Halite particles about 2 micrometers in size were collected by a quartz crystal microbalance cascade impactor from the El Chichón eruption cloud in the lower stratosphere during April and May 1982. These particles are probably derived from the erupted chloride-rich, alkalic magma. Enrichments of hydrogen chloride and increases in optical depolarization in the eruption cloud observed by lidar measurements may reflect the influence of the halite particles. There is evidence that the halite particles reacted with sulfuric acid after about 1 month, releasing gaseous hydrogen chloride, which can influence the catalytic destruction of ozone in the stratosphere.

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Use of an airborne quartz crystal microbalance cascade impactor instrument together with a correlation spectrometer has allowed the flux of particles and their size distribution to be determined at Mount Erebus. The plume contributes 21 -+ 3 metric tonnes/day of aerosol particles to the Antarctic upper troposphere. The aerosol particles consist of larger (5-25/~m) particles of elemental sulfur and silica, a middle sized group of iron oxides and smaller particles (less than 1 #m) of complex liquids. Unlike many volcanic plumes, the Erebus plume has only a small amount of sulfate particles. The concentrations of particles in the Erebus plumes was 70-370 gm/m 3 . Limited sampling of the Antarctic atmosphere at 8 km altitude but hundreds of km away from Erebus obtained a few large particles of sulfur and silicates, suggesting a similarity with the Erebus plume. The fallout of these particles occurs slowly over a broad area of the Antarctic continent.

Measurements of SO2 emission rates and concentrations and of particle distribution, size, shape, and composition were made in quiescent volcanic plumes emitted into the troposphere from Poás and Arenal volcanos, Costa Rica, and Colima volcano, Mexico. SO2 emission rates were 700±180 metric tons per day (t/d) for Poás, 210±30 t/d for Arenal, and 320±50 t/d for Colima. The concentrations of SO2 calculated from the COSPEC/lidar data were 5–380 ppb. Concentrations of SO2 measured directly by flame photometry were 10–250 ppb. Particles collected in the plumes with a quartz crystal microbalance impactor were mostly less than 3 μm in diameter and consisted of droplets of dilute sulfur‐bearing solutions and minor amounts of larger silicate particles coated with a sulfur‐bearing film or crust. Total particle concentrations were 4.7 μg/m3 for Poás and 18.8 μg/m3 for Colima. Comparison of concentrations of SO2 in the plumes with gas samples collected at fumaroles on the ground suggests that the plumes are diluted by the atmosphere by factors of up to 105.

During February 1978 a group of scientists from the National Center for Atmospheric Research, several colleges and universities, the U.S. Geological Survey, and NASA used a specially equipped Beech Queen Air aircraft to make 11 sampling flights in Guatemala through the eruption clouds from the volcanoes Pacaya, Fuego, and Santiguito. Measurements were made of SO42−, SO2, HCl, HF, and 11 cations that were in water‐soluble form, on samples collected by a specially designed filter pack. Particle size distributions were obtained with a piezoelectric cascade impactor, and the particles were identified by energy dispersive X ray analysis. Evacuated canisters were flown to obtain samples for gas Chromatographic analysis. Some of the conclusions reached are that since most of the sulfur was found to be in the form of SO2, the H2SO4 droplets resulting from major explosive eruptions must largely result from the reaction of SO2 with OH, at the same time depleting the atmosphere of OH; the volume concentration ratio [SO2]/[HCl] always somewhat exceeded unity; and the amount of fine ash remaining in the stratosphere for long periods of time may depend on the crystallinity of the magma. Correlation spectrometry showed that each volcano was emitting 300–1500 metric tons of SO2 per day.

Surface acoustic wave (SAW) piezoelectric sensors typically used by researchers in analytical applications are based on SAW delay lines. We report here the development of a 200 MHz SAW instrument based on a SAW resonator instead of a conventional delay line. The instrument is small, compact and uses two separate 200 MHz resonator crystals which operate in the dual difference mode. The difference frequency stability is better than 55× 10−9 (±1 Hz) which is comparable to a 10 MHz bulk crystal (on an absolute frequency basis) and at least an order of magnitude better than other commercially available SAW delay lines that operate at comparable frequencies. The mass sensitivity is about 9 × 1010 Hz cm2/g. Response to temperature change is found to be about 20 Hz/°C from −30 °C to 30 °C. Response to pressure is found to be linear from 760 to 415 Torr at 3 Hz/Torr. Detection limits for HCl vapors were determined to be in the low ppb range using a SAW resonator coated with triethanolamine.

Sulphur dioxide emission rates were measured at Mount Etna, Italy during July 1987 while the volcano was undergoing relatively 'quiet' activity. The SO2 flux averaged 930 -t-587 (1~) Mg/d, excluding 19 July when the flux was 3200 +_ 1730 (1~) Mg/d. Rising magma and/or an influx of less degassed magma could explain the increased SO/flux. The high SO2 flux did not correlate with changes in observed volcanic activity. This suggests that SO2 monitoring may be useful as an indicator of shallow magmatic activity, but not as a predictor of future eruptions of Mount Etna.Particles emitted from the two active craters, Bocca Nuova and Southeast Crater (SE), were composed of silicates, sulphates and dithionites. Chloride species were only observed in particles from SE. Different eruptive styles probably produced the differences in particle compositions emitted from each crater.Vapour-magma enrichment factors were calculated for many elements from both craters. C1, Br and S were the most enriched elements in the sampled fumes. Similar enrichment factors at both craters suggest a common magma supply. C1, S and F have the largest elemental fluxes emitted from Mount Etna. During 'quiet' activity, the C1 flux represents 27% of the global anthropogenic emissions, but its effect is limited to the local region due to atmospheric removal processes. Mount Etna also exhaled significant amounts of Zn, Br, Mo, F and Cu compared with regional anthropogenic emissions.