Geochemistry of Aquatic Sediments

The type and composition of freshwater and marine sediments are key factors in environmental research of (a) natural processes such as sediment transport and accumulation, biodiversity, and biogeochemical reactions within sediments and (b) evaluation of source and progress of contamination, as aquatic sediments act as a sink for nonorganic and organic toxic substances. Above certain levels, such substances could harm biological diversity and human health. Geochemical investigations of aquatic sediments in fluvial, lacustrine, estuarine, and marine environments are of fundamental interest for the assessment of natural ecosystems and the level of pollution that potentially harms them. Detailed determination of the chemical constituents of aquatic sediments assists in detecting sources of pollution as sewage, industry, agriculture, abandoned and active mines, landfills, harbor activities, and oil drilling [leakage]. In addition, natural anomalies may indicate mineral resources in a particular region. New methods and approaches for sampling and analysis are continuously being introduced in aquatic sediment research. More attention is given to qualitative and quantitative monitoring of sediment and sediment fluxes, which is regularly established in most European countries and many others worldwide. Unfortunately, uniform legislation of sediment quality [and load] still does not exist on an international level and in most countries does not exist even on the national level. Therefore, more attention should be given to further expansion of sediment monitoring and of establishing criteria for assessing sediment quality and legislative for toxic inorganic and organic pollutants

On the algorithmic solution of optimization problems subject to probabilistic/robust (probust) constraints

We present an adaptive grid refinement algorithm to solve probabilistic optimization problems with infinitely many random constraints. Using a bilevel approach, we iteratively aggregate inequalities that provide most information not in a geometric but in a probabilistic sense. This conceptual idea, for which a convergence proof is provided, is then adapted to an implementable algorithm. The efficiency of our approach when compared to naive methods based on uniform grid refinement is illustrated for a numerical test example as well as for a water reservoir problem with joint probabilistic filling level constraints

Intergenerational transmission of unemployment : evidence for German sons

This paper studies the association between the unemployment experience of fathers and their sons. Based on German survey data that cover the last decades we find significant positive correlations. Using instrumental variables estimation and the Gottschalk (1996) method we investigate to what extent fathers' unemployment is causal for offsprings' employment outcomes. In agreement with most of the small international literature we do not find a positive causal effect for intergenerational unemployment transmission. This outcome is robust to alternative data structures and to tests at the intensive and extensive margin of unemployment

Integrated Monitoring of Particle-Associated Transport of Persistent Organic Pollutants (PAHs as case study) in Contrasting Catchments in Southwest Germany

Strongly sorbing hydrophobic pollutants such as polycylic aromatic hydrocarbons (PAHs) are primarily subjected to particle-associated transport and thus are mobilized especially during high flow conditions when soils and sediments undergo erosion and urban runoff is intensified. Whereas soil pollutants reach rivers only slowly by erosion, untreated surface runoff from sealed urban space and stormwater releases are major immediate sources of particle bound pollutants. Chemical loads to rivers in general may increase with increasing population density or urban development of watersheds due to abundance of sources and impervious surface. Given the scope of anthropogenic impact, integrated and cost-effective strategies for containment monitoring in catchments are needed

Towards an integrated understanding of how micro scale processes shape groundwater ecosystem functions

Micro scale processes are expected to have a fundamental role in shaping groundwater ecosystems and yet they remain poorly understood and under-researched. In part, this is due to the fact that sampling is rarely carried out at the scale atwhich microorganisms, and their grazers and predators, function and thus we lack essential information. While set within a larger scale framework in terms of geochemical features, supply with energy and nutrients, and exchange intensity and dynamics, the micro scale adds variability, by providing heterogeneous zones at the micro scalewhich enable awider range of redox reactions. Here we outline howunderstanding micro scale processes better may lead to improved appreciation of the range of ecosystemsfunctions taking place at all scales. Such processes are relied upon in bioremediation and we demonstrate that ecosystem modelling as well as engineering measures have to take into account, and use, understanding at the micro scale. We discuss the importance of integrating faunal processes and computational appraisals in research, in order to continue to secure sustainable water resources from groundwater

