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Lead pollution approaches natural background levels

A study of northern Alberta peat bogs indicates that lead emissions controls have been successful

by Jyllian Kemsley
October 10, 2016 | A version of this story appeared in Volume 94, Issue 40

Credit: William Shotyk
University of Alberta engineering mechanic Tommy Noernberg helps collect a core sample from a peat bog.
Photo of a person hitting coring equipment with a mallet.
Credit: William Shotyk
University of Alberta engineering mechanic Tommy Noernberg helps collect a core sample from a peat bog.

Humans have a 3,500-year history of emitting neurotoxic lead into the atmosphere from mining, using leaded gasoline, and other activities. But efforts in the past several decades to reduce lead emissions have worked well, confirms a study of peat bogs in northern Alberta (Geophys. Res. Lett. 2016, DOI: 10.1002/2016gl070952). A team led by William Shotyk of the University of Alberta extracted peat cores from six sites to assess lead deposited from the atmosphere. The team tested samples from various core depths for lead and also for thorium, which is an indicator of general mineral abundance, and dated the samples using 14C and 210Pb methods. Depending on location, the researchers found, lead amounts peaked from 1960 to 1995 as the use of leaded gasoline in on-road vehicles was eliminated in the U.S. and Canada and other lead controls were implemented. Strikingly, the surface layers of the Alberta cores showed lead amounts comparable to samples taken from a Swiss bog and dated to 6,000 to 9,000 years ago, which can be considered natural background levels. “The lack of contemporary lead contamination in the Alberta bogs is testimony to successful international efforts of the past decades to reduce anthropogenic emissions,” the researchers say.

Back to baseline
A line graph showing lead to thorium ratios peaking around 1970 and then declining.
Credit: Geophys. Res. Lett.
Enrichment of lead relative to thorium, an indicator of general mineral abundance, peaked around 1970 and now approaches preindustrial levels in a Canadian peat bog.


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