Ionic Fracture Fluid Leak-Off

The study is motivated by monitoring the space orientation of a hydrolic fracture used in oil production. Streaming potential arises due to the leakage of ionic fracking fluid under the rock elastic forces which make the fracture disclosure disappear after pumping stops. The vector of electric field correlates with the fracture space orientation since the fluid leakage is directed normally to the fracture surfaces. We develop a mathematical model for the numerical evaluation of the streaming potential magnitude. To this end, we perform an asymptotic analysis taking advantage of scale separation between the fracture disclosure and its length. The contrast between the virgin rock fluid and the fluid invading from the fracture is proved to be crucial in a build up of a net charge at the invasion front. Calculations reveal that an increase of the viscosity and resistivity contrast parameters results in an increase of the streaming potential magnitude. Such a conclusion agrees with laboratory experiments

Isotopic Analysis via Multi-Collector Inductively Coupled Plasma Mass Spectrometry in Elemental Speciation

International audienceThis chapter contains sections titled:IntroductionAdvantage of On‐Line versus Off‐Line Separation of Elemental SpeciesCoupling Chromatography with MC‐ICP‐MSEnvironmental and Other ApplicationsConclusion and Future TrendsReference

Higher mass-independent isotope fractionation of methylmercury in the pelagic food web of Lake Baikal (Russia)

cited By 36International audienceMercury undergoes several transformations that influence its stable isotope composition during a number of environmental and biological processes. Measurements of Hg isotopic mass-dependent (MDF) and mass-independent fractionation (MIF) in food webs may therefore help to identify major sources and processes leading to significant bioaccumulation of methylmercury (MeHg). In this work, δ13C, δ15N, concentration of Hg species (MeHg, inorganic Hg), and stable isotopic composition of Hg were determined at different trophic levels of the remote and pristine Lake Baikal ecosystem. Muscle of seals and different fish as well as amphipods, zooplankton, and phytoplankton were specifically investigated. MDF during trophic transfer of MeHg leading to enrichment of heavier isotopes in the predators was clearly established by δ202Hg measurements in the pelagic prey-predator system (carnivorous sculpins and top-predator seals). Despite the low concentrations of Hg in the ecosystem, the pelagic food web reveals very high MIF Δ199Hg (3.15-6.65‰) in comparison to coastal fish (0.26-1.65‰) and most previous studies in aquatic organisms. Trophic transfer does not influence MIF signature since similar Δ199Hg was observed in sculpins (4.59 ± 0.55‰) and seal muscles (4.62 ± 0.60‰). The MIF is suggested to be mainly controlled by specific physical and biogeochemical characteristics of the water column. The higher level of MIF in pelagic fish of Lake Baikal is mainly due to the bioaccumulation of residual MeHg that is efficiently turned over and photodemethylated in deep oligotrophic and stationary (i.e., long residence time) freshwater columns. © 2012 American Chemical Society

Modern mass spectrometry for studying mass-independent fractionation of heavy stable isotopes in environmental and biological sciences

This is the first review to focus specifically on the application of modern mass spectrometry techniques for studying mass-independent or anomalous isotope fractionation for 'heavy' elements. This review covers a period of ten years, starting from 2000. In the first part of the manuscript, we address theoretical aspects of mass-independent isotope fractionation, such as nuclear volume and nuclear spin effects. Secondly, most published articles on this topic to date are reviewed. Mass-independent isotope fractionation was determined by ICP-MS, MC-ICP-MS or TIMS for nineteen elements so far: Hg, Sn, Cd, Zn, Te, Sr, Pb, Cr, U, Ti, Ni, Mo, Ru, Ba, Nd, Sm, Gd, Yb and Hf, as reported in about fifty publications. In addition, mass-independent fractionation was observed for some other elements, silicon, germanium and sulfur, by other techniques

Multi-isotopic determination of plutonium (239Pu, 240Pu, 241Pu and 242Pu) in marine sediments using sector-field inductively coupled plasma mass spectrometry

cited By 26International audienceAmong the transuranic elements present in the environment, plutonium isotopes are mainly attached to particles, and therefore they present a great interest for the study and modelling of particle transport in the marine environment. Except in the close vicinity of industrial sources, plutonium concentration in marine sediments is very low (from 10-4 ng kg-1 for 241Pu to 10 ng kg-1 for 239Pu), and therefore the measurement of 238Pu, 239Pu, 240Pu, 241Pu and 242Pu in sediments at such concentration level requires the use of very sensitive techniques. Moreover, sediment matrix contains huge amounts of mineral species, uranium and organic substances that must be removed before the determination of plutonium isotopes. Hence, an efficient sample preparation step is necessary prior to analysis. Within this work, a chemical procedure for the extraction, purification and pre-concentration of plutonium from marine sediments prior to sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) analysis has been optimized. The analytical method developed yields a pre-concentrated solution of plutonium from which 238U and 241Am have been removed, and which is suitable for the direct and simultaneous measurement of 239Pu, 240Pu, 241Pu and 242Pu by SF-ICP-MS. © 2007 Elsevier B.V. All rights reserved

Rapid fingerprinting of 239Pu and 240Pu in environmental samples with high U levels using on-line ion chromatography coupled with high-sensitivity quadrupole ICP-MS detection

