Development of a Programmed-temperature Pyrolysis/Combustion Reactor System for Radiocarbon Applications

点击翻译按钮获取中文摘要

0929752RosenheimThis proposal will lead to the development of an instrument to separate and age date components of acid insoluble organic material (AIOM) in sediments. Diagenetically-stable or pre-aged AIOM may be more resistant to complete pyrolysis than fresh AIOM. While sediment chronologies can be assessed by a suite of measurements, in certain instances, age dating AIOM may be the only option. The proposed instrument would use both pyrolysis and combustion to generate sufficient quantities of carbon dioxide for radiocarbon dating. The broad applications are to geochronology and carbon cycling. Pyrolysis at varying temperatures differentially "removes" organic matter from a complex matrix. In order to capture pyrolysis-generated carbon dioxide, a prototype flowthrough pyrolysis system has been developed. Thermograms reveal differential temperature-related carbon dioxide evolution based on sample type and location. The PI proposes to develop a trapping system to collect carbon dioxide "fractions." The system differs from any existing design in that it has a flowthrough configuration and a gradual temperature ramp capability. The flowthrough system "ends" in a platinum catalyst oxidation furnace to combust pyrolyzed moieties into carbon dioxide. These carbon dioxide fractions are cryogenically purified, frozen onto copper oxide and granulized silver and sealed for a redundant combustion at 525 °C. This step obviates any incomplete combustion and removes any interfering sulfur compounds before AMS analysis. Basic science questions to be addressed with successful development of this instrumentation include understanding the history of the Ross and Wedell Sea ice sheets will be estimated using pyrolized AIOM which can distinguish between "fresh" autochthonous and diagenetic carbon. The device will also be employed to better understand the oxidation of Amazon-deposited OM in Guianas mud banks. The PI intends to determine which proportions of OM are refractory - even under re-oxidized conditions (sediment turnover). Methods will also be applied to Eel River and Mississippi River sediments. The system will be used to assess the characteristics of kerogen-rich Ganges/Brahmupatra river system deposits. Preliminary data show different ages amongst components of riverine vs shelf environments. Mississippi delta deposits including areas associated with levees will be analyzed in order to age date deposition events. Sediment and organic matter delivery to wetlands will also be assessed. The system will be built and maintained at Tulane. Funds are sought for reactor components and 3 external reactor housings (for maintenance and reducing downtime). An IR carbon dioxide analyzer is requested for "real-time" carbon dioxide quantization. A muffle furnace is requested for system cleaning. Funds are requested for valves, LabView, DAQ hardware, relays, vacuum solenoids and a vacuum pump. Funds are also sought for radiocarbon analysis. This effort will fund a female PhD graduate student assistantship. The instrument development will allow the student to gain valuable instrumentation and electronics skills. The PI participates in NolaSMILE (New Orleans, LA, Science and Mathematics Inquiry, Learning, and Exploring) which is a vehicle for training and educating local teachers. The project will include a volunteer undergraduate from Xavier University (historically black college).***