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Oliveri, Elvira
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- PublicationOpen AccessHydrochemical mercury distribution and air-sea exchange over the submarine hydrothermal vents off-shore Panarea Island (Aeolian arc, Tyrrhenian Sea)(2017-05-27)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; There is a growing concern about the mercury (Hg) vented from submarine hydrothermal fluids to the marine surrounding and exchange of dissolved gaseous mercury (DGM) between the sea surface and the atmosphere. A geochemical survey of thermal waters collected from submarine vents at Panarea Island (Aeolian Islands, southern Italy) was carried out in 2015 (15–17th June and 17–18th November), in order to investigate the concentration of Hg species in hydrothermal fluids and the vertical distribution in the overlying water column close to the submarine exhalative area. Specific sampling methods were employed by Scuba divers at five submarine vents located along the main regional tectonic lines. The analysis of the hydrothermal fluids indicates a site-to-site variation, with filtered total mercury (FTHg) concentrations ranging from 1072 to 4711 pM, as a consequence of the gas bubbles partial dissolution. These results are three orders of magnitude higher than the FTHg concentrations found in the overlying seawater column (ranging from 5.3 to 6.3 pM in the mid waters), where the efficient currents and vertical mixing result in more dilution, and potentially rapid transfer of the dissolved gaseous Hg to the atmosphere. Dissolved gaseous mercury (DGM) and gaseous elemental mercury (GEM) were simultaneously measured and combined in a gas-exchange model to calculate the sea-air Hg0 evasional flux. Based on the data of DGM (range: 0.05–0.22 pM) and atmospheric GEM (range: 1.7 ± 0.35–6.4 ± 2.6 ng m−3), we argue that the surface seawater off Panarea is mostly supersaturated in dissolved elemental gaseous mercury compared to the atmosphere, with a sea-air Hg0 net flux ranging from 0.7 to 9.1 ng m−2 h−1 (average: ~4.5 ± 3.5 ng m−2 h−1). Since the empirical gas-exchange model does not include the contribution of Hg0 released as gas bubbles rising from the vents toward sea-surface, the calculated Hg0 evasional flux for this location is most likely larger.372 55 - PublicationOpen AccessSedimentological analysis of marine deposits off the Bagnoli-Coroglio Site of National Interest (SNI), Pozzuoli (Napoli) Bay(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; We present the results of a sedimentological and mineralogical study conducted on 305 marine sediment samples (32 seafloor grab samples and 273 subsea floor samples from 91 vibrocores) collected in the marine area of the eastern Pozzuoli Bay, offshore the area of Bagnoli, that has been the site of heavy industrial activity for more than a century. The coastal (onland-offshore) area of Bagnoli–Coroglio has been recognised as a contaminated Site of National Interest (SNI) by the Italian Ministry of the Environment (2000–2001) and since then it has been the subject of a series of environmental studies that have documented a severe contamination of soils onland and marine sediments offshore. Based on the outcomes of the sedimentological classification discussed in this study we have constructed a series of thematic maps illustrating the areal distribution of the sedimentary facies at different stratigraphic levels. Our interpretation provides a support in reconstructing the complex set of environmental changes that have affected the offshore of the eastern Pozzuoli Bay prior to and after the termination of the industrial activity of the Bagnoli brownfield.82 39 - PublicationRestrictedThe sea-air exchange of mercury (Hg) in the marine boundary layer of the Augusta basin (southern Italy): concentrations and evasion flux(2013-11)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;The first attempt to systematically investigate the atmospheric mercury (Hg) in the MBL of the Augusta basin (SE Sicily, Italy) has been undertaken. In the past the basin was the receptor for Hg from an intense industrial activity which contaminated the bottom sediments of the Bay, making this area a potential source of pollution for the surrounding Mediterranean. Three oceanographic cruises have been thus performed in the basin during the winter and summer 2011/2012, where we estimated averaged Hgatm concentrations of about 1.5±0.4 (range 0.9-3.1) and 2.1±0.98 (range 1.1-3.1) ng m(-3) for the two seasons, respectively. These data are somewhat higher than the background Hg atm value measured over the land (range 1.1±0.3 ng m(-3)) at downtown Augusta, while are similar to those detected in other polluted regions elsewhere. Hg evasion fluxes estimated at the sea/air interface over the Bay range from 3.6±0.3 (unpolluted site) to 72±0.1 (polluted site of the basin) ng m(-2) h(-1). By extending these measurements to the entire area of the Augusta basin (~23.5 km(2)), we calculated a total sea-air Hg evasion flux of about 9.7±0.1 g d(-1) (~0.004 tyr(-1)), accounting for ~0.0002% of the global Hg oceanic evasion (2000 tyr(-1)). The new proposed data set offers a unique and original study on the potential outflow of Hg from the sea-air interface at the basin, and it represents an important step for a better comprehension of the processes occurring in the marine biogeochemical cycle of this element.24 1 - PublicationRestrictedMobility of mercury in contaminated marine sediments: Biogeochemical pathways(2016)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;The availability of dissolved inorganic mercury(DHg) in sediment pore water is a crucial step for the mechanisms of methylmercury (MeHg) generation in the aquatic system. The geochemical form of Hg in sediments and the redox-controlled microbial reactions taking place during early diagenesis regulate the pool of DHg and, consequently, the bioavailability of Hg for methylation. Here, we report new evidence on the biogeochemical mechanisms controlling the pool of DHg in sediment pore water from two box-cores collected from Augusta Bay (Sicily), a marine coastal zone heavily contaminated by chlor-alkali discharges. The content of the total Hg(THg) in the studied sediments (4.13÷22.2mgKg−1) is largely present as an “immobile” phase, while the labile fractions account for minor percentages (2%). Despite the predominance of Hg “immobile” forms, depth profiles of the pore water suggest relevant DHg production (up to 226 ng L−1) mainly in the deeper levels of the inves tigated sedimentary column. Specifically, most of the THg appearstobepartially mobilized inthe “Fe-Mn reduction” zone, as clearly suggested by significant correlations between DHg and dissolved Fe-Mn concentrations in the porewater.The irregular vertical distribution of SO4 2−, with evident enrichment in theFe-Mn reduction zone, could also indicate mechanisms of sulphate generation by sulphide oxidation. Specific microbial populations identified in the sediments appear dominated by chemolithoautotrophic sulphur oxidizing bacteria (SOB,genera Sulfurovum and Thioalkalispira) which could drive the microbial oxidation of sulphides and support, with effects of Mn-Fe oxide reduction, processes of Hg mobilization.30 1 - PublicationRestrictedDirect determination of total mercury in phosphate rock using alkaline fusion digestion(2014-12-10)
; ; ; ; ; ; ; ; ; ; ;The aim of this work was to develop a new method to determine the mercury (Hg) concentrations in phosphate rock using a dedicated analytical instrument (the DMA80 Tricell by Milestone) that employs an integrated sequence of thermal decomposition followed by catalyst conversion, amalgamation and atomic absorption spectrophotometry. However, this instrument underestimates Hg concentrations when phosphorite and apatite rocks are investigated with a classic thermal decomposition treatment that complies with US EPA method 7473. Therefore, to improve the recovery of total Hg, we performed alkaline fusion digestion (AFD) directly inside the furnace of the instrument, using BCR(32) as a certified reference material (Moroccan phosphate rock--phosphorite). The salts used for the AFD were a mixture of Na2CO3, K2CO3 and Li2CO3, which melt at about 400°C, due to their ability to form a ternary eutectic and to decompose the phosphorite matrices at 700°C. By adopting this analytical approach, the Hg recovery in BCR(32) was about 100%, compared to 40% when the reference material was analysed without using the alkaline fusion salt. We suggest that the AFD allowed the decomposition of the sample matrix and that some Hg compounds linked with other functional groups may be transformed in carbonates that sublimate at lower temperatures than other Hg compounds. This original method was tested on a number of different geological samples to compare the differences between the AFD method and the thermal treatment in order to verify the working range and to check the robustness of the new approach.25 1 - PublicationRestrictedFirst simultaneous mercury and major volatiles characterization of atmospheric hydrothermal emissions at the Pisciarelli's fumarolic system (Campi Flegrei, Italy)(2020-10-12)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Hydrothermal systems with active surface expressions are important natural source of atmospheric mercury. Here we report on the first simultaneous assessment of gaseous elemental mercury (GEM) and major volatiles (H2S and CO2) fluxes from the fumarolic system of Pisciarelli, currently the most active at the Campi Flegrei caldera (CFc), Naples (Italy). Thiswas achieved via a GPS-synchronized Lumex and MultiGAS surveywhich extends similar investigations reported elsewhere. GEM concentrations measured in the fumarolic emissions were consistently above background air level close to the degassing area (mean ~ 8 ± 3 ng m−3 on average) and ranged up to 12,000 ng m−3. Our data evidenced pulsed sequences of GEM increases in the fumarole plume, closely matched by temporally consistent increases in CO2 and H2S (r2 =0.9), supporting the idea that major volatiles, such as CO2 acts as potential carrier in transporting GEM within the magmatic/hydrothermal systems. The slope of the best fit calculated for the dispersion of our data provides a GEM/CO2 molar ratio of 1.1 × 10−8 and a GEM/H2S of5×10−6, respectively. These ratios are comparable to those reported for both low(~ 100 °C) and high-T (~250 °C) fumaroles from non-explosive volcanic/hydrothermal degassing systems elsewhere. We adopted an adhoc method that combines video footages and gas measurements to obtain high precision concentration maps of gas emissions used to estimate the total atmospheric GEM, CO2 and H2S flux of about 0.0113, 225059 and 511 t y−1, respectively. The human health risk assessment related to the GEM emissions at Pisciarelli, confirms that, except for the degassing fumarolic area, all the main sites affected by the plume dispersion, always remain well below the safe threshold recommended by the health authorities.797 3