Chemical variations in fumarolic gases at Vulcano Island (Southern Italy): seasonal and volcanic effects

International audienceBecause of increasing in fumarolic activity at Vulcano since September 1987, regular sampling and analysis is conducted on the well-known F5 crater fumarole (T = 330 ± 5°C). Significant chemical variations have been recorded over the period 1987-1989. Variations of water vapour in the fumarolic fluid follow seasonal pattern and can be related to both external (seasonal) and internal (volcanic) influences suggesting a control by a shallow water aquifer. Significant variations of H$_2$0 and of some species in the anhydrous gas phase (H$_2$, SO$_2$, HCI, HF, N$_2$, He) probably result from chemical or dynamic changes in the feeding system at depth. Several mechanism are considered for explaining the chemical trends results in relationship to the recent increase in activity. A growing input of deep magmatic fluids is not supported by the low CO content and the apparent constancy of the $^3$He/$^4$He ratio. Apparent equilibrium temperatures close to the fumarolic outlet temperature (350-400°C) were calculated, suggesting isothermal expansion of the gas from a shallow equilibration zone. Comparison with the fumaroles at sea level (Porto di Levante) suggests that these latter may be fed a different hydrothermal systems. Variable interaction between both systems may account for some of the chemical variations observed at F5 fumarol

Lead isotopic fingerprint in human scalp hair: The case study of Iglesiasmining district (Sardinia, Italy)

International audienceThe Sulcis-Iglesiente district (SW Sardinia, Italy) has been, until recently, one of the most important Italianpolymetallic mining areas for the extraction of lead. Epidemiological studies conducted over several decadeshave indicated this site at high risk of environmental crisis with possible adverse effects on the public health.In the present paper we discuss Pb isotope signatures in human scalp hair and road dust collected from theSulcis-Iglesiente area in order to trace the exposure of populations to potential Pb sources. A total of 23 determinations(20 on hair samples and 3 on road dust samples) of lead isotope ratios (206Pb/207Pb and 208Pb/206Pb)werecarried out. The obtained results were integratewith literature data regarding the total content of Pb in hair samplesfromthe same study area. Hair fromchildren living in Sant'Antioco exhibited lead isotope ratios in the ranges1.152–1.165 for 206Pb/207Pb and 2.101–2.108 for 208Pb/206Pb,while hair samples fromIglesias resulted less radiogenic:206Pb/207Pb ~ 1.147–1.154 and 208Pb/206Pb ~ 2.106–2.118. These values pointed to a multi-source mixingbetween the less radiogenic sources, corresponding to the Pb ore deposits, and the more radiogenic sources identifiedin local background

Vertical export flux of metals in the Mediterranean Sea

We examined metal (Al, V, Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb) and particulate organic carbon (OC) concentrations of the marine vertical export flux at the DYFAMED time-series station in the Northwestern Mediterranean Sea. We present here the first data set of natural and anthropogenic metals from sediment trap moorings deployed at 1000 m-depth between 2003 and 2007 at the DYFAMED site. A highly significant correlation was observed between most metal concentrations, whatever the nature and emission source of the metal. Cu, Zn and Cd exhibit different behaviors, presumably due to their very high solubility and complexation with organic ligands. The observed difference of atmospheric and marine fluxes in terms of temporal variability and elemental concentration suggests that dense water convection and primary production and not atmospheric deposition control the marine vertical export flux. This argument is strengthened by the fact that significant Saharan dust events did not result in concomitant marine vertical export fluxes nor did they generate significant changes in metal concentrations of trapped particles

Sensitivity of the interannual variability of mineral aerosol simulations to meteorological forcing dataset

International audienceInterannual variability in desert dust is widely observed and simulated, yet the sensitivity of these desert dust simulations to a particular meteorological dataset, as well as a particular model construction, is not well known. Here we use version 4 of the Community Atmospheric Model (CAM4) with the Community Earth System Model (CESM) to simulate dust forced by three different reanalysis meteorological datasets for the period 1990–2005. We then contrast the results of these simulations with dust simulated using online winds dynamically generated from sea surface temperatures, as well as with simulations conducted using other modeling frameworks but the same meteorological forcings, in order to determine the sensitivity of climate model output to the specific reanalysis dataset used. For the seven cases considered in our study, the different model configurations are able to simulate the annual mean of the global dust cycle, seasonality and interannual variability approximately equally well (or poorly) at the limited observational sites available. Overall, aerosol dust-source strength has remained fairly constant during the time period from 1990 to 2005, although there is strong seasonal and some interannual variability simulated in the models and seen in the observations over this time period. Model interannual variability comparisons to observations, as well as comparisons between models, suggest that interannual variability in dust is still difficult to simulate accurately, with averaged correlation coefficients of 0.1 to 0.6. Because of the large variability, at least 1 year of observations at most sites are needed to correctly observe the mean, but in some regions, particularly the remote oceans of the Southern Hemisphere, where interannual variability may be larger than in the Northern Hemisphere, 2–3 years of data are likely to be needed

