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The central goal of this research project is to constrain the origin of the vast amounts of organic carbon (OC) deposited in floodplain sediments of the Rio Beni system, a river that drains the Andes Mountains.  To do so, my research group is using the hydrogen and carbon isotopic signature of two suites of organic compounds, lignin phenols and plant-wax lipids, to determine the elevation at which the OC was produced and what types of plants it derived from.  We are completing this work in two stages: the first establishes the signatures of OC from various environments in this system via analysis of plant samples collected along a large gradient of elevations, and the second uses analysis of floodplain sediments to reconstruct the origins of the deposited carbon.

During the first year of this project (9/08-8/09), I selected and obtained from a colleague around 55 plant samples spanning an elevation range of 176-4687 m.  This sample suite includes at least 10 samples from each of the 1000-m elevation intervals and should be an excellent sample set for this project.  During the academic year, my group purchased equipment and established the basic procedure to extract and analyze lipids from samples.  The lignin method was already established in my lab.

Two undergraduate students worked full-time on this project during the summer, one supported by this grant and the other supported by other funds.  One student was responsible for the lipid part of the project whereas the other took charge of the lignin portion.  I spent the first few weeks of the summer training the students in the lab methods.  During this process, we discovered some serious problems with the lignin procedure and this student spent much of the remaining summer running experiments to pinpoint the part of the procedure that was causing these problems.  We were able to conclusively determine that our wet chemical method was not the source of the problem, which indicated that the issue derived from some aspect of the initial reaction in a Microwave-Assisted Reaction System (MARS).  More testing revealed that the microwave itself was functioning properly, indicating that the problem must have been with the Teflon reaction vessels that go inside the microwave.  It is likely that these vessels developed leaks at elevated temperatures, which affected the reaction, even though the vessels passed leak tests at room temperature.  Other research groups have had similar, though not identical, problems with these vessels.  Currently, I am working with the company to exchange our current vessels for vessels of a different design to solve this problem.  My other student continued development of the lipid extraction method throughout the summer.  She faced a number of challenges with the wet chemical methods but has now worked through almost all of these kinks.

Two of my three trained summer students are continuing to work with me during the school year at no cost to PRF.  They are working 10-15 hours per week to resolve the remaining methodological problems.  At their current pace, I anticipate that both methods will be working well by the end of the semester, allowing them to begin to analyze the Rio Beni plant samples during spring semester.  Next summer, they should be able to complete analysis of the plant samples (stage 1) and begin analyzing the sediment samples (stage 2).  Due to these methodological delays, I anticipate that the project will extend beyond the 2-year grant, but I also expect that PRF funds will remain to pay for this work. 

These undergraduate students have been involved in all aspects of the research funded by this grant.  Despite the many setbacks, this project has provided excellent research opportunities to both students, who thoroughly enjoyed their first taste of scientific research and proved to be excellent lab technicians and problem-solvers.  One of the students will be graduating this year and thus will not continue her work past the academic year, but the other, a junior, plans to write a senior thesis next year based on her work on this PRF-funded project.