Roman-era air pollution … April 1st

An isolated salt marsh on the coast of contemporary Iceland is the last place most people would think of looking for Roman-era air pollution.

But traces of atmospheric lead pollution found in the sedimentary cores of an Iceland salt marsh, most likely originated from first- and second-century C.E. Roman mining and metal-working operations, a new study reports.

The research, which appeared in the April 1 issue of the journal Science of the Total Environment, indicates that the lead most likely found its way aloft from what is now Somerset in Britain.

William Marshall, a research fellow in geoscience at the University of Plymouth in the U.K., and the paper’s lead author, says it’s the most distantly detected example of such Roman atmospheric pollution from Britain. Previous evidence of Roman-era atmospheric lead pollution has been found in peat deposits in Europe, in sediments from Swedish lakes and in ice cores from Greenland.

However, this sedimentary sampling taken at Vidarholmi, on the island’s west coast, shows just how readily and how far a little bit of particle pollution can travel, says Marshall. (The remote spot has also been used to show how sea levels have been rising in the Atlantic.)

Although lead does occur naturally as a byproduct of mankind’s gold, silver, copper and tin mining, this soft, malleable heavy metal has polluted the atmosphere since the onset of metallurgy.

Its signature isotopic ratios are used to link it to specific mining ores after it has rained out and become part of earth’s surface sediments. Marshall and colleagues used the lead’s isotopic signatures and timing of its deposition within the sediment to determine the Icelandic sample’s link to its likely Roman-era origin.

This paper adds another important piece to the geographical jigsaw puzzle of lead pollution history in the Northern Hemisphere, says John Farmer, a geoscientist at the University of Edinburgh and not involved in the study.

At the height of their empire, the Romans were shipping large lead ingots from Britannia’s Mendip minesto the continent in large part for use in their famous plumbing (a word which comes from the Latin plumbum — for lead).

“Detecting ancient Roman pollution in an Icelandic salt marsh provides a cautionary tale for those who expect an ocean or a mountain range to protect them from the impact of highly polluting factories on other continents,” said Thomas Peterson, a research meteorologist at NOAA’s National Climatic Data Center in Asheville, N.C., also not part of the study.

Marshall is now analyzing new samples from a second Iceland location in an effort to extend the record back some 3,000 years to better establish the area’s pre-Roman lead levels.

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