Karl-Ludwig Kratz

Occurrence of antibiotics in the aquatic environment.

The recent monitoring of drug residues in the aquatic environment has gained much interest as many pharmaceutical compounds can frequently be found in sewage treatment plant (STP) effluents and river water at concentrations up to several microgram/l. This article describes the analysis of various water samples for 18 antibiotic substances, from the classes of macrolid antibiotics, sulfonamides, penicillins and tetracyclines. Samples were preconcentrated via lyophilization and quantified using HPLC-electrospray-tandem-mass spectrometry. The investigated STP effluents and surface water samples showed frequent appearance of an erythromycin degradation product, roxithromycin and sulfamethoxazole with concentrations up to 6 micrograms/l. Neither tetracyclines nor penicillins could be detected at concentration levels above 50 and 20 ng/l, respectively. From the large number of ground water samples that were taken from agricultural areas in Germany, no contamination by antibiotics was detected except for two sites. This indicates that intake from veterinary applications to the aquatic environment is of minor importance.

The Extremely Metal-poor, Neutron Capture-rich Star CS 22892-052: A Comprehensive Abundance Analysis*

High-resolution spectra obtained with three ground-based facilities and the Hubble Space Telescope (HST) have been combined to produce a new abundance analysis of CS 22892-052, an extremely metal-poor giant with large relative enhancements of neutron capture elements. A revised model stellar atmosphere has been derived with the aid of a large number of Fe peak transitions, including both neutral and ionized species of six elements. Several elements, including Mo, Lu, Au, Pt, and Pb, have been detected for the first time in CS 22892-052, and significant upper limits have been placed on the abundances of Ga, Ge, Cd, Sn, and U in this star. In total, abundance measurements or upper limits have been determined for 57 elements, far more than previously possible. New Be and Li detections in CS 22892-052 indicate that the abundances of both these elements are significantly depleted compared to unevolved main-sequence turnoff stars of similar metallicity. Abundance comparisons show an excellent agreement between the heaviest n-capture elements (Z ≥ 56) and scaled solar system r-process abundances, confirming earlier results for CS 22892-052 and other metal-poor stars. New theoretical r-process calculations also show good agreement with CS 22892-052 abundances and the solar r-process abundance components. The abundances of lighter elements (40 ≤ Z ≤ 50), however, deviate from the same scaled abundance curves that match the heavier elements, suggesting different synthesis conditions or sites for the low-mass and high-mass ends of the abundance distribution. The detection of Th and the upper limit on the U abundance together imply a lower limit of 10.4 Gyr on the age of CS 22892-052, quite consistent with the Th/Eu age estimate of 12.8± 3 Gyr. An average of several chronometric ratios yields an age 14.2± 3 Gyr.

Determination of antibiotics in different water compartments via liquid chromatography–electrospray tandem mass spectrometry

For the determination of 18 antibiotics in water samples down to the lower ng/l range, an analytical multi method is presented. The analytes belong to different groups of antibiotics such as penicillins, tetracyclines, sulfonamides and macrolid antibiotics. Samples were enriched using a universal freeze-drying procedure or a solid-phase extraction facultatively. Analysis was performed by liquid chromatography with electrospray-tandem MS detection. Chromatography required different columns and eluents. Mean recovery rates were in excess of 70%, however, with one exception and a quantitation limit of 50 ng/l for the tetracyclines and 20 ng/l for all other antibiotics were set.

rp-process nucleosynthesis at extreme temperature and density conditions

We present nuclear reaction network calculations to investigate the influence of nuclear structure on the rp-process between Ge and Sn in various scenarios. Due to the lack of experimental data for neutron-deficient nuclei in this region, we discuss currently available model predictions for nuclear masses and deformations as well as methods of calculating reaction rates (Hauser-Feshbach) and beta-decay rates (QRPA and shell model). In addition, we apply a valence nucleon (NpNn) correlation scheme for the prediction of masses and deformations. We also describe the calculations of 2p-capture reactions, which had not been considered before in this mass region. We find that in X-ray bursts 2p-capture reactions accelerate the reaction flow into the Z greater than or equal to 36 region considerably. Therefore, the rp-process in most X-ray bursts does not end in the Z = 32-36 region as previously assumed and overproduction factors of 10(7)-10(8) are reached for some light p-nuclei in the A = 80-100 region. This might be of interest in respect of the yet unexplained large observed solar system abundances of these nuclei. Nuclei in this region can also be produced via the rp-proces in accretion disks around low mass black holes. Our results indicate that the rp-process energy production in the Z < 32 region cannot be neglected in these scenarios. We discuss in detail the influence of the various nuclear structure input parameters and their current uncertainties on these results. It turns out that rp-process nucleosynthesis is mainly determined by nuclear masses and beta-decay rates of nuclei along the proton drip line. We present a detailed list of nuclei for which mass or beta-decay rate measurements would be crucial to further constrain the models

Isotopic r-process abundances and nuclear structure far from stability : implications for the r-process mechanism

Attempts to explain the source of r-process elements in nature by particular astrophysical sites face the entwined uncertainties, stemming from the extrapolation of nuclear properties far from stability, inconsistent sources of different properties (e.g., nuclear masses and half-lives), and the (poor) understanding of astrophysical conditions, which are hard to disentangle. We utilize the full isotopic r-process abundances in nature [especially in all of the three peaks (A≃80, 130, 195)] and a unified model for all nuclear properties involved (aided by recent experimental knowledge in the r-process path), to deduce uniquely the conditions necessary to produce such an abundance pattern

The astrophysical r-process : A comparison of calculations following adiabatic expansion with classical calculations based on neutron densities and temperatures

The rapid neutron-capture process (r-process) encounters unstable nuclei far from β-stability. Therefore its observable features, like the abundances, witness (still uncertain) nuclear structure as well as the conditions in the appropriate astrophysical environment. With the remaining lack of a full understanding of its astrophysical origin, parameterized calculations are still needed. We consider two approaches: (1) the classical approach is based on (constant) neutron number densities nn and temperatures T over duration timescales τ; (2) recent investigations, motivated by the neutrino wind scenario from hot neutron stars after a supernova explosion, followed the expansion of matter with initial entropies S and electron fractions Ye over expansion timescales τ. In the latter case the freezeout of reactions with declining temperatures and densities can be taken into account explicitly. We compare the similarities and differences between the two approaches with respect to resulting abundance features and their relation to solar r-process abundances, applying for the first time different nuclear mass models in entropy-based calculations. Special emphasis is given to the questions of (a) whether the same nuclear properties far from stability lead to similar abundance patterns and possible deficiencies in (1) and (2), and (b) whether some features can also provide clear constraints on the astrophysical conditions in terms of permitted entropies, Ye values, and expansion timescales in (2). This relates mostly to the A < 110 mass range, where a fit to solar r-abundances in high-entropy supernova scenarios seems to be hard to attain. Possible low-entropy alternatives are presented.

Nuclear level density and the determination of thermonuclear rates for astrophysics

The prediction of cross sections for nuclei far off stability is crucial in the field of nuclear astrophysics. In recent calculations the nuclear level density{emdash}as an important ingredient to the statistical model (Hauser-Feshbach){emdash}has shown the highest uncertainties. We present a global parametrization of nuclear level densities within the back-shifted Fermi-gas formalism. Employment of an energy-dependent level density parameter a, based on microscopic corrections from a recent finite range droplet model mass formula, and a backshift {delta}, based on pairing and shell corrections, leads to a highly improved fit of level densities at the neutron-separation energy in the mass range 20{le}A{le}245. The importance of using proper microscopic corrections from mass formulas is emphasized. The resulting level description is well suited for astrophysical applications. The level density can also provide clues to the applicability of the statistical model which is only correct for a high density of excited states. Using the above description, one can derive a {open_quotes}map{close_quotes} for the applicability of the model to reactions of stable and unstable nuclei with neutral and charged particles. {copyright} {ital 1997} {ital The American Physical Society}

