API src

Found 197 results.

Immobilisation of arsenic in paddy soil by iron(II)-oxidizing bacteria

Arsenic-contaminated ground- and drinking water is a global environmental problem with about 1-2Prozent of the world's population being affected. The upper drinking water limit for arsenic (10 Micro g/l) recommended by the WHO is often exceeded, even in industrial nations in Europe and the USA. Chronic intake of arsenic causes severe health problems like skin diseases (e.g. blackfoot disease) and cancer. In addition to drinking water, seafood and rice are the main reservoirs for arsenic uptake. Arsenic is oftentimes of geogenic origin and in the environment it is mainly bound to iron(III) minerals. Iron(III)-reducing bacteria are able to dissolve these iron minerals and therefore release the arsenic to the environment. In turn, iron(II)-oxidizing bacteria have the potential to co-precipitate or sorb arsenic during iron(II)- oxidation at neutral pH followed by iron(III) mineral precipitation. This process may reduce arsenic concentrations in the environment drastically, lowering the potential risk for humans dramatically.The main goal of this study therefore is to quantify, identify and isolate anaerobic and aerobic Fe(II)-oxidizing microorganisms in arsenic-containing paddy soil. The co-precipitation and thus removal of arsenic by iron mineral producing bacteria will be determined in batch and microcosm experiments. Finally the influence of rhizosphere redox status on microbial Fe oxidation and arsenic uptake into rice plants will be evaluated in microcosm experiments. The long-term goal of this research is to better understand arsenic-co-precipitation and thus arsenic-immobilization by iron(II)-oxidizing bacteria in rice paddy soil. Potentially these results can lead to an improvement of living conditions in affected countries, e.g. in China or Bangladesh.

Diffusion and advection with sorption of anions, cations and non-polar molecules in organo-clays at varying thermo-chemical conditions - validation by analytical methods and molecular simulation

The sorption of anions in geotechnical multibarrier systems of planned high level waste repositories (HLWR) and of non-ionic and organic pollutants in conventional waste disposals are in the center of recent research. In aquatic systems, persistent radionuclides such as 79Se, 99Tc, 129I exist in a form of anions. There is strongly increasing need to find materials with high sorption capacities for such pollutants. Specific requirements on barrier materials are long-term stability of adsorbent under various conditions such as T > 100 C, varying hydrostatic pressure, and the presence of competing ions. Organo-clays are capable to sorb high amounts of cations, anions and non-polar molecules simultaneously having selectivity for certain ions. This project is proposed to improve the understanding of sorption and desorption processes in organo-clays. Additionally, the modification of material properties under varying chemical and thermal conditions will be determined by performing diffusion and advection experiments. Changes by sorption and diffusion will be analyzed by determining surface charge and contact angles. Molecular simulations on models of organo-clays will be conducted in an accord with experiments with aim to understand and analyze experimental results. The computational part of the project will profit from the collaboration of German partner with the group in Vienna, which has a long standing experience in a modeling of clay minerals.

Physicochemical Aging Mechanisms in Soil Organic Matter (SOM- AGING): II. Hydration-dehydration mechanisms at Biogeochemical Interfaces

Soil organic matter (SOM) controls large part of the processes occurring at biogeochemical interfaces in soil and may contribute to sequestration of organic chemicals. Our central hypothesis is that sequestration of organic chemicals is driven by physicochemical SOM matrix aging. The underlying processes are the formation and disruption of intermolecular bridges of water molecules (WAMB) and of multivalent cations (CAB) between individual SOM segments or between SOM and minerals in close interaction with hydration and dehydration mechanisms. Understanding the role of these mediated interactions will shed new light on the processes controlling functioning and dynamics of biogeochemical interfaces (BGI). We will assess mobility of SOM structural elements and sorbed organic chemicals via advanced solid state NMR techniques and desorption kinetics and combine these with 1H-NMR-Relaxometry and advanced methods of thermal analysis including DSC, TGADSC- MS and AFM-nanothermal analysis. Via controlled heating/cooling cycles, moistening/drying cycles and targeted modification of SOM, reconstruction of our model hypotheses by computational chemistry (collaboration Gerzabek) and participation at two larger joint experiments within the SPP, we will establish the relation between SOM sequestration potential, SOM structural characteristics, hydration-dehydration mechanisms, biological activity and biogechemical functioning. This will link processes operative on the molecular scale to phenomena on higher scales.

Charakterisierung des Nichtstruktur-Proteins p4 des neuen Virus European mountain ash ringspot-associated virus aus Eberesche (Sorbus aucuparia L.)

Fließgewässermessstelle Steg oh Emdg. Holzbach, Gollach

Die Messstelle Steg oh Emdg. Holzbach (Messstellen-Nr: 21749) befindet sich im Gewässer Gollach in Bayern. Die Messstelle dient der Überwachung des biologischen Zustands, des chemischen Zustands.

Fließgewässermessstelle Strbr. Moerlach-Haag, Altmühl

Die Messstelle Strbr. Moerlach-Haag (Messstellen-Nr: 3630) befindet sich im Gewässer Altmühl in Bayern. Die Messstelle dient der Überwachung des biologischen Zustands, des chemischen Zustands.

Fließgewässermessstelle Wegbr. Hammerschmiede, Schandtauber

Die Messstelle Wegbr. Hammerschmiede (Messstellen-Nr: 21646) befindet sich im Gewässer Schandtauber in Bayern. Die Messstelle dient der Überwachung des biologischen Zustands, des chemischen Zustands.

Fließgewässermessstelle uh Emdg. Haidelbach (Petersbruecke), Röthenbach

Die Messstelle uh Emdg. Haidelbach (Petersbruecke) (Messstellen-Nr: 17607) befindet sich im Gewässer Röthenbach in Bayern. Die Messstelle dient der Überwachung des biologischen Zustands, des chemischen Zustands.

Fließgewässermessstelle Friedhofsteg, Pegnitz

Die Messstelle Friedhofsteg (Messstellen-Nr: 17655) befindet sich im Gewässer Pegnitz in Bayern. Die Messstelle dient der Überwachung des biologischen Zustands, des chemischen Zustands.

Fließgewässermessstelle Pegel Roth oh Mdg., Roth

Die Messstelle Pegel Roth oh Mdg. (Messstellen-Nr: 16631) befindet sich im Gewässer Roth in Bayern. Die Messstelle dient der Überwachung des biologischen Zustands, des chemischen Zustands.

1 2 3 4 5 … 18 19 20