A simple, rapid on-line analytical method for the determination of plutonium (Pu) isotopes in soil and sediment samples was developed. Microwave leaching was used to extract Pu from the major sample matrix. L-ascorbic acid was found to be the most appropriate agent to convert all the Pu to Pu(IV) for chromatography. Flow injection chromatography using TEVA resin was optimized to separate, preconcentrate and elute Pu from other constituents of the sample including 238U. An APEX desolvation unit with a PEEK Mira Mist nebulizer was used to minimize clogging and hydride interferences. The advantage of using a high sensitivity quadrupole ICP-MS instrument for Pu detection was demonstrated. The detection limit was found to be 3 and 0.3 pg kg-1 for 239Pu and other Pu isotopes, respectively, while for 239+240Pu it was 10 mBq kg-1. To demonstrate the applicability of the method, Pu activities and atom ratios were measured for different sediments from the northern Asian region

Species-specific stable isotope fractionation of mercury during Hg(II) methylation by an anaerobic bacteria (Desulfobulbus propionicus) under dark conditions

International audienceThis work reports the first results on the stable isotope fractionation of Hg during methylation by anaerobic bacteria under dark conditions.TheGC-MC- ICPMSmethodologyemployed is capable of simultaneously measuring the species-specific isotopic composition of different Hg species within the same sample. We have studied Hg isotopic fractionation caused by methylation of Hg(II) standard reference material NIST-3133 in the presence of the pure bacterial strain Desulfobulbus propionicus MUD10 (DSM 6523) under fermentative conditions. We have measured the isotopic composition of Hg(II) and monomethyl mercury (MMHg) in these cultures as a function of time and calculated delta-values for both species versus the starting material (NIST-3133) as a delta-zero standard. Two differentstrategiesfortheincubationwereapplied: singlesampling cultures and a continuous sampling culture. The results obtained have shown that under the conditions employed in this work the methylation of Hg(II) causes mass-dependent fractionation of the Hg isotopes for both Hg(II) substrate and producedMMHg.Suchaprocess occurred under the exponential growth of the bacteria which preferentially methylate the lighter isotopes of Hg. After 96 h for the continuous culture and 140 h for the single sampling cultures,weobserved a change in the fractionation trend in the samples at a similar cell density value (ca. 6.0 × 107 cells mL -1) which suggests the increasing contribution of a simultaneous process balancing methylation extent such as demethylation.Assumingthat Rayleigh type fractionation conditions are met before such suppression, we have obtained a α202/198 fractionation factor of 1.0026 ± 0.0004 for the single sampling cultures

Species-specific stable isotope analysis by the hyphenation of chromatographic techniques with MC-ICPMS

International audienceThis work reviews the basis and all the existing publications on the hyphenation of chromatography-based techniques to MC-ICPMS for isotopic studies that were published until the end of 2010. A brief historical retrospective of the measurement of isotope ratios from transient signals by ICPMS with different sample introduction techniques is also included. The most important experimental parameters and data reduction strategies affecting the accurate and precise measurement of compound-specific isotope ratios by either HPLC or GC coupled to MC-ICPMS are discussed. All the applications are reported and critically reviewed in terms of analytical characteristics, performances, optimization, advantages and disadvantages and future applicability to the environmental, geochemical, or bioinorganic studies

Approach to measure isotopic ratios in species using multicollector-ICPMS coupled with chromatography

cited By 41International audienceA new approach was demonstrated for the isotope ratio measurement in different elemental species of Hg using transient signal obtained by chromatography coupled with multicollector-inductively coupled plasma mass spectrometry (MC-ICPMS). The method based on the slope of linear regression by transient intensities of different isotopes shows improved accuracy and reproducibility (0.2-0.5 as 2 standard deviation (SD)). Internal precision (RSD) of the method is very close to the theoretical value given by the counting statistic and is better by a factor of 6 in comparison with previous conventional methods of calculation. We demonstrated that internal RSD (uncertainty) depends on regression coefficients of the linear function (R 2). The typical internal precision of isotopic ratio measurements (0.003-0.02%) was achieved for δ202Hg when injecting as low as 90 pg of Hg species. With the new methodology, it is possible to (i) measure the isotopic composition when a sample and a bracketing standard have significantly different concentrations, (ii) measure the isotopic composition of different species in samples versus single species in a bracketing standard, and (iii) measure the isotopic ratios for low abundant isotopes. We demonstrated application of this method for different environmental samples and processes

Natural Hg isotopic composition of different Hg compounds in mammal tissues as a proxy for in vivo breakdown of toxic methylmercury

International audienceIn the last decade, specific attention has been paid to total mercury (HgT) stable isotopic composition, especially in natural samples such as aquatic organisms, due to its potential to track the cycle of this toxic element in the environment. Here, we investigated Hg Compound Specific stable Isotopic Composition (CSIC) of natural inorganic Hg (iHg) and methylmercury (MMHg) in various tissues of aquatic mammals (Beluga whale from the Arctic marine environment and seals from the freshwater lake Baikal, Russia). In seals' organs the variation in mass dependent fractionation (MDF, δ202Hg) for total Hg was significantly correlated to the respective fraction of iHg and MMHg compounds, with MMHg being enriched by ∼3‰ in heavier isotopes relative to iHg. On the other hand, we observe insignificant variation in Hg mass independent isotope fractionation (MIF, Δ199Hg) among iHg and MMHg in all organs for the same mammal species and MMHg in prey items. MIF signatures suggest that both MMHg and iHg in aquatic mammals have the same origin (i.e., MMHg from food), and are representative of Hg photochemistry in the water column of the mammal ecosystem. MDF signatures of Hg compounds indicate that MMHg is demethylated in vivo before being stored in the muscle, and the iHg formed is stored in the liver, and to a lesser extent in the kidney, before excretion. Thus, Hg CSIC analysis in mammals can be a powerful tool for tracing the metabolic response to Hg exposur