Composition of Kerogen in Kupferschiefer from Southwest Poland

Thirty-seven Kupferschiefer samples from southwestern Poland were analyzed by microscopy, Rock-Eval approach and instrumental neutron activation analysis to understand the geochemical and morphological characteristics of kerogen present in the samples. The analytical results indicate that there are two different types of kerogens. One type was only subjected to thermal alteration processes, and the other was further oxidized after deposition of the sediment.In the oxidized samples migrabitumen was transformed into pyrobitumen. Rock-Eval analyses show a significant decrease in HI values in the oxidized samples and an increase in OI values in relation to the samples that were not influenced by oxidation. Variations in S2 versus Corg contents indicate a change in kerogen from Type II to Type III with progressing oxidation. The presence of pyrobitumen and the depletion of hydrogen in the altered kerogen allow one to conclude that the kerogen was used as hydrogen donor for thermochemical sulfate reduction(TSR).     

Space-time mapping of soil salinity using probabilistic bayesian maximum entropy

The mapping of saline soils is the first task before any reclamation effort. Reclamation is based on the knowledge of soil salinity in space and how it evolves with time. Soil salinity is traditionally determined by soil sampling and laboratory analysis. Recently, it became possible to complement these hard data with soft secondary data made available using field sensors like electrode probes. In this study, we had two data sets. The first includes measurements of field salinity (EC_a) at 413 locations and 19 time instants. The second, which is a subset of the first (13 to 20 locations), contains, in addition to EC_a, salinity determined in the laboratory (EC_2.5). Based on a procedure of cross-validation, we compared the prediction performance in the space-time domain of 3 methods: kriging using either only hard data (HK) or hard and mid interval soft data (HMIK), and Bayesian maximum entropy (BME) using probabilistic soft data. We found that BME was less biased, more accurate and giving estimates, which were better correlated with the observed values than the two kriging techniques. In addition, BME allowed one to delineate with better detail saline from non-saline areas.     

Managed water levels and the expansion of emergent vegetation along a lakeshore

Water-level fluctuations may be used to promote the expansion of emergent vegetation along lakeshores. We present the case of the lake Volkerak-Zoommeer in the Netherlands, a fresh-water lake created in 1987 after the enclosure of an estuary. Using an experimental area in which the water level could be manipulated, it was shown that partial summer drawdown of the shoreline created suitable conditions for germination and growth of tall emergent species (in particular Phragmites australis). Plant survival and growth depended on subsequent water-level fluctuations and grazing by waterbirds. Based on the experiment and empirical data, a model was developed to predict the effects of the water-level regime on potential reed bed development. The model was applied for four hydrological scenarios that have been considered for the water-level management of the lake.     

Decoupling of As and Fe release to Bangladesh groundwater under reducing conditions. Part I: Evidence from sediment profiles

This study reexamines the notion that extensive As mobilization in anoxic groundwater of Bangladesh is intimately linked to the dissolution of Fe oxyhydroxides on the basis of analyses performed on a suite of freshly collected samples of aquifer material. Detailed sediment profiles extending to 40 to 70 m depth below the surface were obtained at six sites where local groundwater As concentrations were known to span a wide range. The sediment properties that were measured include (1) the proportion of Fe(II) in the Fe fraction leached in hot 1.2 N HCl, (2) diffuse spectral reflectance, and (3) magnetic susceptibility.In parallel with local concentrations of dissolved As ranging from <5 to 600 μg/L, Fe(II)/Fe ratios in shallow (gray) Holocene sands tended to gradually increase with depth from values of 0.3 to 0.5 to up to 0.9. In deeper (orange) aquifers of presumed Pleistocene age that were separated from shallow sands by a clay layer and contained <5 μg/L dissolved As, leachable Fe(II)/Fe ratios averaged ∼0.2. There was no consistent relation between sediment Fe(II)/Fe and dissolved Fe concentrations in groundwater in nearby wells. The reflectance measurements indicate a systematic linear relation (R² of 0.66; n = 151) between the first derivative transform of the reflectance at 520 nm and Fe(II)/Fe. The magnetic susceptibility of the shallow aquifer sands ranged from 200 to 3600 (x 10⁻⁹ m³/kg SI) and was linearly related (R² of 0.75; n = 29) to the concentrations of minerals that could be magnetically separated (0.03 to 0.79% dry weight). No systematic depth trends in magnetic susceptibility were observed within the shallow sands, although the susceptibility of deeper low-As aquifers was low (up to ∼200 × 10⁻⁹ m³/kg SI).This set of observations, complemented by incubation results described in a companion paper by van Geen et al. (this volume), suggests that the release of As is linked to the transformation of predominantly Fe (III) oxyhydroxide coatings on sand particles to Fe(II) or mixed Fe(II/III) solid phases with a flatter reflectance spectrum such as siderite, vivianite, or magnetite, without necessarily resulting in the release of Fe to groundwater. The very low As/Fe ratio of magnetically separated minerals compared to the As/Fe of bulk acid leachate (2 vs. 40 10⁻⁶, respectively) suggests that such a transformation could be accompanied by a significant redistribution of As to a mobilizable phase on the surface of aquifer particles.     

