Search results for "Gypsum"

Geological development of a gypsum lake formed at the beginning of the 20th century in central Sicily, Italy: Integration of historical data with mod…

2006

A limnological investigation was carried out on the small, endorheic lake, called Lake Sfondato, located in central Sicily (Italy). All the aquatic environments in the central part of the island are rich in salt, with conductivity values above 5 mS cm−1, and are characterized by high alkalinity values and hard waters. In addition, due to intensive agriculture, many of these ecosystems have experienced a strong anthropogenic eutrophication over the last decades. In order to better understand the functioning of these peculiar environments, the morphology, hydrology, and geochemistry, as well as several selected physical and biological characteristics of Lake Sfondato, were studied in the year…

A new calcium sulfate hemi-hydrate

2010

Calcium sulfate hydrates receive significant attention due to numerous large scale industrial applications. There has been a long debate on the possible existence of two gypsum hemi-hydrate polymorphs, denoted alpha- and beta-CaSO(4).0.5H(2)O. In this work, a new crystal structure of calcium sulfate hemi-hydrates is presented, denoted beta-CaSO(4).0.5H(2)O. The structure was solved using powder neutron diffraction data, the space group is P3(1) and the unit cell in a hexagonal setting a = 6.9268(1), c = 12.7565(3) A. The structure has two calcium-oxygen coordination polyhedra: Ca1 is eight coordinated and has Ca-O bond lengths in the range 2.31(3) to 2.89(2) A and Ca2 is nine coordinated an…

Successive alkalinity producing system for the treatment of acid sulphate soil runoff: preliminary results of a field trial

2005

A successive alkalinity producing system (SAPS) has been investigated as a potential passive treatment option for acid, metal containing runoff from acid sulphate soil. A pilot-scale system was installed at an agricultural land site in Rintala embankment area in mid-western Finland. The experimental layout consists of three parallel treatment units: two different SAPS cells and one limestone-filled cell for comparison of performance. The SAPS cells are composed of a bottom layer of limestone and a top layer of compost supplemented with sand. One of the SAPS cells contains sulphate-rich, waste gypsum mixed with the compost layer in order to enhance the metal reduction by sulphate reducing-ba…

The effects of anthropogenic particulate emissions on roadway dust and Nerium oleander leaves in Messina (Sicily, Italy)

2003

Complementary studies on the inorganic chemical composition of Nerium oleander leaves collected in the town of Messina (Sicily, Italy) and seven grain-size fractions of local roadway dust have been carried out. Data and maps are presented to show that the particulate matter present in the air of Messina contains trace elements significantly in excess with respect to the average continental earth crust. The anomalies follow the outline of the urban area, the highest concentrations of trace elements being observed where traffic density is highest. Chemical and isotopic analyses of both road dust and Nerium oleander leaves indicate that Pb contamination still characterizes roads with heavy tra…

Formation of secondary carbonates and native sulphur in sulphate-rich Messinian strata, Sicily

2010

Abstract Microbially formed authigenic carbonates accompanied by native sulphur are present in the ‘Calcare Solfifero’ below a thick succession of gypsum deposited during the Messinian salinity crisis in Sicily. We sampled these carbonates and associated sulphur in five former sulphur mines to subject them to a detailed petrographic and geochemical study in order to explore their different modes of formation. Native sulphur formed in conjunction with microbial sulphate reduction, which is reflected in its depletion in 34S (δ34S values as low as − 2‰ vs. V-CDT) and an enrichment of 34S in the residual sulphate (δ34S values as high as + 61‰). The oxidation of organic matter by sulphate reduct…

Investigations of Surface Forces between Gypsum Microcrystals in Air Using Atomic Force Microscopy

2000

This article introduces a new approach to the study of the interactions between gypsum faces in air. We have mounted a gypsum crystal on the end of a microcantilever to measure local forces (van der Waals, capillary forces, electrostatic) directly between two crystals. A systematic study with respect to the orientation of crystalline faces, relative humidity, and the duration of contact between crystals improves the understanding of the mechanism involved in the hardening of plaster in air. In dry air, a physicochemical process of matter transfer is added to the van der Waals forces to ensure the cohesion. Others force measurements were performed by varying the shape of the contact (interac…

How to tackle the stringent sulfate removal requirements in mine water treatment-A review of potential methods.

2018

Abstract Sulfate (SO₄²⁻) is a ubiquitous anion in natural waters. It is not considered toxic, but it may be detrimental to freshwater species at elevated concentrations. Mining activities are one significant source of anthropogenic sulfate into natural waters, mainly due to the exposure of sulfide mineral ores to weathering. There are several strategies for mitigating sulfate release, starting from preventing sulfate formation in the first place and ending at several end-of-pipe treatment options. Currently, the most widely used sulfate-removal process is precipitation as gypsum (CaSO₄·2H₂O). However, the lowest reachable concentration is theoretically 1500 mg L⁻¹ SO₄²⁻ due to gypsum’s solu…

Soils with Gypsic horizon in southern Sicily, Italy

2005

Acqua Fitusa cave: An example of inactive water-table sulphuric acid cave in Central Sicily

2012

Description of the sulphuric acid cave in Sicily (see pdf attached)

Environmental impact assessment on the Monza cathedral (Italy): A multi-analytical approach

2020

This research deals with the characterization of black crusts collected from the Dome of Monza (Milan, Italy). Air pollution is responsible for the degradation of historical buildings surfaces. In urban and industrial areas, the degradation process is accelerated, due to carbonaceous particles and heavy metals emitted by combustion processes which contribute to the formation of black crust (BCs). In this study the characterization of BC was performed using different analytical techniques such as: HRSEM-EDX, IC, LA-ICP/MS and digital image analysis. In particular, the research focused on the study of "heavy metals" which contribute to the identify the main sources of pollution responsible fo…