Open AccessOxygen and sulfur isotopic composition of volcanic sulfate aerosol at the point of emission
Author(s) -
Mather T. A.,
McCabe J. R.,
Rai V. K.,
Thiemens M. H.,
Pyle D. M.,
Heaton T. H. E.,
Sloane H. J.,
Fern G. R.
Publication year - 2006
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005jd006584
Subject(s) - aerosol , sulfate , sulfate aerosol , volcano , sulfur , geology , volcanic gases , isotopes of oxygen , environmental chemistry , oxygen , isotopic signature , mineralogy , chemistry , geochemistry , stable isotope ratio , physics , organic chemistry , quantum mechanics
Volcanic sulfate aerosol is emitted from the vents of many active volcanoes, but its origin has not yet been explained. We report the first measurements of the isotopic compositions of near‐vent volcanic aerosol sulfate and use the combined sulfur and oxygen isotope systematics of the aerosol and magma at Masaya volcano, Nicaragua, to draw preliminary conclusions about the production mechanism of near‐source volcanic sulfate. The sulfate aerosol does not display a significant mass‐independent oxygen or sulfur isotopic signature, which suggests that primary volcanic aerosol does not contribute to the larger mass‐independent anomalies found in some ambient atmospheric aerosols and as preserved in ice cores. The oxygen isotope composition of the sulfate appeared to become heavier on the particle filters with increasing amount of sample collected and suggests that the δ 18 O value of the sulfate aerosol is <8‰. The sulfur isotopic composition of the sulfate did not vary with sample loading on the filters and had a mean δ 34 S value of 7.7 ± 0.8‰, similar to that of the magma (6.6 ± 0.2‰). The low Δ 17 O value, the δ 18 O value of the magma (6.6 ± 0.3‰) and the high δ 18 O value of atmospheric oxygen (23.5‰) suggest that known atmospheric oxidation pathways at ambient temperatures are not the major routes of production for this sulfate. Instead, the isotopic systematics of aerosol and magma are consistent with sulfate production either by high‐temperature equilibration of the magmatic gas mixture with small amounts of atmospheric oxygen or by direct emission of SO 4 2− from the magma.