Atmospheric mercury concentrations observed at ground-based monitoring sites globally distributed in the framework of the GMOS network

Long-term monitoring of data of ambient mercury (Hg) on a global scale to assess its emission, transport, atmospheric chemistry, and deposition processes is vital to understanding the impact of Hg pollution on the environment. The Global Mercury Observation System (GMOS) project was funded by the European Commission (http://www.gmos.eu) and started in November 2010 with the overall goal to develop a coordinated global observing system to monitor Hg on a global scale, including a large network of ground-based monitoring stations, ad hoc periodic oceanographic cruises and measurement flights in the lower and upper troposphere as well as in the lower stratosphere. To date, more than 40 ground-based monitoring sites constitute the global network covering many regions where little to no observational data were available before GMOS. This work presents atmospheric Hg concentrations recorded worldwide in the framework of the GMOS project (2010–2015), analyzing Hg measurement results in terms of temporal trends, seasonality and comparability within the network. Major findings highlighted in this paper include a clear gradient of Hg concentrations between the Northern and Southern hemispheres, confirming that the gradient observed is mostly driven by local and regional sources, which can be anthropogenic, natural or a combination of both.

Mercury contamination in fanned fish setup on former garimpo mining areas in the Northern Mato Grosso State, Amazonian region, Brazil

The garimpo gold mining activity has released about 2.500 tons of mercury in the Brazilian Amazonian environment in the 1980-1995 period. The northern region of Mato Grosso State, an important gold mining and trading area during the Arnazonian gold rush is now at a turning point regarding its economic future. Nowadays, the activities related to gold mining have only a low relevance on its economy. Thus, the local communities are looking for economic alternatives for the development of the region. Cooperative fish farming is one of such alternatives. However, some projects are directly implemented on areas degraded by the former garimpo activity and the mercury left behind still poses risks, especially by its potential accumulation in fish. The objective of the present study was to evaluate the levels of mercury contamination in two fish farming areas, Paranaita and Alta Floresta, with and without records of past gold-washing activity, respectively. Data such as mercury concentration in fish of different trophic level, size, and weight as well as the water physical and chemical parameters were measured and considered. These preliminary data have shown no significant difference between these two fish fanning areas, relatively to mercury levels in fish. (c) 2004 Elsevier B.V. All rights reserved.

Selenite and Selenate Effects on Mercury (Hg2+) Uptake and Distribution in Tilapia, Oreochromis niloticus L., Assessed by Chronic Bioassay

Aquatic organisms are considered excellent biomarkers of mercury (Hg) occurrence in the environment. Selenium (Se) acts in antagonism to this metal, stimulating its elimination, and reducing its toxicity. In this paper, tilapia (Oreochromis niloticus) were chronically acclimated in sub-lethal Hg2+, Hg2+ + Se4+ and Hg2+ + Se6+ concentrations. Distribution and bioaccumulation of both elements were evaluated in fish tissues. The kidney was the main target of the Hg and Se uptake, and the presence of Hg induced the Se hepatic elimination. The Hg bioaccumulation in the gill, spleen and heart were higher in the presence of Se6+ than in the presence of Se4+.

Mercury in Gas Operations - Occupational Health Risk Assessment

The project goal was to determine plant operations and maintenance worker’s level of exposure to mercury during routine and non-routine (i.e. turnarounds and inspections) maintenance events in eight gas processing plants. The project team prepared sampling and analysis plans designed to each plant’s process design and scheduled maintenance events. Occupational exposure sampling and monitoring efforts were focused on the measurement of mercury vapor concentration in worker breathing zone air during specific maintenance events including: pipe scrapping, process filter replacement, and process vessel inspection. Similar exposure groups were identified and worker breathing zone and ambient air samples were collected and analyzed for total mercury. Occupational exposure measurement techniques included portable field monitoring instruments, standard passive and active monitoring methods and an emerging passive absorption technology. Process sampling campaigns were focused on inlet gas streams, mercury removal unit outlets, treated gas, acid gas and sales gas. The results were used to identify process areas with increased potential for mercury exposure during maintenance events. Sampling methods used for the determination of total mercury in gas phase streams were based on the USEPA Methods 30B and EPA 1631 and EPA 1669. The results of four six-week long sampling campaigns have been evaluated and some conclusions and recommendations have been made. The author’s role in this project included the direction of all field phases of the project and the development and implementation of the sampling strategy. Additionally, the author participated in the development and implementation of the Quality Assurance Project Plan, Data Quality Objectives, and Similar Exposure Groups identification. All field generated data was reviewed by the author along with laboratory reports in order to generate conclusions and recommendations.

Selective Mercury Sequestration from a Silver/Mercury Cyanide Solution

Silver and mercury are both dissolved in cyanide leaching and the mercury co-precipitates with silver during metal recovery. Mercury must then be removed from the silver/mercury amalgam by vaporizing the mercury in a retort, leading to environmental and health hazards. The need for retorting silver can be greatly reduced if mercury is selectively removed from leaching solutions. Theoretical calculations were carried out based on the thermodynamics of the Ag/Hg/CN- system in order to determine possible approaches to either preventing mercury dissolution, or selectively precipitating it without silver loss. Preliminary experiments were then carried out based on these calculations to determine if the reaction would be spontaneous with reasonably fast kinetics. In an attempt to stop mercury from dissolving and leaching the heap leach, the first set of experiments were to determine if selenium and mercury would form a mercury selenide under leaching conditions, lowering the amount of mercury in solution while forming a stable compound. From the results of the synthetic ore experiments with selenium, it was determined that another effect was already suppressing mercury dissolution and the effect of the selenium could not be well analyzed on the small amount of change. The effect dominating the reactions led to the second set of experiments in using silver sulfide as a selective precipitant of mercury. The next experiments were to determine if adding solutions containing mercury cyanide to un-leached silver sulfide would facilitate a precipitation reaction, putting silver in solution and precipitating mercury as mercury sulfide. Counter current flow experiments using the high selenium ore showed a 99.8% removal of mercury from solution. As compared to leaching with only cyanide, about 60% of the silver was removed per pass for the high selenium ore, and around 90% for the high mercury ore. Since silver sulfide is rather expensive to use solely as a mercury precipitant, another compound was sought which could selectively precipitate mercury and leave silver in solution. In looking for a more inexpensive selective precipitant, zinc sulfide was tested. The third set of experiments did show that zinc sulfide (as sphalerite) could be used to selectively precipitate mercury while leaving silver cyanide in solution. Parameters such as particle size, reduction potential, and amount of oxidation of the sphalerite were tested. Batch experiments worked well, showing 99.8% mercury removal with only ≈1% silver loss (starting with 930 ppb mercury, 300 ppb silver) at one hour. A continual flow process would work better for industrial applications, which was demonstrated with the filter funnel set up. Funnels with filter paper and sphalerite tested showed good mercury removal (from 31 ppb mercury and 333 ppb silver with a 87% mercury removal and 7% silver loss through one funnel). A counter current flow set up showed 100% mercury removal and under 0.1% silver loss starting with 704 ppb silver and 922 ppb mercury. The resulting sphalerite coated with mercury sulfide was also shown to be stable (not releasing mercury) under leaching tests. Use of sphalerite could be easily implemented through such means as sphalerite impregnated filter paper placed in currently existing processes. In summary, this work focuses on preventing mercury from following silver through the leaching circuit. Currently the only possible means of removing mercury is by retort, creating possible health hazards in the distillation process and in transportation and storage of the final mercury waste product. Preventing mercury from following silver in the earlier stages of the leaching process will greatly reduce the risk of mercury spills, human exposure to mercury, and possible environmental disasters. This will save mining companies millions of dollars from mercury handling and storage, projects to clean up spilled mercury, and will result in better health for those living near and working in the mines.

A preliminary characterization of mercury uptake by the sulfate-reducing bacteria Desulfovibrio desulfuricans

The focus of this research is to determine if a relationship exists between the stability constant and the initial uptake rate of a mercury species by bacteria. Cultures of the sulfate-reducing bacteria (SRB) strain Desulfovibrio desulfuricans G20 were washed with a bicarbonate buffer solution containing either lactate and sulfate or pyruvate and fumarate. The washed cell solutions were then spiked with either mercury bound to natural organic matter (Hg-NOM) or neutral mercury chloride (HgCl2), followed by sampling over time to provide kinetic data. Despite the significantly different stability constants for Hg-NOM and HgCl2, the calculated initial rate constants for mercury uptake for these two types of complexes appeared to be comparable. Uptake of mercury sulfide species was inconclusive due to possible formation of cinnabar. A simple model that is based on assumptions of passive diffusion and facilitated uptake of mercury by bacteria was evaluated for its potential to simulate the uptake. The model results only agreed with experimental data for HgCl2 uptake.