The complete genome sequence of the acarbose producer Actinoplanes sp. SE50/110

Schwientek P, Szczepanowski R, Rückert C, et al. The complete genome sequence of the acarbose producer Actinoplanes sp. SE50/110. BMC Genomics. 2012;13(1): 112.Background Actinoplanes sp. SE50/110 is known as the wild type producer of the alpha-glucosidase inhibitor acarbose, a potent drug used worldwide in the treatment of type-2 diabetes mellitus. As the incidence of diabetes is rapidly rising worldwide, an ever increasing demand for diabetes drugs, such as acarbose, needs to be anticipated. Consequently, derived Actinoplanes strains with increased acarbose yields are being used in large scale industrial batch fermentation since 1990 and were continuously optimized by conventional mutagenesis and screening experiments. This strategy reached its limits and is generally superseded by modern genetic engineering approaches. As a prerequisite for targeted genetic modifications, the complete genome sequence of the organism has to be known. Results Here, we present the complete genome sequence of Actinoplanes sp. SE50/110 [GenBank:CP003170], the first publicly available genome of the genus Actinoplanes, comprising various producers of pharmaceutically and economically important secondary metabolites. The genome features a high mean G + C content of 71.32% and consists of one circular chromosome with a size of 9,239,851 bp hosting 8,270 predicted protein coding sequences. Phylogenetic analysis of the core genome revealed a rather distant relation to other sequenced species of the family Micromonosporaceae whereas Actinoplanes utahensis was found to be the closest species based on 16S rRNA gene sequence comparison. Besides the already published acarbose biosynthetic gene cluster sequence, several new non-ribosomal peptide synthetase-, polyketide synthase- and hybrid-clusters were identified on the Actinoplanes genome. Another key feature of the genome represents the discovery of a functional actinomycete integrative and conjugative element. Conclusions The complete genome sequence of Actinoplanes sp. SE50/110 marks an important step towards the rational genetic optimization of the acarbose production. In this regard, the identified actinomycete integrative and conjugative element could play a central role by providing the basis for the development of a genetic transformation system for Actinoplanes sp. SE50/110 and other Actinoplanes spp. Furthermore, the identified non-ribosomal peptide synthetase- and polyketide synthase-clusters potentially encode new antibiotics and/or other bioactive compounds, which might be of pharmacologic interest

Contributions of catchment and in-stream processes to suspended sediment transport in a dominantly groundwater-fed catchment

Suspended sediments impact stream water quality by increasing the turbidity and acting as a vector for strongly sorbing pollutants. Understanding their sources is of great importance to developing appropriate river management strategies. In this study, we present an integrated sediment transport model composed of a catchment-scale hydrological model to predict river discharge, a river-hydraulics model to obtain shear stresses in the channel, a sediment-generating model, and a river sediment-transport model. We use this framework to investigate the sediment contributions from catchment and in-stream processes in the Ammer catchment close to Tübingen in southwestern Germany. The model is calibrated to stream flow and suspended-sediment concentrations. We use the monthly mean suspended-sediment load to analyze seasonal variations of different processes. The contributions of catchment and in-stream processes to the total loads are demonstrated by model simulations under different flow conditions. The evaluation of shear stresses by the river-hydraulics model allows the identification of hotspots and hot moments of bed erosion for the main stem of the Ammer River. The results suggest that the contributions of suspended-sediment loads from urban areas and in-stream processes are higher in the summer months, while deposition has small variations with a slight increase in summer months. The sediment input from agricultural land and urban areas as well as bed and bank erosion increase with an increase in flow rates. Bed and bank erosion are negligible when flow is smaller than the corresponding thresholds of 1.5 and 2.5 times the mean discharge, respectively. The bed-erosion rate is higher during the summer months and varies along the main stem. Over the simulated time period, net sediment trapping is observed in the Ammer River. The present work is the basis to study particle-facilitated transport of pollutants in the system, helping to understand the fate and transport of sediments and sediment-bound pollutants.</p