0000000000290321
AUTHOR
W. D'alessandro
Multiple origins of methane in fluids circulating in the Othrys ophiolite, central Greece
The complex geology of Greece includes two important parallel running ophiolitic belts. The Othrys Massif in central Greece belongs to westernmost of them. In and around this wide ophiolite outcrop, some cold hyperalkaline and some hypothermal (T < 40°C) alkaline springs are present. Thirty water samples were collected at 17 different sites and both bubbling and dissolved gases were analysed for their chemical (He, Ne, H2, O2, N2, CH4, C2H6, CO2 and H2S) and isotope (He, δ13C-CO2, δ 13C-CH4, δ 2H-CH4) composition. All samples except one have H2S contents below detection limit (10 μmol/mol), whilst H2 (from <2 to 2500 μmol/mol), CO2 (up to 26,000 but generally below 1000 μmol/mol) and …
Geochemistry of Zr, Hf, and REE in a wide spectrum of Eh and water composition: The case of Dead Sea Fault system (Israel)
International audience; 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 …
Measurements of Hg0 (and H2S) at the Solfatara Crater (Southern Italy): Estimating the atmospheric distribution with a real-time approach
Volcanic and geothermal areas are important emitters of natural gas compounds into the atmosphere, which can be of concern when discharging close to densely, populated sites. Mercury has a strong environmental impact, its organic and inorganic complexes being toxic. The dominant form of Hg in the atmosphere is gaseous elemental mercury (GEM), which has high volatility and residence time of 1-2 years. Volcanic degassing accounts for a significant part of the natural mercury emissions. No mercury limits or target values in ambient air are present in the EU legislations, whereas US-EPA and ATSDR impose 300 and 200 ng/m3, respectively, as a limit for chronic exposure. WHO has proposed the annua…
Geochemical comparison of natural and anthropogenic metal fluxes in extreme environments: Mt. Etna volcano (Italy) and Šalek Valley (Slovenia)
Geochemical comparison between some metals (As, Cd, Cu, Pb, Se, V, Zn) emissions from an active volcano (Mt. Etna) and a highly industrialized area (Šalek Valley) showed some interesting similarities: in general, most of the elements emitted into the atmosphere do not return to the Earth’s surface and are therefore dispersed into the environment. Exceptions for Šalek Valley are Cd, which probably derives in large part from rock leaching, and in part As and Pb, which fall mostly as ash. Also, Etna’s emissions are richer in Cd and Cu, whereas industrial emissions at Šalek Valley are richer in V and Zn. All other metals have similar fluxes in the two types of emissions.
Trace elements in Mirror of Venus lake waters (Pantelleria Island, Italy)
Mirror of Venus lake (MV) is a small (1.5 km2) endorheic alkaline lake located in a calderic depression on the northern side of Pantelleria Island (South Italy), a quiescent Pleistocenic stratovolcano located in the NW-SE trending continental rift developed between North Africa and Sicily. The lake, sub-squared in shape (around ca 450 m long and ca 350 m wide and 13 m depth) water input contribution is essentially from the thermal springs situated on its shores (Q = 0.1 l.s-1) and from meteoric waters. A total volume of 580.000 m3 has been estimated in June 2014. CO2 flux measurements made with a floating accumulation chamber in 2014 on the MV surface (both diffusive and bubbling CO2) highl…