Search results for "gypsum"

Per una via siciliana dei gessi. Quando le parole portano alle cose

2023

Secondo il metodo Wörter und Sachen, parole e cose, suoni e referenti, devono essere studiati insieme. Questa simbiosi ha particolare necessità di essere applicata quando si tratti di cultura materiale. Il contributo è la storia di un’esperienza di indagine sul campo, svolta in un periodo di tempo di circa 15 anni, che ha riguardato le parole del gesso e le cose di gesso nella Sicilia centrale. L’individuazione di questo ambito di studio è stata parallela, ma marginale, rispetto ad una più significativa esperienza dialettologica relativa al lessico zolfifero. Eppure, grazie a questo approfondimento, sono emerse conoscenze inedite dal punto di vista linguistico ed etnodialettale, tali da avv…

Towards a checklist of the Italian gypsophilous vascular flora.

2016

The strict relationship between plants and particular types of substrate has long been known to botanists and plant ecologists who have dealt with this issue. The peculiar flora growing on Italian gypsum substrates has been underlined since the nineteenth century (1, 2, 3). The concept of plant gypsophily can be defined as the exclusiveness or marked preference for living on gypsum outcropping rocks. Thus, only those plant species which show preference, or even exclusivity, for gypsum substrates, should be classified as gypsophilous (4). The main aim of this research has been to provide a checklist of the Italian gypsophilous flora. The study was made possible through international collabor…

Incorporation of trace metals Cu, Zn, and Cd into gypsum: Implication on their mobility and fate in natural and anthropogenic environments

2020

Abstract The coexistence of calcium (Ca2+), sulfate (SO42−) with trace metal cations (M(II)) can possibly lead to M(II)-gypsum coprecipitation and solid solution formation. However, gypsum's role in the fixation of M(II) is still largely unknown. This study investigated the precipitation of Ca2+ and SO42− in the presence of M(II) (i.e., Cu2+, Zn2+, or Cd2+) and the incorporation of the metal cations into the gypsum structure at different environmental conditions. Trace metals in two natural gypsum samples (Yunnan and Neimeng, China) and one hydrometallurgical byproduct gypsum sample from a Cu refinery were also assessed. X-ray diffraction, scanning electron microscopy-energy dispersive X-ra…

The Complex of tectonic caves of the Vallone di Margi Paolino (Valle Grovello) area - Sant'Angelo Muxaro (AG).

2010

Soil chemical and biochemical properties of a salt-marsh alluvial Spanish area after long-term reclamation

2009

Marisma, one of the largest salt-marsh alluvial areas in SW Spain, has been reclaimed since 1970 by artificial drainage and amendment with phosphogypsum (PG) so as to reduce Na+ saturation. Within the reclaimed area, two 250- × 20-m plots were treated as follows: (1) amendment with 25 Mg/ha of PG every 2 to 3 years between 1979 and 2003 (plot PY); (2) like PY but PG treatment stopped after 1997 (plot DR). A contiguous virgin Marisma salt-marsh plot (MV), neither drained nor amended, was the control. In MV, soil microbial biomass C, most enzyme activities and total organic C content were much greater than in PY and DR soils, despite the salinity stress. The decrease in soil organic matter co…

Unveiling species assemblage rules in gypsum plant communities

2023

Plant communities are not merely snapshots of species located in the same area. Instead, they are dynamic entities connected through complex biotic interactions. Understanding the interplay of processes that bind species within a community is vital for comprehending species maintenance and may assist us in predicting how communities respond to the perturbations of a changing world. This Ph.D. aims to unveil how abiotic conditions, plant strategies, and biotic interactions shape plant communities growing in stressful environments. Plant species can thrive in stressful environments through contrasted strategies, either showing species-specific adaptive strategies or reliance on facilitative i…

Testing Soil Encasing Materials for Measuring Hydraulic Conductivity of a Sandy-Loam Soil by the Cube Methods

2008

The Cube Method (CM) and the Modified Cube Method (MCM) were developed for measuring vertical (K v ) and horizontal (K h ) saturated hydraulic conductivity of a single soil sample. By these methods, a cube of soil is carved out in situ and a suitable material is applied to enclose the cube in a tightly fitting casing before moving the sample to the laboratory. Problems may be associated with the use of gypsum, originally used to encase soil. The suitability of molten wax and expandable polyurethane foam to encase a soil cube was tested for a sandy-loam soil. Wax-treated samples yielded lower conductivity results than untreated samples by a maximum factor of 3.7. The observed discrepancies w…

Interaction of CaSO4 with water vapour at high relative humidity

2010

16 pages. Prepublication en attente d'un complément expérimental; Soluble anhydrite β-CaSO4 reacts with water vapour at room temperature to form CaSO4-0.5H2O at 20-30% RH and CaSO4-0.6H2O at 70-80% RH. At higher RH, additional water uptake can only add-up to an adsorbed water layer. The present work provides evidence that a small amount of the adsorbent dissolves in the adsorbed layer and gypsum starts precipitating at 97-98 %RH even though condensation of the vapour phase does not take place. After several days the adsorbent is almost entirely and irreversibly converted. The kinetics of weight gain clearly discriminates between adsorption and dissolution-precipitation. If a minute amount o…

Irreversible modifications of the porous microstructure of soluble anhydrite β-CaSO4 induced by hydration-dehydration cycles

2006

26 pages; The internal surface area of hexagonal (soluble) primary anhydrite CaSO4 produced by dehydration of gypsum decreases by about 70 % when the anhydrite is successively subjected to rehydration and dehydration at room temperature in humid air and in vacuum respectively. In the rehydration step, the hemihydrate is formed; its dehydration yields secondary anhydrite. Additional hydration-dehydration cycles in the same conditions have a much smaller effect. The first cycle also brings about a modification of the t-plot, which reveals that the micropores of primary anhydrite are irreversibly healed. Mercury intrusion porosimetry shows that the primary dehydration of gypsum also generates …

Influence of aluminates phases hydration in presence of calcium sulfate on silicates phases hydration : consequences on cements optimum sulfate

2012

The mechanical properties of hydrated cements need to be optimized according to the nature of cement products. Among the factors of optimization, the addition of calcium sulphate intended to regulate the reactivity of tricalcium aluminate (C3A), in quantity and quality in cement is an essential parameter.The advancement of knowledge on the mechanisms of hydration of each cement phase allows a study devoted entirely to the concept of optimum of sulphate. We studied simple system that we complicated and we studied the evolution of hydration, porosity and mechanical properties of cement at different age. The first system studied was the mixture C3S/gypsum, the objective was to determine whethe…