Dieter Zachmann

Biogeochemistry of Iron and Sulfur in Sediments of an Acidic Mining Lake in Lusatia, Germany

Chemical, microbiological and stable isotope analyses of sediments from an acidic mining lake were used to evaluate whether biogeochemical processes, such as iron and sulfate reduction, are extant, because such processes can potentially generate alkalinity. Sediment cores were sliced in cm intervals to achieve a high resolution for spatial distribution of organic and inorganic components. Iron, sulfur, carbon, nitrogen and phosphorus as well as the most probable number (MPN) of iron reducing bacteria, the amount of lipid phosphate and the stable isotope compositions of various sedimentary sulfur compounds were measured. Accumulation of degradable organic material, reduced mass fractions of iron, enhanced concentrations of lipid phosphate, high concentrations of DOC and ferrous iron in the pore water and a drastic change of sulfur isotope ratios in the upper 3 cm of the sediment all indicated a highly reactive zone of biogeochemical transformations. The data provide clear evidence for iron and sulfate reducing processes in the sediments that result in an increase of pH with depth.

Binding of Sulfurated Molybdenum Cofactor to the C-terminal Domain of ABA3 from Arabidopsis thaliana Provides Insight into the Mechanism of Molybdenum Cofactor Sulfuration

The molybdenum cofactor sulfurase ABA3 from Arabidopsis thaliana is needed for post-translational activation of aldehyde oxidase and xanthine dehydrogenase by transferring a sulfur atom to the desulfo-molybdenum cofactor of these enzymes. ABA3 is a two-domain protein consisting of an NH2-terminal NifS-like cysteine desulfurase domain and a C-terminal domain of yet undescribed function. The NH2-terminal domain of ABA3 decomposes l-cysteine to yield elemental sulfur, which subsequently is bound as persulfide to a conserved protein cysteinyl residue within this domain. In vivo, activation of aldehyde oxidase and xanthine dehydrogenase also depends on the function of the C-terminal domain, as can be concluded from the A. thaliana aba3/sir3-3 mutant. sir3-3 plants are strongly reduced in aldehyde oxidase and xanthine dehydrogenase activities due to a substitution of arginine 723 by a lysine within the C-terminal domain of the ABA3 protein. Here we present first evidence for the function of the C-terminal domain and show that molybdenum cofactor is bound to this domain with high affinity. Furthermore, cyanide-treated ABA3 C terminus was shown to release thiocyanate, indicating that the molybdenum cofactor bound to the C-terminal domain is present in the sulfurated form. Co-incubation of partially active aldehyde oxidase and xanthine dehydrogenase with ABA3 C terminus carrying sulfurated molybdenum cofactor resulted in stimulation of aldehyde oxidase and xanthine dehydrogenase activity. The data of this work suggest that the C-terminal domain of ABA3 might act as a scaffold protein where prebound desulfo-molybdenum cofactor is converted into sulfurated cofactor prior to activation of aldehyde oxidase and xanthine dehydrogenase.

Sugarcane bagasse treated with hydrous ferric oxide as a potential adsorbent for the removal of As(V) from aqueous solutions.

The mechanism of As(V) removal from aqueous solutions by means of hydrated ferric oxide (HFO)-treated sugarcane bagasse (SCB-HFO) (Saccharum officinarum L.) was investigated. Effects of different parameters, such as pH value, initial arsenic concentration, adsorbent dosage, contact time and ionic strength, on the As(V) adsorption were studied. The adsorption capacity of SCB-HFO for As(V) was found to be 22.1 mg/g under optimum conditions of pH 4, contact time 3h and temperature 22 °C. Initial As(V) concentration influenced the removal efficiency of SCB-HFO. The desorption of As(V) from the adsorbent was 17% when using 30% HCl and 85% with 1M NaOH solution. FTIR analyses evidenced two potential binding sites associated with carboxyl and hydroxyl groups which are responsible for As(V) removal. Adsorption, surface precipitation, ion exchange and complexation can be suggested as mechanisms for the As(V) removal from the solution phase onto the surface of SCB-HFO.

Geostatistical Analysis of Surface Sediments in an Acidic Mining Lake

An exact morphometric description of Mining Lake 111, Brandenburg, Germany, was obtained after a new survey in 1996 by the staff of the water research department. Volume and surface area of ML111 were calculated based on values of this survey. An actual bathymetric map was created from the datapool which was the basis for the selection of sampling sites where we obtained sediment cores to describe the geochemistry of the lake sediments. Principal Component Analysis (PCA) was carried out to examine patterns and similarities between concentrations of different heavy metals. The patterns are different for the three basins within the lake. The spatial distributions of 12 elements in the sediment surface were estimated with a geostatistical procedure (Ordinary Kriging) as well as with a conventional interpolation method. The structure found with PCA was confirmed by the plots from spatial interpolation. Due to the complexity of the lake morphometry and bathymetry 66 sediment cores taken at 47 sampling sites were not sufficient to reduce the spatial variance distributions to acceptable values.

