Lake Shala: Water chemistry,mineralogy and geochemistry of sediments in an Ethiopian Rift lake

Lake Shala, the deepest lake in the internal Galla lakes basin of the Ethiopian Rift, fills a depression in Pleistocene volcanic rocks. Its sodium-bicarbonate (-chloride) water (salinity 16 g/l) is remarkably low in earth alkalines and sulphate. Stratification is indicated by different ion concentrations in the surface and bottom waters and by a thermocline in a water depth of 50–70 m. Hot soda springs emerging on the shores of Lakes Shala and Langano are believed to be derived from a hot saline underground reservoir recharged by meteoric waters. The ion composition of the hot spring waters is uniform and matches that in the Galla Lakes except for total salinities. Anomalous heavy metal concentrations are lacking in lake and hot spring waters. Sediments of Lake Shala belong to an extremely fine-grained group of deposits. They are poorly sorted and the lateral distribution of the grain sizes does not follow the normal scheme for aquatic depositional environments. A belt, 50–100 m below lake level containing the finest-grained sediments, separates the shallow periphery of the lake bottom from the deep center, both characterized by coarser-grained deposits. The sediments consist of a large portion of glassy components. A poorly cristallized smectite is most abundant in the clay mineral group. The components of the sand fraction are quartz, feldspar, glass particles and occasionally calcite. Nickel, cobalt and lead are depleted in the Lake Shala sediments compared with the averages of shales. Iron, manganese and zinc are relatively high. Silver, cadmium and some of the rare earth elements are enriched by factors of > 5.     

Die Liegendschichten der devonischen Pyrit- u. Schwerspat-Lager von Eisen (Saarland), Meggen und des Rammelsberges

Detailed petrographic and geochemical investigations on the rocks underlying the Devonian stratiforme pyrite and barite deposits of Eisen (Saar district), Meggen (Westphalia), and Rammeisberg (Harz Mountains) in the Rhenish Schiefergebirge have led to the following conclusions:

1. These deposits are tied to dark shales of the pelagic basin facies. In all cases a local depression of the sea floor coincides largely with the spatial extension of the overlying pyrite and barite bodies. These depressions are marked by a large number of sand and silt intercalations, accumulations of reef debris and a significant lower carbonate content.
2. The dark shales underneath the deposits have conspicuously high, but strongly varying contents of Mn, Zn and Pb. This, corresponding with the low carbonate content, is characteristic for the presence of hydrothermal, metalliferous emissions.
3. Predepositional phases of sulfide and barite emplacement are indicated by small layers and lenses.

     

A Comparison of an Ecological Model and GIS Spatial Analysis to Describe Niche Partitioning Amongst Carrion Beetles in Nebraska

Carrion beetles depend on vertebrate carcasses to rear their young. Carcasses are a limited resource with patchy distribution, and there is an intense competition among many species for these carcasses. This situation is expected to lead to niche partitioning, such that different beetle species use different resources and thus escape direct competition. Our project used a geographic information system (GIS) and pitfall sampling to characterize carrion beetle preferences for soil texture and land use in Kearney County, Nebraska. The GIS was used to select sites where sampling was conducted using pitfall traps baited with rat carcasses. Attracted beetles were counted, identified to species, and released. The resulting data were used to construct occurrence maps of eleven species of carrion beetles by overlaying soil texture and land use. We then compared the results of EcoSim (an ecological simulation model of niche overlap) with GIS–generated maps of probability of carrion beetle occurrence. Our results are consistent with landscape–level niche partitioning by seven of the eleven examined species. Our application of GIS to the spatial analysis of carrion beetle distributions demonstrates how this technology can be used to test ecological and evolutionary hypotheses, predict habitat associations, and examine the effects of land use on a community of insects. This work could easily be extended to study the habitat preferences of the federally endangered American burying beetle, Nicrophorus americanus .     

Fossil bacterial ecosystem at methane seeps : Origin of organic matter from Be’eri sulfur deposit, Israel

