Presentation on theme: "Content of molecular hydrogen in the bottom section of ice sheet near Vostok Station: first results of studies of ice cores from borehole 5G-1N Chetverikov."— Presentation transcript:
Content of molecular hydrogen in the bottom section of ice sheet near Vostok Station: first results of studies of ice cores from borehole 5G-1N Chetverikov Yu. О. 1 Ezhov V.F. 1, Lipenkov V.Ya. 2, Klyamkin S.N. 3, Eliseev А.A. 3, Aruev N.N. 4, Fedichkin I. L. 4, Tyukaltcev R.V. 4, Dubenskiy B. M. 5, Yasinetckiy A.I. 5 1 PNPI, St. Petersburg 2 AARI, St. Petersburg 3 MSU, Moscow 4 IPTI, St. Petersburg 5 CFTI «ANALYTIC» St. Peterburg
Tectonic activity of bottom of lake Vostok and light gases in the lake Chemosynthesis of the thermal spring is the basis of life at the bottom of deep water reservoir Gases, throw into the lake in process of tectonic activity: Radioactive-decay gases: He – до 0.04% volume of ground water Ar; Rn Thermal decomposition gases: CO 2 (CO); SO 2 (SO 3 ); Н 2 S; HCl; HF Н 2 4H 2 +CO 2 →CH 4 +2H 2 O Observation of thermophilic hydrogen-oxidizing bacteria from the depths of the glacier 3561 and 3608 meters.  It is known that these bacteria live in the hydrogen content is 25 times higher, than the value in equilibrium with the atmosphere  Hydrogen in ice Synthesis of hydrogenobacter thermophilus bacteria: * ** High concentrations of hydrogen at the base of the Greenland glacier  S.А.Bulat et.al, International Journal of Astrobiology, 3, 1, p 1-12 (2004)  H. Francis et. al, Letters to nature, 415, (2002)  В.С.Сhristner et. al, Polar biol., 35, 11, 1735(2012)
The penetration of light gases in Glacier Model of a uniform distribution of the gas in the lake under the glacier Diffusion of gas into ice L pen =sqrt(6D t LAKE ) L PEN - the depth of penetration of gas; D- gas diffusion coefficient; t LAKE - time of glacier location above the lake D H2 = 2*10 -8 m 2 /sec  D He =10 -9 m 2 /sec  The flow of the glacier H(м) С H2 (lake) С He (lake) L PEN (D H2 ;t=40тыс.лет)=400 m L PEN (D He ;t=40тыс.лет)=93 m Depth concentration profile in the borehole 5G  H.L. Strauss, Z. Chen, C.K. Loong, J. Chem. Phys. 101, 7177 (1994)  K.Satoh, T. Uchida, T. Hondoh, S. Mae, Proc. NIPR Symp. Polar Meteorol. Glaciol. 10, (1996)
H(м) С H2 (lake) С He (lake) Alleged place of occurrence content and depth profile of the light gases The source of gas close to the dome of subglacial island Source of gas at the interface ice-water-to-shore H(м) С H2 (lake) С He (lake) * * * * Prospective ice- bound space of hydrogen-oxidizing bacteria Depth of drilling at this year Gas trail Center of gas trail
Dynamics of degassing and method of sampling Ice cylinders degassing (d = 9mm; h = 50 mm), saturated by hydrogen at a pressure of 300 bar Model of degassing of ice cylinder with dimension of d = 100 mm, h = 1000 mm, previously saturated with a gas Sampler Sealed container Ice core The model of gas adsorption from an cylinder[1,2]: M- gas solubility; D- diffusion constant; t- time since the beginning of the absorption; a- radius of the cylinder; =h/( a 2 ), h- height of the cylinder; q n - positive non-zero solutions of the equation q n J 0 (q n )+2J 1 (q n )=0 Degassing dynamics for the glacier ice same as for the ice from an tap water  J. Crank, The mathematics of diffusion, Oxford University press, (1975)  K.Satoh, T. Uchida, T. Hondoh, S. Mae, Proc. NIPR Symp. Polar Meteorol. Glaciol. 10, (1996)
The experimental equipment ) container for ice; 2) container lid; 3) sampling vessel; 4) vacuum pump; 5) vacuum valve; 6) pressure sensor; 7) temperature sensor; 8) measuring with the data acquisition module; 9) vacuum fittings
Technical problems Gas sourceThe saturation vapor pressure (mbar) at T = C Time of pressure increasing to saturation * (h) Evaporation jars with 10 ml of matter after 15 min. pumping * Published Measured Ice almost no vaporized Kerosene 1 2almost no vaporized Freon **vaporized completely Vaporization in a sealed container The surface of the core contaminated with drilling fluid (70-80% kerosene 20-30% Freon)! Leakage and the temperature dependence of the pressure sensor *- used pump was unproductive with Pmin = 2-3 mbar **- interpolation of degassing dynamics data where freon fully turned into vapour Leakage occurs due to loss of elasticity of Viton seals at a temperature below C Temperature correction of pressure sensor registration:: P COR =P MEAS + (T MEAS - T AVER )*С TEMP P MEAS и T MEAS - measured values of pressure and temperature; T AVER - the average temperature in the measurement cycle; С TEMP – factor, picked by minimizing such bumps and dips in the pressure curve such correlating with extremes of temperature curve Gassing in a sealed container with a core from storage
