Molecules In Sediments Research Articles

Molecular differences between water column and sediment pore water SPE-DOM in ten Swedish boreal lakes

Boreal lakes are considered hot spots of dissolved organic matter (DOM) processing within the global carbon cycle. This study has used FT-ICR mass spectrometry and comprehensive data evaluation to assess the molecular differences of SPE-DOM between lake column water SPE-DOM and sedimentary pore water SPE-DOM in 10 Swedish boreal lakes of the Malingsbo area, which were selected for their large diversity of physicochemical and morphological characteristics. While lake column water is well mixed and fairly oxygenated, sedimentary pore water is subject to depletion of oxygen and to confinement of molecules. Robust trends were deduced from molecular compositions present in all compartments and in all 10 lakes (“common compositions”) with recognition of relative abundance. Sedimentary pore water SPE-DOM featured higher proportions of heteroatoms N and S, higher average H/C ratios in presence of higher DBE/C ratios, and higher average oxygenation than lake column water SPE-DOM. These trends were observed in all lakes except Ljustjärn, which is a ground water fed kettle lake with an unique lake biogeochemistry. Analogous trends were also observed in case of single or a few lakes and operated also for compounds present solely in either lake column water or sedimentary pore water. Unique compounds detected in either compartments and/or in a few lakes showed higher molecular diversity than the “common compositions”. Processing of DOM molecules in sediments included selective preservation for polyphenolic compounds and microbial resynthesis of selected molecules of considerable diversity.

A New Reference Material for Tritium Organic Molecules in Sediment: Results of an International Intercomparison Exercise

Solid matrix 3H reference materials are challenging to prepare given the volatile nature of 3H and are often unrepresentative of the range of 3H forms that may be encountered during routine analysis. As a result, few 3H reference materials are currently available, undermining verification of analytical techniques for environmental 3H measurement. To address this, an International Working Group on Organically‐Bound Tritium Analysis determined to produce a tritium natural matrix reference material (NMRM). The reference material comprises marine sediment blended with sewage sludge contaminated with 3H‐organic species arising from authorised discharges from a radiopharmaceutical manufacturing site. Previous studies have demonstrated that the 3H species have persisted in the environment over three decades providing valuable supporting data to underpin the characterisation of the NMRM. The preparation and characterisation of the NMRM are described along with the subsequent application of the reference material in an international intercomparison exercise involving nineteen laboratories from nine countries. A reference value of 168 ± 22 Bq kg−1 was derived from the data arising from the proficiency test.

δ 13C and δD identification of sources of lipid biomarkers in sediments of Lake Haruna (Japan)

Organic materials in lacustrine sediments are from multiple terrestrial and aquatic sources. In this study, carbon (δ 13C) and hydrogen isotopic compositions (δD) of phytol, various sterols, and major n-fatty acids in sediments at Lake Haruna, Japan, were determined in their solvent-extractable (free) and saponification-released forms (bound). The δ 13C-δD distributions of these lipid molecules in sediments are compared with those of terrestrial C3 and C4 plants, aquatic C3 plants, and plankton to evaluate their relative contributions. δ 13C-δD of free phytol in sediments is very close to that of phytol in plankton samples, whereas δ 13C-δD of bound phytol in sediments is on a mixing line between terrestrial C3 plant and plankton material. Unlike phytol, no significant δ 13C-δD difference between free and bound forms was found in sterols and n-fatty acids. δ 13C-δD values of algal sterols such as 24-methylcholesta-5,22-dien-3β-ol in sediments are close to those of plankton, whereas δ 13C-δD of multiple-source sterols such as 24-ethylcholest-5-en-3β-ol and of major n-fatty acids such as n-hexadecanoic acid in sediments are between those of terrestrial C3 plants and plankton samples. Thus, δ 13C-δD distributions clearly indicate the specific source contributions of biomarkers preserved in a lacustrine environment. Free phytol and algal sterols can be attributed to phytoplankton, and bound phytol, multiple source sterols, and major n-fatty acids are contributed by both terrestrial C3 plants and phytoplankton.