THORIUM AND URANIUM CHRONOMETERS APPLIED TO CS 31082-001

We use the classical r-process model to explore the implications of the recently reported first observation of U in the extremely metal-poor, r-process element–enriched halo star CS 31082-001 for U and Th cosmochronometry. Using updated nuclear physics input and performing a new, conservative, analysis of the remaining uncertainties in the classical r-process model, we confirm that U (together with Th) abundance observations in metal-poor stars are a promising tool for dating r-process events in the early Galaxy, independent of assumptions on Galactic chemical evolution. We show that nuclear physics uncertainties limit the present accuracy of estimated U/Th ages to about 2 Gyr. Critical nuclear data that are required to lower this uncertainty include � -delayed fission branchings and reliable predictions of the onset of deformation in the vicinity of the N ¼ 184 shell closure around 244 Tl, as both directly affect predicted U/Th ratios in r-process models. In this paper we apply, for the first time, the new HFBCS-1 mass model within the framework of the classical r-process model. We find that the predicted U and Th abundances are incompatible with the solar U and Th abundances and trace this back to a different prediction of the onset of deformation around 244 Tl. In the case of CS 31082-001, we find it likely that the zero-age U and Th abundances were enhanced by about a factor of 2.5 compared to both (1) a theoretical extrapolation from the observed stable elements using the classical r-process model and (2) the zero-age abundances of Th and U in other r-process–enhanced, metalpoor halo stars. Although presently ad hoc, this ‘‘ actinide boost ’’ assumption solves the apparent problem of the relative age difference compared with other metal-poor halo stars and, at the same time, the problem of the inconsistency of ages based on U/(stable nucleus), Th/(stable nucleus) and U/Th ratios. There clearly exist differences, among some r-process–enhanced, metal-poor stars, in the level of the elemental abundances of actinides beyond the third r-process peak. Whether CS 31082-001 is a relatively rare case or commonplace awaits the identification of larger numbers of r-process–enhanced, metal-poor stars in which both U and Th can be measured. Using the U/Th ratio, we obtain a best age estimate for the r-process elements in CS 31082001 of 15:5 � 3:2 Gyr. Future observations of Pb and Bi and a better determination of the r-process contribution to solar Pb are needed to put the age estimates for this and other stars on a more solid basis. For our most likely scenario, we provide predictions of the expected upper and lower limits on the abundances of the elements Pb and Bi in CS 31082-001. Subject headings: Galaxy: abundances — Galaxy: evolution — nuclear reactions, nucleosynthesis, abundances — stars: abundances — stars: Population II

Are highly siderophile elements PGE, Re and Au fractionated in the upper mantle of the earth? New results on peridotites from Zabargad

