Vincenzo Allocca

Role of organic matter and clay fraction on migration of Escherichia coli cells through pyroclastic soils, southern Italy

A comparative study on the adsorption of Escherichia coli cells to two different pyroclastic soils collected in southern Italy (carbonate Apennines) was performed in laboratory using surfactant-free solutions and solutions with the surfactants sodium dodecyl sulphate (SDS, anionic) and octylphenoxypolyethoxyethanol (Triton X-100, non-ionic). Both soils are rich in organic matter (up to 35%), but only one contains a clay fraction (2-5%). The experiments demonstrated that E. coli cells are significantly adsorbed to the clay fraction of the soil, while the organic matter content does not play a significant role. The pore size exclusion phenomenon is another factor to consider when analyzing the retention of E. coli cells within such soils. However, despite the existence of different factors that enhance bacterial cells retention, a high percent of E. coli cells is transported through soil media. The not absolute protection of such soils against microbial pollution is supported not only by the results of the column experiments at lab scale, but also by the findings of a field monitoring at site scale.

Winter survival of microbial contaminants in soil：An in situ verification

The aim of the research was to evaluate, at site scale, the influence of freezing and freeze/thaw cycles on the survival of faecal coliforms and faecal enterococci in soil, in a climate change perspective. Before the winter period and during grazing, viable cells of faecal coliforms and faecal enterococci were detected only in the first 10 cm below ground, while, after the winter period and before the new seasonal grazing, a lower number of viable cells of both faecal indicators was detected only in some of the investigated soil profiles, and within the first 5 cm. Taking into consideration the results of specific investigations, we hypothesise that the non-uniform spatial distribution of grass roots within the studied soil can play an important role in influencing this phenomenon, while several abiotic factors do not play any significant role. Taking into account the local trend in the increase of air temperature, a different distribution of microbial pollution over time is expected in spring waters, in future climate scenarios. The progressive increase in air temperature will cause a progressive decrease in freeze/thaw cycles at higher altitudes, minimising cold shocks on microbial cells, and causing spring water pollution also during winter.

Microorganisms as contaminants and natural tracers: a 10-year research in some carbonate aquifers (southern Italy)

Limestone aquifers provide the main drinking water resources of southern Italy. Due to cattle grazing and/or manure spreading, these aquifers are often characterized by microbial contamination of groundwater. The aim of this paper is to summarize the results obtained during a 10-year research carried out in experimental field sites in southern Italy, analyzing (1) the influence of the topsoil of pyroclastic origin on the migration of microbial cells from the ground towards the groundwater, and then on the groundwater vulnerability, (2) the influence of the rainfall regime on the breakthrough at the springs, (3) the reliability of thermotolerant coliforms and fecal enterococci as bacterial indicators of microbial contamination, and (4) the effectiveness of microorganisms as natural tracers for some hydrogeological purposes. The results obtained showed that fecal enterococci are a more reliable indicator than thermotolerant coliforms for detecting contamination and that the entity and distribution over time of microbial contamination of fecal origin are influenced by several factors, such as precipitation regime, thermal regime and existence and thickness of the topsoil of pyroclastic origin. Moreover, the migration of a significant amount of bacterial cells through the topsoil and the underlying carbonate rocks allows the utilization of microorganisms as effective natural tracers, to be coupled with other classic tracers to study the recharge and the flow processes. In a broader perspective, these results can be used to optimize the investigations in other hydrogeological scenarios, with emphasis on those where different water types coexist and interact in same aquifer systems.

Long-Term Hydrological Modelling of Pyroclastic Soil Mantled Slopes for Assessing Rainfall Thresholds Triggering Debris Flows: The Case of the Sarno Mountains (Campania—Southern Italy)

Air-fall pyroclastic deposits covering Campanian mountain slopes (southern Italy) are very prone to instability under heavy and prolonged rainfall. In such a geo-hazard framework, to understand hydrological dynamics of pyroclastic mantle is a step further toward the deterministic assessment of rainfall thresholds and landslide hazard. In this research, the hydrological modelling of a pyroclastic soil mantled slope of the Sarno Mountains is proposed to assess the role of antecedent hydrological conditions on rainfall triggering debris flows. The approach is based on the finite difference modelling, from seasonal to inter-annual timescales, of unsaturated/saturated flows occurring into the pyroclastic mantle upslope of a source area of a debris flow. Modelling results were calibrated by means of field measurements achieved by a tensiometer monitoring station. Among the main results, the pressure head distribution into the pyroclastic deposits showed a dominant unsaturated condition and a relevant seasonal variation extending below the root zone and down to the bedrock interface, about 4 m deep. This hydrological regime is attributable both to the distinctive water retention properties of pyroclastic soils and to the existence of a deciduous forest, which concentrates water losses due to evapotranspiration during the dry season. This behavior highlights the remarkable role of antecedent hydrological conditions as a not negligible predisposing factor to instability during short and heavy rainstorms.

