TY - JOUR A1 - Vaz da Cruz, Vinicius A1 - Büchner, Robby A1 - Fondell, Mattis A1 - Pietzsch, Annette A1 - Eckert, Sebastian A1 - Föhlisch, Alexander T1 - Targeting individual tautomers in equilibrium by resonant inelastic X-ray scattering JF - The journal of physical chemistry letters N2 - Tautomerism is one of the most important forms of isomerism, owing to the facile interconversion between species and the large differences in chemical properties introduced by the proton transfer connecting the tautomers. Spectroscopic techniques are often used for the characterization of tautomers. In this context, separating the overlapping spectral response of coexisting tautomers is a long-standing challenge in chemistry. Here, we demonstrate that by using resonant inelastic X-ray scattering tuned to the core excited states at the site of proton exchange between tautomers one is able to experimentally disentangle the manifold of valence excited states of each tautomer in a mixture. The technique is applied to the prototypical keto-enol equilibrium of 3-hydroxypyridine in aqueous solution. We detect transitions from the occupied orbitals into the LUMO for each tautomer in solution, which report on intrinsic and hydrogen-bond-induced orbital polarization within the pi and sigma manifolds at the proton-transfer site. KW - Equilibrium KW - Molecular structure KW - Molecules KW - Nitrogen KW - Solvents Y1 - 2022 U6 - https://doi.org/10.1021/acs.jpclett.1c03453 SN - 1948-7185 VL - 13 IS - 10 SP - 2459 EP - 2466 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Eckert, Sebastian A1 - Mascarenhas, Eric Johnn A1 - Mitzner, Rolf A1 - Jay, Raphael Martin A1 - Pietzsch, Annette A1 - Fondell, Mattis A1 - Vaz da Cruz, Vinicius A1 - Föhlisch, Alexander T1 - From the free ligand to the transition metal complex BT - FeEDTA(-) formation seen at ligand K-Edges JF - Inorganic chemistry N2 - Chelating agents are an integral part of transition metal complex chemistry with broad biological and industrial relevance. The hexadentate chelating agent ethylenediaminetetraacetic acid (EDTA) has the capability to bind to metal ions at its two nitrogen and four of its carboxylate oxygen sites. We use resonant inelastic X-ray scattering at the 1s absorption edge of the aforementioned elements in EDTA and the iron(III)-EDTA complex to investigate the impact of the metal-ligand bond formation on the electronic structure of EDTA. Frontier orbital distortions, occupation changes, and energy shifts through metal- ligand bond formation are probed through distinct spectroscopic signatures. KW - Energy KW - Ligands KW - Metals KW - Nitrogen KW - Oxygen Y1 - 2022 U6 - https://doi.org/10.1021/acs.inorgchem.2c00789 SN - 0020-1669 SN - 1520-510X VL - 61 IS - 27 SP - 10321 EP - 10328 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Olas, Justyna Jadwiga A1 - Apelt, Federico A1 - Watanabe, Mutsumi A1 - Höfgen, Rainer A1 - Wahl, Vanessa T1 - Developmental stage-specific metabolite signatures in Arabidopsis thaliana under optimal and mild nitrogen limitation JF - Plant science : an international journal of experimental plant biology N2 - Metabolites influence flowering time, and thus are among the major determinants of yield. Despite the reported role of trehalose 6-phosphate and nitrate signaling on the transition from the vegetative to the reproductive phase, little is known about other metabolites contributing and responding to developmental phase changes. To increase our understanding which metabolic traits change throughout development in Arabidopsis thaliana and to identify metabolic markers for the vegetative and reproductive phases, especially among individual amino acids (AA), we profiled metabolites of plants grown in optimal (ON) and limited nitrogen (N) (LN) conditions, the latter providing a mild but consistent limitation of N. We found that although LN plants adapt their growth to a decreased level of N, their metabolite profiles are strongly distinct from ON plant profiles, with N as the driving factor for the observed differences. We demonstrate that the vegetative and the reproductive phase are not only marked by growth parameters such as biomass and rosette area, but also by specific metabolite signatures including specific single AA. In summary, we identified N-dependent and -independent indicators manifesting developmental stages, indicating that the plant's metabolic status also reports on the developmental phases. KW - Amino acids KW - Floral induction KW - Flowering time KW - Nitrogen KW - Metabolites KW - Vegetative phase KW - Reproductive phase Y1 - 2021 U6 - https://doi.org/10.1016/j.plantsci.2020.110746 SN - 0168-9452 SN - 1873-2259 VL - 303 PB - Elsevier Science CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Schmidt, Martin A1 - Lischeid, Gunnar A1 - Nendel, Claas T1 - Microclimate and matter dynamics in transition zones of forest