NWO Awards Spinoza Prize

The Netherlands Organisation for Scientific Research (NWO) honored the winners of the NWO Spinoza Prize for 2004 at a ceremony this past November in The Hague. This prize is the Netherlands’ top award to researchers for their scientific work. Each winner received C1.5 million ($1.7 million) and a statuette of 17th-century Dutch philosopher and theologian Benedict de Spinoza. Ben Feringa, Jacobus van ’t Hoff Distinguished Professor of molecular sciences at the University of Groningen, was hailed by NWO for his “work on molecular motors and extremely selective catalysts.” He invented the first molecular motor powered by light, and his research group focuses on design and synthesis of complex molecules that can be used as molecular motors, switches, or catalysts.NWO cited Jaap Sinninghe Damsté for his “biological, geological, and chemical work on fossil molecules in sediments.” According to NWO, “his research into chemical fossils rewrote the theories about the carbon and sulphur cycles.” As a molecular biogeochemist, he analyzes specific organic compounds and uses the information to reconstruct the life and climate of earlier epochs. Sinninghe Damsté is head of marine biogeochemistry and toxicology at the Royal Netherlands Institute for Sea Research and a professor of molecular paleontology at Utrecht University. Astronomer Michiel van der Klis received the award for his “pioneering research into x-ray radiation from binary stars,” according to the citation. Van der Klis is a professor of astronomy at the University of Amsterdam’s astronomical institute. In the 1990s, his group discovered the first x-ray star that rotated at 400 times per second, the existence of which had been predicted 16 years previously but had not yet been proved. His studies provide data about the mass, radius, and rotational speed of neutron stars and black holes, as well as insights into the general theory of relativity. © 2005 American Institute of Physics.

The microbial world and the case for Mars

Microbial prokaryotes have flourished on Earth for more than 3.5 Ga. They dominated the Earth's biosphere during the first 2 Ga of its history before the first unicellular mitotic eukaryotes appeared. Therefore, in a search for extant life beyond the Earth, microorganisms are the most likely candidates for a putative biota of an extraterrestrial habitat. On Earth, life has developed strategies to cope with the so-called extreme conditions, such as hot vents, permafrost, permanent ice, subsurface regions, high atmosphere, rocks or salt crystals. By analogy with terrestrial extremophile communities, potential protected niches have been postulated for Mars, such as sulfur-rich sub-surface areas for chemoautotrophic communities, rocks for endolithic communities, permafrost regions, hydrothermal vents, soil, or evaporite crystals. Several methods exist to trace and identify microbial communities on Earth. Some of these biogenic signatures and biomarkers may also be applicable in attempts to search for life on Mars. However, the search for signatures indicative for putative extant life on Mars can only be the final steps in a research strategy in the quest for extraterrestrial life. In particular, prior to any “search for extant life” experiment, more data are required on the geology (paleolakes, volcanism, hydrothermal vents, carbonates), climate (hydrosphere, duration of phases which allow liquid water) and radiation environment, present state and past evolution as well as organic molecules in sediments. The search for possible biological oases will be connected with the detection of areas where liquid water still exists under the current conditions on that planet.

Thiophenic biomarkers for palaeoenvironmental assessment and molecular stratigraphy

RECONSTRUCTION of ancient depositional environments is an important objective in the Earth sciences. The complex assemblages of organic molecules in sediments include compounds that can be related to known biochemicals produced by specific biota from well defined habitats1–3, and these 'chemical fossils' are applied frequently to reconstruct palaeoenvironments, especially in studies of organic and petroleum geochemistry and in chemical oceanography. Most of the compounds used in this way are hydro-carbons2–4, although oxygenated (for example, alcohols, acids and ketones) and nitrogen-containing (for example, porphyrins) compounds have also been applied successfully1,2. Here we report on the use of organic sulphur compounds as geochemical tools for palaeoenvironmental and stratigraphic assessment. Depth profiles of specific sulphur compounds related to certain organisms show significant variations reflecting changes both in sources of organic matter and in physical conditions (such as salinity) of the depositional environment. In a number of cases these variations are not otherwise revealed by changes in lithology, geochemical bulk data and/or absolute and relative amounts of hydrocarbon biological markers. Moreover, several organic sulphur compounds reveal the presence of unprecedented biochemicals in these palaeoenvironments.

KEROGEN PRECURSORS: CHEMICAL AND BIOLOGICAL ALTERATION OF LIPIDS IN THE SEDIMENTARY SURFACE LAYER

A study of the processes operating upon organic molecules in present day sediments can illuminate kerogen-petroleum inter-relationships. The starting point for kerogen formation is not the initial biological inputs to a sediment but rather those organic molecules which survive the active upper 1 to 2 cm of surface sediment where biological diagenesis is most marked. Depth profile studies on fatty acids, alcohols, sterols, and dicarboxylic acids emphasise the differing sensitivity of lipid classes to chemical and biological processes. Distribution patterns for these lipids in older sediments thus reflect the changed weightings which result from utilisation and preservation within the biologically active zone.Environmental effects are discussed in terms of stability of chlorophyll-a and bacteriochlorophyll-a molecules in sediments taken from temperate zones and contrasted with those in sediments from tropical zones. Whilst demetallation is an important degradative pathway for bacteriochlorophyll-a, this is not the case for chlorophyll-a. In this latter molecule the pigment ring system is chemically unstable, but the phytyl ester appears to remain substantially unhydrolysed. The data given in the tables bear on alkane genesis and on the origin of the isoprenoid alkane biological markers. The consequences of this type of study for side chain structures in the coal macromolecule and industrial conversion processes are noted.