Natural and anthropogenic bismuth in Central Greenland

Abstract

We report here Bismuth (Bi) measurements in recent snow and ancient ice from Central Greenland, The results indicate that during the last 26,000 years, the relative importance of the different sources of atmospheric Bi has strongly varied, From similar to 26.000 to similar to 20,000 years ago, Bi mainly originated from both rock and soil dust (similar to 50%) and volcanic activity (similar to 50%), Bi concentration in ice was 1 pg g(-1). From similar to 20,000 to similar to 8000 years ago, Bi concentration decreased down to very low values close to 0.03 pg g (-1) while the Bi/Al ratio strongly increased up to - 40 x 10-6 indicating that other sources became predominant. Rock and soil dust contribution strongly decreased to represent only similar to 5%, Volcanism stays at that time the main contributor of Bi, Finally, Bi concentrations remained very low from similar to 8000 to 6000 years ago, with contribution from rock and soil dust reaching again similar to 50%. Bi contribution from volcanism fall down to similar to 0.015 pg g-L and represent similar to 50% of natural sources, Enhanced Bi concentrations are observed for ice and snow dated from the time of the fallout from known major volcanic events such as the big eruption of Laki (1783-1784). During this last event, similar to 0.14 metric tonnes of volcanic Bi were deposited onto the Greenland ice sheet. During the last three decades: Bi/Al ratio is as high as similar to 25 x 10(-6), i.e., similar to 6 times natural Holocene values, This recent increase is attributed to the influence of anthropogenic emissions from oil and coal combustion, refuse incineration and ferromanganese alloys and aluminium production. (C) 2000 Elsevier Science Ltd. All rights reserved.