculation and compared giving actually different results. The mean recharge altitude of the aquifer, as evaluated by weighted mean of isotopes, is about 100 m higher than the average elevation of the aquifer outcrop; moreover, it was proven that the vast majority of the recharge is due to the more permeable members of the aquifer (about 20% of the outcropping rocks, located at higher elevation). The recharge mechanism of the aquifer is therefore depending both on the isotope values of the local precipitation and on the distinct infiltration conditions existing in the lithotypes.

DNA and fluorescein tracer tests to study the recharge, groundwater flowpath and hydraulic contact of aquifers in the Umbria-Marche limestone ridge (central Apennines, Italy)

The purpose of this paper is to highlight the hydrogeological contact among aquifers in karst and fissured systems and study the different flowpaths present in said aquifers; given the complex hydrogeological and tectonics settings, detailed surveys in the Umbria-Marche limestone ridges and tracer field tests were used to achieve this goal. DNA and fluorescent tracers were injected into a sinkhole and thereafter recovered at different points, allowing both for the identification of contact among aquifers, as well as the main and secondary directions of groundwater. The tracer tests have shown that the majority of the groundwater flow is directed towards the axis of the tectonic structures, emerging in more depressed areas. In addition, they have confirmed the influence of karstification on the recharge, which allows for a more detailed characterisation of water circulation in the unsaturated zone of the Maiolica and the Calcare Massiccio limestone aquifers thus offering confirmation of the hydrogeological survey results, and providing additional information that was previously unknown. Furthermore, the DNA tracer provided good results in the field especially in the karst systems and fissured rocks, thus confirming its appropriacy for flowpath investigations and vulnerability analyses of springs. In particular, DNA is suitable for very large amounts of groundwater owing to its very low detection limit. Further investigations and studies are, however, required to assess its validity also for the evaluation of hydrogeological parameters.

Natural Hazard Analysis in the Aspio Equipped Basin

The purpose of this paper is to study floods, groundwater pollution and landslides in a small watershed characterized by high hydrogeological hazard, high population density and widespread industrial and commercial settlements. Measurements were performed to study hydrogeological hazard in the watershed during 2011, 2012 and 2013. First the relation between groundwater and surface water was estimated; second, the rainfall-runoff relationship was assessed. Some rainfall events were analysed to investigate the watershed behaviour in different periods over the hydrologic year. The analysis stressed the importance of the rainfall events, soil moisture and hydrological conditions. From this study it’s apparent that the natural hazard (i.e. floods, landslides and pollution hazard) can be better individuated and predicted in a small basin rather than in a wider one. Furthermore, these studies can be easily implemented in other basins with similar features in all the northern Mediterranean area.