TY - JOUR A1 - Duc, L. A1 - Noll, Matthias A1 - Meier, B.E. A1 - Bürgmann, H. A1 - Zeyer, J. T1 - High Diversity of Diazotrophs in the Forefield of a Receding Alpine Glacier N2 - Forefields of receding glaciers are unique and sensitive environments representing natural chronosequences. In such habitats, microbial nitrogen fixation is of particular interest since the low concentration of bioavailable nitrogen is one of the key limitations for growth of plants and soil microorganisms. Asymbiotic nitrogen fixation in the Damma glacier (Swiss Central Alps) forefield soils was assessed using the acetylene reduction assay. Free-living diazotrophic diversity and population structure were resolved by assembling four NifH sequence libraries for bulk and rhizosphere soils at two soil age classes (8- and 70-year ice-free forefield). A total of 318 NifH sequences were analyzed and grouped into 45 unique phylotypes. Phylogenetic analyses revealed a higher diversity as well as a broader distribution of NifH sequences among phylogenetic clusters than formerly observed in other environments. This illustrates the importance of free-living diazotrophs and their potential contribution to the global nitrogen input in this nutrient-poor environment. NifH diversity in bulk soils was higher than in rhizosphere soils. Moreover, the four libraries displayed low similarity values. This indicated that both soil age and the presence of pioneer plants influence diversification and population structure of free-living diazotrophs. KW - Diazotrophs KW - Glacier forefield KW - Chronosequence KW - Pioneer plant KW - NifH diversity PY - 2009 DO - https://doi.org/10.1007/s00248-008-9408-5 SN - 0095-3628 SN - 1432-184X VL - 57 IS - 1 SP - 179 EP - 190 PB - Springer CY - New York, NY ; Heidelberg ; Berlin AN - OPUS4-18646 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Urmann, K. A1 - Schroth, M.H. A1 - Noll, Matthias A1 - Gonzalez-Gil, G. A1 - Zeyer, J. T1 - Assessment of microbial methane oxidation above a petroleum-contaminated aquifer using a combination of in situ techniques N2 - Emissions of the greenhouse gas CH4, which is often produced in contaminated aquifers, are reduced or eliminated by microbial CH4 oxidation in the overlying vadose zone. The aim of this field study was to estimate kinetic parameters and isotope fractionation factors for CH4 oxidation in situ in the vadose zone above a methanogenic aquifer in Studen, Switzerland, and to characterize the involved methanotrophic communities. To quantify kinetic parameters, several field tests, so-called gas push-pull tests (GPPTs), with CH4 injection concentrations ranging from 17 to 80 mL L-1 were performed. An apparent Vmax of 0.70 ± 0.15 mmol CH4 (L soil air)-1 h-1 and an apparent Km of 0.28 ± 0.09 mmol CH4 (L soil air)-1 was estimated for CH4 oxidation at 2.7 m depth, close to the groundwater table. At 1.1 m depth, Km (0.13 ± 0.02 mmol CH4 (L soil air)-1) was in a similar range, but Vmax (0.076 ± 0.006 mmol CH4 (L soil air)-1 h-1) was an order of magnitude lower. At 2.7 m, apparent first-order rate constants determined from a CH4 gas profile (1.9 h-1) and from a single GPPT (2.0 ± 0.03 h-1) were in good agreement. Above the groundwater table, a Vmax much higher than the in situ CH4 oxidation rate prior to GPPTs indicated a high buffer capacity for CH4. At both depths, known methanotrophic species affiliated with Methylosarcina and Methylocystis were detected by cloning and sequencing. Apparent stable carbon isotope fractionation factors a for CH4 oxidation determined during GPPTs ranged from 1.006 to 1.032. Variability was likely due to differences in methanotrophic activity and CH4 availability leading to different degrees of mass transfer limitation. This complicates the use of stable isotopes as an independent quantification method. KW - In situ quantification KW - Kinetics of microbial methane (CH4) oxidation KW - Stable isotope fractionation PY - 2008 DO - https://doi.org/10.1029/2006JG000363 SN - 0148-0227 VL - 113 SP - 02006-1-02006-11 PB - American Geophysical Union CY - Washington, DC AN - OPUS4-17332 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Koudelka, L. A1 - Mosner, P. A1 - Petrík, J. A1 - Zeyer, M. A1 - Jäger, Christian T1 - Study of the structure of mixed lead borophosphate glasses by NMR, RAMAN and IR Spectroscopy PY - 2002 SN - 0918-4783 VL - 13 SP - 165 EP - 170 CY - Tokyo AN - OPUS4-11021 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Koudelka, L. A1 - Mosner, P. A1 - Jirák, J. A1 - Zeyer-Düsterer, Michaela A1 - Jäger, Christian T1 - Medium range order in lead borophosphate glasses N2 - The structure of 50PbO-xB2O3-(50-x)P2O5 glasses with x=0-25 mol% B2O3 was refined by Raman and 11B MQMAS NMR. The analysis of Raman spectra, using the concentration step of 2 mol% B2O3 within the range of 0-12 mol% B2O3, showed that the evolution of changes in the type of oxygen bridges can be observed from the Raman bands within the range of 600-800 cm-1. 11B MQMAS NMR spectra of glasses with x=15, 20 and 25 mol% B2O3 revealed the presence of two BO4 sites in these glasses. The first site B1O4, characterised by the chemical shift of d=-3·8 — (-3·4) ppm, was assigned to tetrahedral B(OP)4 structural units. Within the concentration range x=15-25 mol% B2O3, the site B1O4 is gradually replaced by the site B2O4 with the chemical shift of d=-1·8 — (-1·1) ppm. This second site was assigned to the presence of B(OP)3(OB) units in which the central boron atom is linked to three PO4 groups and one BO3 group. KW - NMR KW - Raman KW - Struktur KW - Gläser PY - 2006 SN - 0031-9090 VL - 47 IS - 4 SP - 471 EP - 475 PB - Thornton CY - Sheffield AN - OPUS4-14811 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -