HR: 0800h
AN: V21E-0670    [Abstracts]
TI: The Oxygen and Sulfur Isotopic Composition of Near-source Volcanic Sulfate Aerosol and Implications for its Origin
AU: * Mather, T A
EM: tam21@cam.ac.uk
AF: Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ United Kingdom
AU: McCabe, J R
EM: jmccabe@chem.ucsd.edu
AF: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093 United States
AU: Rai, V K
EM: rai@chem.ucsd.edu
AF: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093 United States
AU: Thiemens, M H
EM: mht@chem.ucsd.edu
AF: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093 United States
AU: Pyle, D M
EM: dmp11@cam.ac.uk
AF: Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ United Kingdom
AU: Heaton, T H
EM: theh@nigl.nerc.ac.uk
AF: NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham, NG12 5GG United Kingdom
AU: Sloane, H J
EM: hjs@nigl.nerc.ac.uk
AF: NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham, NG12 5GG United Kingdom
AU: Fern, G
EM: g.fern@gre.ac.uk
AF: Medway School of Science, University of Greenwich at Medway, Central Avenue, Chatham Maritime, Kent, ME4 4TB United Kingdom
AB: Near-source tropospheric volcanic sulfate aerosol has been observed at a number of volcanoes. Here we use sulfur and oxygen isotope systematics of the aerosol, magma and gaseous SO₂ at Masaya volcano, Nicaragua to further understand its production. The sulfate aerosol displays a mass-dependent oxygen isotopic signature. This suggests that it does not contribute to the mass-independent oxygen anomalies found in ambient atmospheric aerosol and that O₃ and H₂O₂ do not play an important role in its production. The low δ¹⁸O value (~5.5 ‰) of the aerosol, coupled with the low δ¹⁸O value of the magma (6.6 ‰), also implies that atmospheric oxygen has not been involved in its production. Comparison of the difference between the δ³⁴S values of the SO₂ (~6 ‰) and aerosol (7.7 ‰) in the volcanic plume with models of fractionation during gas-phase oxidation of SO₂ with OH suggest that oxidation via the route at ambient conditions is not responsible for near-source sulfate formation. Comparison of the δ³⁴S values of the magma (6.6 ‰) and the aerosol suggest that primary emission of SO₄^2- cannot be ruled out as the production mechanism. High-temperature OH oxidation of SO₂ or high-temperature equilibration of the volcanic gases to form sulfate are also possible. The δ³⁴S value of the primary sulfate from Masaya is higher than both that of the gas and the bulk magma.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0365 Troposphere: composition and chemistry
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
DE: 8409 Atmospheric effects (0370)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005