An improved method for decontaminating polar snow or ice cores for heavy metal analysis

An improved method has been developed for the decontamination of Greenland and Antarctic snow or ice cores for heavy metal analysis. The investigated core sections are chiselled while being held horizontal in a polyethylene lathe inside a laminar flow clean bench in a cold room. Each veneer layer and the final inner core are then analysed for Pb, Cd, Zn and Cu by graphite furnace atomic absorption spectrometry in clean room conditions. The procedural blank was found to range from 0.015 pgg for Cd up to 0.25 pgg for Cu. The quality of the decontamination was checked by studying changes in heavy metals concentrations from the outside to the center of each core section. In most cases, good plateaus of concentrations were observed in the central parts, then indicating that contamination present on the outside of the cores was not transferred to these central parts. Various Greenland and Antarctic cores were decontaminated, giving new insights into the past and recent occurrence of heavy metals in the atmosphere of both hemispheres.