MEASUREMENT OF BISMUTH AT PG G(-1) CONCENTRATIONS IN SNOW AND ICE SAMPLES BY THERMAL IONIZATION MASS-SPECTROMETRY

A technique has been developed to measure bismuth in small volumes of snow and ice at pg g(-1) concentrations by thermal ionisation mass spe ctrometry (TIMS). The analysis of Greenland snow accumulated at Summit from 1967 to 1989 and 8 ky old ice has yielded values between 0.02-0. 9 pg g(-1). After normalising to aluminium concentrations, enhancement s in bismuth concentrations were found to correlate significantly with three volcanic events. These enhancements are consistent with high bi smuth concentrations observed in emissions from volcanoes. Compared wi th ancient ice recent bismuth concentrations are enhanced relative to aluminium implying either increased volcanic activity in the recent ti mes or, more likely, a contribution from anthropogenic sources.