Abstract. The incorporation of heavy metals into carbonate tests of the shallow water benthic foraminifer Ammonia tepida was investigated under controlled laboratory conditions. Temperature, salinity, and pH of the culture solutions were kept constant throughout the duration of this experiment, while trace metal concentrations were varied. Concentrations of Ni, Cu, and Mn were set 5-, 10-, and 20 times higher than levels found in natural North Sea water; for reference, a control experiment with pure filtered natural North Sea water was also analysed. The concentrations of Cu and Ni from newly grown chambers were determined by means of both µ-synchrotron XRF and Laser Ablation Inductively Coupled Plasma Mass Spectroscopy (LA-ICP-MS). The results of both independent analytical techniques agreed within the analytical uncertainty. In general, the concentration of the analysed elements in the tests increased in line with their concentration in the culture solutions. Potential toxic and/or chemical competition effects might have resulted in the decreased incorporation of Ni and Cu into the calcite of the specimens exposed to the highest elemental concentrations. Mn incorporation exhibited large variability in the experiment with the 20-fold increased element concentrations, potentially due to antagonistic effects with Cu. The partition coefficients of Cu and Ni were calculated to be 0.14 ± 0.02 and 1.0 ± 0.5, respectively, whereas the partition coefficient of Mn was estimated to be least 2.4. These partition coefficients now open the way for reconstructing past concentrations for these elements in sea water.
Three low molecular weight model compounds for poly(phenylene-ethynylene)s were inserted into the channels of zeolite L by using gas phase insertion. The absorption and emission spectra in solution and dye/zeolite L are reported. Two compounds show emission properties in zeolite L comparable to that in solution. In contrast, the bipyridine containing compound shows a red shift toward longer excitation wavelengths. Matrix rank analysis of the emission spectra gave three contributing species. Quantum chemical calculations provide different conformations depending on the Si/Al distribution of the framework and the extraframework cations and attached protons.
Abstract. The incorporation of heavy metals into the test of the shallow water benthic foraminifer Ammonia tepida was investigated under controlled laboratory conditions. Except for the concentrations of the trace elements, all other culture conditions such as pH, temperature and salinity were kept constant. In the experiments, the concentrations of Ni, Cu and Mn were 5, 10, and 20 times higher than those in natural North Sea water, whereas in a control experiment foraminifera were cultured in filtered natural North Sea water. Concentrations of Cu and Ni from newly grown chambers were determined by means of both μ-synchrotron XRF and laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS). Both independent analytical approaches agreed within the analytical uncertainty intervals. The calculated partition coefficients were 0.17±0.09 and 1.3±0.7 for Cu and Ni, respectively. Potential toxic and/or chemical competition effects might have lead to a decreasing incorporation rate of Cu and Ni into the calcite of the specimens of the tank with the highest chemical concentrations. Mn showed great scattering in the aquarium with the 20-fold higher element concentrations potentially due to antagonism effects with Cu. Nevertheless, the established partition coefficients now open the way for reconstructing past concentrations for these elements in sea water.
The origin and deposition of spherule-bearing, dominantly sandy beds in a sandstone complex (also called ''event deposit'') below the biostratigraphic Cretaceous-Tertiary (KT) boundary plays a key role in models linking the KT mass extinction to the Chicxulub impact. This study, which focuses on the chemostratigraphy of this complex exposed in a ca. 60-cm-thick succession along the Brazos River, Falls County, Texas, U.S.A., aims to constrain the source of the material as well as the depositional conditions and postdepositional history of this highly controversial stratigraphic unit. Major and trace elements, as well as the isotopic composition of the Ca carbonate, contrast sharply with the underlying Corsicana Formation, indicating a dramatic change in the source of material and depositional conditions. Evaluation of geochemical data by principal-component analysis permits identification of (1) siliciclastic components, (2) ejecta material, consisting of altered impact-glass spherules, and (3) Ca carbonate. The ejecta material, originally represented chiefly by glass spherules with carbonate infill, is strongly altered to clay minerals with dominantly smectitic composition and is characterized by the element association Al 2 O 3 , TiO 2 , Fe 2 O 3 , P 2 O 5 , and SO 2 and the trace elements (TE) V, Cr, Ni, Cu, Zn, Ga, and Mo. The occurrence of two moderately high Ir peaks (0.2 and 1.1 lg/kg) suggests the presence of tiny amounts of extraterrestrial material within the sandstone complex. Based on the contrasting abundance of Ni and Cu in chondritic meteorites and middle crust, the Ni/Cu ratio was used to trace the portion of extraterrestrial material in the sequence. The distribution of this ratio reflects changes in the amount of siliciclastic components added during deposition of the sandstone complex rather than variations in the amount of meteoritic material. The disagreement between evidence suggesting a prevalence of reducing conditions during the alteration of the ejecta material (pyrite inclusions in spherules; accommodation of Mn 2þ by secondary calcite) and sedimentologic features which indicate that the sandstone complex was deposited in a dominantly oxic, high-energy environment strongly supports the case that the ejecta material in these deposits was subjected to reworking.
Trace element chemistry and isotopic composition of calcareous foraminiferal tests reflect the environment in which they grow. Consequently, geochemical parameters of the tests are often used as paleo-proxies to constrain the environmental conditions in ancient seas (e.g. Boyle, 1981).Currently only a limited number of trace elements is used as proxies. Difficulties arise from the fact that often a proxy depends on several parameters and that seawater-chemistry may be influenced by local sources such as hydrothermalism or by changes in redox conditions. Reliable experimental data on elements which can be considered as diagnostic for hydrothermal activity and/or changing redox conditions are non-existent to scarce.We have cultured shallow benthic foraminifera (Ammonia tepida) under controlled conditions at defined trace element levels (5, 10, 20-fold average seawater concentration) representing two distinct environmental simulations, one for hydrothermal (Mn, Cu, Co, Ni) and another for changing redox conditions (Mo, As, Cr, and V). The goal of our investigations is to provide diagenetically unbiased experimental trace element data in foraminiferal shells as a basis for a more complete understanding of trace element partition between seawater and foraminifera shell calcite as a function of environmental conditions.The foraminifers did not reproduce in culture but grew new chambers as evidenced by labelling with calcein (Bernhard et al., 2004). The trace element uptake into old (field grown) and new chambers was subsequently analysed.Using excitation energies of 12.5 keV and focusing by refractive lenses to a spot size of 2x5 µm at FLUO-beamline of ANKA and 25 keV and confocal poly capillary optics at HASYLAB Beamline L, old chambers and new ones of the same foraminifera have been analyzed separately for Ni, Cu, Zn, Mn, As, Cr, V, Sr and Mo. The data will be compared with results from LA-ICP/MS analytics. Concentrations of the elements of interest in the newly grown chambers are varying in the 0.x to 1xx µg/g range. Because of these low concentrations long measuring times (∼500 s) were necessary at each spot. The trace element contents in the foraminiferal test were quantified by fundamental parameters. Path length of the incoming beam was determined from the ratio of the primary and secondary monitor. Since the foraminifera shells consist of nearly pure calcite, Ca was used as internal standard to calculate the average path length of the outgoing beam.Arsenic, V and Ni concentrations in the test correlate with their concentration in seawater. Nevertheless considerable variations, possibly reflecting vital effects, are observed between newly grown chambers of individuals grown under identical culture conditions.Boyle, E.A.
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