Mass-dependent cadmium isotopic variations in nature with emphasis on the marine environment     

Anne-Désirée Schmitt  Stephen J.G. Galer  Wafa Abouchami 《Earth and Planetary Science Letters》2009,277(1-2):262-272

We report a survey of natural mass-dependent cadmium isotope fractionation measured by thermal ionization mass spectrometry using a double-spike technique (DS-TIMS). Over sixty samples of natural terrestrial Cd from diverse environments, including MORB, OIB, continental loess, hydrogenic and hydrothermal ferromanganese deposits, and sphalerites (both oceanic and from major continental ore deposits) were analysed. Our results are expressed in terms of ε^112/110Cd, which are deviations in ¹¹²Cd/¹¹⁰Cd from our in-house JMC Cd standard in parts per 10⁴. The total ε^112/110Cd variation is relatively small, with a range of only 5 ε-units, and is one-to-two orders of magnitude smaller than that previously found in meteorites.The MORB, OIB and loess ε^112/110Cd values are similar and provide a good estimate for the bulk silicate Earth (BSE) value which is ? 0.95 ± 0.12 relative to our Cd standard (ε^112/110Cd = + 0.16 relative to Münster JMC Cd). Taken together, these data suggest little Cd isotope fractionation takes place during crust–mantle segregation. Cd isotopic compositions of continental sphalerite (ZnS) deposits worldwide and high-temperature oceanic hydrothermal sulphides show remarkably similar ε^112/110Cd values, consistent with our estimate for the BSE. In contrast, mid-temperature oceanic sulphides from a single extinct hydrothermal chimney display over 4 ε-units variation — along with the most negative values. These variations are most probably caused by precipitation/redissolution of sulphide phases en route within the hydrothermal system.The ε^112/110Cd variability found in worldwide marine Fe–Mn deposits reflects the seawater Cd isotope signal upon precipitation from ambient seawater. A decrease in ε^112/110Cd is observed in passing from shallow-water Fe–Mn deposits to those from deeper waters (> 2000 m depth). This shift is explained by biological fractionation related to the uptake of dissolved seawater Cd by phytoplankton in the upper water column. The relatively uniform ε^112/110Cd values close to zero at great depths are consistent with regeneration and remineralization of Cd at depth. Our data suggest that Cd isotopes – much like the Cd/Ca ratio in foraminifera – could potentially serve as a proxy for past changes in biological productivity. The temporal Cd isotope record in a Fe–Mn crust archive at 2000 m depth from the NE Atlantic suggests no gross long-term changes in Cd cycling took place over the past 8 Ma.  相似文献   

Meteorology and oceanography of the Atlantic sector of the Southern Ocean—a review of German achievements from the last decade     

Hartmut H. Hellmer  Monika Rhein  Günther Heinemann  Janna Abalichin  Wafa Abouchami  Oliver Baars  Ulrich Cubasch  Klaus Dethloff  Lars Ebner  Eberhard Fahrbach  Martin Frank  Gereon Gollan  Richard J. Greatbatch  Jens Grieger  Vladimir M. Gryanik  Micha Gryschka  Judith Hauck  Mario Hoppema  Oliver Huhn  Torsten Kanzow  Boris P. Koch  Gert König-Langlo  Ulrike Langematz  Gregor C. Leckebusch  Christof Lüpkes  Stephan Paul  Annette Rinke  Bjoern Rost  Michiel Rutgers van der Loeff  Michael Schröder  Gunther Seckmeyer  Torben Stichel  Volker Strass  Ralph Timmermann  Scarlett Trimborn  Uwe Ulbrich  Celia Venchiarutti  Ulrike Wacker  Sascha Willmes  Dieter Wolf-Gladrow 《Ocean Dynamics》2016,66(11):1379-1413

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A Common Reference Material for Cadmium Isotope Studies – NIST SRM 3108     

Wafa Abouchami  Stephen J. G. Galer  Tristan J. Horner  Mark Rehkämper  Frank Wombacher  Zichen Xue  Myriam Lambelet  Melanie Gault‐Ringold  Claudine H. Stirling  Maria Schönbächler  Alyssa E. Shiel  Dominique Weis  Philip F. Holdship 《Geostandards and Geoanalytical Research》2013,37(1):5-17

