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Alkane

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Ansgar Kahmen – 1st expert on this subject based on the ideXlab platform

  • Concentrations and δ^2H values of cuticular n-Alkanes vary significantly among plant organs, species and habitats in grasses from an alpine and a temperate European grassland
    Oecologia, 2015
    Co-Authors: Bruno Gamarra, Ansgar Kahmen

    Abstract:

    n –Alkanes are long-chained hydrocarbons contained in the cuticle of terrestrial plants. Their hydrogen isotope ratios (δ^2H) have been used as a proxy for environmental and plant ecophysiological processes. Calibration studies designed to resolve the mechanisms that determine the δ^2H values of n –Alkanes have exclusively focused on n –Alkanes derived from leaves. It is, however, unclear in which quantities n –Alkanes are also produced by other plant organs such as roots or inflorescences, or whether different plant organs produce distinct n –Alkane δ^2H values. To resolve these open questions, we sampled leaves, sheaths, stems, inflorescences and roots from a total of 15 species of European C3 grasses in an alpine and a temperate grassland in Switzerland. Our data show slightly increased n –Alkane concentrations and n –Alkane δ^2H values in the alpine compared to the temperate grassland. More importantly, inflorescences had typically much higher n –Alkane concentrations than other organs while roots had very low n –Alkane concentrations. Most interestingly, the δ^2H values of the carbon autonomous plant organs leaves, sheaths and stems were in general depleted compared to the overall mean δ^2H value of a species, while non-carbon autonomous organs such as roots and inflorescences show δ^2H values that are higher compared to the overall mean δ^2H value of a species. We attribute organ-specific δ^2H values to differences in the H-NADPH biosynthetic origin in different plant organs as a function of their carbon relationships. Finally, we employed simple mass balance calculations to show that leaves are in fact the main source of n –Alkanes in the sediment. As such, studies assessing the environmental and physiological drivers of n –Alkanes that focus on leaves produce relationships that can be employed to interpret the δ^2H values of n –Alkanes derived from sediments. This is despite the significant differences that we found among the δ^2H values in the different plant organs. Our study brings new insights into the natural variability of n –Alkane δ^2H values and has implications for the interpretation of n –Alkane δ^2H values in ecological and paleohydrological research.

  • leaf water deuterium enrichment shapes leaf wax n Alkane δd values of angiosperm plants i experimental evidence and mechanistic insights
    Geochimica et Cosmochimica Acta, 2013
    Co-Authors: Ansgar Kahmen, Enno Schefus, Dirk Sachse

    Abstract:

    Leaf wax n-Alkanes of terrestrial plants are long-chain hydrocarbons that can persist in sedimentary records over geologic timescales. Since meteoric water is the primary source of hydrogen used in leaf wax synthesis, the hydrogen isotope composition (δD value) of these biomarkers contains information on hydrological processes. Consequently, leaf wax n-Alkane δD values have been advocated as powerful tools for paleohydrological research. The exact kind of hydrological information that is recorded in leaf wax n-Alkanes remains, however, unclear because critical processes that determine their δD values have not yet been resolved. In particular the effects of evaporative deuterium (D)-enrichment of leaf water on the δD values of leaf wax n-Alkanes have not yet been directly assessed and quantified. Here we present the results of a study where we experimentally tested if and by what magnitude evaporative D-enrichment of leaf water affects the δD of leaf wax n-Alkanes in angiosperm C3 and C4 plants. Our study revealed that n-Alkane δD values of all plants that we investigated were affected by evaporative D-enrichment of leaf water. For dicotyledonous plants we found that the full extent of leaf water evaporative D-enrichment is recorded in leaf wax n-Alkane δD values. For monocotyledonous plants we found that between 18% and 68% of the D-enrichment in leaf water was recorded in the δD values of their n-Alkanes. We hypothesize that the different magnitudes by which evaporative D-enrichment of leaf water affects the δD values of leaf wax n-Alkanes in monocotyledonous and dicotyledonous plants is the result of differences in leaf growth and development between these plant groups. Our finding that the evaporative D-enrichment of leaf water affects the δD values of leaf wax n-Alkanes in monocotyledonous and dicotyledonous plants – albeit at different magnitudes – has important implications for the interpretation of leaf wax n-Alkane δD values from paleohydrological records. In addition, our finding opens the door to employ δD values of leaf wax n-Alkanes as new ecohydrological proxies for evapotranspiration that can be applied in contemporary plant and ecosystem research.

