Airborne aerosol measurements in the quiescent plume of Mount St. Helens: September, 1980

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.