to arable land JF - Agricultural and forest meteorology N2 - Human-driven fragmentation of landscapes leads to the formation of transition zones between ecosystems that are characterised by fluxes of matter, energy and information. These transition zones may offer rather inhospitable habitats that could jeopardise biodiversity. On the other hand, transition zones are also reported to be hotspots for biodiversity and even evolutionary processes. The general mechanisms and influence of processes in transition zones are poorly understood. Although heterogeneity and diversity of land use of fragments and the transition zones between them play an important role, most studies only refer to forested transition zones. Often, only an extrapolation of measurements in the different fragments themselves is reported to determine gradients in transition zones. This paper contributes to a quantitative understanding of agricultural landscapes beyond individual ecotopes, and towards connected ecosystem mosaics that may be beneficial for the provision of ecosystem services. KW - Edge effects KW - Environmental gradients KW - Fragmentation KW - Ecosystem services KW - Carbon KW - Nitrogen Y1 - 2019 U6 - https://doi.org/10.1016/j.agrformet.2019.01.001 SN - 0168-1923 SN - 1873-2240 VL - 268 SP - 1 EP - 10 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Reverey, Florian A1 - Ganzert, Lars A1 - Lischeid, Gunnar A1 - Ulrich, Andreas A1 - Premke, Katrin A1 - Grossart, Hans-Peter T1 - Dry-wet cycles of kettle hole sediments leave a microbial and biogeochemical legacy JF - The science of the total environment : an international journal for scientific research into the environment and its relationship with man N2 - Understanding interrelations between an environment's hydrological past and its current biogeochemistry is necessary for the assessment of biogeochemical and microbial responses to changing hydrological conditions. The question how previous dry-wet events determine the contemporary microbial and biogeochemical state is addressed in this study. Therefore, sediments exposed to the atmosphere of areas with a different hydrological past within one kettle hole, i.e. (1) the predominantly inundated pond center, (2) the pond margin frequently desiccated for longer periods and (3) an intermediate zone, were incubated with the same rewetting treatment. Physicochemical and textural characteristics were related to structural microbial parameters regarding carbon and nitrogen turnover, i.e. abundance of bacteria and fungi, denitrifiers (targeted by the nirK und nirS functional genes) and nitrate ammonifiers (targeted by the nrfA functional gene). Our study reveals that, in combination with varying sediment texture, the hydrological history creates distinct microbial habitats with defined boundary conditions within the kettle hole, mainly driven by redox conditions, pH and organic matter (OM) composition. OM mineralization, as indicated by CO2-outgassing, was most efficient in exposed sediments with a less stable hydrological past. The potential for nitrogen retention via nitrate ammonification was highest in the hydrologically rather stable pond center, counteracting nitrogen loss due to denitrification. Therefore, the degree of hydrological stability is an important factor leaving a microbial and biogeochemical legacy, which determines carbon and nitrogen losses from small lentic freshwater systems in the long term run. KW - Desiccation KW - DNRA KW - Denitrifiers KW - Organic matter mineralization KW - Carbon KW - Nitrogen Y1 - 2018 U6 - https://doi.org/10.1016/j.scitotenv.2018.01.220 SN - 0048-9697 SN - 1879-1026 VL - 627 SP - 985 EP - 996 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - López-Tarazón, José Andrés A1 - Lopez, Pilar A1 - Lobera, Gemma A1 - Batalla Villanueva, Ramon J. T1 - Suspended sediment, carbon and nitrogen transport in a regulated Pyrenean river JF - The science of the total environment : an international journal for scientific research into the environment and its relationship with man N2 - Regulation alters the characteristics of riversty transforming parts of them into lakes, affecting their hydrology and also the physical, chemical, and biological characteristics and dynamics. Reservoirs have proven to be very effective retaining particulate materials, thereby avoiding the downstream transport of suspended sediment and the chemical substances associated with it (e.g. Carbon, C or Nitrogen, N). The study of fluvial transport of C and N is of great interest since river load represents a major link to the global C and N cycles. Moreover, reservoirs are the most important sinks for organic carbon among inland waters and have a potential significance as nitrogen sinks. In this respect, this paper investigates the effects of a Pyrenean reservoir on the runoff, suspended sediment, C and N derived from the