A compilation of field surveys on gaseous elemental mercury (GEM) from contrasting environmental settings in Europe, South America, South Africa and China: separating fads from facts

Mercury is transported globally in the atmosphere mostly in gaseous elemental form (GEM, Hg0 gas), but still few worldwide studies taking into account different and contrasted environmental settings are available in a single publication. This work presents and discusses data from Argentina, Bolivia, Bosnia and Herzegovina, Brazil, Chile, China, Croatia, Finland, Italy, Russia, South Africa, Spain, Slovenia and Venezuela. We classified the information in four groups: (1) mining districts where this contaminant poses or has posed a risk for human populations and/or ecosystems; (2) cities, where the concentration ofatmospheric mercury could be higher than normal due to the burning of fossil fuels and industrial activities; (3) areas with natural emissions from volcanoes; and (4) pristine areas where no anthropogenic influence was apparent. All the surveys were performed using portable LUMEX RA-915 series atomic absorption spectrometers. The results for cities fall within a low GEM concentration range that rarely exceeds 30 ng m-3, that is, 6.6 times lower than the restrictive ATSDR threshold (200 ng m-3) for chronic exposure to this pollutant. We also observed this behavior in the former mercury mining districts, where few data were above 200 ng m-3.We noted that high concentrations of GEM are localized phenomena that fade away in short distances. However, this does not imply that they do not pose a risk for those working in close proximity to the source. This is the case of the artisanal gold miners that heat the Au–Hg amalgam to vaporize mercury. In this respect, while GEM can be truly regarded as a hazard, because of possible physical–chemical transformations into other species, it is only under these localized conditions, implying exposure to high GEM concentrations, which it becomes a direct risk for humans.Grants CGL2009-13171 and CTM2012-33918 from the Spanish Ministry of Economy and Competitiveness and PII1I09-0142- 4389 from theCastilla-LaMancha (Spain)RegionalGovernment.Published713-7346A. Monitoraggio ambientale, sicurezza e territorioJCR Journalrestricte

ПРОГРАММИРОВАНИЕ ДВУХБИТНОГО PIN-ДИОДА В СРЕДЕ SYNOPSYS SENTAURUS TCAD

The article is devoted to the modeling of a two-bit pin-diode. The possibility of programming opening time of the device based on the pin-diode is shown. The design consisting of a pin diode and two floating gates on the surface of i-region is considered. The addition of electrodes to the surface of the i-region makes it possible to regulate the concentration of electrons and holes within the larger limits in compare with the single-gate structure creating enriched and depleted are-as in the structure. Programming is carried out by applying the appropriate voltage to the control electrodes of the floating gates. It is shown that the charge generated on the floating gate changes characteristics of the i-region of the pin diode.The key elements of complex simulation of the two-gate pin diode are simulation of charge accumulation mechanism on the floating gate, simulation of pin-diode opening time and calibration of numerical model. Simulation is performed in Synopsys Sentaurus TCAD. Physical models describing traps and their parameters, particle tunneling, transport phenomena in dielectrics and amorphous films are used in simulation. As a result of modeling, the opening time dependences on size, floating gate location and floating gate charge magnitude are obtained.It is shown that the pin-diode 2-gate structures allow to change the opening time in a wider range than the single-gate ones. To program a large range of pin-diode opening times, it is 2 gate structure that is advisable to use. The obtained results indicate that it is possible to implement a two-bit programming pin-diode and expand its functionality.Статья посвящена моделированию двухбитного pin-диода. Показана возможность программирования времени открытия устройства на основе pin-диода. Рассмотрена конструкция, состоящая из pin-диода и двух плавающих затворов на поверхности i-области. Добавление электродов на поверхность i-области дает возможность регулировать концентрацию электронов и дырок в больших пределах в сравнении с однозатворной структурой, создавая обогащенные и обедненные области в структуре. Программирование осуществляется подачей соответствующего напряжения на управляющие электроды плавающих затворов. Показано, что создаваемый на плавающем затворе заряд изменяет характеристики i-области pin-диода.Важными элементами комплексного моделирования двухзатворного pin-диода являются моделирование механизма накопления заряда на плавающих затворах, моделирование времени открытия pin-диода, калибровка численной модели. Моделирование выполнено в среде Synopsys Sentaurus TCAD. При моделировании были использованы физические модели, описывающие ловушки и их параметры, туннелирование частиц, явления переноса в диэлектриках и аморфных пленках. В результате моделирования получены зависимости времени открытия от размеров, расположения плавающих затворов и значения заряда на плавающих затворах.Показано, что двухзатворные структуры pin-диода позволяют изменять время открытия в более широких пределах, чем однозатворные. Для программирования большого диапазона времен открытия pin-диода целесообразно использовать именно двухзатворные структуры. Полученные результаты свидетельствуют о расширении функциональных возможностей двухзатворной структуры

Atomic absorption by free atoms in solution following chemical reduction from the ionic state

The initial stages of chemical reduction of metallic ions in solution must proceed through the formation of single atoms, followed by the rapid formation of clusters with other atoms until continued coalescence produces observable precipitates or evidence of stable sol formation. Dilute solutions of sodium borohydride (0.0025%) merged with microgram per milliliter concentration solutions of Ag, Pd, and Cu in a custom spectrophotometric flow cell produce transient background-corrected atomic absorption signals during the initial few seconds of the reaction. High-resolution atomic absorption with both a hollow cathode line source and a continuum source reveals that the absorption line profile of the absorbing species is extremely narrow (11 pm for Ag) and not influenced by the aqueous environment. Such selective absorption of radiation suggests that free atoms are being observed in aqueous solution.NRC publication: Ye

The application of tree bark as bio-indicator for the assessment of Cr(VI) in air pollution

The impact of a chromium smelter on pollution was evaluated by determining Cr(VI) in topsoil, grass and tree bark by electhrothermal atomic absorption spectrometry (ETAAS). It was found that bark reflected the levels of air pollution better than soil and grass due to its high accumulative ability of Cr(VI). The tree bark was contaminated with Cr(VI) by a factor of 9 than in soil. It is therefore suggested that the bark be used as an indicator of air pollution for long-term exposure. The concentration of Cr(VI) in the bark was always a fraction of the total concentration of Cr and ranges between 1.6 and 3%. The method used in the preparation of samples was validated by the analysis of certified reference materials

Determination of the mercury content of lichens and comparison to atmospheric mercury levels in the South African Highveld Region

Abstract The concentration of mercury vapour in ambient air is routinely determined using specialised instruments. As an economical alternative, actively pumped Hopcalite sorbent tubes can be used to trap atmospheric mercury, which is subsequently analysed by cold vapour atomic absorption spectroscopy. Plant materials are also readily available in most regions and can be analysed to obtain information on time averaged atmospheric mercury levels. Lichen and tree bark samples were collected in the cities of Pretoria and Witbank, dried and acid digested with subsequent cold vapour atomic absorption spectroscopy. Average mercury concentrations ranging from 74 to 193 μg.kg-1 were found in lichens from three Pretoria suburbs, whilst average Hg levels of 228 μg.kg-1 were determined in lichens collected in Witbank. The average mercury concentration in tree bark was consistently lower than in lichens, with concentrations between 28 and 72 μg.kg-1 determined in samples from three Pretoria suburbs and 75 μg.kg-1 determined in samples taken in Witbank. This study is the first in South Africa to determine mercury levels in lichens and tree bark. Average total gaseous mercury concentrations in ambient air at the three Pretoria suburban sites, as determined by a semi-continuous spectroscopic method using Hopcalite sampling, ranged between 1.6 and 2.5 ng.m-3, while an average of 1.7 ng.m-3 was measured in Witbank over the sampling interval

Condensation of analyte vapor species in graphite furnace atomic absorption spectrometry

NRC publication: Ye

PROGRAMMING 2-BIT PIN DIODE IN SYNOPSYS TCAD

The article is devoted to the modeling of a two-bit pin-diode. The possibility of programming opening time of the device based on the pin-diode is shown. The design consisting of a pin diode and two floating gates on the surface of i-region is considered. The addition of electrodes to the surface of the i-region makes it possible to regulate the concentration of electrons and holes within the larger limits in compare with the single-gate structure creating enriched and depleted are-as in the structure. Programming is carried out by applying the appropriate voltage to the control electrodes of the floating gates. It is shown that the charge generated on the floating gate changes characteristics of the i-region of the pin diode.The key elements of complex simulation of the two-gate pin diode are simulation of charge accumulation mechanism on the floating gate, simulation of pin-diode opening time and calibration of numerical model. Simulation is performed in Synopsys Sentaurus TCAD. Physical models describing traps and their parameters, particle tunneling, transport phenomena in dielectrics and amorphous films are used in simulation. As a result of modeling, the opening time dependences on size, floating gate location and floating gate charge magnitude are obtained.It is shown that the pin-diode 2-gate structures allow to change the opening time in a wider range than the single-gate ones. To program a large range of pin-diode opening times, it is 2 gate structure that is advisable to use. The obtained results indicate that it is possible to implement a two-bit programming pin-diode and expand its functionality

CONSUMPTION OF MINE WATER BY WILD UNGULATES IN THE SOURCES OF THE USSURI RIVER, ON THE TERRITORY OF THE NATIONAL PARK «CALL OF THE TIGER»

Link for citation: Panichev A.M., Baranovskaya N.V., Aramilev V.V., Chekryzhov I.Yu., Vakh E.A., Vetoshkina  A.V., Lutsenko T.N., Strepetov D.A.  Consumption of mine water by wild ungulates in the sources of the Ussuri river, on the territory of the national park «Call of the tiger». Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 111-121. In Rus. The relevance of the study is determined by the need to clarify the reason for the use of mineralized water by wild animals, which is typical for many areas of the world. The new knowledge is closely related to the geophagy problem, the solution of which opens a wide prospect of fundamental research in the fields of landscape biogeochemistry, ecology and medicine. Purpose: to study chemical composition of the mineralized mine water in the lake located on the territory of the out-of-operation tin-polymetallic ores concentrator dump in the upper Ussuri river which is being consumed actively by wild ungulates; to reveal number of animal visitors to the lake during an annual cycle; to reveal the reason of mine water consumption. Objects: ungulates visiting the lake with mine water; lake water and bottom sediments. Methods: estimation of visitation of the mine lake by animals by means of photographic traps; chemical composition determination: inductively coupled plasma mass spectrometry (ICP-MS) (Agilent 7700x spectrometer, Agilent Techn., USA); atomic emission spectrometry (spectrometer iCAP 7600 Duo); ion chromatography (LC-20 ion-liquid chromatograph, Shimadzu, Japan). Results. It was revealed that animals come to the lake uniformly throughout the year, except for the winter period, when the water is covered by a thick layer of ice. In high concentrations trace elements were found, including both elements with high toxicity (Cd and Pb) exceeding MAC for drinking water from 20 to 80 times and essential elements such as Fe, Mn, Cu, Zn, Co, Cr, Ni, Se, Li, which concentration either does not exceed MPC or exceeds it insignificantly. The concentration of REE, especially of the light subgroup, is also very high. The reason for mine water consumption by animals, most likely, is the high concentration of rare-earth elements of the light subgroup in it