Claudio Inguaggiato

Total CO2 output from Vulcano island (Aeolian Islands, Italy)

[1]xa0Total CO2 output from fumaroles, soil gas, bubbling gas discharges and water dissolved gases discharged from the island, was estimated for Vulcano island, Italy. The CO2 emission from fumaroles from the La Fossa summit crater was estimated from the SO2 crater output, while CO2 discharged through diffuse soil emission was quantified on the basis of 730 measurements of CO2 fluxes from the soil of the island, performed by using the accumulation chamber method. The results indicate an overall output of ≅500 t day−1 of CO2 from the island. The main contribution to the total CO2 output comes from the summit area of the La Fossa cone (453 t day−1), with 362 t day−1 from crater fumaroles and 91 t day−1 from crater soil degassing. The release of CO2 from peripheral areas is ≅20 t day−1 by soil degassing (Palizzi and Istmo areas mainly), an amount comparable to both the contribution of water dissolved CO2 (6 t day−1), as well as to seawater bubbling CO2 (4 t day−1 measured in the Istmo area). Presented data (September 2007) refer to a period of moderate solphataric activity, when the fumaroles temperature were 450°C and gas/water molar ratio of fumaroles was up to 0.16. The calculated total CO2emission allows the estimation of the mass release and related thermal energy from the volcanic-hydrothermal system.

Long-time variation of soil CO2 fluxes at the summit crater of Vulcano (Italy)

Here, we report the first continuous data of geochemical parameters acquired directly from the active summit crater of Vulcano. This approach provides a means to better investigate deep geochemical processes associated with the degassing system of Vulcano Island. In particular, we report on soil CO2 fluxes from the upper part of Vulcano, a closed-conduit volcano, from September 2007 to October 2010. Large variations in the soil CO2 and plume SO2 fluxes (order of magnitude), coinciding with other discontinuous geochemical parameters (CO2 concentrations in fumarole gas) and physical parameters (increase of shallow seismic activity and fumarole temperatures) have been recorded. The results from this work suggest new prospects for strengthening geochemical monitoring of volcanic activity and for improving the constraints in the construction of a “geochemical model”, this being a necessary condition to better understand the functioning of volcanic systems.

RARE EARTHS AND TRACE ELEMENTS CONTENTS IN LEAVES: A NEW INDICATOR OF THE COMPOSITION OF ATMOSPHERIC DUST

The relationship between the trace element distribution in atmospheric particles and leaves of some exposed plants in the environment was recently demonstrated. This indication would suggest that the trace element analysis of leaves in these plants could provide information about the composition, nature and origin of the atmospheric dust dispersed in the environment. In order to corroborate this hypothesis, the distribution of trace elements and Rare Earths were studied in leaves of some endemic plants, in the atmospheric fallout and in soils of rural, urban and industrial ecosystems in Sicily. These elements have been chosen to discriminate the source and nature of different source on atmospheric dust and the larger capability of the composition of the latter materials to influence the metal ion distribution in leaves of studied plants rather than the soil composition. These evidences are related to the recognition both of positive La anomaly and trace element enrichments in studied leaves and to their particular V/Th and Co/Ni signature. On the other hand, some particular normalised REE features recognised in leaves suggest that a limited contribution to the REE budget in studied leaves is provided by the REE migration from roots.

Weathering of evaporites: natural versus anthropogenic signature on the composition of river waters

Weathering of evaporites strongly influences the chemistry of continental runoff, making surface waters poorly exploitable for civil uses. In south-central Sicily, this phenomenon is worsened by the occurrence of abandoned landfills of old sulphur and salt mines. The industrial evolution of the Bosco-S. Cataldo mining site leaved two landfills from the early exploitation of a sulphur mine followed by that of a kainite deposit. In particular, the weathering of these landfills leads the dissolved salt (TDS) values up to about 200xa0gxa0l−1 in the Stincone–Salito Stream waters. This process induces the V, Cr and Fe desorption from sediments and particulates in the aqueous phase under reducing conditions. At the same time, the weathering of salt minerals releases Rb and Cs, originally contained in halite. The overall processes lead to the V, Cr, Fe, Rb and Cs enrichment of waters from the Stincone–Salito Stream system accompanied by a sharp growth of As content, up to about 13xa0µgxa0l−1, caused by As release from Fe-bearing solids due to the high salinity. Therefore, the scenario of the weathering of Bosco-S. Cataldo mine landfills depicts an environment strongly influenced by effects of the growing salinity and euxinic water conditions where the attained TDS, Eh and pH conditions reduce the natural scavenging capability of the interested river system, favouring a growth of residence time of toxic elements in river waters.