highly active Esera and Isabena rivets. Key findings indicate that the reservoir causes a considerable impact on the Esera-Isabena river fluxes, reducing them dramatically as almost all the inputs are retained within the reservoir. Despite the very dry study year (2011-2012), it can be calculated that almost 300,000 t of suspended sediment were deposited into the Barasona Reservoir, from which more than 16,000 were C (i.e. 2200 t as organic C) and 222 t were N. These values may not be seen as remarkable in a wider global context but, assuming that around 30 hm(3) of sediment are currently stored in the reservoir, figures would increase up to ca. 2.6 x 10(6) t of C (i.e. 360,000 t of organic C) and 35,000 t of N. Nevertheless, these values are indicative and should be treated with caution as there is incomplete understanding of all the processes which affect C and N. Further investigation to establish a more complete picture of C and N yields and budgets by monitoring the different processes involved is essential. (C) 2015 Elsevier B.V. All rights reserved. KW - Suspended sediment KW - Carbon KW - Nitrogen KW - Temporal dynamics KW - Barasona Reservoir KW - River Esera KW - Ebro basin Y1 - 2016 U6 - https://doi.org/10.1016/j.scitotenv.2015.06.132 SN - 0048-9697 SN - 1879-1026 VL - 540 SP - 133 EP - 143 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Leuschner, Christoph A1 - Wulf, Monika A1 - Bäuchler, Patricia A1 - Hertel, Dietrich T1 - Soil C and nutrient stores under Scots pine afforestations compared to ancient beech forests in the German Pleistocene - the role of tree species and forest history JF - Forest ecology and management N2 - In the diluvial lowlands of northern Germany, the Netherlands and northern Poland, an estimated similar to 5 Mio ha of Scots pine plantations (Pinus sylvestris) has been established on sandy soil in the last 250 years replacing the former temperate broad-leaved forests after extended periods of cultivation in the Middle Ages. We examined the effect of variable stand continuity of pine plantations (recent vs. ancient: 51-128 vs. >230 years) on the soil organic carbon (SOC) store and soil nutrient capital in comparison to ancient beech forests (>230 years of continuity) which represent the potential natural forest vegetation. Recent and ancient pine stands had c. 75% larger organic layer C stores than ancient beech forests, while the total C stock in the soil (organic layer and mineral soil to 100 cm) was similar to 25% larger in the beech forests due to higher C concentrations in 0-50 cm depth of the mineral soil. The soil stores of N-tot were similar to 50% and the exchangeable Ca, K and Mg pools about three times larger under beech than under the pine stands. Resin-exchangeable P was enriched in the soils under ancient pine stands probably due to manuring in the past. After clear-cut and long cultivation, it may take >230 years of forest presence to restore the greatly reduced mineral soil C and N pools. The C and N sequestration potential of the soils appeared to be particularly small under pine indicating a pronounced tree species (pine vs. beech) effect on soil C and N dynamics. We conclude that, in the face of rising greenhouse gas emissions, the limited soil C and nutrient storage potential of Scots pine plantations on sandy soils needs consideration when selecting suitable tree species for future forestry. (C) 2013 Elsevier B.V. All rights reserved. KW - Sandy soil KW - Pinus sylvestris KW - Fagus sylvatica KW - Forest continuity KW - Historic land use KW - Nitrogen Y1 - 2013 U6 - https://doi.org/10.1016/j.foreco.2013.08.043 SN - 0378-1127 SN - 1872-7042 VL - 310 IS - 6 SP - 405 EP - 415 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Hancock, Christine A1 - Wäschke, Nicole A1 - Schumacher, Uta A1 - Linsenmair, Karl Eduard A1 - Meiners, Torsten A1 - Obermaier, Elisabeth T1 - Fertilizer application decreases insect abundance on Plantago lanceolata - a large-scale experiment in three geographic regions JF - Arthropod-plant interactions : an international journal devoted to studies on interactions of insects, mites, and other arthropods with plants N2 - Humans have substantially altered the nitrogen cycle of ecosystems through the application of agricultural fertilizer. Fertilization may not only affect plant species diversity, but also insect dynamics by altering plant nitrogen supplies. We investigated the effect of experimental fertilization on the vegetation, with the ribwort plantain as the focal plant, and on higher trophic levels on differently managed grasslands throughout Germany. Over a period of 2 years, we examined two specialist herbivores and their parasitoid on Plantago lanceolata L., and the composition and structure of the surrounding vegetation. Over 70 sites in three geographic regions, within the large-scale project "German Biodiversity Exploratories", were included in the study. The model system consisted of the host plant P. lanceolata L., the monophagous weevils Mecinus labilis Herbst and M. pascuorum Gyllenhal, and their parasitoid Mesopolobus incultus Walker. Fertilization decreased plant species richness and host plant abundance, whereas it enhanced the total vegetation growth. The increased size and heigher leaf nitrogen content did not improve herbivore performance. On the contrary, the abundance of the two herbivores was decreased by fertilization. The parasitoid depended on the abundance of one of its hosts, M. pascuorum (positively density-dependent). Reduced herbivore abundance due to fertilization might be explained by a lower abundance of the host plant, a lower stalk number, and by changed patterns of host localization within higher vegetation. Fertilization negatively affected the third trophic level by cascading up via host abundance. The relationships between fertilization, surrounding vegetation and the tritrophic system were measured throughout the three regions and over the 2-year period. Our findings present consequences of intensification for a plant-herbivore-parasitoid system, and may have significant implications for the conservation of multitrophic systems in managed grasslands. KW - Fertilization KW - Nitrogen KW - Tritrophic interaction KW - Plant species richness KW - Grassland management KW - Vegetation structure Y1 - 2013 U6 - https://doi.org/10.1007/s11829-012-9237-9 SN - 1872-8855 SN - 1872-8847 VL - 7 IS - 2 SP - 147 EP - 158 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Klaus, Valentin H. A1 - Kleinebecker, Till A1 - Prati, Daniel A1 - Gossner, Martin M. A1 - Alt, Fabian A1 - Boch, Steffen A1 - Gockel, Sonja A1 - Hemp, Andreas A1 - Lange, Markus A1 - Müller, Jörg A1 - Oelmann, Yvonne A1 - Pasalic, Esther A1 - Renner, Swen C. A1 - Socher, Stephanie A. A1 - Türke, Manfred A1 - Weisser, Wolfgang W. A1 - Fischer, Markus A1 - Hölzel, Norbert T1 - Does organic grassland farming benefit plant and arthropod diversity at the expense of yield and soil fertility? JF - Agriculture, ecosystems & environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere N2 - Organic management is one of the most popular strategies to reduce negative environmental impacts of intensive agriculture. However, little is known about benefits for biodiversity and potential worsening of yield under organic grasslands management across different grassland types, i.e. meadow, pasture and mown pasture. Therefore, we studied the diversity of vascular plants and foliage-living arthropods (Coleoptera, Araneae, Heteroptera, Auchenorrhyncha), yield, fodder quality, soil phosphorus concentrations and land-use intensity of organic and conventional grasslands across three study regions in Germany. Furthermore, all variables were related to the time since conversion to organic management in order to assess temporal developments reaching up to 18 years. Arthropod diversity was significantly higher under organic than conventional management, although this was not the case for Araneae, Heteroptera and Auchenorrhyncha when analyzed separately. On the contrary, arthropod abundance, vascular plant diversity and also yield and fodder quality did not considerably differ between organic and conventional grasslands. Analyses did not reveal differences in the effect of organic management among grassland types. None of the recorded abiotic and biotic parameters showed a significant trend with time since transition to organic management, except soil organic phosphorus concentrations which decreased with time. This implies that permanent grasslands respond slower and probably weaker to organic management than crop fields do. However, as land-use intensity and inorganic soil phosphorus concentrations were significantly lower in organic grasslands, overcoming seed and dispersal limitation by re-introducing plant species might be needed to exploit the full ecological potential of organic grassland management. We conclude that although organic management did not automatically increase the diversity of all studied taxa, it is a reasonable and useful way to support agro-biodiversity. KW - Agri-environmental schemes KW - Fertilization KW - Fodder quality KW - Land-use intensity KW - Nitrogen KW - Biomass nutrient concentrations KW - Organic farming KW - Phosphorus KW - Species richness KW - Nutrient availability Y1 - 2013 U6 - https://doi.org/10.1016/j.agee.2013.05.019 SN - 0167-8809 VL - 177 IS - 3 SP - 1 EP - 9 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Klaus, Valentin H. A1 - Kleinebecker, Till A1 - Boch, Steffen A1 - Müller, Jörg A1 - Socher, Stephanie A. A1 - Prati, Daniel A1 - Fischer, Markus A1 - Hoelzel, Norbert T1 - NIRS meets Ellenberg's indicator values prediction of moisture and nitrogen values of agricultural grassland vegetation by means of near-infrared