Mercury emissions in volcanic gases from Mt. Etna, Italy.

Mercury is a global pollutant that can be found in different forms and different ecosystems. Special attention has recently been devoted to mercury due to its high chemical reactivity, its global spreading, its biogeochemical cycling, its transformations in the environment, its ability for biomagnification and its high toxicity. Beside anthropogenic sources, mercury can also be of natural origin. Among natural Hg sources, volcanoes can be important. Volcanic gas emissions may be rich in elemental gaseous mercury (Hg0), reactive gaseous mercury (HgII) and other mercury forms. Mt. Etna (Sicily, Italy) is one of the most active volcanoes in the world and one of the largest contributors of magmatic volatiles to the environment; consequently, we tried to estimate its contribution to regional and global Hg budgets and tested the eligibility of Hg as a tool for volcano monitoring. Mercury concentrations have been measured on Mt. Etna during several campaigns carried out between 2004 and 2007 in fumaroles, mofettes and diffuse degassing areas, as well as in the air inside and across the volcanic plume. In addition, Hg fluxes have been measured by flux chamber technique. Mercury concentrations measured in air below the volcanic plume in November 2004 ranged between 4 and 30 ng m-3 at low altitude, and between 65 and 132 ng m-3 close to the summit craters. A profile of Hg in the air below the volcanic plume carried out on helicopter on November 2006 showed Hg concentrations up to 60 ng m-3. Hg contents in fumarole gases reached 64,200 ng m-3, and soil gas Hg showed temporal variations that reached the highest values (up to 240 ng m-3) in fall 2005. The highest Hg fluxes were measured in bubbling gas from mud volcanoes at the SW foot of Etna, reaching 1300 ng m-2 h-1. Mercury contents were found highly correlated both with water/mud temperature at mud volcanoes and with concurrent soil CO2 effluxes. In the latter case, hydrothermal gases showed higher values and a higher correlation than “cold”gases. Our results, therefore, look promising for the use of mercury in geochemical monitoring of volcanic activity

Biogeochemical, isotopic and bacterial distributions trace oceanic abyssal circulation

We explore the possibility of tracing routes of dense waters toward and within the ocean abyss by the use of an extended set of observed physical and biochemical parameters. To this purpose, we employ mercury, isotopic oxygen, biopolymeric carbon and its constituents, together with indicators of microbial activity and bacterial diversity found in bottom waters of the Eastern Mediterranean. In this basin, which has been considered as a miniature global ocean, two competing sources of bottom water (one in the Adriatic and one in the Aegean seas) contribute to the ventilation of the local abyss. However, due to a recent substantial reduction of the differences in the physical characteristics of these two water masses it has become increasingly complex a water classification using the traditional approach with temperature, salinity and dissolved oxygen alone. Here, we show that an extended set of observed physical and biochemical parameters allows recognizing the existence of two different abyssal routes from the Adriatic source and one abyssal route from the Aegean source despite temperature and salinity of such two competing sources of abyssal water being virtually indistinguishable. Moreover, as the near-bottom development of exogenous bacterial communities transported by convectively-generated water masses in the abyss can provide a persistent trace of episodic events, intermittent flows like those generating abyssal waters in the Eastern Mediterranean basin may become detectable beyond the availability of concomitant measurements.We explore the possibility of tracing routes of dense waters toward and within the ocean abyss by the use of an extended set of observed physical and biochemical parameters. To this purpose, we employ mercury, isotopic oxygen, biopolymeric carbon and its constituents, together with indicators of microbial activity and bacterial diversity found in bottom waters of the Eastern Mediterranean. In this basin, which has been considered as a miniature global ocean, two competing sources of bottom water (one in the Adriatic and one in the Aegean seas) contribute to the ventilation of the local abyss. However, due to a recent substantial reduction of the differences in the physical characteristics of these two water masses it has become increasingly complex a water classification using the traditional approach with temperature, salinity and dissolved oxygen alone. Here, we show that an extended set of observed physical and biochemical parameters allows recognizing the existence of two different abyssal routes from the Adriatic source and one abyssal route from the Aegean source despite temperature and salinity of such two competing sources of abyssal water being virtually indistinguishable. Moreover, as the near-bottom development of exogenous bacterial communities transported by convectively-generated water masses in the abyss can provide a persistent trace of episodic events, intermittent flows like those generating abyssal waters in the Eastern Mediterranean basin may become detectable beyond the availability of concomitant measurements. © 2016 Rubino et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Mercury emissions in volcanic gases from Mt. Etna, Italy.

