scholarly journals A theoretical study of abiotic methylation reactions of gaseous elemental mercury by halogen containing molecules

2010 ◽  
Vol 10 (9) ◽  
pp. 22369-22394 ◽  
Author(s):  
L. Castro ◽  
A. Dommergue ◽  
C. Larose ◽  
C. Ferrari ◽  
L. Maron
Keyword(s):  
Experimental Data ◽  
Reaction Rate ◽  
Theoretical Study ◽  
Elemental Mercury ◽  
Thermal Reaction ◽  
Visible Range ◽  
Electronic Data ◽  
Subsequent Formation ◽  
Gaseous Elemental Mercury ◽  
Methyl Transfer

Abstract. Methylation reactions of gaseous elementary mercury by halogen containing molecules such as halogenomethane species CH3X (with X=Cl, Br and I) and the dimethylchlorinium ion CH3ClCH3+ were investigated at the DFT level. With CH3X, the reaction is predicted to be almost athermic and kinetically demanding for a thermal reaction. The reaction can proceed photochemically in the visible range; therefore sunlight may increase the reaction rate. These results compare well with the experimental data. Consecutive methylation of the CH3HgX products (with X=Cl, Br and I) and subsequent formation of CH3HgCH3 were also studied. These reactions are predicted to be kinetically inaccessible and thermodynamically unfavorable. With CH3ClCH3+, the reaction is predicted to be athermic but kinetically easy. This is due to the suitability of the methyl transfer reagent. Geometrical and electronic data were systematically analyzed in order to rationalize the results.

A Theoretical Study of Abiotic Methylation Reactions of Gaseous Elemental Mercury by Halogen-Containing Molecules

2011 ◽  
Vol 115 (22) ◽  
pp. 5602-5608 ◽  
Author(s):  
Ludovic Castro ◽  
Aurélien Dommergue ◽  
Catherine Larose ◽  
Christophe Ferrari ◽  
Laurent Maron
Keyword(s):  
Theoretical Study ◽  
Elemental Mercury ◽  
Gaseous Elemental Mercury

scholarly journals Air Concentrations of Gaseous Elemental Mercury and Vegetation–Air Fluxes within Saltmarshes of the Tagus Estuary, Portugal

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 228
Author(s):  
Rute Cesário ◽  
Nelson J. O’Driscoll ◽  
Sara Justino ◽  
Claire E. Wilson ◽  
Carlos E. Monteiro ◽  
...  
Keyword(s):  
Leaf Area ◽  
Elemental Mercury ◽  
Ambient Air ◽  
Tagus Estuary ◽  
Contaminated Site ◽  
Gaseous Elemental Mercury ◽  
Mercury Flux ◽  
Sarcocornia Fruticosa ◽  
Air Concentrations

In situ air concentrations of gaseous elemental mercury (Hg(0)) and vegetation–atmosphere fluxes were quantified in both high (Cala Norte, CN) and low-to-moderate (Alcochete, ALC) Hg-contaminated saltmarsh areas of the Tagus estuary colonized by plant species Halimione portulacoides (Hp) and Sarcocornia fruticosa (Sf). Atmospheric Hg(0) ranged between 1.08–18.15 ng m−3 in CN and 1.18–3.53 ng m−3 in ALC. In CN, most of the high Hg(0) levels occurred during nighttime, while the opposite was observed at ALC, suggesting that photoreduction was not driving the air Hg(0) concentrations at the contaminated site. Vegetation–air Hg(0) fluxes were low in ALC and ranged from −0.76 to 1.52 ng m−2 (leaf area) h−1 for Hp and from −0.40 to 1.28 ng m−2 (leaf area) h−1 for Sf. In CN, higher Hg fluxes were observed for both plants, ranging from −9.90 to 15.45 ng m−2 (leaf area) h−1 for Hp and from −8.93 to 12.58 ng m−2 (leaf area) h−1 for Sf. Mercury flux results at CN were considered less reliable due to large and fast variations in the ambient air concentrations of Hg(0), which may have been influenced by emissions from the nearby chlor-alkali plant, or historical contamination. Improved experimental setup, the influence of high local Hg concentrations and the seasonal activity of the plants must be considered when assessing vegetation–air Hg(0) fluxes in Hg-contaminated areas.

scholarly journals An Integrated Investigation of Atmospheric Gaseous Elemental Mercury Transport and Dispersion Around a Chlor-Alkali Plant in the Ossola Valley (Italian Central Alps)

Toxics ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 172
Author(s):  
Laura Fantozzi ◽  
Nicoletta Guerrieri ◽  
Giovanni Manca ◽  
Arianna Orrù ◽  
Laura Marziali
Keyword(s):  
Elemental Mercury ◽  
Background Concentration ◽  
Dispersion Pattern ◽  
Central Alps ◽  
Gaseous Elemental Mercury ◽  
Mercury Transport ◽  
Close Proximity ◽  
Potential Impact ◽  
Hg Accumulation

We present the first assessment of atmospheric pollution by mercury (Hg) in an industrialized area located in the Ossola Valley (Italian Central Alps), in close proximity to the Toce River. The study area suffers from a level of Hg contamination due to a Hg cell chlor-alkali plant operating from 1915 to the end of 2017. We measured gaseous elemental Hg (GEM) levels by means of a portable Hg analyzer during car surveys between autumn 2018 and summer 2020. Moreover, we assessed the long-term dispersion pattern of atmospheric Hg by analyzing the total Hg concentration in samples of lichens collected in the Ossola Valley. High values of GEM concentrations (1112 ng m−3) up to three orders of magnitude higher than the typical terrestrial background concentration in the northern hemisphere were measured in the proximity of the chlor-alkali plant. Hg concentrations in lichens ranged from 142 ng g−1 at sampling sites located north of the chlor-alkali plant to 624 ng g−1 in lichens collected south of the chlor-alkali plant. A north-south gradient of Hg accumulation in lichens along the Ossola Valley channel was observed, highlighting that the area located south of the chlor-alkali plant is more exposed to the dispersion of Hg emitted into the atmosphere from the industrial site. Long-term studies on Hg emission and dispersion in the Ossola Valley are needed to better assess potential impact on ecosystems and human health.

scholarly journals Occurrence of Volcanogenic Inorganic Mercury in Wild Mice Spinal Cord: Potential Health Implications

2021 ◽  
Author(s):  
A. Navarro-Sempere ◽  
M. García ◽  
A. S. Rodrigues ◽  
P. V. Garcia ◽  
R. Camarinho ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Inorganic Mercury ◽  
Elemental Mercury ◽  
Potential Health ◽  
Wild Mice ◽  
Gaseous Elemental Mercury ◽  
Lumbar Level ◽  
Quantification Analysis ◽  
Spinal Cord Potential ◽  
Cord Potential

AbstractMercury accumulation has been proposed as a toxic factor that causes neurodegenerative diseases. However, the hazardous health effects of gaseous elemental mercury exposure on the spinal cord in volcanic areas have not been reported previously in the literature. To evaluate the presence of volcanogenic inorganic mercury in the spinal cord, a study was carried out in São Miguel island (Azores, Portugal) by comparing the spinal cord of mice exposed chronically to an active volcanic environment (Furnas village) with individuals not exposed (Rabo de Peixe village), through the autometallographic silver enhancement histochemical method. Moreover, a morphometric and quantification analysis of the axons was carried out. Results exhibited mercury deposits at the lumbar level of the spinal cord in the specimens captured at the site with volcanic activity (Furnas village). A decrease in axon calibre and axonal atrophy was also observed in these specimens. Given that these are relevant hallmarks in the neurodegenerative pathologies, our results highlight the importance of the surveillance of the health of populations chronically exposed to active volcanic environments.

Explanation of the Influence of Inflow Air Content on the Lift of Cavitating Hydrofoils

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Eduard Amromin
Keyword(s):  
Experimental Data ◽  
Theoretical Study ◽  
Lift Coefficient ◽  
Cavity Surface ◽  
Air Bubbles ◽  
Incoming Flow ◽  
Fluid Density ◽  
Air Content ◽  
Theoretical Results ◽  
Good Agreement

According to several known experiments, an increase of the incoming flow air content can increase the hydrofoil lift coefficient. The presented theoretical study shows that such increase is associated with the decrease of the fluid density at the cavity surface. This decrease is caused by entrainment of air bubbles to the cavity from the surrounding flow. The theoretical results based on such explanation are in a good agreement with the earlier published experimental data for NACA0015.

scholarly journals Simulation of atmospheric mercury depletion events (AMDEs) during polar springtime using the MECCA box model

2008 ◽  
Vol 8 (23) ◽  
pp. 7165-7180 ◽  
Author(s):  
Z.-Q. Xie ◽  
R. Sander ◽  
U. Pöschl ◽  
F. Slemr
Keyword(s):  
Aqueous Phase ◽  
Ozone Depletion ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Box Model ◽  
Rate Coefficients ◽  
Mercury Species ◽  
Phase Reaction ◽  
Gaseous Elemental Mercury ◽  
Sea Salt Aerosol

Abstract. Atmospheric mercury depletion events (AMDEs) during polar springtime are closely correlated with bromine-catalyzed tropospheric ozone depletion events (ODEs). To study gas- and aqueous-phase reaction kinetics and speciation of mercury during AMDEs, we have included mercury chemistry into the box model MECCA (Module Efficiently Calculating the Chemistry of the Atmosphere), which enables dynamic simulation of bromine activation and ODEs. We found that the reaction of Hg with Br atoms dominates the loss of gaseous elemental mercury (GEM). To explain the experimentally observed synchronous depletion of GEM and O3, the reaction rate of Hg+BrO has to be much lower than that of Hg+Br. The synchronicity is best reproduced with rate coefficients at the lower limit of the literature values for both reactions, i.e. kHg+Br≈3×10−13 and kHg+BrO≤1×10−15 cm3 molecule−1 s−1, respectively. Throughout the simulated AMDEs, BrHgOBr was the most abundant reactive mercury species, both in the gas phase and in the aqueous phase. The aqueous-phase concentrations of BrHgOBr, HgBr2, and HgCl2 were several orders of magnitude larger than that of Hg(SO3)22−. Considering chlorine chemistry outside depletion events (i.e. without bromine activation), the concentration of total divalent mercury in sea-salt aerosol particles (mostly HgCl42−) was much higher than in dilute aqueous droplets (mostly Hg(SO3)22−), and did not exhibit a diurnal cycle (no correlation with HO2 radicals).

Residual Stress Measurement and Simulation of 3C-SiC Single and Poly Crystal Cantilevers

2010 ◽  
Vol 645-648 ◽  
pp. 865-868 ◽  
Author(s):  
Ruggero Anzalone ◽  
Massimo Camarda ◽  
Daniel Alquier ◽  
M. Italia ◽  
Andrea Severino ◽  
...  
Keyword(s):  
Experimental Data ◽  
Theoretical Study ◽  
Stress Measurement ◽  
Bulk Material ◽  
Raman Shift ◽  
Silicon Substrates ◽  
Free Standing ◽  
Element Analysis ◽  
Micro Fabrication ◽  
Sic Films

The fabrication of SiC MEMS-based sensors requires new processes able to realize microstructures on either bulk material or on the SiC surface. The hetero-epitaxial growth of 3C-SiC on silicon substrates allows one to overcome the traditional limitations of SiC micro-fabrication. In this work a comparison between single crystal and poly crystal 3C-SiC micro-machined structures will be presented. The free-standing structures realized (cantilevers and membrane) are also a suitable method for residual field stress investigation in 3C-SiC films. Measurement of the Raman shift indicates that the mono and poly-crystal 3C-SiC structures release the stress in different ways. Finite element analysis was performed to determine the stress field inside the films and provided a good fit to the experimental data. A comprehensive experimental and theoretical study of 3C-SiC MEMS structures has been performed and is presented.

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