spectral characteristics JF - Ecological indicators : integrating monitoring, assessment and management N2 - Ellenberg indicator values are widely used ecological tools to elucidate relationships between vegetation and environment in ecological research and environmental planning. However, they are mainly deduced from expert knowledge on plant species and are thus subject of ongoing discussion. We researched if Ellenberg indicator values can be directly extracted from the vegetation biomass itself. Mean Ellenberg "moisture" (mF) and "nitrogen" (mN) values of 141 grassland plots were related to nutrient concentrations, fibre fractions and spectral information of the aboveground biomass. We developed calibration models for the prediction of mF and mN using spectral characteristics of biomass samples with near-infrared reflectance spectroscopy (NIRS). Prediction goodness was evaluated with internal cross-validations and with an external validation data set. NIRS could accurately predict Ellenberg mN, and with less accuracy Ellenberg mF. Predictions were not more precise for cover-weighted Ellenberg values compared with un-weighted values. Both Ellenberg mN and mF showed significant and strong correlations with some of the nutrient and fibre concentrations in the biomass. Against expectations, Ellenberg mN was more closely related to phosphorus than to nitrogen concentrations, suggesting that this value rather indicates productivity than solely nitrogen. To our knowledge we showed for the first time that mean Ellenberg indicator values could be directly predicted from the aboveground biomass, which underlines the usefulness of the NIRS technology for ecological studies, especially in grasslands ecosystems. KW - Biodiversity exploratories KW - Cover-weighting KW - Near-infrared reflectance spectroscopy (NIRS) KW - Nitrogen KW - Nutrient concentrations KW - Phosphorus Y1 - 2012 U6 - https://doi.org/10.1016/j.ecolind.2011.07.016 SN - 1470-160X VL - 14 IS - 1 SP - 82 EP - 86 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Blüthgen, Nico A1 - Dormann, Carsten F. A1 - Prati, Daniel A1 - Klaus, Valentin H. A1 - Kleinebecker, Till A1 - Hoelzel, Norbert A1 - Alt, Fabian A1 - Boch, Steffen A1 - Gockel, Sonja A1 - Hemp, Andreas A1 - Müller, Jörg A1 - Nieschulze, Jens A1 - Renner, Swen C. A1 - Schöning, Ingo A1 - Schumacher, Uta A1 - Socher, Stephanie A. A1 - Wells, Konstans A1 - Birkhofer, Klaus A1 - Buscot, Francois A1 - Oelmann, Yvonne A1 - Rothenwöhrer, Christoph A1 - Scherber, Christoph A1 - Tscharntke, Teja A1 - Weiner, Christiane N. A1 - Fischer, Markus A1 - Kalko, Elisabeth K. V. A1 - Linsenmair, Karl Eduard A1 - Schulze, Ernst-Detlef A1 - Weisser, Wolfgang W. T1 - A quantitative index of land-use intensity in grasslands integrating mowing, grazing and fertilization JF - Basic and applied ecology : Journal of the Gesellschaft für Ökologie N2 - Land use is increasingly recognized as a major driver of biodiversity and ecosystem functioning in many current research projects. In grasslands, land use is often classified by categorical descriptors such as pastures versus meadows or fertilized versus unfertilized sites. However, to account for the quantitative variation of multiple land-use types in heterogeneous landscapes, a quantitative, continuous index of land-use intensity (LUI) is desirable. Here we define such a compound, additive LUI index for managed grasslands including meadows and pastures. The LUI index summarizes the standardized intensity of three components of land use, namely fertilization, mowing, and livestock grazing at each site. We examined the performance of the LUI index to predict selected response variables on up to 150 grassland sites in the Biodiversity Exploratories in three regions in Germany(Alb, Hainich, Schorlheide). We tested the average Ellenberg nitrogen indicator values of the plant community, nitrogen and phosphorus concentration in the aboveground plant biomass, plant-available phosphorus concentration in the top soil, and soil C/N ratio, and the first principle component of these five response variables. The LUI index significantly predicted the principal component of all five response variables, as well as some of the individual responses. Moreover, vascular plant diversity decreased significantly with LUI in two regions (Alb and Hainich). Inter-annual changes in management practice were pronounced from 2006 to 2008, particularly due to variation in grazing intensity. This rendered the selection of the appropriate reference year(s) an important decision for analyses of land-use effects, whereas details in the standardization of the index were of minor importance. We also tested several alternative calculations of a LUI index, but all are strongly linearly correlated to the proposed index. The proposed LUI index reduces the complexity of agricultural practices to a single