Natural hexavalent chromium in groundwaters interacting with ophiolitic rocks

Thirty of the 58 groundwaters sampled in September-October 2000 in the study area (La Spezia Province, Italy) have Mg-HCO₃ to Ca-HCO₃ composition, undetectable Cr(III) contents, and virtually equal concentrations of total dissolved Cr and Cr(VI). Therefore, dissolved Cr is present in toto as Cr(VI), with concentrations of 5-73 ppb. These values are above the maximum permissible level for drinking waters (5 ppb). Local ophiolites, especially serpentinites and ultramafites, are Cr-rich and represent a Cr source for groundwaters. However, since Cr is present as Cr(III) in rock-forming minerals, its release to the aqueous solution requires oxidation of Cr(III) to Cr(VI). This can be performed by different electron acceptors, including Mn oxides, H₂O₂, gaseous O₂, and perhaps Fe(III) oxyhydroxides. Based on this evidence and due to the absence of anthropogenic Cr sources, the comparatively high Cr(VI) concentrations measured in the waters of the study area are attributed to natural pollution.     

Structural evolution of the Pleistocene Cimini trachytic volcanic complex (Central Italy)

Structural, geomorphological, geophysical and volcanological data have been processed for the implementation of a dedicated GIS through which the structural evolution of the Pleistocene trachytic Cimini volcano (central Italy) has been reconstructed. The evolution of the Cimini complex includes three main close-in time phases: (1) intrusion of a shallow laccolith, rising along NW and NE trending faults and stagnating at the contact between the Mesozoic-Cenozoic and the Pliocene-Pleistocene sedimentary units constituting the bedrock of the volcano; (2) emplacement of lava domes along radial and tangential fractures formed by the swelling induced by the laccolith growth; (3) ignimbrite eruptions and final effusion of olivine-latitic lavas. Domes are both of Pelean and low lava dome type and their morphology was controlled by the location on the inclined surface of the swelled area. Some domes show to have uplifted upper Pliocene thermally metamorphosed clay sediments, suggesting a cryptodome-like growth. Comparison of the top of the Mesozoic-Cenozoic units with the top of the upper Pliocene-Pleistocene sedimentary complex, suggests that the laccolith emplaced in a graben of the Mesozoic-Cenozoic sedimentary complex filled by the Pliocene–Pleistocene sediments uplifted by the shallow intrusion. Stress patterns acting on the Cimini area have been deduced analysing the drainage network and the morphotectonic lineaments. Rose diagrams show a large dispersion of the lineaments reflecting the local presence of radial and tangential fractures. The most frequent extensional NW and NE trending lineaments have regional significance and controlled the magma uprise leading to the laccolith emplacement.     

Volcanic ash hazard in the Central Mediterranean assessed from geological data

Volcanic ash produced during explosive eruptions can have very severe impacts on modern technological societies. Here, we use reconstructed patterns of fine ash dispersal recorded in terrestrial and marine geological archives to assess volcanic ash hazards. The ash-dispersal maps from nine Holocene explosive eruptions of Italian volcanoes have been used to construct frequency maps of distal ash deposition over a wide area, which encompasses central and southern Italy, the Adriatic and Tyrrhenian seas and the Balkans. The maps are presented as two cumulative-thickness isopach maps, one for nine eruptions from different volcanoes and one for six eruptions from Somma-Vesuvius. These maps represent the first use of distal ash layers to construct volcanic hazard maps, and the proposed methodology is easily applicable to other volcanic areas worldwide.     

Diagnostics,deterioration and provenance of stone materials from the Jefferson Page tomb (Non-Catholic Cemetery of Rome,Italy)

The monumental tomb of Jefferson Page, an officer in the American Navy, was built in 1899 and is located in the Non-Catholic Cemetery of Rome (Italy). This study presents complementary diagnostic studies characterizing the stone of the tomb and the weathering and decay phenomena it has undergone. The monument is made of a single type of whitish marble, variously veined and often covered with black patinas. Petrographic, isotopic and LA-ICP-MS analyses attribute the marble to the Carrara district. SEM/EDS and microbiological analyses indicate that the black patinas are due to cyanobacterial autotrophic and fungin heterotrophic colonization. Fourier-transform infrared spectroscopy revealed the presence of organic material on some portions of the tomb, due to undocumented restoration carried out with a mixture of marble powder and a polyester resin.