Zr, Hf and REE distribution in river water under different ionic strength conditions

The Platani River flowing in south-central Sicily, interacting with evaporite rocks, generates a wide range of ionic strength in the water catchment from 0.1 to 5.0molkg-1. We sampled 38 river sites and analysed the composition for the dissolved fraction filtered through 0.45μm, the truly dissolved fraction obtained through ultrafiltration (10kDa) and the relative included colloidal fraction. This study was focused on the recognition of Zr, Hf and REE behaviour under changing ionic strength conditions, since this is one of parameters responsible for colloid stability in natural waters. In turn, this phenomenon leads to REE release from the colloidal fraction and their scavenging onto surfaces of suspended particles or sediment, or their complexation with dissolved ligands. Our results indicated that in both dissolved and ultra-filtrated fractions REE increases either in the middle (Sm - Dy) or in the heavier (Ho - Lu) part of the PAAS-normalised distribution, while the Zr/Hf ratio value ranges from sub-chondritic to super-chondritic. Scanning Electron Microscopic and Energy Dispersive X-ray Spectrometric (SEM-EDS) analyses and dissolved Mg, Al and Fe concentrations suggested that the studied colloids consist of aggregations of Al-oxyhydroxides, carbonate nanoparticles and clays where organic traces were not found. The studied colloids showed greater affinity with dissolved Zr than Hf determining Zr/Hf values larger than the chondritic values. The largest Zr/Hf values were found in colloidal fractions from waters with ionic strength larger than 0.6molkg-1. These Zr/Hf values up to 280 (w/w) are provided by the faster removal of Hf relative to Zr from coagulating colloids and its preferential scavenging onto authigenic Fe-oxyhydroxides in bottom sediment. Further studies are needed to clarify is this suggested process can represent a suitable starting point for the Zr-Hf decoupling observed in seawater.

Geochemistry of Zr, Hf, and REE in a wide spectrum of Eh and water composition: The case of Dead Sea Fault system (Israel)

Along the Jordan Valley-Dead Sea Fault area several natural waters in springs, wells, and catchments occur. The chemical-physical characters of the studied waters allowed for the first time the investigation of the Zr and Hf geochemical behavior, apart from REE, extended to a wide range of Eh, temperature, salinity, and pH conditions. The results of this study indicate that the dissolved Zr and Hf distribution in natural waters is strongly influenced by redox conditions since these in turn drive the deposition of Fe-oxyhydroxides or pyrite. In oxidizing waters saturated or oversaturated in Fe-oxyhydroxides (Group 1), superchondritic Zr/Hf values are measured. On the contrary, in waters where Eh< 0 values occur (Group 2), chondritic Zr/Hf values are found. Superchondritic Zr/Hf values are produced by the preferential Hf scavenging onto Fe-oxyhydroxides that is inhibited under reducing conditions consistent with the water oversaturation relative to pyrite. Redox conditions also influence the amplitude of Ce and Eu anomalies. Oxidized Group-1 waters show negative Ce anomalies related to the oxidative Ce scavenging as CeO2 onto Fe-oxyhydroxide. Reduced Group-2 waters show positive Eu anomaly values consistent with the larger Eu concentration relative to Eu in these waters suggested by model calculations. The higher stability of Eu with respect to its trivalent neighbors along the REE series can explain the above mentioned positive Eu anomaly values. The middle-REE enrichment observed in shale-normalized REE patterns of studied waters can be ascribed to carbonate and/or gypsum dissolution.