Scientists have reconstructed the environmental history of a Celtic mining town by digging through a peat bog near Dijon in France in search of lead residues and pollen grains1. Their results confirm some historical theories about the settlement says Fabrice Monna from the University of Bourgogne in Dijon, who led the study. "Archaeologists suspected that there had been mining there before the first century AD, but there was no direct proof until now."But the results also serve as a sobering reminder about how long pollution lasts. Monna's team concludes that about 20% of the lead pollution in the peat today was introduced before the eleventh century, and about 50% before the eighteenth century. "This demonstrates that any lead pollution we create today will persist for thousands of years into the future," says Monna."Today, the area is absolutely green, there is no industry there at all," Monna notes. Yet the fingerprint of human activity is still obvious in the peat bogs. Lead that was mined in the nineteenth century, for example, is still around at levels of about 80 micrograms per gram of peat. "That's quite a lot," says Monna.The finding isn't particularly surprising to environmental chemists. Once lead is locked up in organic material such as peat, it tends to stay put rather than being washed away by water. But the study emphasizes that researchers should pay more attention to where pollution comes from, says Monna.

In particular, he says, environmental surveys should consider the history of sites when looking at current pollution levels so that the impact of modern activities is not overestimated.


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