Viruses as potential regulators of regional brown tide blooms caused by the alga,Aureococcus anophagefferens

Blooms of the brown tide organismAureccoccus anophagefferens have recurred in the coastal bays in New Jersey since 1995 and in the coastal bays of Long Island since 1985. Intracellular viral-like particles (VLPs) were documented during 1999–2000 brown tide blooms in Little Egg Harbor, New Jersey, but it was not determined whether cells were infected during the termination of the bloom. The objective of this study was to determine if VLPs infected and lysed natural populations ofA. anophagefferens in coastal bays of New Jersey and New York in 2002 with the same frequency as in 1999–2000 and especially at the termination of the bloom. Our results confirmed that the highest percentage (37.5%) of VLP-infected cells occurred at the termination of the brown tide bloom in New Jersey in 2002. Intracellular VLPs were present throughout the bloom event. The percentage of visibly infected cells was higher at the beginning of the bloom than during the peak of the bloom. The intracellular VLPs in natural populations ofA. anophagefferens were consistent in size and shape (approximately 140 nm in diameter) and comparable to those in previous studies. Concentrated viral isolates, prepared from waters during brown tide blooms in New York and New Jersey in 2002, infected healthy laboratoryA. anophagefferens cultures in vitro. The viral isolates associated with the highest laboratory viral activity (lysis positive) were concentrated from water samples having the highest viral and bacteria concentrations. The intracellular viruses in these virally infected laboratory cultures ofA. anophagefferens were similar in size and shape to those found in natural populations. The successful isolation of a virus specific toA. anophagefferens from a brown tide bloom in the field, the similarity of ultrastructure of VLPs infecting both natural populations and laboratory infected cultures, and the pattern of VLP infection during bloom activity in combination with the observed high percentage of VLP-infected cells during bloom termination, supports, the hypothesis that viruses may be a major source of mortality for brown tide blooms in regional coastal bays of New Jersey and New York.     

Crustal thickening in an extensional regime: application to the mid-Norwegian Vøring margin

The structure of the mid-Norwegian volcanic Vøring margin at the onset of the Maastrichtian–Paleocene extension phase reflects the cumulative effect of earlier consecutive rifting events. Lateral structural differences present on the margin at that time are a consequence of migration of the location of maximum extension in time between Norway and Greenland. The most important imprints (Moho depth, thermal structure) of these events on the lithosphere are incorporated in a numerical simulation of the final extension phase. We focus on a possible mechanism of formation of the Vøring Marginal High and address the relationship between spatial and temporal evolution of crustal thinning and thickening, uplift of the surface and strength of the lithosphere.It is found that the Vøring Basin formed the strongest part of the margin which explains why the Maastrichtian–Paleocene rift axis was not located here but instead jumped westward with respect to the earlier rift axes locations. The modeling study predicts that local crustal thickening during extension can be expected when large lateral thermal variations are present in the lithosphere at the onset of extension. Negative buoyancy induced by lateral temperature differences increases downwelling adjacent to the rifting zone; convergence of material at the particular part of the margin is mainly taken up by the lower crust. The model shows that during the final phase of extension, the crust in the Vøring Marginal High area was thickened and the surface uplifted. It is likely that this dynamic process and the effects of magmatic intrusions both acted in concert to form the Marginal High.     

The influence of particle composition on thorium scavenging in the NE Atlantic ocean (POMME experiment)

²³⁰Th, ²³²Th and ²³⁴Th were analyzed in sinking particles collected by moored and drifting sediment traps in the NE Atlantic Ocean (POMME experiment) in order to constrain the phase(s) carrying Th isotopes in the water column. It reveals a contrasted behaviour between ²³⁴Th and ²³⁰Th. ²³⁴Th is correlated to the particulate organic carbon suggesting that it is primarily scavenged by organic compounds in the surface waters. ²³⁰Th_xs is correlated with Mn, Ba and the lithogenic fraction that are enriched in small suspended particles and incorporated in the sinking particulate flux throughout the water column. The lack of correlation between ²³⁰Th_xs and CaCO₃ or biogenic silica (bSi) indicates that CaCO₃ and bSi are not responsible for ²³⁰Th scavenging in the deep waters of this oceanic region. ²³⁰Th is generally correlated with the lithogenic content of the trapped material but this correlation disappears in winter during strong atmospheric dust inputs suggesting that lithogenic matter is not directly responsible for ²³⁰Th scavenging in the deep waters or that sufficient time is required to achieve particle–solution equilibration. MnO₂ could be the prevalent ²³⁰Th_xs-bearing phase. The narrow range of K_{d_MnO2}^Th obtained for very contrasted oceanic environments supports a global control of ²³⁰Th_xs scavenging by MnO₂ and raises the possibility that the ²³⁰Th–²³¹Pa fractionation is controlled by the amount of colloidal MnO₂ in seawater.