dimension and may serve as a baseline to test how different groups of organisms and processes respond to land use. In combination with more detailed analyses, this index may help to unravel whether and how land-use intensities, associated disturbance levels or other local or regional influences drive ecological processes. KW - Agro-ecosystems KW - Biodiversity exploratories KW - Grassland management KW - Land-use impacts KW - Livestock density KW - Meadows KW - Nitrogen KW - Pastures Y1 - 2012 U6 - https://doi.org/10.1016/j.baae.2012.04.001 SN - 1439-1791 VL - 13 IS - 3 SP - 207 EP - 220 PB - Elsevier CY - Jena ER - TY - JOUR A1 - Klaus, Valentin H. A1 - Kleinebecker, Till A1 - Hoelzel, Norbert A1 - Bluethgen, Nico A1 - Boch, Steffen A1 - Müller, Jörg A1 - Socher, Stephanie A. A1 - Prati, Daniel A1 - Fischer, Markus T1 - Nutrient concentrations and fibre contents of plant community biomass reflect species richness patterns along a broad range of land-use intensities among agricultural grasslands JF - Perspectives in plant ecology, evolution and systematics N2 - Understanding changes in biodiversity in agricultural landscapes in relation to land-use type and intensity is a major issue in current ecological research. In this context nutrient enrichment has been identified as a key mechanism inducing species loss in Central European grassland ecosystems. At the same time, insights into the linkage between agricultural land use and plant nutrient status are largely missing. So far, studies on the relationship between chemical composition of plant community biomass and biodiversity have mainly been restricted to wetlands and all these studies neglected the effects of land use. Therefore, we analyzed aboveground biomass of 145 grassland plots covering a gradient of land-use intensities in three regions across Germany. In particular, we explored relationships between vascular plant species richness and nutrient concentrations as well as fibre contents (neutral and acid detergent fibre and lignin) in the aboveground community biomass. We found the concentrations of several nutrients in the biomass to be closely linked to plant species richness and land use. Whereas phosphorus concentrations increased with land-use intensity and decreased with plant species richness, nitrogen and potassium concentrations showed less clear patterns. Fibre fractions were negatively related to nutrient concentrations in biomass, but hardly to land-use measures and species richness. Only high lignin contents were positively associated with species richness of grasslands. The N:P ratio was strongly positively related to species richness and even more so to the number of endangered plant species, indicating a higher persistence of endangered species under P (co-)limited conditions. Therefore, we stress the importance of low P supply for species-rich grasslands and suggest the N:P ratio in community biomass to be a useful proxy of the conservation value of agriculturally used grasslands. KW - Biodiversity exploratories KW - Fertilization KW - Grazing KW - Land use KW - Mowing KW - Nitrogen KW - Nutrient limitation KW - Phosphorus KW - Productivity Y1 - 2011 U6 - https://doi.org/10.1016/j.ppees.2011.07.001 SN - 1433-8319 VL - 13 IS - 4 SP - 287 EP - 295 PB - Elsevier CY - Jena ER - TY - JOUR A1 - Balcke, Gerd U. A1 - Hahn, M. A1 - Oswald, Sascha Eric T1 - Nitrogen as an indicator of mass transfer during in-situ gas sparging JF - Journal of contaminant hydrology N2 - Aiming at the stimulation of intrinsic microbial activity, pulses of pure oxygen or pressurized air were recurrently injected into groundwater polluted with chlorobenzene. To achieve well-controlled conditions and intensive sampling, a large, vertical underground tank was filled with the local unconfined sandy aquifer material. In the course of two individual gas injections, one using pure oxygen and one using pressurized air, the mass transfer of individual gas species between trapped gas phase and groundwater was studied. Field data on the dissolved gas composition in the groundwater were combined with a kinetic model on gas dissolution and transport in porous media. Phase mass transfer of individual gas components caused a temporary enrichment of nitrogen, and to a lower degree of methane, in trapped gas leading to the formation of excess dissolved nitrogen levels downgradient from the dissolving gas phase. By applying a novel gas sampling method for dissolved gases in groundwater it was shown that dissolved nitrogen can be used as a partitioning tracer to indicate complete gas dissolution in porous media. KW - Inter-phase mass transfer KW - Groundwater KW - Remediation KW - Gas sparging KW - Nitrogen KW - Methane KW - Kinetics KW - Bitterfeld Y1 - 2011 U6 - https://doi.org/10.1016/j.jconhyd.2011.05.005 SN - 0169-7722 VL - 126 IS - 1-2 SP - 8 EP - 18 PB - Elsevier CY - Amsterdam ER -