Mercury is a global pollutant that can be found in different forms and different ecosystems. Special attention has recently been devoted to mercury due to its high chemical reactivity, its global spreading, its biogeochemical cycling, its transformations in the environment, its ability for biomagnification and its high toxicity. Beside anthropogenic sources, mercury can also be of natural origin. Among natural Hg sources, volcanoes can be important. Volcanic gas emissions may be rich in elemental gaseous mercury (Hg0), reactive gaseous mercury (HgII) and other mercury forms. Mt. Etna (Sicily, Italy) is one of the most active volcanoes in the world and one of the largest contributors of magmatic volatiles to the environment; consequently, we tried to estimate its contribution to regional and global Hg budgets and tested the eligibility of Hg as a tool for volcano monitoring. Mercury concentrations have been measured on Mt. Etna during several campaigns carried out between 2004 and 2007 in fumaroles, mofettes and diffuse degassing areas, as well as in the air inside and across the volcanic plume. In addition, Hg fluxes have been measured by flux chamber technique. Mercury concentrations measured in air below the volcanic plume in November 2004 ranged between 4 and 30 ng m-3 at low altitude, and between 65 and 132 ng m-3 close to the summit craters. A profile of Hg in the air below the volcanic plume carried out on helicopter on November 2006 showed Hg concentrations up to 60 ng m-3. Hg contents in fumarole gases reached 64,200 ng m-3, and soil gas Hg showed temporal variations that reached the highest values (up to 240 ng m-3) in fall 2005. The highest Hg fluxes were measured in bubbling gas from mud volcanoes at the SW foot of Etna, reaching 1300 ng m-2 h-1. Mercury contents were found highly correlated both with water/mud temperature at mud volcanoes and with concurrent soil CO2 effluxes. In the latter case, hydrothermal gases showed higher values and a higher correlation than “cold”gases. Our results, therefore, look promising for the use of mercury in geochemical monitoring of volcanic activity.Ministry for Foreign Affairs, Iceland Samorka – Icelandic Energy and Utilities University of Iceland The Icelandic Institute of Natural History Icelandic Road Administration Icelandic Meteorological Office Iceland GeoSurvey Viðlagatrygging Íslands Soil Conservation Service of Iceland Ministry for the Environment Ministry of Education, Science and CulturePublishedReykjavík, Iceland4.5. Degassamento naturaleope

Influence of sulphur cycle on mercury methylation in estuarine sediment (Seine estuary, France)

In order to investigate interaction between mercury speciation and reduced sulfur, speciation of mercury and sulfur were determined in sediment cores sampled in saline and freshwater wetlands of the Seine estuary, France. Solid phase was analyzed for total (HgT) and monome- thyl mercury (MMHg), total sulfur, acid volatile sulfides (AVS), chro- mium reducible sulfur (CRS) and organic carbon. In porewater, in addition to total and methyl mercury, ion, manganèse and sulfates were aiso determined. Levels of the HgT (0. 5 – 2.0 mgkg$^{-1}$ d.w.) in sediment of the Seine estuary were relatively high and typical for sedirnents in industrial area. The sediment contained 0.5 – 1. 5 $\mu$gkg$^{-1}$ d.w. of MMHg, which made an average 0. 1% of the HgT in sediment. Concentration of MMHg was found to be dependant more on the chemical conditions in sediment than on the level of HgT. Depth profiles of MMHg in the solid phase and HgT in porewater at two sites studied could be related to the production of AVS in sediment as well as to the redox conditions of porewater (defined by Eh and dissolved iron and manganese)

Benthic flux measurements of Hg species in a northern Adriatic lagoon environment (Marano and Grado Lagoon, Italy).

As part of the \u201cMIRACLE\u201d project, the biogeochemical cycling of mercury (Hg) at the sediment-water interface was studied in the field in the Marano and Grado Lagoon (Northern Adriatic Sea). Seasonal investigations were conducted at selected experimental sites, where Manila Clams (Tapes philippinarum) were previously seeded. Measurements were performed seasonally during three campaigns, using two benthic chambers, one transparent and one dark, to evaluate the effect of light on Hg cycling. Total dissolved Hg (THg), methylmercury (MeHg), and dissolved gaseous Hg (DGM) species were considered. Diurnal benthic fluxes were found to significantly exceed the diffusive fluxes at all stations. The assessment of the annual recycling of Hg species from sediments to the water column showed that up to 99% of MeHg is recycled annually to the water column, while Hg recycling ranges from 30 to 60%. MeHg poses the higher risk for potential bioaccumulation in clams, but it is partially mitigated by Hg reduction, which seems to be an important process leading to evasion losses of Hg from these environments. Estimated benthic fluxes suggest that Hg recycling at the sedimentewater interface is more active in the Grado sector. Hence, based on the estimated release of MeHg from sediments, it is suggested that the western sector seems to be more suitable for clam farming and the extension of rearing activities