Integration of a Sedimentation Module to a Hydrologic Model and its Application to a Mercury TMDL Analysis

This research is part of continued efforts to correlate the hydrology of East Fork Poplar Creek (EFPC) and Bear Creek (BC) with the long term distribution of mercury within the overland, subsurface, and river sub-domains. The main objective of this study was to add a sedimentation module (ECO Lab) capable of simulating the reactive transport mercury exchange mechanisms within sediments and porewater throughout the watershed. The enhanced model was then applied to a Total Maximum Daily Load (TMDL) mercury analysis for EFPC. That application used historical precipitation, groundwater levels, river discharges, and mercury concentrations data that were retrieved from government databases and input to the model. The model was executed to reduce computational time, predict flow discharges, total mercury concentration, flow duration and mercury mass rate curves at key monitoring stations under various hydrological and environmental conditions and scenarios. The computational results provided insight on the relationship between discharges and mercury mass rate curves at various stations throughout EFPC, which is important to best understand and support the management mercury contamination and remediation efforts within EFPC.

Barn owl feathers as biomonitors of mercury: sources of variation

Given their central role in mercury (Hg) excretion and suitability as reservoirs, bird feathers are useful Hg biomonitors. Nevertheless, the interpretation of Hg concentrations is still questioned as a result of a poor knowledge of feather physiology and mechanisms affecting Hg deposition. Given the constraints of feather availability to ecotoxicological studies, we tested the effect of intraindividual differences in Hg concentrations according to feather type (body vs. flight feathers), position in the wing and size (mass and length) in order to understand how these factors could affect Hg estimates. We measured Hg concentration of 154 feathers from 28 un-moulted barn owls (Tyto alba), collected dead on roadsides. Median Hg concentration was 0.45 (0.076–4.5) mg kg-1 in body feathers, 0.44 (0.040–4.9) mg kg-1 in primary and 0.60 (0.042–4.7) mg kg-1 in secondary feathers, and we found a poor effect of feather type on intra-individual Hg levels. We also found a negative effect of wing feather mass on Hg concentration but not of feather length and of its position in the wing. We hypothesize that differences in feather growth rate may be the main driver of between-feather differences in Hg concentrations, which can have implications in the interpretation of Hg concentrations in feathers. Finally, we recommend that, whenever possible, several feathers from the same individual should be analysed. The five innermost primaries have lowest mean deviations to both betweenfeather and intra-individual mean Hg concentration and thus should be selected under restrictive sampling scenarios.

Yellowing And Bleaching Of Grey Hair Caused By Photo And Thermal Degradation.

Yellowing is an undesirable phenomenon that is common in people with white and grey hair. Because white hair has no melanin, the pigment responsible for hair colour, the effects of photodegradation are more visible in this type of hair. The origin of yellowing and its relation to photodegradation processes are not properly established, and many questions remain open in this field. In this work, the photodegradation of grey hair was investigated as a function of the wavelength of incident radiation, and its ultrastructure was determined, always comparing the results obtained for the white and black fibres present in grey hair with the results of white wool. The results presented herein indicate that the photobehaviour of grey hair irradiated with a mercury lamp or with solar radiation is dependent on the wavelength range of the incident radiation and on the initial shade of yellow in the sample. Two types of grey hair were used: (1) blended grey hair (more yellow) and (2) grey hair from a single-donor (less yellow). After exposure to a full-spectrum mercury lamp for 200 h, the blended white hair turned less yellow (the yellow-blue difference, Db(*) becomes negative, Db(*)=-6), whereas the white hair from the single-donor turned slightly yellower (Db(*)=2). In contrast, VIS+IR irradiation resulted in bleaching in both types of hair, whereas a thermal treatment (at 81 °C) caused yellowing of both types of hair, resulting in a Db(*)=3 for blended white hair and Db(*)=9 for single-donor hair. The identity of the yellow chromophores was investigated by UV-Vis spectroscopy. The results obtained with this technique were contradictory, however, and it was not possible to obtain a simple correlation between the sample shade of yellow and the absorption spectra. In addition, the results are discussed in terms of the morphology differences between the pigmented and non-pigmented parts of grey hair, the yellowing and bleaching effects of grey hair, and the occurrence of dark-follow reactions.

