Grant: $460,487 - National Science Foundation - Jun. 25, 2009
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Award Description: Although natural radioisotopes, such as Th(IV), Pa(IV, V), Po(IV, II, -II), and Be(II), are important proxies that have long been used in oceanographic investigations, the molecular interactions and binding relationships between radionuclides and marine organic matter remain unclear. Through years of research, it has become evident that metal ions in the ocean are mostly controlled by biopolymers and other organic molecules excreted by marine micro-organisms, and that biopolymers play a significant role in the biogeochemical cycles of the natural radionuclides that are used as oceanographic tracers. To identify and characterize the relationships between these biopolymeric carrier compounds and the radionuclides used in tracer research, scientists from Texas A&M University and the University of Southern Mississippi will conduct a comparative study on radioisotopes of thorium (Th), protactinium (Pa), polonium (Po), lead (Pb), and beryllium (Be). This laboratory and field experiment will identify the radioisotope carriers that are effective marine binding ligands and clarify the basics of oceanographic chemical tracer applications of various natural radioisotopes. Broader Impacts: The results from this research will enhance our fundamental understanding of the biogeochemical controls on natural radionuclide and carbon cycling, in the oceans. This research will also refine the interpretation of data collected in the GEOTRACES program. The project also involves the training of students and international collaborations.
Project Description: Th(IV), Pa(IV,V), Po(IV, II,-II), Pb(II) and Be(II) radioisotopes are important proxies in oceanographic investigations, e.g., for tracing particle dynamics and particulate organic matter (POC) fluxes out of the euphotic zone, and for studying boundary scavenging, paleo-productivity and ocean circulation. Even though considered routine, these approaches rely on often poorly constrained, empirically determined and variable isotope ratios or ratios to POC. Previously conducted laboratory and field investigations suggest that a number of biopolymers, potentially produced by both phytoplankton and bacteria, are carrier molecules for most of these isotopes, rather than purely inorganic surfaces. We hypothesize that specific binding and redox processes control marine scavenging and the most efficient binding would occur to acid polysaccharide- and protein-containing biomolecules. Proposed experiments will attempt to separate, identify and characterize radioisotope carriers that are hypothesized to be effective binding ligands. Our proposed interdisciplinary research project will require instrumental approaches for characterization studies, in combination with controlled laboratory and field experimentation. Laboratory studies consist of comparative uptake experiments of a suite of naturally occurring radionuclides to a number of substrates, including model organic and inorganic compounds, marine colloidal and particulate organic matter, and biopolymers harvested from cultures. The proposed field program will include collections and characterization of diverse types of suspended and sinking organic matter from different parts of the ocean.
Jobs Summary: 1 graduate student created, 1 research scientist retained (Total jobs reported: 2)
Project Status: Less Than 50% Completed
This award's data was last updated on Jun. 25, 2009. Help expand these official descriptions using the wiki below.