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Bonsignore, Maria
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Bonsignore, Maria
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- 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 - PublicationOpen AccessDegassing and Cycling of Mercury at Nisyros Volcano (Greece)(2019-07)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Nisyros Island (Greece) is an active volcano hosting a high-enthalpy geothermal system. During June 2013, an extensive survey on Hg concentrations in different matrices (fumarolic fluids, atmosphere, soils and plants) was carried out at Lakki Plain, an intra-caldera area affected by widespread soil and fumarolic degassing. Concentrations of gaseous elemental mercury (GEM), H2S and CO2, were simultaneously measured in both the fumarolic emissions and the atmosphere around them. At the same time, 130 samples of top soils and 31 samples of plants (Cistus Creticus and Salvifolius and Erica Arborea and Manipuliflora) were collected for Hg analysis. Mercury concentrations in fumarolic gases ranged from 10,500 to 46,300 ng/m3, while Hg concentrations in the air ranged from high background values in the Lakki Plain caldera (10-36 ng/m3) up to 7100 ng/m3 in the fumarolic areas. Outside the caldera, the concentrations were relatively low (2-5 ng/m3). The positive correlation with both CO2 and H2S in air highlighted the importance of hydrothermal gases as carrier for GEM. On the other hand, soil Hg concentrations (0.023-13.7 µg/g) showed no significant correlations with CO2 and H2S in the soil gases, whereas it showed a positive correlation with total S content and an inverse one with the soil-pH, evidencing the complexity of the processes involving Hg carried by hydrothermal gases while passing through the soil. Total Hg concentrations in plant leaves (0.010-0.112 μg/g) had no direct correlation with soil Hg, with Cistus leaves containing higher values of Hg respect to Erica. Even though GEM concentrations in air within the caldera are sometimes orders of magnitude above the global background, they should not be considered dangerous to human health. Values exceeding the WHO guideline value of 1000 ng/m3 are very rare (<0.1%) and only found very close to the main fumarolic vents, where the access to tourists is prohibited.572 45