Research into natural mass‐dependent stable isotope fractionation of cadmium has rapidly expanded in the past few years. Methodologies are diverse with MC‐ICP‐MS favoured by all but one laboratory, which uses thermal ionisation mass spectrometry (TIMS). To quantify the isotope fractionation and correct for instrumental mass bias, double‐spike techniques, sample‐calibrator bracketing or element doping has been used. However, easy comparison between data sets has been hampered by the multitude of in‐house Cd solutions used as zero‐delta reference in different laboratories. The lack of a suitable isotopic reference material for Cd is detrimental for progress in the long term. We have conducted a comprehensive round‐robin assay of NIST SRM 3108 and the Cd isotope offsets to commonly used in‐house reference materials. Here, we advocate NIST SRM 3108 both as an isotope standard and the isotopic reference point for Cd and encourage its use as ‘zero‐delta’ in future studies. The purity of NIST SRM 3108 was evaluated regarding isobaric and polyatomic molecular interferences, and the levels of Zn, Pd and Sn found were not significant. The isotope ratio ¹¹⁴Cd/¹¹⁰Cd for NIST SRM 3108 lies within ～ 10 ppm Da^?1 of best estimates for the Bulk Silicate Earth and is validated for all measurement technologies currently in use.  相似文献   

Characterisation of organic matter and microbial communities in contrasting arsenic-rich Holocene and arsenic-poor Pleistocene aquifers,Red River Delta,Vietnam     

Wafa M. Al Lawati  Athanasios Rizoulis  Elisabeth Eiche  Christopher Boothman  David A. Polya  Jonathan R. Lloyd  Michael Berg  Patricio Vasquez-Aguilar  Bart E. van Dongen 《Applied Geochemistry》2012

High concentrations of geogenic As in the groundwaters of south and SE Asia, which are used as drinking waters, are causing severe health impacts to the exposed human populations. It is widely accepted that As mobilisation from sediments into these shallow reducing groundwaters requires active metal-reducing microbes and electron donors such as organic matter (OM). Although OM in such Holocene aquifers has been characterised, there is a dearth of data on Pleistocene aquifers from the same areas. Reported here are preliminary studies of OM and microbial communities present in two aquifers, one of Pleistocene and one of Holocene age, with contrasting concentrations of As (viz. Pleistocene: low As <10 μg/L; Holocene: high As up to 600 μg/L) from Van Phuc village in the Red River Delta, Vietnam. Results revealed OM inputs from multiple sources, including potential contributions from naturally occurring petroleum seeping into the shallow aquifer sediments from deeper thermally mature source rocks. Although concentrations vary, no noticeable systematic differences in biomarker distribution patterns within the OM were observed between the two sites. Microbial analyses did not show a presence of microbial communities previously associated with As mobilisation. All clone libraries were dominated by α-, β-, and γ-Proteobacteria not known to be able to reduce Fe(III) or sorbed As(V). Furthermore, representatives of the Fe(III)-reducing genus Geobacter could only be detected at very low abundance by PCR, using highly selective 16S rRNA gene primers, supporting the hypothesis that metal reduction is not a dominant in situ process in these sediments. No correlation between As concentration in groundwater and OM composition nor microbial community in the host sediments was found. This suggests that either (i) As is not being significantly mobilised in situ in these sediments, instead As appears to be mobilised elsewhere and transported by groundwater flow to the sites or (ii) sorption/desorption processes, as implicated by geochemical data from the cores, play a critical role in controlling As concentrations at these sites.  相似文献   

On the use of mean monthly runoff to predict the flow–duration curve in ungauged catchments     

Wafa Chouaib  Younes Alila  Peter V. Caldwell 《水文科学杂志》2013,58(13):1573-1587

ABSTRACT

We examine the applicability of predicting the daily flow–duration curve (FDC) using mean monthly runoff represented in its stochastic form (MM_FDC) to aid in predictions in ungauged basins, using long-term hydroclimatic data at 73 catchments of humid climate, in the eastern USA. The analysis uses soil hydrological properties, soil moisture storage capacity and the predominant runoff generation mechanism. The results show that MM_FDC did not distinguish the shapes of the upper and lower thirds of the FDC. The upper third is where the precipitation pattern and the antecedent moisture conditions are dominant, while the lower third is where drought-induced low flows and the evapotranspiration effect are prevalent. It is possible to use the MM_FDC to predict the middle third of the FDC (exceedence probabilities between 33% and 66%). The method is constrained by the catchment flow variability (slope of FDC), which changes in accordance with landscape properties and the predominant runoff generation mechanism.  相似文献   

GSD‐1G and MPI‐DING Reference Glasses for In Situ and Bulk Isotopic Determination     

Klaus Peter Jochum  Steven A. Wilson  Wafa Abouchami  Marghaleray Amini  Jérome Chmeleff  Anton Eisenhauer  Ernst Hegner  Linda M. Iaccheri  Bruno Kieffer  Joachim Krause  William F. McDonough  Regina Mertz‐Kraus  Ingrid Raczek  Roberta L. Rudnick  Denis Scholz  Grit Steinhoefel  Brigitte Stoll  Andreas Stracke  Sonia Tonarini  Dominique Weis  Ulrike Weis  Jon D. Woodhead 《Geostandards and Geoanalytical Research》2011,35(2):193-226