Rising groundwater levels and impacts in urban and semirural areas around Naples (southern Italy)

The rising of groundwater levels in urban and rural areas is a relevant topic of the Urban Hydrogeology because it affects different areas of the world requiring specific analyses and mitigation measures by the institutions involved in the protection and security of the territory.In the last century, in many developed countries processes of deindustrialization and urban transformation have caused the rising of groundwater levels and severe economic and social impacts.The aim of this paper is to analyse the rising of groundwater levels in a multi-layered pyroclastic-alluvial aquifer, located in the coastal plain eastward of Naples (southern Italy) and its interactions with buildings and agricultural lands.The research has been carried out by means of: i) analysis of stratigraphic settings by 86 boreholes and reconstruction of hydraulic conductivity logs; ii) reconstruction of a 2D hydrostratigraphic model of the multi-layered pyroclastic-alluvial aquifer; iii) slug test and multi-temporal hydrogeological monitoring of 83 wells, 9 piezometers and 12 river water levels; iv) analysis of daily rainfall time series; v) hydrogeological monitoring of impacted buildings and agricultural lands.For the monitored period (November 2013-March 2015), the groundwater table showed a generalized rise, although with a spatial variability. The rise of groundwater levels ranged from a minimum of 0.10 meters, in the central and eastern sector of the study area, to a maximum of 2.05 meters, in the south-western sector, with an average growth rate of about 0.16 m.The distribution of the impacted areas is not spatially homogeneous, and it was observed to vary over time. The hydrogeological interactions between groundwater and urban and rural areas are affected by: i) foundation types of buildings and the depth of the underground structures; ii) presence of shallow aquicludes (marshy clay-sands, clay-silts and peat levels) that determine local conditions of confinement for groundwater; iii) hydraulic efficiency and maintenance state of the dense network of drainage channels and micro-channels, which were historically built to drain surface water and groundwater in rural areas.The obtained results provide the basic data to set up a numerical groundwater flow model, which is an indispensable tool to simulate and predict the hydrogeological effects of possible safeguard actions on urban and agricultural areas.

Hydrogeological and hydrogeochemical monitoring in the Cumae archaeological site (Phlegraean Fields, southern Italy)

1 Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, via Cintia-80126 Naples, Italy, silvioco88@gmail.com 2 Dipartimento di Scienze Chimiche, Università degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, via Cintia-80126 Naples, Italy 3 Dipartimento di Biologia, Università degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia-80126 Naples, Italy 4 Centre for Isotopic Research on Cultural and Environmental heritage (CIRCE), Dipartimento di Matematica e Fisica, Università degli Studi della Campania-Caserta, Italy

The Instability of Colluvial Mantle in Turbidite Flysch Series of the Cilento Region (Campania–Southern Italy): the November 26, 2010, Ostigliano Translational Slide

On November 26, 2010, heavy rainfall triggered a shallow landslide which threatened the historical center of Ostigliano (Cilento and Vallo di Diano National Park, southern Italy). Faint but diffused damages on ancient buildings led to the evacuation of 60 families and to the assessment of the reactivation hazard by a monitoring campaign. The landslide caused a very low morphological impact due to: displacement of the depleted mass, limited to less than 1 m, shallowness of the surface of rupture and translational kinematics. Geological surveys, boreholes, inclinometric measurements, dynamic penetration and geotechnical laboratory tests were carried out to characterize and monitor the mass movement. The analysis of these data allowed to reconstruct an engineering geological model of the landslide, and to characterize it as a shallow phenomenon involving the colluvial deposits formed over a turbidite flysch bedrock. Based on peak and residual shear strength tests, infinite slope stability analyses of surficial deposits were carried out, simulating different thicknesses and pore pressure conditions. Among principal results, the landslide extension was observed constrained to zones where the thickness of colluvial deposits is greater than 2 m. Moreover, instability conditions were found for residual value of shear strength only. Results of this study are proposed as a first contribute to depict this type of shallow mass movements affecting the Cilento region, whose most part is characterized by turbitide flysch series and colluvial mantled slopes.

Recharge in karst aquifers: from regional to local and annual to episodic scale

The assessment of groundwater recharge for karst aquifers of southern Italy is a major scientific task due to the relevant socio-economic and environmental role of the related groundwater resources. In this paper, the results of two methods, applied at different spatial and time scales, are reported.At regional and mean annual scales, through a multidisciplinary approach, the mean Annual Groudwater Recharge Coefficient (AGRC) was estimated for four sample karst aquifers, with available long-lasting spring discharge time series. Such estimations were extended to other karst aquifers of southern Italy by means of an empirical law that was found linking the AGRC to percentages of outcropping lithologies and endorheic/summit plateau areas.At local and episodic scales, the groundwater recharge of a test perched karst aquifer, belonging to the Mount Terminio hydrogeological structure (Campania region, southern Italy) was estimated. For such a purpose, an improvement of the Water Table Fluctuation (WTF) method, known as Episodic Master Recession (EMR), was applied to estimate the Recharge to Precipitation Ratio (RPR) coefficient, which represents the amount of precipitation recharging groundwater.Results obtained through the first approach furnished AGRC values varying between 50% and 79% and well matching with estimations of infiltration coefficients known in literature for other karst aquifers of Europe. Moreover, the mean value of RPR determined for the local karst aquifer (73%) resulted well matching with the AGRC estimated for the whole Mount Terminio karst aquifer (79%).By the comparison of these outcomes, at the regional and mean annual scales, the groundwater recharge of karst aquifers was found as mainly controlled by both the extension of outcropping lithologies and endorheic/summit plateau zones. While at the local and episodic scales, the groundwater recharge was recognized as chiefly influenced by the rainfall intensity and soil hydrological condition.