Heavy metals in ancient tropical ice: initial results

Although a wealth of fascinating data have been obtained through the investigation of heavy metals in Greenland, Antarctic and Alpine snow and ice cores, heavy metals have until now never been measured in tropical snow and ice cores despite the great interest of such low latitude cores. We present here preliminary data on the occurrence of Al, Na, Ti, V, Cr, Mn, Co, Cu, Zn, Mo, Pd, Ag, Cd, Sb, Ba, Pt, Au, Pb, Bi and U in a dated ice core drilled at an altitude of 6542 m on the top of Sajama in Bolivia. These data were obtained by analysing four core sections dated 22,000 BP (Last Glacial Maximum, LGM), 8000 BP (early Holocene, EH), AD1650 and AD 1897, using ultrasensitive ICP-SF-MS. Concentrations observed in LGM ice are similar to those measured in EH ice. Al, Na, Ti, V, Cr, Mn, Co, Ba and U are found to derive mainly from rock and soil dust. For the other metals, additional contributions from other sources are needed to explain the observed concentrations.