The Be’eri sulfur mine (Israel) is a unique deposit mainly composed of sandstone intercalated with biogenic mats and possessing organic matter exceptionally depleted in ¹³C. Molecular and isotopic studies of free and bound biomarkers were performed to unravel the source of the organic matter co-occurring with sulfur in this deposit and to propose a paleoenvironmental model of bacterial life in a type of extreme environment. They showed that the biomarkers are all extremely ¹³C-depleted and almost exclusively composed of hopanoids and biphytane derivatives of bacterial origin, notably methanotrophic bacteria and acidophilic archaea. δ¹³C values of individual components and of bulk organic carbon are in the −80% to −90% range and are among the lowest values ever measured for hopanoids. Organic matter in the sandstone and the mats differ mainly by the occurrence of 3-methylated hopanoids in the mats, which may reflect either different bacterial populations or different conditions of growth.These data demonstrate that the complete biomass of this deposit primarily derives from methanotrophic hopanoid-synthesizing bacteria consuming methane having seeped toward the surface, and that all other organisms—apparently only archaea and bacteria—must have been thriving on methane-derived carbon (methane, CO₂, biomass of methanotrophic bacteria). Unambiguous evidence for photosynthetic organisms in the environment of deposition could not be found. The Be’eri sulfur deposit is thus a fossil remain of an exclusively bacterial ecosystem fueled by methane as sole carbon source and having developed in an interstitial aqueous medium within the sandstone.Elemental sulfur from the deposit probably originates from the oxidation of hydrogen sulfide seeping along with methane, which could have been oxidized either abiotically or biologically by sulfur-oxidizing Beggiatoa-like bacteria and archaea. Further oxidation of elemental sulfur might explain the high acidity of the deposit.The oxidizing conditions now prevailing in the Be’eri deposit were revealed by the occurrence of degraded, oxidized, or thiophenic hopanoid structures. Some of them, unambiguously characterized by synthesis, were also obtained by heating hopenes with elemental sulfur, thus suggesting that the latter could play a role, as dehydrogenating and oxidizing agent, in the transformations undergone by organic matter in the Be’eri deposit.     

U-Th chronology and paleoceanographic record in a Fe-Mn crust from the NE Atlantic over the last 700 ka

Hydrogenetic ferromanganese crusts (Fe-Mn crusts) provide a secular record of the variations of seawater composition responding to changes in ocean circulation and erosion processes. In this respect, the acquisition of an absolute and reliable chronology in Fe-Mn crusts is a prerequisite. Here we combine four different and complementary chronometers (¹⁰Be, ²³⁰Th_ex, ²³⁰Th_ex/²³²Th, ²³⁴U/²³⁸U) in a Fe-Mn crust dredged at ∼2000 m depth in the east Atlantic to first establish a reliable chronology over the Quaternary period. Then, we use EDS chemical analysis to look for correlation between major element chemistry and climate changes. (²³⁰Th_ex), (²³⁰Th_ex/²³²Th), and Be data give very consistent growth rates. In particular, the good match between (²³⁰Th_ex) and (²³⁰Th_ex/²³²Th) data indicates that at the location of crust 121DK, ²³⁰Th and ²³²Th fluxes in the water column change simultaneously and suggests that the normalization of ²³⁰Th_ex to ²³²Th makes (²³⁰Th_ex/²³²Th) a better chronometer. Our best-fit model suggests that crust 121DK experienced changes in growth rates at ∼122 and 312 ka and a growth with a constant ²³⁰Th initial flux. This chronology returns an age of 680 ka for the uppermost 1.5 mm. The (²³⁴U/²³⁸U) depth profile, however, was clearly affected by diffusion of ²³⁴U in the porous crust and can therefore not be used to derive a reliable chronology. One part of the crust seems isolated from pore water diffusion and can be physically recognized as a zone of very small porosity. On the basis of the (²³⁰Th_ex/²³²Th) chronology, major element chemistry is shown to be linked to climate change. Mn/Fe variations compare well with those in a Fe-Mn crust from the Pacific, showing systematic maxima during glacial stages 2 and 4. High Mn/Fe are tentatively interpreted to reflect expansion of the oxygen minimum zone during glacial periods, resulting from higher bioproductivity. In addition we note that the surface (²³⁰Th/²³²Th) activity ratio of crust 121DK is entirely consistent with advection of deep water from the western toward the eastern Atlantic basin.     

On sediment pollution in selected german coastal waters of the Baltic Sea

In order to determine and assess their status sediments from the German coastal waters of the baltic sea were analyzed for structural parameters and for several groups of harmful substances. Regarding all groups of harmful substances, i.e. nutrients, heavy metals and organic toxicants the sediments of the eastern sections investigated (Strelasund, Peenestrom and Stettin Lagoon) are generally more polluted than the sediments of the other ones.The sediments of the examined sections of the Baltic coast compare with North Sea sediments by factors of between 0.05 and 4 with regard to heavy metals.Because of the variability of the concentration of harmful substances in the various coastal sections, it is imperative to make a differentiated assessment of the polluted sediments and to set district-related targets for the various sections of the Baltic coast.     

Simulation analysis of domestic water demand and its future uncertainty in water scarce areas

This paper demonstrates a practical simulation approach to analyze domestic water demand and its future uncertainty in water scarce areas through a case study of Beijing, China. Analytic models and a forecasting model were constructed using statistic and econometric regression approaches. The analytic models were used to analyze the interrelationships between domestic water demand and some socio-economic factors of Beijing. The forecasting model was applied to predict domestic water demand from 2009 to 2015, and this model was validated by comparing the prediction values with the observations. Scenario analysis was applied to simulate uncertainty and risks in domestic water demand in the future. The simulation results proved that domestic water demand will increase from 13.9×10⁸ m³ to 16.7×10⁸ m³ from 2009 to 2015. Three more sustainable strategies were also found through scenario analysis. The simulation and modeling approaches and results would be very supportive for water decision makers in allocating water efficiently and making sustainable water strategies.