Sinkhole susceptibility evaluation in Apulia, southern Italy

In some regions in Italy sinkholes are frequent and pose a serious threat to structures and infrastructures. Apulia region is largely affected by sinkholes of both natural and anthropogenic origin, due to the karst nature of large portions of the regional territory and to high diffusion of artificial cavities. For this reasons, susceptibility, hazard and risk posed by sinkholes must be estimated in order to gain more insights into their spatial and temporal distribution, and to apply appropriate risk management and to take proper mitigation strategies. In order to estimate the susceptibility to sinkholes in Apulia, the ensemble statistical modelling proposed by Rossi et al. (2010) and later refined by Rossi & Reichenbach (2016) is used. This allows assessing susceptibility using differentiated statistical approaches, quantifying accurately the modelling performances, and evaluating the associated uncertainty. In order to obtain accurate and reliable results thematic layers related to the sinkholes occurrence were carefully evauated and selected. This contribution shows the preliminary results of the analyses to evaluate the susceptibility to natural sinkholes, which used as training dependent (i.e. grouping) set, data extracted from the regional inventory of natural caves, edited by the Apulian Speleological Federation (www.catasto.fspuglia.it), and as validation set the natural sinkholes occurred in Apulia, collected in the chronological catalogue of sinkholes in Italy (Parise & Vennari, 2013, 2017). Appropriate thematic layers, were selected heuristically on the base of the knowledge on the triggering mechanisms and the nature of the phenomenon gained previously in the study area. Resulting regional-scale susceptibility map will be appropriately validated. The methodological procedure will be applied to the evaluation of susceptibility for anthropogenic sinkholes as well

Karst geomorphology of the “Canale di Pirro” polje, Apulia (Southern Italy).

In karst environment, a geomorphological map is a powerful instrument, which play a crucial role in understanding earth surface processes and landscape evolution. Furthermore, it could be very useful for speleological perspectives, natural resources exploitation and geo-hazards management (flood, sinkhole, subsidence, etc.), providing useful information that enhance the knowledge of the territory. In this work, we present a geomorphological map of the polje of “Canale di Pirro”, sited in the central part of Apulia Region, in Southern Italy, among the most interesting karst lands in the Mediterranean area. The map covers150km2withanelevationrangeof100-450ma.s.l.Thisareaisoneofthemostremarkablekarstlandforms in the region, characterized underground by a very interesting system of caves, that reaches the water table at a depth of -264 meters. The karst system, known as “Inghiottitoio di Masseria Rotolo”, following scuba-diving exploration below the watertable, has become with a depth of 324m, the deepest known cave in Apulia. The polje is bounded on both sides by tectonically-controlled ridges, showing an overall length of some 12 km. In ancient maps, dating back to the 16th century, the area is represented as crossed by a long river, called Cana. The map obtained derives from the integration of interpretation of aerial photographs, analysis of a digital elevation model and field surveys in order to obtain a correct distribution of landforms and fluvial processes, such as different varieties of karst depressions, conical hills, erosional gullies, alluvial fans and tectonic structures. It provides relevant information about the surface drainage processes, and for understanding, among other things, the groundwater circulation and the related recharge processes. This geomorphological map is part of a wider project, that combined geological, hydrogeological research and chemical analyses of the groundwater. It provides support to the ongoing studies of this part of Apulia region aimedto betterunderstand thegeological processes that originatedthe polje and its later evolution, and the related underground cave system. Further, it might also suggest possible improvements in land management and in the future choice of useful tools for the control of the quality and quantity of karst groundwater

Au@MNPs-based electrochemical immunosensor for vitamin D3 serum samples analysis

We report a new sensitive label-free electrochemical immunosensor to detect Vitamin D3 (25-OHD3) in untreated serum samples. To this aim, a graphite screen printed electrode (SPE) was modified using cysteamine (CYM) functionalized core-shell magnetic nanoparticles (Au@MNPs) then, the 25-OHD3 antibody (AbD) was immobilized via glutaraldehyde crosslinking. The several steps involved in the immunosensor development and 25-OHD3 analysis were monitored by using differential pulse voltammetry (DPV). The developed immunosensor showed a LOD of 2.4 ng mL−1 and a linear range between 7.4 and 70 ng mL−1. The effectiveness of the immunosensor in human serum analysis was assessed by comparing the results obtained with the chemiluminescence-immunoassay (CLIA) reference method. The high sensitivity and excellent agreement with the reference method suggest its potential use as a POCT to monitor hypovitaminosis 25-OHD levels

An integrated framework to identify and analyze karst sinkholes.

