Greenland snow and ice cores: unique archives of large-scale pollution of the troposphere of the Northern Hemisphere by lead and other heavy metals

Since the pioneering work of C. Patterson and his coworkers, great improvements have been made in our understanding of the changing occurrence of heavy metals in the dated snow and ice archives deposited in Greenland. The available reliable data, which have been obtained using improved ultraclean and ultrasensitive analytical procedures, confirm that Pb, Cd, Zn, and Cu concentrations markedly increased in Greenland snow during the period from the industrial revolution more than 200 years ago to about the mid-1960s. The sharpest increase is clearly observed for Pb, mainly as a consequence of the introduction of Pb alkyl additives in gasoline, as confirmed by recent isotopic and speciation studies. During the past two decades, a clear decrease has been documented, following the great improvements made in the control of industrial emissions and the strong decline in the use of Pb alkyl additives.