Atmospheric particulate matter and condensed volatile species were collected in the quiescent plume of Mount St. Helens volcano in Sept. 1980 using air filter systems mounted aboard a NASA turbo‐prop P‐3 aircraft. Concentrations of 27 elements were determined by instrumental neutron activation analysis and ion chromotagraphy. The volatile elements Cl, Br, F, Zn, W, In, S, Cd, Se, Sb, Hg, As and Au were enriched relative to bulk ash emitted during the earlier eruptions by factors of 50 to 20,000. Particulate S concentrations were ˜3 µg/m³ and accounted for 6% of the total plume sulfur. Gasphase Hg concentrations were 2.5 to 16 ng/m³. Fluxes of elements were estimated by normalizing elemental concentrations to the concurrently measured total sulfur flux. Emission rates vary from 3500 kg/day for particulate Cl to 3 kg/day for Au, with substantial quantities of the enriched elements Zn, As, Hg, Sb, Se, and Cd also being released. Estimated global fluxes of these elements from volcanoes to the atmosphere are in reasonable agreement with other literature estimates.
Atmospheric particulate material collected from the stratosphere in the plume of the 18 May 1980 eruption of the Mount St. Helens volcano was quite similar in composition to that of ash that fell to the ground in western Washington. However, there were small but significant differences in concentrations of some elements with altitude, indicating that the stratospheric material was primarily produced from fresh magma, not fragments of the mountain.
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