Abstract Seven peridotite samples from Zabargad Island (Red Sea) were analyzed for highly siderophile elements (HSE), including five platinum-group elements (PGE: Os, Ir, Ru, Rh, Pd) and Re and Au. Petrography and chemical composition of the samples had been published earlier [Kurat, G., Palme,xa0h., Embey-Isztin, A., Touret, J., Ntaflos, T., Spettel, B., Brandstatter, F., Palme, C., Dreibus, G., Prinz,xa0m., 1993. Petrology and geochemistry of peridotites and associated vein rocks of Zabargad Island, Red Sea, Egypt. Mineralogy and Petrology 48, 309–341]. Five samples with chemical compositions typical of upper mantle rocks, from fertile to increasingly depleted mantle (CaO: 3.39 to 0.21%), have Ir concentrations from 1.98 to 3.28xa0ppb, within the range in spinel and garnet-lherzolites from worldwide occurrences. There is, in Zabargad and in other localities, no systematic dependence of the contents of Ir and other PGE on the degree of fertility of the host rock (amount of cpx) nor on the geologic setting, xenolith or massive peridotite. Two samples, an orthopyroxenite (7.9xa0ppb Ir) and a plagioclase wehrlite (29.08xa0ppb) have significantly higher oncentrations of all HSE, except Re, reflecting the mobility of these elements in a metasomatized mantle. The more or less unfractionated PGE-patterns and the comparatively low Re contents of the enriched rocks indicate that the PGE were apparently transported with a single mobile phase, presumably sulfides, and that Re is chemically decoupled from the other HSE. However, because of the approximately constant level of PGE in upper mantle rocks, it is unlikely that such phases are the main carriers of PGE in these rocks. Although the CI-normalized patterns of the HSE in the Zabargad samples are to a first order chondritic a detailed inspection reveals deviations from chondritic ratios within about a factor of two, significantly beyond analytical uncertainties. Six of the seven samples show enrichments in Pd (factor of two)and some enrichments in Ru (30%)and Rh (30%)relative to the CI-concentrations of Ir, Os. Rhenium contents are variable and decoupled from the PGE abundances. If the HSEs were added to the Earths mantle with a late chondritic veneer ratios among these elements should better agree with chondritic ratios. Variations within the groups of chondritic meteorites are too small to explain the observed “anomalies’’. The fractionated patterns of PGE in the Zabargad rocks either indicate the presence of additional, perhaps local, components of HSEs in the mantle, or they reflect processing of the PGE within the upper mantle, or, alternatively, the late veneer hypothesis is invalid. It is important in future work to better define the lateral and/or vertical extent of such anomalies in the Earths mantle.

HIGHLY SIDEROPHILE ELEMENTS (RE, OS, IR, RU, RH, PD, AU) IN IMPACT MELTS FROM THREE EUROPEAN IMPACT CRATERS (SAAKSJARVI, MIEN, AND DELLEN) : CLUES TO THE NATURE OF THE IMPACTING BODIES

Twenty-two large (10 g) impact melt samples from three Scandinavian craters (i.e., Saaksjarvi, Finland; and Mien and Dellen, Sweden) were analyzed for highly siderophile elements (HSE: platinum group elements, Rh, and Au) by the nickel sulfide technique in combination with neutron activation. The ten impact melt samples from Saaksjarvi are enriched in Ir and other highly siderophile elements (Ir = 2.48 ± 0.73 ng/g) relative to average upper crust concentrations (0.03 ± 0.02 ng/g Ir). The twelve Dellen and Mien samples are marginally enriched in Ir (0.48 ± 0.23 ng/g for Dellen, and 0.37 ± 0.23 ng/g for Mien). n nThe amount of meteoritic component corresponds to 0.5% of a nominal CI component for Saaksjarvi, and about 0.1% for Mien and Dellen. The Saaksjarvi pattern is fractionated relative to CI-chondrites. Normalized abundances increase from the refractory to the more volatile siderophile elements (Ir < Ni). The trend is qualitatively similar to magmatic iron meteorites and corresponds to 0.4% of a nominal magmatic iron meteorite component (Tamarugal, IIIAB). For Mien and Dellen no projectile assignment can be made. n nAll samples from the three impact craters have low OsIr ratios compared to chondritic ratios. Either the projectile had low OsIr ratios or Os was lost during the impact as volatile OsO4. n nBased on the results of this study and on a compilation of literature data, average upper crustal abundances of the highly siderophile elements in the target area (Baltic shield) are estimated as 0.03 ng/g for Ir and Os, 1.1 ng/g for Ru, 0.38 ng/g for Rh, 2.0 ng/g for Pd, 8 μg/g for Co, and 37 μg/g for Cr. These data are representative of the upper crust. They allow, for the first time, reliable estimates of crustal abundances for Rh and Ru. n nUpper crustal abundances also show that Ir and Os are the most favourable elements for the identification of meteoritic signatures. Fractionated OsIr ratios in magmatic iron meteorites or potential losses of Os during the impact leaves Ir as the best indicator element for meteoritic contamination. With Ir, extraterrestrial components as low as 2 × 104 × CI may be identified.