A history of mining activity in Celtic Aeduan territory, and its environmental impact (Morvan-France)

International audienc

Alternative dry separation of PM10 from soils for characterization by kinetic extraction: example of new Caledonian mining soils

A simple new device for dry separation of fine particulate matter from bulk soil samples is presented here. It consists of a stainless steel tube along which a nitrogen flow is imposed, resulting in the displacement of particles. Taking into account particle transport, fluid mechanics, and soil sample composition, a tube 6-m long, with a 0.04-m diameter, was found best adapted for PM10 separation. The device rapidly produced several milligrams of particulate matter, on which chemical extractions with EDTA were subsequently performed to study the kinetic parameters of extractable metals. New Caledonian mining soils were chosen here, as a case-study. Although the easily extracted metal pool represents only 0.5–6.4 % of the total metal content for the elements studied (Ni, Co, Mn), the total concentrations are extremely high. This pool is therefore far from negligible, and can be troublesome in the environment. This dry technique for fine particle separation from bulk parent soil eliminates the metal-leaching risks inherent in wet filtration and should therefore ensure safe assessment of environmental quality in fine-textured, metal-contaminated soils

Global distribution of atmospheric phosphorus sources, concentrations and deposition rates, and anthropogenic impacts

A worldwide compilation of atmospheric total phosphorus (TP) and phosphate (PO4) concentration and deposition flux observations are combined with transport model simulations to derive the global distribution of concentrations and deposition fluxes of TP and PO4. Our results suggest that mineral aerosols are the dominant source of TP on a global scale (82%), with primary biogenic particles (12%) and combustion sources (5%) important in nondusty regions. Globally averaged anthropogenic inputs are estimated to be ~5 and 15% for TP and PO4, respectively, and may contribute as much as 50% to the deposition over the oligotrophic ocean where productivity may be phosphorus-limited. There is a net loss of TP from many (but not all) land ecosystems and a net gain of TP by the oceans (560 Gg P a-1). More measurements of atmospheric TP and PO4 will assist in reducing uncertainties in our understanding of the role that atmospheric phosphorus may play in global biogeochemistry

Atmospheric Iron Deposition: Global Distribution, Variability, and Human Perturbations

Atmospheric inputs of iron to the open ocean are hypothesized to modulate ocean biogeochemistry. This review presents an integration of available observations of atmospheric iron and iron deposition, and also covers bioavailable iron distributions. Methods for estimating temporal variability in ocean deposition over the recent past are reviewed. Desert dust iron is estimated to represent 95% of the global atmospheric iron cycle, and combustion sources of iron are responsible for the remaining 5%. Humans may be significantly perturbing desert dust (up to 50%). The sources of bioavailable iron are less well understood than those of iron, partly because we do not know what speciation of the iron is bioavailable. Bioavailable iron can derive from atmospheric processing of relatively insoluble desert dust iron or from direct emissions of soluble iron from combustion sources. These results imply that humans could be substantially impacting iron and bioavailable iron deposition to ocean regions, but there are large uncertainties in our understanding

Anthropogenic Perturbations to the Atmospheric Molybdenum Cycle

International audienceMolybdenum (Mo) is a key cofactor in enzymes used for nitrogen (N) fixation and nitrate reduction, and the low availability of Mo can constrain N inputs, affecting ecosystem productivity. Natural atmospheric Mo aerosolization and deposition from sources such as desert dust, sea salt spray, and volcanoes can affect ecosystem function across long timescales, but anthropogenic activities such as combustion, motor vehicles, and agricultural dust have accelerated the natural Mo cycle. Here we combined a synthesis of global atmospheric concentration observations and modeling to identify and estimate anthropogenic sources of atmospheric Mo. To project the impact of atmospheric Mo on terrestrial ecosystems, we synthesized soil Mo data and estimated the global distribution of soil Mo using two approaches to calculate turnover times. We estimated global emissions of atmospheric Mo in aerosols (-1, with 40%-75% from anthropogenic sources. We approximated that for the top meter of soil, Mo turnover times range between 1,000 and 1,000,000 years. In some industrialized regions, anthropogenic inputs have enhanced Mo deposition 100 fold, lowering the soil Mo turnover time considerably. Our synthesis of global observational data, modeling, and a mass balance comparison with riverine Mo exports suggest that anthropogenic activity has greatly accelerated the Mo cycle, with potential to influence N limited ecosystems