Sinkholes are the most typical surface feature of karst landscapes. Their correct mapping is of great importance for a proper assessment of the possible occurrence of new events , and the likely effects they could have on the anthropogenic environment. In this work we compare and discuss different ways to map sinkholes, including heuristic approach, automatic mapping through different resolution DTMs, and digital aerial photo interpretation, aimed at highlighting advantages and drawbacks of the different approaches, using a study area in the Murge of Apulia, SE Italy, where many sinkholes of different typologies are present to characterize the landscape. To evaluate the reliability of the mapped sinkholes, we set up a conceptual methodology that integrates a semi-automatic method with the heuristic approach, with a special focus on the importance of incorporating digital stereoscopic interpretation. In detail, we used as input two DTMs at different resolution, aimed to test the robustness of the automatic method in different circumstances. Comparison of the data produced by the different approaches illustrated how the number, density and boundaries of the sinkholes may vary as a function of the input data. The automated mapping provides reliable results in terms of number, dimension, and morphometric attributes of sinkholes, and appears to be particularly useful when large areas must be analyzed. Within the whole process, we stress the role of the expert geomorphologist who must determine the accuracy of the product obtained with the automated mapping by correcting/eliminating features not attributable to karst processes. The presented approach highlights the potential of digital stereoscopy in substantially decreasing the errors encountered with traditional analog mapping, simultaneously reducing the working time significantly

Detection and analysis of sinkholes through integration of field surveys and semi-automated techniques

Sinkholes are among the most typical landforms of karst terrains. They may originate from a simple downward process, through dissolution of carbonate rocks, or through rapid, sometimes catastrophic, collapse, due to the presence of an underground void or cavity, from where the instability may eventually reach the ground surface. These two extremes imply a great variety in both vulnerability of man-made structures, and eects on the population, which make the analysis of sinkholes extremely important to society. In this contribution we present an integration of techniques to detect, classify and analyze sinkholes, aimed at contributing to the evaluation of sinkhole susceptibility and hazard. The methodology used will be illustrated by means of a variety of examples from the karst of Apulia, south-eastern Italy

Applicability and future perspective of a multi-component approach to map karst dolines: a case study from the Apulian karst (SE Italy)

Depressions due to solution, subsidence or collapse are a major geohazard in regions characterized by prevailing carbonate rocks. Compiling rigorous karst doline catalogues is important not only from a geomorphological standpoint, but also as a contribution toward the most accurate estimate of karst hazards. Further, arranging such type of database is usually a time demanding, difficult task. Nowadays high-resolution digital terrain surveys techniques (LIDAR), and GIS tools are gaining ground in providing support to geomorphologists for karst depression mapping. In this work, different mapping approaches are integrated and analyzed to the case study of Ceglie Messapica, in the Apulian karst of southern-east Italy. First, a more traditional geomorphological approach based on analogical aerial photo interpretation is applied; secondly, the study area is investigated using the automatic mapping based on GIS tools, exploiting two DEMs with different resolutions: 1x1m (LIDAR) and 8x8m, and analyzed using a digital stereographic photo interpretation. The obtained doline catalogues are compared and the main morphometric parameters are calculated and discussed. Advantages and weaknesses, problems or uncertainties of the methods are highlighted, in order to understand how one technique could fill the gap(s) of the other. The catalogues are synthetized and some critical cases are clarified through field survey. The aim of this application is to propose a comprehensive method, integrating different mapping techniques with the purpose to demonstrate how nowadays automatic or manual mapping cannot be considered standalone procedures. The results show that automatic mapping can detect a larger number of features than through the classical approach; nevertheless, the geomorphologist expertise remain unvaluable to supervise the results and to clean the dataset from misinterpreted features. The method used allows to compile accurate and complete karst doline catalogues, and may potentially contribute to provide reliable data aimed at a correct evaluation of the karst hazards

Integrated mapping method of sinkholes, through an application in the Apulian karst (Southern Italy)