  • leaf water deuterium enrichment shapes leaf wax n Alkane δd values of angiosperm plants ii observational evidence and global implications
    Geochimica et Cosmochimica Acta, 2013
    Co-Authors: Ansgar Kahmen, Enno Schefus, Bernd Hoffmann, Stefan K Arndt, Lucas A Cernusak, Jason B West, Dirk Sachse

    Abstract:

    Leaf wax n-Alkanes are long-chain hydrocarbons that can persist in sedimentary records over geological timescales. Since their hydrogen isotopic composition (expressed as a δD value) can be correlated to the δD values of precipitation, leaf wax n-Alkane δD values have been advocated as new and powerful proxies for paleohydrological research. The exact type of hydrological information that is recorded in the δD values of leaf wax n-Alkanes remains, however, unclear. In a companion paper we provide experimental evidence showing that the δD values of leaf wax n-Alkanes of angiosperm plants grown under controlled environmental conditions not only reflect δD values of precipitation – as has often been assumed – but that evaporative deuterium (D)-enrichment of leaf water has an additional critical effect on their δD values. Here we present a detailed observational study that illustrates that evaporative D-enrichment of leaf water also affects the δD values of leaf wax n-Alkanes in plants from natural ecosystems along a 1500 km climate gradient in Northern Australia. Based on global simulations of leaf water D-enrichment we show that the effects of evaporative D-enrichment of leaf water on leaf wax n-Alkane δD values is relevant in all biomes but that it is particularly important in arid environments. Given the combined influence of precipitation δD values and leaf water D-enrichment we argue that leaf wax n-Alkane δD values contain an integrated signal that can provide general hydrological information, e.g. on the aridity of a catchment area. We also suggest that more specific hydrological information and even plant physiological information can be obtained from leaf wax n-Alkanes if additional indicators are available to constrain the plant- and precipitation-derived influences on their δD values. As such, our findings have important implications for the interpretation of leaf wax n-Alkane δD values from paleohydrological records. In addition, our investigations open the door to employ δD values of leaf wax n-Alkanes as new ecohydrological proxies in contemporary plant and ecosystem sciences.

Dirk Sachse – 2nd expert on this subject based on the ideXlab platform

  • leaf water deuterium enrichment shapes leaf wax n Alkane δd values of angiosperm plants i experimental evidence and mechanistic insights
    Geochimica et Cosmochimica Acta, 2013
    Co-Authors: Ansgar Kahmen, Enno Schefus, Dirk Sachse

    Abstract:

    Leaf wax n-Alkanes of terrestrial plants are long-chain hydrocarbons that can persist in sedimentary records over geologic timescales. Since meteoric water is the primary source of hydrogen used in leaf wax synthesis, the hydrogen isotope composition (δD value) of these biomarkers contains information on hydrological processes. Consequently, leaf wax n-Alkane δD values have been advocated as powerful tools for paleohydrological research. The exact kind of hydrological information that is recorded in leaf wax n-Alkanes remains, however, unclear because critical processes that determine their δD values have not yet been resolved. In particular the effects of evaporative deuterium (D)-enrichment of leaf water on the δD values of leaf wax n-Alkanes have not yet been directly assessed and quantified. Here we present the results of a study where we experimentally tested if and by what magnitude evaporative D-enrichment of leaf water affects the δD of leaf wax n-Alkanes in angiosperm C3 and C4 plants. Our study revealed that n-Alkane δD values of all plants that we investigated were affected by evaporative D-enrichment of leaf water. For dicotyledonous plants we found that the full extent of leaf water evaporative D-enrichment is recorded in leaf wax n-Alkane δD values. For monocotyledonous plants we found that between 18% and 68% of the D-enrichment in leaf water was recorded in the δD values of their n-Alkanes. We hypothesize that the different magnitudes by which evaporative D-enrichment of leaf water affects the δD values of leaf wax n-Alkanes in monocotyledonous and dicotyledonous plants is the result of differences in leaf growth and development between these plant groups. Our finding that the evaporative D-enrichment of leaf water affects the δD values of leaf wax n-Alkanes in monocotyledonous and dicotyledonous plants – albeit at different magnitudes – has important implications for the interpretation of leaf wax n-Alkane δD values from paleohydrological records. In addition, our finding opens the door to employ δD values of leaf wax n-Alkanes as new ecohydrological proxies for evapotranspiration that can be applied in contemporary plant and ecosystem research.

