HR: 14:25h
AN: B23D-04    [Abstracts]
TI: The Organic Chemistry of Volcanoes: Case Studies at Cerro Negro, Nicaragua and Oldoinyo Lengai, Tanzania
AU: * Teague, A J
EM: teague@erdw.ethz.ch
AF: Institute for Mineralogy and Petrography, ETH Zurich Sonneggstrasse 16, Zurich, 8092 Switzerland
AU: Seward, T M
EM: terry.seward@erdw.ethz.ch
AF: Institute for Mineralogy and Petrography, ETH Zurich Sonneggstrasse 16, Zurich, 8092 Switzerland
AU: Gize, A P
EM: andy_gize@msn.com
AF: Department of Earth Sciences, University of Manchester, Manchester, M13 9PL United Kingdom
AU: Hall, T
EM: tony@hallanalytical.co.uk
AF: Hall Analytical, Millbrook Business Centre Floats Rd, Manchester, M23 9YJ United Kingdom
AB: Though it has long been known that volcanoes emit organic compounds within their fumarolic gases, it is only in recent years that a concerted attempt has been made to catalogue and quantify the species and fluxes. Two general lines of interest dominate this study. Firstly, volcanic gases represent some of the most likely environments in which the precursor molecules necessary for the origin of life were synthesised. The existence of an active, abiotic, organic chemistry in such settings today is fundamental to our understanding of the early Earth. Secondly, the presence of halogenated organic compounds is of interest to the atmospheric sciences, particularly with respect to their ozone depleting potential. It is clear that natural sources of halocarbons must exist, and though current natural fluxes are low with respect to the anthropogenic signature, volcanogenic halocarbons may have proved to be significant during the eruption of supervolcanoes and continental flood basalts. In this study, gases were collected from fumaroles in the craters of two, very different, active volcanoes. Cerro Negro, a young basaltic cinder cone belonging to the Central American Volcanic Belt, could be defined as a typical subduction zone volcano. Gases were collected from Cerro Negro during March 2003 and 2004 from a single fumarole discharging close to the crater floor. In contrast, Oldoinyo Lengai is the world's only active carbonatite volcano and represents the most extreme case of alkali volcanism in the East African Rift system. Fieldwork was conducted in the northern summit crater of Lengai over 8 days in October 2003. In this period, the volcano was in near continuous eruption and gases were sampled from two fumaroles situated within 20m of the eruptive centre, though measured gas temperatures were low at around 195°C. Organic compounds were collected using a variety of activated carbon, molecular sieve type adsorbents, packed into glass cartridges. The water and acid matrix of the gas was first removed using a pair of condensation flasks cooled in ice/water slush. The gas was then passed through the adsorbent cartridges using a low flow battery powered pump. The gases were analysed using GCMS techniques. At Oldoinyo Lengai a wide variety of simple biomolecules such as acetic acid, pyrole and ethanol is noted. However, the low gas temperatures imply that these compounds are the result of bacterial activity within the system rather than abiotic synthesis. At Cerro Negro a rich organic chemistry was found. Alkanes, alkenes and aromatics are present in significant concentrations up to C12. Additionally, halogenated compounds such as trichlorofluoromethane (CFC11), chlorobenzene and tetrachloroethene were discovered in concentrations of up to 10ppbv, permitting revised estimates of the global volcanogenic flux of such halocarbons.
DE: 0370 Volcanic effects (8409)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 8409 Atmospheric effects (0370)
DE: 8430 Volcanic gases
DE: 8494 Instruments and techniques
SC: Biogeosciences [B]
MN: Fall Meeting 2005