Sampling: dynamics of degassing Degassing of ice core from borehole 5G-3 extracted from a depth of 3457 m The pressure drop due to the opening of the sampler The pressure rise in the free volume of the sealed container Data was approximated by using model of desorption from ice cylinder with D=110 mm H=1000 mm. Diffusion coefficient for hydrogen in ice D= 2*10 -8 m 2 /sec (found in ) was used. Fitting parameter is saturation pressure P S. The gas pressure in the ice P GASICE normalization of the value found for P S :P GASICE =P S *V FS /V ICE V FS - free volume, V ICE - ice volume Found values: P GASICE (3457)=6 mbar; С GASICE (3457)=271mкМ P GASICE (3484)=6.2 mbar; С GASICE (3484)=280mкМ С H2ICE (М) Hydrogen pressure of atmospheric ice Hydrogen pressure from ice which placed in a gas environment with P H2 = 350bar Is it hydrogen ???  H.L. Strauss, Z. Chen, C.K. Loong, J. Chem. Phys. 101, 7177 (1994) Degassing of ice core from borehole 5G-3 extracted from a depth of 3484 m
Mass spectrometric analysis of the gas composition of samples: oxygen penetration and nitrogen from kerosene into the ice cores In the air: 78% N 2 ; 21% O 2 In degassing core samples (from the mass spectrum): 70% N 2 ;29% O 2 The gases from the air, dissolved in kerosene: 68%N 2 ; 30% O 2 (solubility of oxygen in the kerosene is more than the solubility of nitrogen) O2O2 N2N2 H 2 O HO NO freon B141 H2HH2H The content of N 2 and O 2 The main content of the gas from the cores is air which dissolved in kerosene
Mass spectrometric analysis of the gas composition of samples: hydrogen content in the samples, the problem of water H 2 line intensity decreases with time as well as the intensity of the line of H 2 O: strong correlation!!! Measurements of samples were alternated with measurements of local air. Samples: 1) The reference gas mixture containing 0.5% hydrogen 2) Air sampled at Vostok 3) The gas from the core of 3450 m 4) The gas from the core of 3457 m Samples: 5) The gas from the core of 3484 m 6) The gas from the core from storage 7) The gas from the core of 3400 m 8) The gas, which contained a vapour of kerosene The intensity of the H 2 line The intensity of the H 2 O line
If we subtract the intensity of the "contribution of water" from the hydrogen peak, and then normalized to the intensity of the resulting model, we get the hydrogen content in the sample. Putting aside the same graph intensity 81st line becomes clear that most of the hydrogen correlated with Freon Mass spectrometric analysis of the gas composition of samples: hydrogen content in the samples, the problem of freon H 2 (%) Samples: 1) The reference gas mixture containing 0.5% hydrogen 2) Air sampled at Vostok 3) The gas from the core of 3450 m 4) The gas from the core of 3457 m Samples: 5) The gas from the core of 3484 m 6) The gas from the core from storage 7) The gas from the core of 3400 m 8) The gas, which contained a vapour of kerosene If hydrogen is formed during the ionization of Freon in the mass spectrometer??? Volumetrically contaminated sample
Decrease in the intensity of the peaks in the mass spectrum during the freezing: Mass spectrometric analysis of the gas composition of samples: hydrogen content in the samples frozen in liquid nitrogen Decrease of intensities (times) Local airGas from 3400m core dI H2O dI M81 ->2580 After freezing the samples, their spectra have turned out very "clean" - not visible spectral lines of freon; greatly weakened spectral lines of water. After freezing the hydrogen content is still correlated with the content of Freon. The measured hydrogen is not a splinter of ionization of freon. Samples: 1) The gas from the core of 3450 m 2) The gas from the core of 3457 m 3) The gas from the core of 3484 m 4) The gas from the core of 3400 m 5) The gas from the core from storage Presence of Freon contamination is correlated with a hydrogen concentration in ice cores. In order to reduce hydrogen content to natural level, it is necessary to clean cores from 99.9% Freon.
Conclusions -Nondestructive technique of sampling of light gases from ice cores, was developed. -Developed technique was first applied during the 58th RAE to ice cores from the depth interval meters. -As a result of testing the developed technique a number of technical deficiencies in its implementation were identified. -Analysis of the samples detects contamination of ice cores by vapor of freon B141. The concentration of molecular hydrogen in the studied cores of ice are correlated with the concentrations of vapor of freon. The maximum concentration of 0.2 volume percent of hydrogen is observed in ice core of quick frozen lake water from a depth of 3400 meters (volumetrically contaminated ice core). -For a further research is necessary to use only Glacier ice cores and provides a procedure for cleaning the surface and near-surface layer of ice cores. Contents of components of the drilling fluid must reduced to a level of less than 0.1% of the concentration which observed in cores investigated in this work.