This paper contains the results of an extensive isotopic study of United States Geological Survey GSD‐1G and MPI‐DING reference glasses. Thirteen different laboratories were involved using high‐precision bulk (TIMS, MC‐ICP‐MS) and microanalytical (LA‐MC‐ICP‐MS, LA‐ICP‐MS) techniques. Detailed studies were performed to demonstrate the large‐scale and small‐scale homogeneity of the reference glasses. Together with previously published isotopic data from ten other laboratories, preliminary reference and information values as well as their uncertainties at the 95% confidence level were determined for H, O, Li, B, Si, Ca, Sr, Nd, Hf, Pb, Th and U isotopes using the recommendations of the International Association of Geoanalysts for certification of reference materials. Our results indicate that GSD‐1G and the MPI‐DING glasses are suitable reference materials for microanalytical and bulk analytical purposes.  相似文献   

Characterization of Ain M’Dheker clay deposits for sunflower oil and Acid Black 194 dye clarification     

Salima Chakroun  Wafa Mechti  Mongi Herchi  Mohamed Essghaier Gaied 《Arabian Journal of Geosciences》2018,11(3):60

Three mixtures (M1, M2, and M3) of the Eocene clay deposits were collected from Ain M’Dheker (Enfidha, Tunisia). These mixtures have been treated by hydrochloric acid in order to improve their physico-chemical characteristics. Optimum conditions for activation were conducted by varying several parameters such as the acid concentration, time, and temperature activation. The activation condition effect on surface area is studied. A representative raw (M3) and activated (AM3) mixtures were used in industrial application: Sunflower oil and Black 194 dyes (textile waste). M3 and AM3 were used to leach sunflower oil by varying the clay amount introduced. Results of the bleaching power of used samples were compared to that found by commercial bentonite imported from Germany (Tonsil), having a surface area of 725 m²/g. Indeed, an amount of 1% of AM3 gives a 60% decolorization similar to that found by commercial clay. Also, the ability of raw and activated clay to remove the dye (Acid Black 194) from effluent has been studied firstly at different pH and in second time by varying the adsorbent amount. Then, an amount of 0.025 g is sufficient to give a higher adsorption capacity for M3 than AM3. Consequently, Ain M’Dheker clay deposits can be use in other environmental application even without any treatment.  相似文献   

Hydrochemistry of aquifers in the southern Dead Sea area,southern Jordan     

N. S. Abu-Jaber  N. A. Wafa 《Environmental Geology》1996,28(4):213-222

 The demand for water resources in the area south of the Dead Sea due to continued development, especially at the Arab Potash Company (APC) works necessitates that water quality in the area be monitored and evaluated based on the local geology and hydrogeology. The objective of this paper is to provide information on the past and present status of the main aquifers under exploitation or planned for future development. Two main aquifers are discussed: the Safi water field, presently being operated, and the Dhiraa water field, which is being developed. The aquifer developed in the Safi water field is shallow and fed by the Hasa fault system, which drains a significant portion of the Karak mountains. This aquifer seems to be well replenished within the core, where no obvious long-term degradation in water quality can be identified. However, in the low recharge areas within the distal portions of the alluvial fan, there has been a degradation in water quality with time. The degradation is caused by the dissolution of the Lisan Marl, which is present at the outskirts of the fan system, based on hydrochemistry of water in the wells. The Dhiraa field is a deep (800–950 m) aquifer drilled specifically for the extraction of brackish water present in the Kurnub aquifer. Available data indicate that there are at least three distinct water types within this field. These water types are variable in quality, and there may be potential for mixing of these waters, thus affecting the quality of the freshest waters presently available. Tritium and oxygen isotope analysis indicate that the water is old and possibly nonrenewable. Received: 24 July 1995 · Accepted: 26 September 1995  相似文献   

Using a naive Bayes classifier to explore the factors driving the harmful dinoflagellate Karenia selliformis blooms in a southeastern Mediterranean lagoon     

Feki-Sahnoun  Wafa  Njah  Hasna  Hamza  Asma  Barraj  Nouha  Mahfoudi  Mabrouka  Rebai  Ahmed  Bel Hassen  Malika 《Ocean Dynamics》2020,70(7):897-911

Ocean Dynamics - The blooms of the toxic dinoflagellate Karenia selliformis can be predicted with accuracy derived from knowledge of the main forcing variables. A naive Bayes classifier modeling...  相似文献