Quantificação de fluxos de mercúrio gasoso na interface solo/atmosfera utilizando câmara de fluxo dinâmica: aplicação na bacia do Rio Negro

Gaseous mercury sampling conditions were optimized and a dynamic flux chamber was used to measure the air/surface exchange of mercury in some areas of the Negro river basin with different vegetal coverings. At the two forest sites (flooding and non-flooding), low mercury fluxes were observed: maximum of 3 pmol m-2 h-1 - day and minimum of -1 pmol m-2 h-1 - night. At the deforested site, the mercury fluxes were higher and always positive: maximum of 26 pmol m-2 h-1 - day and 17 pmol m-2 h-1 - night. Our results showed that deforestation could be responsible for significantly increasing soil Hg emissions, mainly because of the high soil temperatures reached at deforested sites.

Variabilidade espacial e sazonal da concentração de elementos-traço em sedimentos do sistema estuarino de Santos-Cubatão (SP)

Multi-element analyses of sediment samples from the Santos-Cubatão Estuarine System were carried out to investigate the spatial and seasonal variability of trace-element concentrations. The study area contains a rich mangrove ecosystem that is a habitat for tens of thousands of resident and migratory birds, some of them endangered globally. Enrichments of metals in fine-grained surface sediments are, in decreasing order, Hg, Mn, La, Ca, Sr, Cd, Zn, Pb, Ba, Cu, Cr, Fe, Nb, Y, Ni and Ga, relative to pre-industrial background levels. The maximum enrichment ranged from 49 (Hg) to 3.1 (Ga). Mercury concentrations were greater in the Cubatão river than in other sites, while the other elements showed greater concentrations in the Morrão river. Concentrations of Mn were significantly greater in winter and autumn than in summer and spring. However, other elements (e.g. Cd and Pb) showed the opposite, with greater concentrations in summer and spring. This study suggests that seasonal changes in physical and chemical conditions may affect the degree of sediment enrichment and therefore make the assessment of contamination difficult. Consequently, these processes need to be considered when assessing water quality and the potential contamination of biota.

Um novo método para quantificar mercúrio orgânico (Hg orgânico) empregando a espectrometria de fluorescência atômica do vapor frio

In this work a simple and sensitive procedure to extract organic mercury from water and sediment samples, using methylene chloride in acidic media followed by CVAFS quantification has been developed. The method was evaluated for possible interferents, using different inorganic mercury species and humic acid, no effects being observed. The detection limit for organic mercury was 160 pg and 396 pg for water and sediment samples respectively. The accuracy of the method was evaluated using a certified reference material of methylmercury (BCR-580, estuarine sediment). Recovery tests using methylmercury as surrogate spiked with 1.0 up to 30.0 ng L-1 ranged from 90 up to 109% for water samples, whereas for sediments, recoveries ranged from 57 up to 97%.

Determinação da densidade de corrente de corrosão em meios de baixa condutividade: uso de microeletrodos para minimizar a queda ôhmica

The gravimetric and electrochemical tests are the most common techniques used in determining the corrosion rate. However, the use of electrochemical polarization is limited to electrolytes with sufficient conductivity for which Tafel curves are linear. In this study, we investigated a technique in which working microelectrodes of AISI 1020 steel were used to obtain the Tafel curves in diesel oil. The strategy was to reduce the electrode area and hence the ohmic drop. The diameter of the microelectrode was reduced to a value where the compensation of the Tafel curves became unnecessary. The results showed that for electrodes with diameters below 50 μm, the ohmic drop tends to a minimum and independent of the microelectrode diameter.

Estudo comparativo das respostas autonomicas cardiovasculares entre corredores de provas de fundo, halterofilistas e sedentarios

Universidade Estadual de Campinas . Faculdade de Educação Física

Qualidade de vida e avaliação fisica em intoxicados por mercurio : estudo observacional transversal descritivo

Universidade Estadual de Campinas . Faculdade de Educação Física