The hydrogeological processes driving the hydrochemical composition of groundwater in the alpine pristine aquifer system of the Port del Comte Massif (PCM) are characterized through the multivariate ...statistical techniques Principal Component Analysis (PCA) and Gaussian Mixture Models (GMM) in the framework of Compositional Data (CoDa) analysis. Also, the groundwater Natural Background Levels (NBLs) for NO3 and SO4 and Cl are evaluated, which are specially important for indicating the occurrence of groundwater contamination derived from the anthropic activities conducted in the PCM.
The different hydrogeochemical facies found in the aquifer system of the PCM comprises low mineralized Ca-HCO3 water for the main Eocene karst aquifer, and Ca-SO4 and highly mineralized NaCl water types in the minor aquifers discharging from the PCM. The NBL values of SO4, Cl and NO3 obtained for the main karst aquifer are 14.33, 4.06 and 6.55 mg/L, respectively. These values are 35, 3 and 1.2 times lower than the respective official NBLs values that were determined by the water administration to be compared with in the case of conducting a pollution assessment characterization in the main karst aquifer. Official overestimation of NBLs can put important groundwater resources in the PCM at risk.
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•The Gaussian Mixture Models are used to cluster springs by hydrochemical response.•The clustering analysis groups the springs of the aquifer system into four families.•The compositional analysis approach is required for hydrochemical data analysis.•The hydrogeological characterization of Port del Compte Aquifer system is presented.•Natural base levels of nitrate and sulphate in the Port del Compte Aquifers are given.
The diversity of small, medium, and large solution features of zonal karsts and high mountain karsts is described here. It was taken into consideration how diversity changes according to the ...distance from the Equator in case of small, medium and large features of various zonal karsts and how it varies based on the distance from altitude in case of the karren features (small features) of high mountain karsts. It can be established that the diversity of karst features decreases according to the distance from the Equator (independent of the size of the features), while in high mountains the diversity of karren features first increases with altitude and then it decreases. The decrease of the diversity of medium and large features moving away from the Equator can be explained by the decrease of dissolution intensity. The diversity change of karren features shows a relation with the diversity of the inclination of the bearing slope. Since on tropical karsts and in the medium elevated areas of high mountains (1600-2100 m) where bare slopes with large expansion and various slope inclination occur, the diversity of karren is great. On tropical karsts, slopes with diverse inclination were created by karstification and in high mountains by glacial erosion.
Spatial data were used to develop complex characteristics of a high-mountain karst. The numeric elaboration was conducted using the analytical capabilities of GIS software. Analysis was based on ...spatial data gained by elaborating aerial photography. The results were presented in map sets, as well as Geographic Information System format. The set of matched numerical methods used and the proposed algorithm for data analysis may be applied at other karst sites.
Small, rather shallow cylindrical dolines were found on the sub-horizontal surface of the Pale di San Martino plateau (Dolomites, Italian Eastern Alps) at an altitude ranging from 2,500 to 2,650 m a. ...s. l. Measurements of their dimensions were carried out on a population of more than 100 dolines, revealing that they have an average diameter of 4.4 m and a depth of 0.8 m. The dolines’ bottoms are usually flat, formed by outcropping rock (often a sub-horizontal bedding plane) or by debris and fine soil. To investigate the dolines’ microclimate five data-loggers were installed, for more than one year in different positions: in a karst fissure open on the wall of a doline, on the soil, buried in the bottom’s fillings up to a depth of 0.5 m. Temperature data taken with the interval of one hour show that few freezing/melting cycles occur during fall season, whilst fewer have been detected in spring time, because of the protection of the snow cover and the maintenance of temperature at 0°C by water coming from melting snow. The described dolines are found to be landforms due to karstic and periglacial processes acting on an epikarstic layer interested by bundles of fissures differently oriented. As regards age, most dolines developed in postglacial time, but some larger depressions are probably older and were partly modified by glaciers abrasion during the last Glaciation., Karst- und periglaziale Dolinen im hohen alpine Karst von Pale di S. Martino Hochplateau (Dolomiten): geomorphologische und Klimaaspekte. – Besondere Dolinen zylindrischer Form, welche auf dem Hochplateau von Pale di S. Martino zwischen 2.500 und 2.650 m auftreten, wurden studiert. Die Vermessung einer Population von mehr als 100 Dolinen ergab einen durchschnittlichen Durchmesser von 4,4 m und eine durchschnittliche Tiefe von 0,8 m. Der Grund der Dolinen ist üblicherweise eben und besteht entweder aus anstehendem Gestein (häufig schichtverbandparallel) oder aus Lockermaterial und feinkörnigem Bodenmaterial. Zur Erforschung des Mikroklimas wurden fünf Data-logger an den Wänden und den Böden der Dolinen in bis zu einem halben Meter Tiefe platziert, welche die Temperatur stündlich über einen Zeitraum von mehr als einem Jahr aufzeichneten. Die gewonnenen Daten belegen, dass die Frost/Schmelz-Zyklen am Übergang Sommer/Winter einsetzen, während am Anfang des Sommers solche aufgrund der Schneebedeckung und des Schmelzwassers selten oder überhaupt nicht einsetzen. Die untersuchten Dolinen wurden durch Karst und periglaziale Prozesse geformt, welche auf die Karstoberfläche einwirkten, welche von Bündeln vertikaler und horizontaler Spalten durchzogen war. Der Großteil der Dolinen wurde während des Postglazial geformt, einzelne größere Depressionen sind vermutlich älter und gehen auf das letzte Glazial zurück.
Dolines karstiques-periglaciales dans le plateau de haute montagne des Pale di San Martino (Dolomites): aspects geomorfologiques et conditions du milieu. – Sur le plateau des Pale di San Martino (Dolomites, Italie) on a étudié de petites dolines cylindriques. Elles se trouvent sur une surface sub-horizontale haute de 2.500 à 2.650 m sur mer. On a mesuré les dimensions principales entre une population de plus de cent dolines: il on résulte que le diamètre moyen est long de 4,4 m et la profondeur est de 0,8 m. D’habitude le fond des dolines est plat, formé par une surface de stratification de la roche ou par débris et sols fins. Pour étudier le microclimat des doline, cinq data-loggers (laissés pour plus d’une année sur le paroi d’une doline et dans le sol jusqu’à une profondeur de 0,5 m) ont enregistré les températures toutes les heures. Les données démontrent que des cycles gel/dégel ont lieu dans le passage de l’été à la saison froid, tandis qu’au printemps ces cycles sont rares ou absentes, à cause de la couverture de la neige et de l’eau de fusion qui maintiennent la température autour de 0°C. Ces dolines étudiées sont le résultat des processes karstique et periglaciale qui ont agit sur l’epikarst affecté par fractures soit verticales soit horizontales. En ce qui concerne l’age, cettes formes se sont développées après le Tardiglaciaire, tandis que les plus grandes dolines sont plus agées et ont étées modelées par le glacier dans la dernière glaciation.
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