  • leaf water deuterium enrichment shapes leaf wax n Alkane δd values of angiosperm plants ii observational evidence and global implications
    Geochimica et Cosmochimica Acta, 2013
    Co-Authors: Ansgar Kahmen, Enno Schefus, Bernd Hoffmann, Stefan K Arndt, Lucas A Cernusak, Jason B West, Dirk Sachse

    Abstract:

    Leaf wax n-Alkanes are long-chain hydrocarbons that can persist in sedimentary records over geological timescales. Since their hydrogen isotopic composition (expressed as a δD value) can be correlated to the δD values of precipitation, leaf wax n-Alkane δD values have been advocated as new and powerful proxies for paleohydrological research. The exact type of hydrological information that is recorded in the δD values of leaf wax n-Alkanes remains, however, unclear. In a companion paper we provide experimental evidence showing that the δD values of leaf wax n-Alkanes of angiosperm plants grown under controlled environmental conditions not only reflect δD values of precipitation – as has often been assumed – but that evaporative deuterium (D)-enrichment of leaf water has an additional critical effect on their δD values. Here we present a detailed observational study that illustrates that evaporative D-enrichment of leaf water also affects the δD values of leaf wax n-Alkanes in plants from natural ecosystems along a 1500 km climate gradient in Northern Australia. Based on global simulations of leaf water D-enrichment we show that the effects of evaporative D-enrichment of leaf water on leaf wax n-Alkane δD values is relevant in all biomes but that it is particularly important in arid environments. Given the combined influence of precipitation δD values and leaf water D-enrichment we argue that leaf wax n-Alkane δD values contain an integrated signal that can provide general hydrological information, e.g. on the aridity of a catchment area. We also suggest that more specific hydrological information and even plant physiological information can be obtained from leaf wax n-Alkanes if additional indicators are available to constrain the plant- and precipitation-derived influences on their δD values. As such, our findings have important implications for the interpretation of leaf wax n-Alkane δD values from paleohydrological records. In addition, our investigations open the door to employ δD values of leaf wax n-Alkanes as new ecohydrological proxies in contemporary plant and ecosystem sciences.

Zhaoxia Dong – 3rd expert on this subject based on the ideXlab platform

  • dispersion property of co2 in oil 1 volume expansion of co2 Alkane at near critical and supercritical condition of co2
    Journal of Chemical & Engineering Data, 2012
    Co-Authors: Zihao Yang, Mingyuan Li, Bo Peng, Zhaoxia Dong

    Abstract:

    To investigate the effect of Alkane molecular structure on the volume expansion of CO2 + Alkane systems, the solubility of CO2 in hexane, octane, decane, and cyclohexane and the volume of CO2 + Alkanes at different temperature and pressure was measured with a PVT apparatus. The results imply that the dispersion state of CO2 molecules in the Alkane phase under near critical or supercritical condition of CO2 plays a dominate role in increasing the volume of CO2 + Alkane systems. The solubility of CO2 in the Alkanes, the volume expansion of the CO2 + Alkane systems, and the London force operating within Alkane molecules are strongly influenced by molecular structure of the Alkanes and pressure.

  • Dispersion Property of CO2 in Oil. 1. Volume Expansion of CO2 + Alkane at near Critical and Supercritical Condition of CO2
    Journal of Chemical & Engineering Data, 2012
    Co-Authors: Zihao Yang, Mingyuan Li, Bo Peng, Zhaoxia Dong

    Abstract:

    To investigate the effect of Alkane molecular structure on the volume expansion of CO2 + Alkane systems, the solubility of CO2 in hexane, octane, decane, and cyclohexane and the volume of CO2 + Alkanes at different temperature and pressure was measured with a PVT apparatus. The results imply that the dispersion state of CO2 molecules in the Alkane phase under near critical or supercritical condition of CO2 plays a dominate role in increasing the volume of CO2 + Alkane systems. The solubility of CO2 in the Alkanes, the volume expansion of the CO2 + Alkane systems, and the London force operating within Alkane molecules are strongly influenced by molecular structure of the Alkanes and pressure.