Sulfur Isotope Fractionations in Biological Systems: Insight into the Proterozoic Biosphere

نویسندگان

  • David T. Johnston
  • Alan J. Kaufman
  • James Farquhar
چکیده

Title of Document: SULFUR ISOTOPE FRACTIONATIONS IN BIOLOGICAL SYSTEMS: INSIGHT INTO THE PROTEROZOIC BIOSPHERE David T. Johnston, Ph.D. 2007 Directed By: Professor J. Farquhar, Department of Geology and ESSIC This study focuses on developing a framework for interpreting isotopic fractionations in the four stable sulfur isotopes, with a special focus on microbial effects. Calculations of low temperature equilibrium fractionations between various sulfur species were performed and suggest a tightly constrained fractionation relationship between the isotopes. This work was followed by conducting a series of batch culture experiments with two prominent sulfur metabolisms: sulfate reduction and sulfur disproportionation. The results of these experiments illustrate that measurable deviations from the equilibrium predictions exist, and further serve to highlight the ability of these measurements to differentiate between fractionations produced by these two metabolisms. This is a distinction not possible from traditional isotope measurements alone (S/S). In addition, models constructed to describe these observations provide insight into the intra-workings of these metabolic pathways, with the most recent experiments suggesting that the traditionally accepted model for isotope fractionation produced by sulfate reducers be re-evaluated. The microbial fractionations were also used to calibrate global sulfur cycle box models. These models have been coupled with the measurement of natural samples to illustrate the onset of microbial disproportionation ~800 million years earlier in Earth history than previously thought and to describe the sulfur cycle of three Proterozoic marine basins. SULFUR ISOTOPE FRACTIONATIONS IN BIOLOGICAL SYSTEMS: INSIGHT INTO THE PROTEROZOIC BIOSPHERE

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Sulfur isotope biogeochemistry of the Proterozoic McArthur Basin

Previous geochemical and biomarker studies of the late Paleo-Mesoproterozoic propose a stratified world, with strongly reducing (possibly sulfidic) deep-ocean conditions overlain by an oxygenated surface-ocean and atmosphere. To investigate such a scenario, we look to the structure of the biogeochemical sulfur cycle. We present sulfur (S, S, S, and S in sulfides) isotope data from the McArthur ...

متن کامل

The Archean sulfur cycle and the early history of atmospheric oxygen.

The isotope record of sedimentary sulfides can help resolve the history of oxygen accumulation into the atmosphere. We measured sulfur isotopic fractionation during microbial sulfate reduction up to 88 degrees C and show how sulfate reduction rate influences the preservation of biological fractionations in sediments. The sedimentary sulfur isotope record suggests low concentrations of seawater ...

متن کامل

Multiple Sulfur Isotope Fractionations in Biological Systems: a Case Study with Sulfate Reducers and Sulfur Disproportionators

Multiple sulfur isotope measurements of sulfur compounds associated with dissimilatory sulfate reduction, elemental sulfur disproportionation and sulfite disproportionation indicate that different types of metabolic processes impart different multiple isotope signatures. An established network for sulfate reduction was used previously to explain the multiple isotope variability. Here, we revisi...

متن کامل

Active microbial sulfur disproportionation in the Mesoproterozoic.

The environmental expression of sulfur compound disproportionation has been placed between 640 and 1050 million years ago (Ma) and linked to increases in atmospheric oxygen. These arguments have their basis in temporal changes in the magnitude of 34S/32S fractionations between sulfate and sulfide. Here, we present a Proterozoic seawater sulfate isotope record that includes the less abundant sul...

متن کامل

Mass-independent sulfur of inclusions in diamond and sulfur recycling on early Earth.

Populations of sulfide inclusions in diamonds from the Orapa kimberlite pipe in the Kaapvaal-Zimbabwe craton, Botswana, preserve mass-independent sulfur isotope fractionations. The data indicate that material was transferred from the atmosphere to the mantle in the Archean. The data also imply that sulfur is not well mixed in the diamond source regions, allowing for reconstruction of the Archea...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2007