HR: 17:45h
AN: OS44B-08    [Abstracts]
TI: Microscale Phosphorus Distribution and Chemistry in Marine Particles: New Insights From X-ray Absorption Near Edge Structure (XANES) Spectroscopy and X-ray Microscopy
AU: * Ingall, E
EM: ingall@eas.gatech.edu
AF: Georgia Institute of Technology, Earth and Atmospheric Sciences, Atlanta, GA 30332-0340
AU: Brandes, J
EM: brandes@utmsi.utexas.edu
AF: University of Texas, Marine Science Institute, Port Aransas, TX 78373
AU: Paterson, D
EM: paterson@aps.anl.gov
AF: Argonne National Lab, Advanced Photon Source, Argonne, IL 60439
AU: Northrup, P
EM: northrup@bnl.gov
AF: Brookhaven National Lab, National Synchrotron Light Source, Upton, NY 11973
AU: Benitez-Nelson, C
EM: cbnelson@geol.sc.edu
AF: University of South Carolina, Dept. of Geological Sciences, Columbia, SC 29208
AB: Dissolved and particulate organic materials are a significant source of bioavailable phosphorus (P) in many aquatic environments. In order to gain a better understanding of marine P cycling, the bulk composition of dissolved and particulate materials has been the focus of studies using nuclear magnetic resonance (NMR) techniques. One puzzling observation of NMR studies is the high proportion of P as phosphonate compounds (containing a direct C-P bond) in dissolved organic matter (DOM) compared to the almost undetectable quantities of phosphonates in most living organisms and particulate organic matter. The source of phosphonates in DOM has remained a mystery and has driven the search for new methods to examine P cycling in natural samples. Scanning tandem fluorescence and transmission X-ray microscopy, together with P x-ray absorption near edge structure spectroscopy (P-XANES), provide a way to examine P composition in natural samples on sub-micron scales. These techniques were used to compositionally characterize Cariaco Basin sediment trap particulates as well as freeze-dried DOM. Elemental mapping of particulates revealed a heterogeneous P distribution characterized by several micron diameter P rich regions associated with organic phases. The proportion of P esters and phosphonates in these regions varied from 100% P esters to some areas containing greater than 50% phosphonates. The results imply a source or concentrating mechanism capable of producing highly phosphonate rich particulates. Solubilization of such particulates along with selective decompostion of non-phosphonate P may be one possible mechanism to explain the high proportion of phosphonates in DOM.
DE: 4845 Nutrients and nutrient cycling
DE: 4850 Organic marine chemistry
DE: 4894 Instruments and techniques
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting