SO2-HCL RATIOS IN THE PLUMES FROM MT ETNA AND VULCANO DETERMINED BY FOURIER-TRANSFORM SPECTROSCOPY

Volcanic gases have important climatic and environmental effects, and provide insights into magmatic processes. Direct sampling of volcanic gases is inherently difficult and often hazardous. Here, we report the results of long path measurements of SO2 and HCl from Mt. Etna and Vulcano (Italy) obtained by active mode Fourier Transform InfraRed (FTIR) spectroscopy. Spectra recorded in September 1994 over path lengths of up to 2 km indicate SO2:HCl ratios of 3-5:1 for Etna, and 0.7-1.4:1 for Vulcano, consistent with their different styles of activity. Combined with contemporaneous Correlation Spectrometer (COSPEC) SO2 flux measurements, these ratios indicate an HCl flux for Etna of about 1700 t/d (about 16% of the present global anthropogenic flux) and for Vulcano of about 13 t/d. We also report the first remote spectroscopic detection of volcanic SiF4.