2,403 research outputs found
Climate-related variations in atmospheric Sb and Tl in the EPICA Dome C ice (East Antarctica) during the past 800,000 years
No full textA record of antimony (Sb) and thallium (Tl) from the European Project for Ice Coring in Antarctica (EPICA) Dome C Antarctic ice core provides the characteristics of climate-related natural changes in concentrations and fluxes of these toxic elements over the time period back to Marine Isotope Stage 20.2, similar to 800kyrB.P. A strong variability in concentrations and fluxes are observed for both elements, with considerably higher values during glacial maxima and lower values during intermediate and warm periods. Rock and soil dust accounts for, on average, 58% of Sb and 76% of Tl in ice during glacial maxima. This contribution remains significant during warm periods, accounting for 21% for Sb and 27% for Tl. The contribution from volcanoes appears to be very important particularly for Tl when climatic conditions become warmer, with an estimated volcanic contribution of 72% for Tl during interglacials. The sea-salt contribution is significant for Sb, particularly during intermediate climatic periods, with an average contribution of 17%. This sea-salt contribution is most likely caused by greater production of sea salt from highly saline frost flowers and relatively more efficient transport of Sb-enriched sea-ice salt from source areas on the East Antarctic Plateau. Our ice core data, along with snow data recently reported from the Antarctic snow layers at Dome Fuji, shows that the present-day Sb flux (6.6ng/m(2)/yr) is approximately double the highest natural level (2.8ng/m(2)/yr) during glacial maxima throughout the last successive eight glacial/interglacial cycles. This result indicates that human activity has induced the greatest perturbation of the atmospheric cycle of Sb ever experienced over a period of similar to 800 kyr in the most remote area on Earth
A two century record of strontium isotopes from an ice core drilled at Mt Blanc, France
No full textInternational audienceNew techniques which allow small amounts of Sr to be reliably analysed [G.R. Burton, V.I. Morgan, C.F. Boutron, K.J.R. Rosman, High-sensitivity measurements of strontium isotopes in polar ice, Anal. Chim. Acta 469 (2002) 225–233] by TIMS (Thermal Ionisation Mass Spectrometry) have been used to measure the isotopic composition of Sr and the concentration of Rb and Sr at sub-nanogram per gram levels in a Mt Blanc snow and ice core. This two century time series of Sr isotopes is the first to be reported in an Alpine glacier. The Sr and Rb concentrations range from 3 ng/g to 20 pg/g and 1 ng/g to 10 pg/g, respectively, with higher concentrations evident in more recent times. This trend is consistent with that reported previously for other metals such as Cd, Cu and Zn [K. Van de Velde, C. Barbante, G. Cozzi, I. Moret, T. Bellomi, C. Ferrari, C. Boutron, Changes in the occurrence of silver, gold, platinum, palladium and rhodium in Mont Blanc ice and snow since the 18th century, Atmos. Environ. 34 (2000) 3117–3127; K. Van de Velde, C. Boutron, C. Ferrari, T. Bellomi, C. Barbante, S. Rudnev, M. Bolshov, Seasonal variations of heavy metals in the 1960s Alpine ice: sources versus meteorological factors, Earth Planet. Sci. Lett. 164 (1998) 521–533; K.J.R. Rosman, C. Ly, K. Van de Velde, C.F. Boutron, A two century record of lead isotopes in high altitude Alpine snow and ice, Earth Planet. Sci. Lett. 176 (2000) 413–424]. The 87Sr/86Sr ratios vary between 0.7020 and 0.7176 and display relatively larger variations in recent times which have been attributed to seasonal variations made evident by the increased sampling resolution available at shallower depths. No change with time is evident in this ratio which has a mean value of ∼0.712 and is similar to Glacial ice at Summit Greenland, suggesting that aerosols reaching Mt Blanc represent the same mixture of sources. Also, anthropogenic sources would appear to have the same isotopic ratio. The presence of Saharan dust in some samples is confirmed here by their strontium isotopic ratios
Temporal variability of trace elements in Antarctic (Dome C) ice over the last 45,000 years
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Direct determination of heavy metals at pg/g level in recent snow from Central Greenland by HR-ICP-MS.
No full textDouble focusing ICP-MS for the determination of rhodium, palladium and platinum in ultraclean environmental matrices.
No full textAir-Surface exchange of elemental mercury in uncontaminated grasslands : determination of fluxes and identification of forcing factors with micrometeorological methods and controlled laboratory studies
No full textThe burning of fossil fuels, incineration of waste, smelting of metals and other industrial processes and applications have been adding considerable amounts of mercury to the atmosphere. Of the total atmospheric mercury, Hg0 (elemental mercury) represents more than 95%, a species which is highly volatile and dispersed globally. Eventually Hg0 is transformed and deposited to land and sea where various processes may produce organic mercury species that have the power to bioaccumulate to levels that are toxic for humans. In Europe and North America mission controls are in place for more than two decades and have reduced mercury emissions substantially. However, due to large uncertainties in global emission estimates and uncertainties regarding the potential of different ecosystems to act as sources or sinks for atmospheric mercury, it is yet not known if deposited Hg0 is stored permanently in soils and if the atmospheric pool is actually reduced. Attempts to estimate the magnitude of the air-surface mercury exchange have focused on polluted sites, boreal regions and arid zones of North America. In contrast, uncontaminated, continental regions of the temperate climate belt haven’t received much attention and respective studies have been mostly limited to spot measurements with flux chambers. The first objective of our study was to describe and evaluate the influence of microbiological activity on the emission of Hg0 from terrestrial background soils. It has been discussed that apart from physically and chemically mediated Hg0 emission, microbial activity might contribute to the emission flux. The importance of this contribution in uncontaminated terrestrial soils is still unclear. Under controlled laboratory conditions it was tested how stimulation and inhibition of microbial activity would affect Hg0 emissions. This was done by comparing sterilised with intact soil samples in an incubation chamber and investigating the response of Hg0 emissions to environmental variables such as temperature and soil moisture. The results of these experiments showed consistent changes of Hg0 emissions with stimulation and inhibition of microbiological activity. Stimulatory effects were observed after addition of glucose, after inoculation of sterilised soil as well as upon temperature shifts and re-moistening of dried samples. We conclude that Hg0 emissions from uncontaminated, terrestrial soils are partly controlled by microbiological activity. Microorganisms might reduce Hg2+ either directly in order to detoxify their immediate environment, or they might indirectly induce Hg0 evasion by producing reductive soil compounds such as humic and fulvic acids.
To obtain a comprehensive picture of elemental mercury exchange of background
areas we performed measurements on an ecosystem scale at three temperate lowland
and subalpine grassland sites. A subalpine meadow at Fruebuel in central Switzerland
was chosen to record the seasonal cycle of the Hg0 exchange and with two additional
sites in Oensingen/Switzerland and Neustift/Austria the spacial variability
was addressed. By measuring concentration gradients, fluxes of elemental mercury
and CO2 were estimated by application of two micrometeorological methods – the flux
gradient method and the modified Bowen ratio method. Due to the low atmospheric
concentrations (between 1.2 and 1.7 ng
(Table 8) Element composition of snow samples from Dome C, Antarctica
No full text(Table 8) Element composition of snow samples from Dome C, Antarctic
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