A Pan-African alkaline pluton intruding the Saramuj Conglomerate, south-west Jordan

The geological setting, petrography and bulk mineral chemistry of a monzodiorite and a presumably consanguineous megaporphyry with large (up to 25 cm) labradorite megacrysts, both intruding the upper Proterozoic Saramuj Conglomerate in south-west Jordan (south eastern shore of the Dead Sea), were examined. The crystallization temperatures of the monzodiorite and the megaporphyry as determined from pyroxene thermometry and supported by contact metamorphic mineralogy are about 700 and 900°C, respectively. The intrusion depth of the monzodiorite is about 3–4 km. The monzodiorite was emplaced in the Saramuj Conglomerate at about 595 + 2 Ma ago according to Rb/Sr and U/Pb age determinations.The stratigraphic positions of the monzodiorite, megaporphyry and their host rock (the Saramuj Conglomerate) were compared with time-equivalent lithologies in the Arabian-Nubian Shield.

The role of pressure in control of potassium, sodium, and copper concentration in hypabyssal intrusives as demonstrated in late Precambrian dikes in southwest Jordan

Abstract The formation of dikes in southwest Jordan took place during the late Proterozoic and represents the subsequent magmatic activity of the Pan-African orogeny. Dikes studied in detail include a zoned, multiple, composite dike of rhyolitic—trachytic and latitic composition, an andesitic dike and two devitrified rhyolitic dikes. High-level (near-surface) dikes are characterized by an extreme potassium metasomatism, which is caused by pressure effects. The shallower the intrusion the more intensive will be the potassium metasomatism. Some dikes display anomalously high copper concentrations. The copper is originally incorporated in silicates and has been enriched along flow lines and vesicules by autometasomatism. The formation of secondary copper minerals (e.g., cuprite, malachite, chrysocolla) can be considered as contemporaneous with the solidification of the congealing rhyolitic—trachytic melt.

Removal of arsenic (V) from aqueous medium using manganese oxide coated lignocellulose/silica adsorbents

ABSTRACT Arsenic (V) adsorption on manganese oxide coated rice wastes was investigated in this study. The modified adsorbents were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, and pH measurements to determine the point of zero charge. Batch adsorption equilibrium experiments were conducted to study the effects of pH, contact time, and initial concentration on arsenic removal efficiency. The adsorption capacity of rice waste was significantly improved after modification with permanganate. The Langmuir isotherm model fitted the equilibrium data better than the Freundlich model which confirms surface homogeneity of the adsorbent. Maxima adsorption capacities are determined as 10 and 12 mg/g at pH 3 for manganese oxide coated rice husk and straw, respectively. The adsorption energy indicates that the adsorption process may be dominated by chemisorption. Pseudo-second-order rate equation described the kinetics sorption of arsenic with good correlation coefficients, better than a pseudo-first-order equation. Manganese oxide coated rice husk and straw appear to be promising low cost adsorbents for removing arsenic from water.

Synthesis of iron oxyhydroxide-coated rice straw (IOC-RS) and its application in arsenic(V) removal from water.

Because of the recognition that arsenic (As) at low concentrations in drinking water causes severe health effects, the technologies of As removal have become increasingly important. In this study, a simplified and effective method was used to immobilize iron oxyhydroxide onto a pretreated naturally occurring rice straw (RS). The modified RS adsorbent was characterized, using scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analyzer, and surface area analyzer. Experimental batch data of As(V) adsorption were modeled by the isotherms and kinetics models. Although all isotherms, the Langmuir model fitted the equilibrium data better than Freundlich and Dubinin-Radushkevich models and confirmed the surface homogeneity of adsorbent. The iron oxyhydroxide-coated rice straw (IOC-RS) was found to be effective for the removal of As(V) with 98.5% sorption efficiency at a concentration of <50 mg/L of As(V) solution, and thus maximum uptake capacity is ∼22 and 20 mg As(V)/g of IOC-RS at pH 4 and 6, respectively. The present study might provide new avenues to achieve the As concentrations required for drinking water recommended by the World Health Organization.

Zeitliche Belastungsentwicklung von Sedimenten aus Elbaue-Stillgewässern

Die Problematik der Schwermetallbelastung der Elbe fur die okologische Entwicklung im Flus und seinen Uberschwammungsflachen wird seit 1989 auch in den neuen Bundeslandern intensiv untersucht. Als einer der grosten Flusse Europas nimmt die Elbe die Schwermetallfracht eines z.T. hochindustrialisierten Einzugsgebiets von 148268 km2 auf. Zu weiteren Schwermetallquellen im Einzugsgebiet zahlen die naturlichen Akkumulationen, wie z.B. die Lagerstatten umweltrelevanter Elemente im Erzgebirge und nicht zuletzt auch die Staube und Abgase. Die Kontaminanten treten dabei selten in geloster Form auf, sondern werden uberwiegend an Schwebstoffe gebunden im Flus transportiert. In welchem Mase die Schwermetalle in Sedimenten von Elbauen-Stillgewassern angereichert sind, sollte in dieser Arbeit unter anderem untersucht werden.

Schwermetalle in einer Elbaue bei Wittenberge

Die Verteilung von Schwermetallen wurde in einer Aue an der Mittelelbe untersucht (van der Veen 1998). Hierzu wurden die Oberboden des Gebietes geochemisch charakterisiert. Die gesammelten Daten wurden in Kartenform dargestellt (Abb. 2, 3). Mit Hilfe weiterer statistischer Verfahren, u. a. Korrelations-, Cluster- und Faktorenanalyse, wurden die fur die Anreicherung der Schwermetalle relevanten Prozesse ermittelt.