D. Stueben

Age and paleoenvironment of the Maastrichtian to Paleocene of the Mahajanga Basin, Madagascar: a multidisciplinary approach

Abstract Lithology, geochemistry, stable isotopes and integrated high-resolution biostratigraphy of the Berivotra and Amboanio sections provide new insights into the age, faunal turnovers, climate, sea level and environmental changes of the Maastrichtian to early Paleocene of the Mahajanga Basin of Madagascar. In the Berivotra type area, the dinosaur-rich fluvial lowland sediments of the Anembalemba Member prevailed into the earliest Maastrichtian. These are overlain by marginal marine and near-shore clastics that deepen upwards to hemipelagic middle neritic marls by 69.6 Ma, accompanied by arid to seasonally cool temperate climates through the early and late Maastrichtian. An unconformity between the Berivotra Formation and Betsiboka limestone marks the K–T boundary, and juxtaposes early Danian (zone Plc? or Pld) and latest Maastrichtian (zones CF2–CF1, Micula prinsii ) sediments. Seasonally humid warm climates began near the end of the Maastrichtian and prevailed into the early Danian, accompanied by increased volcanic activity. During the late Danian (zones P1d–P2), a change to seasonally arid climates was accompanied by deepening from middle to outer neritic depths.

Characterization of aquifers conducting groundwaters with low and high arsenic concentrations: a comparative case study from West Bengal, India

Abstract Possible relationships between groundwater arsenic concentration and alluvial sediment characteristics in a ~19 km2 area in West Bengal have been investigated using a combination of hydrogeochemical, lithogeochemical and geophysical techniques. Arsenic hotspots, typically associated with elevated groundwater Fe and Mn, were found to be correlated to some extent with old river channels (abandoned meanders, oxbow lakes), where sandy aquifers included intercalated fine-grained overbank deposits, rich in As, Fe, Mn and Corg. Otherwise no demonstrably significant overall differences in any of lithology, grain-size distribution, mineral composition or Fe, Mn and organic C content of the sediments were found between two representative sites with contrastingly low (<50 μg 1-1) and high (>200 μg 1-1) As groundwater contents. Our results are consistent with microbially mediated redox reactions controlled by the presence of natural organic matter within the aquifer and the occurrence of As-bearing redox traps, primarily formed by Fb and Mn oxides/hydroxides, being the most important factors which control the release of As into shallow groundwaters at the study site.

Verteilung verkehrsbedingter Edelmetallimmissionen in Böden

ZusammenfassungDie Verteilung verkehrsbedingter Platingruppenelemente (PGE) aus Kfz-Abgaskatalysatoren in straßennahen Böden wurde an verschiedenen Standorten untersucht. Entlang senkrecht zur Fahrbahn verlaufender Traversen (0,1–10 m) wurden Bodenproben aus drei unterschiedlichen Bodentiefen entnommen. Die Bestimmung der Gehalte an Platin, Rhodium und Palladium erfolgte nach Abtrennung und Anreicherung durch Nickelsulfid-Dokimasie und naßchemischem Aufschluß (HCl/H2O2) mittels ICP-MS. Die Platinkonzentrationen im straßennahen Boden liegen zwischen 250 μg/kg und den geogenen Hintergrundwerten. Die Platin/Rhodium-Verhältnisse in Straßensedimenten und kontaminierten Oberböden liegen bei 6∶1 und entsprechen somit weitgehend den langjährig in der Katalysatorproduktion eingesetzten Mengenverhältnissen. Deutliche Abhängigkeiten der Immissionen von der Entfernung zur Fahrbahn, der Bodentiefe und Standortmerkmalen, wie Hauptwindrichtung, Barrieren durch Vegetation oder Morphologie sowie der Verkehrsdichte und Stauhäufigkeit zeichnen sich anhand der gemessenen Konzentrationsprofile ab.AbstractContents and distribution of platinum-group-elements (PGE) in soils caused by automobile emissions were investigated at three transects perpendicular to the road at various depths. Concentrations of platinum, rhodium and palladium were determined by ICP-MS after separation and preconcentration by nickel-sulphide fire-assay. Platinum contents in roadside soils range from 250 μg/kg to the local background values which are below 0.5–0.8 μg/kg. Ratios of platinum and rhodium (about 6∶1) are similar to the ratios in catalytic converters. There is evidence for a significant correlation of PGE input and local parameters such as traffic-conditions, distance from the trafficlane, prevailing wind direction, and barriers such as vegetation or morphology.

The Application of Microelectrodes for the Measurements of Trace Metals in Water

Abstract The analytical approaches for the determination of trace concentrations of heavy metals in aquatic systems are briefly introduced. A detailed review on the recent advances of microelectrodes is presented, including the definitions, types, advantages, theory, and fabrication of microelectrodes. The application of microelectrodes on the measurements of trace metals in water is focused on the voltammetric‐, potentiometric‐, and in situ electrochemical sensors.