Peat bogs in northern Alberta, Canada reveal decades of declining atmospheric Pb contamination

Abstract

Abstract Peat cores were collected from six bogs in northern Alberta to reconstruct changes in the atmospheric deposition of Pb, a valuable tracer of human activities. In each profile, the maximum Pb enrichment is found well below the surface. Radiometric age dating using three independent approaches ( 14 C measurements of plant macrofossils combined with the atmospheric bomb pulse curve, plus 210 Pb confirmed using the fallout radionuclides 137 Cs and 241 Am) showed that Pb contamination has been in decline for decades. Today, the surface layers of these bogs are comparable in composition to the “cleanest” peat samples ever found in the Northern Hemisphere, from a Swiss bog ~ 6000 to 9000 years old. The lack of contemporary Pb contamination in the Alberta bogs is testimony to successful international efforts of the past decades to reduce anthropogenic emissions of this potentially toxic metal to the atmosphere.