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Erika Sternberg Catherine Jeandel Juan-Carlos Miquel Beat Gasser Marc Souhaut Roseanna Arraes-Mescoff Roger Francois 《Marine Chemistry》2007,105(3-4):281-295
Biogenic barium, mostly in the barite (BaSO4) form, has been proposed as a tracer for export production in the ocean. Here we report on biogenic barium (Baxs) and particulate organic carbon (POC) fluxes from sediment traps deployed at the DYFAMED site in the Northwestern Mediterranean Sea. Baxs fluxes display average values of 37 ± 45 and 50 ± 58 μg/m2/d at 200 and 1000 m respectively, and are linearly correlated to POC fluxes (mean values of 7.9 ± 9.3 and 6.8 ± 6.8 mg C/m2/d at 200 and 1000 m). Export production estimates, calculated using published Baxs- or POC-based algorithms, all fall below or close to the lower limit of potential export values proposed in the literature. This work clearly demonstrates the usefulness of Baxs as a tracer of oceanic export production in the Northwestern Mediterranean Sea. However, development of a quantitative export production proxy requires a clear understanding of the underlying cause(s) for the observed spatial variations in the relationship between Baxs and POC fluxes. The present study confirms that the processes leading to barite formation differ between margin and open-ocean sites and probably account for much of the regional variability in the POC/Baxs ratio. 相似文献
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The distribution of the metal ions Zn and Pb between particulate and dissolved phase in river Glatt was studied by field measurements and compared with calculated simulations, using parameters obtained by adsorption experiments with natural suspended particulate material. Differences in distribution coefficients obtained from field data are observed in function of the sampling locations and of the composition of the particulate matter.Experiments in which metal ion solutions are titrated with a suspension of natural particles and analyzed by anodic stripping voltammetry, are interpreted in terms of binding capacities and conditional stability constants of Zn and Pb with the surface sites. Binding constants of a particular metal ion varied very little for all samples. We obtained mean values for the conditional average complex formation constants at pH 8 of: logcond
K
Pb = 9.44 ± 0.18 and logcond
K
Zn = 8.17 ± 0.20. At this pH, binding capacities of 5 10–3 – 1.7 10–2 mol/kg of particles were obtained for samples collected at different locations and times; organic material, iron and manganese oxides are considered to be the main components that control the adsorption to the particles.Distribution coefficients are calculated from the experimentally obtained binding capacities and conditional stability constants. Calculated distribution coefficients for Zn agree with those obtained from the field data and are not very sensitive to changes in the composition of the solution. Good agreement was obtained for lead as well; for some samples it was important to take two types of sites with different affinity into consideration. 相似文献
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The Paleozoic of Graz is an isolated nappe complex of about 1,500 km2 size and belongs to the Austroalpine units of the eastern European Alps. Despite more than 500 publications on stratigraphy,
paleontology and local structure, many aspects of the internal geometry of this complex as a whole remained unclear. In this
contribution, we present integrated geological profiles through the entire nappe complex. Based on these profiles, we present
(1) a simplified lithological subdivision into 13 rock associations, (2) a modified tectonostratigraphy where we consider
only two major tectonic units: an upper and a lower nappe system and in which we abandon the traditionally used facies nappe
concept, and (3) a modified paleogeography for the whole complex. Finally, we discuss whether the internal deformation of
the Paleozoic of Graz is of Variscan or Eo-Alpine age and which of the published models best explain the tectonic evolution
of the Paleozoic of Graz. 相似文献
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International Journal of Earth Sciences - Im Rahmen eines Forschungsprojektes des Landes Nordrhein-Westfalen wurde ein Untertageaufschluß — das sog. Referenzprofil — und 19... 相似文献
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John M. Livingston Vladimir N. Kapustin Beat Schmid Philip B. Russell Patricia K. Quinn Timothy S. Bates Philip A. Durkee Peter J. Smith Volker Freudenthaler Matthias Wiegner Dave S. Covert Santiago Gassó Dean Hegg Donald R. Collins Richard C. Flagan John H. Seinfeld Vito Vitale Claudio Tomasi 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):594-619
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