Evaporite Dissolution Rate through an on-site Experiment into Piezometric Tubes Applied to the Real Case-Study of Quinis (NE Italy)

Abstract

The present paper deals with a field experiments on evaporite rock samples and groundwater investigations in the Quinis test site, a hamlet of the Enemonzo municipality in NE Italy, were sinkholes occurred in the past and are still occurring causing severe damage to the existing infrastructures. The area is characterised by a Carnian evaporitic bedrock made of gypsum and anhydrite mantled by alluvial and colluvial deposits. In order to evaluate the loss of weight and volume of the subcropping evaporites as responsible for sinkholes, a field-experiment was carried out. Inside seven piezometers, at different depths, evaporitic rock samples were exposed to the naturally occurring variable climatic conditions such as degree of humidity, different air flow and hydrodynamic. The rock samples were installed at the beginning of April 2017 in the dry sections of piezometric tubes, in the vadose zone and in the phreatic zone. Data related to water level fluctuations were recorded by using data-logger devices and highlight significant changes in the water table. After 13 months of data recording (May 2018), rock samples were removed, reweighted and the volume loss measured. In addition, water from piezometer-experiment, representative of the groundwater circulation, were collected at different depths. The obtained results indicate that rock sample reduction is dependent on the hydrological regime and water chemistry and not on the number of days during which the samples remained submersed. In particular, the water geochemistry highlights the possible role in gypsum/anhydrite dissolution due to NaCl water admixing in a complex scenario. In additional, the geochemical data highlight the occurrence of some potentially toxic elements (As, Fe, Mn) at concentrations of concern in some water. This approach represents a novel contribution in the study of karst hazard in evaporites adding a tile to the knowledge of the fast evolutionary processes which cause sinkhole formation.

Calcium sulfate precipitation pathways in natural and engineered environments

“…This problem is of course specific to areas with a subground rich in gypsum/anhydrite, such as the aforementioned Montmatre neighbourhood in Paris, the Permian gypsums of northern England (see Fig. 5d), gypsum terrains in NE Spain or in the NE of Italy (Benito et al, 1995;Cooper, 2002;Gutierrez et al, 2008;Calligaris et al, 2019). (Rosenberg et al, 2012), (b) gypsum crystallization on the surface of building material accelerates its deterioration (reproduced from Winkler (1975) by permission of Springer Nature, Photos by Dr. Schmidt-Thomsen), (c) swelling behaviour in sulfate rich rocks can induce severe floor heave (Pimentel, 2015), and (d) sinkhole formation in sulfate rich rocks causing severe damage to buildings (photo credit BGS NERC).…”

Non-Invasive Methodological Approach to Detect and Characterize High-Risk Sinkholes in Urban Cover Evaporite Karst: Integrated Reflection Seismics, PS-InSAR, Leveling, 3D-GPR and Ancillary Data. A NE Italian Case Study

“…Calligaris et al [63] described the field experiment of placing rock evaporitic samples into piezometric tubes at different depths, demonstrating a dissolution rate of the evaporites up to 2.8 mm/y, almost three times greater than that expected if compared with the available literature data ( [63] and in text references).…”

A joint geophysical approach to tune an integrated sinkhole monitoring method in evaporitic environments

“…They often have serious consequences in urban areas, causing physical and socio‐economic damage to existing man‐made structures and have a high risk factor due to their rapid occurrence and evolution (Intrieri et al., 2015; Martinotti et al., 2017; Zini et al., 2015 and all the references therein). Unfortunately, it is nearly impossible to precisely predict when and where sinkholes will occur, while monitoring the evolution of those which have already developed is somehow easier (Calligaris et al., 2019; Galve et al., 2011; Parise, 2015). Studying these geo‐hydrological hazards more in‐depth would facilitate a better understanding of their prodromal and triggering factors in order to prevent their intrinsic hazard and risk.…”