Karst landscape is a remarkably interesting and complex environment, where the numerous natural processes in act may determine consequences for human assets and changes in the landscape itself. Understanding the karst processes should proceed through accurate identification of their geomorphological features, and their correct interpretation and representation on maps. In particular, recognition of landforms such as sinkholes allows, besides the actions above recalled, to predict and manage future consequences associated with the evolution of such a hazard. With this in mind, we propose a multi-disciplinary sinkhole mapping methodology that exploits heuristic (geomorphological) and GIS modeling approach in a workflow that optimize the time consumption and minimize errors in the final results. According to these intentions, we use a study area in the Apulia region (Southeast Italy), characterized by the presence of sinkholes of different typologies, to apply: i) an automatic mapping method, ii) a manual mapping method carried out with digital stereoscopic interpretation, and iii) a final field survey. In order to test the robustness of the automatic method we run it by using as input two DTMs at different resolutions, and we compare the results with a sinkhole map obtained with geomorphological interpretation. The results show the reliability of the automatic mapping method and point out that the accuracy of the features detected is linked to the resolution of the input DTM. However, it was noticed that it tends, in some cases, to overestimate the number of sinkholes by including artifacts or features attributable to other non-karst processes. On the other side, the automatic procedure could be very handy for the analysis of wide areas, and to provide the geomorphologist with a draft map to be cleaned and completed by using digital stereoscopy as well. Hence, we underline the importance of the expert geomorphologist contribution, who must check and integrate the product obtained with the automated mapping. The integration of these two approaches determines a substantial decrease of errors in the mapping, and a substantial saving of time as well

Built-up area exposure to landslides and related social impacts in Molise (Italy)

Italy is historically affected by a number of natural hazards, which include landslides, floods, earthquakes, snow avalanches and sinkholes, all of them posing severe threats to the socio-economic development in many portions of the country. In central-southern Italy, Molise stands among the sectors most prone to landslide occurrence where mass movements regularly affect towns and villages, causing frequent damages to assets such as infrastructures or houses. For these reasons landslides may influence the life quality of the population in the area. Aim of this study is to explore the relationships between the spatial distribution of landslides and the social environment in Molise, with a particular focus on the impact that landslides produce on the local population. We present an exposure analysis that considers the interaction of the highest susceptible areas with the built-up environment. Furthermore, for each municipality of the region we attempt to find a correspondence between the average level of landslide susceptibility with the Demographic Malaise State indicator (SMD). The SMD is a composite index that analyses the changes of growing/decreasing rates in the local population. In this way we attempt to achieve a better understanding of how the environment degradation (in terms of landslide occurrence and evolution) could promote out-migration from the affected areas. This study is a contribution to improve the knowledge of the relationships among landslide prone areas and social effects in the Molise territory, which can be essential for the development of efficient strategies for landslide risk reduction

Caves intercepting groundwater: special sites to investigate underground water resources

A very high percentage of outcropping soluble rocks characterize the Apulia Region of Southern Italy. As a consequence, remarkable karst phenomena are widespread in the territory, making this area one of the most interesting as regards karst processes in the Mediterranean Basin. The spatial anisotropy and inhomogeneity of subsurface make hydrogeological studies very complex. In Apulia, two important karst sites are considered extraordinary natural hydrogeological laboratories because they allow cavers to directly reach the groundwater. VoraBosco,inSalentoPeninsula(SouthernApulia),reacheswatertableatadepthofabout60mfromtopographic surface (elevation of cave entrance: 64 m a.s.l.); Inghiottitoio di Masseria Rotolo (within the polje of Canale di Pirro, central Apulia) is the deepest cave in the region, reaching groundwater at a depth of about 260 m below the ground (elevation of cave entrance: 300 m a.s.l.). At this latter site, scuba-divers explorations brought the total depth of the cave system to 324 m. Within the framework of a project funded by Apulia Region, several monitoring actions have been started at the two caves. In detail, multiparameter probes have been installed inside the caves to collect continuous series of data like groundwater level, temperature and conductivity. Further, cavers and researchers have performed biospeleological surveys, taking samplings to detect some chemical and microbiological groundwater parameters. In addition, cave temperature and humidity have been recorded by means of HOBO sensors, positioned along the caves pathway, at different depths and locations. The combined analyses of monitoring data will be very useful to increase the regional hydrogeological knowledge, with particular reference to the responses of the karst systems to meteorological events. Chemical and microbiological analyses, together with the biospeleological data, will indicate the status of groundwater health in order to determine threshold values of groundwater base parameters, certifying the absence of anthropogenic contamination, and to promote actions for freshwater resource safeguard and protection. Acknowledgments: this work was funded through the Protocollo d’intesa con Regione Puglia per l’attuazione dell’art. 45 “Interventi per esplorazione dei fenomeni carsici”, comma 1 della L.R. n. 45 del 30/12/2013